University of Alberta

TECTONOMETAMORPHIC EVOLUTION OF THE KLUANE METAMORPHIC ASSEMBLAGE, SW YUKON: EVIDENCE FOR LATE CRETACÇOUS EASWARD SUBDUCTION OF OCEANIC CRUST UNDERNEATH NORTH AMERICA

JOCHEN ERNST MEZGER (c)

A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY

Department of Geology

Edmonton, Alberta Fa11 1997 National Library Bibliothèque nationale du Canada Acquisitions and Acquisitions et BiMiogiaphic SeMces setvices bibliographiques 395 WeUiingtorr Street 395, rue Wellinw WONK1AW -ON K1AW Canada Canada

The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bîbîiotheque nationale du Canada de reproduce, loan, distriaute or seIl reproduire, prêter, distniuer ou copies of this thesis in microfonn, vendre des copies de cette thése sous paper or elecîronic formats. la forme de microfiche/film, de reproduction sur papier ou sur format électronique.

The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiek may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. "Ma perche, se ha percezione di sè non deve aver memoria? La rnemoria B una potenza dell'anima, e per piccola che sia Sanima che la pietra ha, avrà memoria in proporzione."

"But why. if the stone perceives itself, should it not have memory? Memory is a power of the soul, and however small the sou1 of a stone, it will have a proportionate mernory."

Umberto Eco, "The Island of the Day beforen Abstract

The Kluane metamorphic assemblage (KMA) foms a 160 km NWSE striking belt of graphitic micaquartz schist with inteilayered ultramafic lenses.

It is located east of the Denali fauit at the northwestem margin of the Coast

Belt of the Western North American Cordillera. between island arc rocks of the

lnsular Superterrane (INS) to the West and pericratonic assemblages to the east. The lithology of the KMA is distinct Rom any metamorphic assemblage in the Cordillera

The dominant structural fabric of the KMA is a pervasiw NEdipping

schistosity with a generally east-trending mineral stretching lineation. Mylonitic

schists are characterized by a distinct monoclinic fabric that defines westward

hangingwall up sense of shear.

The KMA has experienced Late Cretaceous syndeformational high

Pnow T metamorphism followed by low PBigh T thermal overprinting resulting

from Early Eocene emplacement of the Ruby Range Batholith (RRB).

Trace element and neodymiurn isotope signatures of the KMA

distinguish its protolith from adjacent liysch of the Dezadeash Formation (DF)

which has juvenile signatures and Late Proteroroic model ages. and schists of

the pericratonic Aishihik Metamorphic Suite (AMS), part of the Yukon Tanana

terrane, with ancient continental cnist source and Late Archean mode1 ages.

The KMA has intemediate ~~(0)values of 4 and T,, of 1.3 Ga, indicative of homogeneous mking of ancient and jwenile material.

A possible tectonic rnodel for the evolution of the KMA involves deposiüon of fine grained pelitic seditnents in a backarc basin proximal to a volcanic arc and distal to an ancient continent. Late Cretaceous eastward motion of the Kula plate resulted in collapse of the basin and oblique eastward subduction, with a leff-lateral strike-slip component, undemeath the North

American continental margin (AMS). Sediments of the KMA and parts of the oceanic cnist experienced dudile deformation and high Pnow T metamorphism dunng subduction and were added to the upper plate.

Change of plate motion in the latest Cretaceous resulted in Eariy

Eocene sill-like intrusion of the RRB along the suture between the KMA and

AMS.

Continuous northward plate motion caused rapid late Eoœne upiift of the KMA and juxtaposition with the DF and INS. ACKNOWLEOGEMENTS

Dr. Philippe Erdmer is thanked for introducing me ?O the exciang geology of the Northem Canadian Cordillera. His rdentless support and guidanœ throughout the course of my Ph.D. thesis is sincerely appreciated. The Yukon Geology Program, fonnerly the Yukon Geoscienœ Onice, in Whitehorse provided valuable logistical support and is thanked for usage of faciiities and field equipment, as well as sharing heliwpter tirrte. In the field discussions of the KMA and AMS with Dr. Steve Johnston of the Yukon Geoscience ûffice and of the Dezadeash Formation with Dr. Grant Lowey are sincerely appreciated. Important geochronological data was provided by Dr. Jim Mortensen of the University of British Columbia. Together with his thorough knowledge of the geology of the southwestem Yukon. it helped to improve this thesis. Able assistance and wmpanionship in the field was provided by Rob Brown (1993). Kevin Deck (1994) and Brys Francis (1995). The Bayshore Restaurant along the Alaska Highway at the southwestem end of Kluane Lake always welcomed Idirty" geologists and senred some of the best food north of latitude 60. The members of my supenrisor cornmittee, Dr. Tomas Chacko, Dr. Robert Creaser and Dr. Karlis Muehlenbachs are thanked for guidanœ during the my Ph.D. program. I am very thankfid to Dr. Thomas Chacko for lengthy discussions on metamorphic petroIogy and geothennobarometry. Introduction to the unstabk world of radiogenic isotopes by Dr. Creaser was fundamental in developing ideas on the origin of the Kluane metamorphic assemblage. It could not have been done without them. Dr. Robert Luth is thanked for help on petrochemical problems. I am abo grateful for discussions with other geologists a various meetings. In particular I would like to thank Dave Brew (USGS Menlo Park), Carol Evenchick (GSC Vancouver). Paul Wlliams (University of New Brunswick) and Lincoln Hollister (Princeton University). Even if these discussions were short, they provided me with better understanding and helped to improve my thesis. Geochemical analyses were provided by Washington State University. Oxygen isotope deteminations of the olivine serpentinïtes were undertaken by Dr. Frsd Longstafiie of the University of Western Ontario. One 4Ar-a~ranalysis was done at Queen's University of Kingston, Ontario, by Karen Fallas. The relentless help and prompt assistance of Paul Wagner of the electron microprobe lab at the ûepartrnent of Earth & Atmospheric Sciences at the University of Alberta is gratefirlly acknowleciged. The help and friendship of my fellow graduate students at the University of Alberta in the last four and a haff years made the highand lows of graduate student life more enjoyable and bearable. I am thanml to Rob Stevens for welcoming me to Edmonton and sheitering me for the first weeks. 1 have leamed a lot from discussions with Suman De, Karen Fallas, Steve Grant, George Morris, Dinu Pan& Rob Stevens, Steve Wetherup, and Taro Yamashita. Karen Fallas and George Moms read parts of my thesis and made valuable suggestions that helped to improve my English. Further thanks to Liane Schlickenrieder, Darlene Atkinson, Leslie Driver, Mario Houle, Keme-An n Shannon, Harald Hübscher and Ruth Noronha for their friendship. But most of al1 I am grateful for the support and friendship of Sabrina Trupia. The next beers will be on me! I am very grateful for the moral, and often financial, support of my fiiends and family in Germany, and especially my parents, Trude and Werner Mezger. Fieldwork for this project was funded by NSERC operating grants to P. Erdmer and reseanh grants from the Canadian Circumpolar Institute (CCI) and the Geological Society of America to the author. Several University of Alberta scholanhips provided further financial support that helped to complete this projed. TABLE OF CONTENTS

CHAPTER 1 .INTROOUCTlON ...... 1 Statement of problem ...... 2 Previouswork ...... 4 Outline of present study ...... 5 CHAPTER 2 - ROCK TYPES AND STRATlGRAPHlC RELATIONSHIPS ..... 7 INTRODUCTlON ...... 8 THE KLUANE METAMORPHIC ASSEMBLAGE (KMA) ...... 8 Muscovite-chlontequarh schist (calcic schist) ...... 12 Biotitequartz schist (aluminous schist) ...... 21 Olivine serpentinite ...... 42 RUBY RANGE BATHOLITH ...... 49 POST-EOCENE IGNEOUS INTRUSIONS ...... 54 DEZADEASH FORMATION (Jb) ...... 56 GREENSCHIST (PMvs) ...... 59 CHAPTER 3 .STRUCTURAL STYLES OF THE KLUANE METAMORPHIC ASSEMBLAGE ...... 61 INTRODUCTION ...... 62 PRWIOUSWORK ...... 66 DUCTILE FABRICS OF THE KLUANE METAMORPHIC ASSEMBLAGE . 66 Planarfabncs ...... 66 Linearfabrics ...... 72 Shear-sense indicators ...... 74 Folds ...... 85 BRlTTLE STRUCTURES ...... 88 Faub ...... 88 Jointing ...... 93 STRUCTURALANALYSIS OF THE KMA ...... 94 Introduction ...... 94 Resuits and discussion ...... 94 REGIONAL CORREtATiON ...... 100 EVOLUTION MODEL OF THE KMA IN THE NORTHWESTERN COAST BELT ...... 103 4 ...... 103 O,, ...... 103 O,, ...... 103 O,, ...... 106

Dw e...... 107 O, ...... 108 CONCLUSIONS ...... 110 CHAPTER 4 - METAMORPHIC WOLUTION OF THE KLUANE METAMORPHIC ASSEMBLAGE ...... 112 INTRODUCTION ...... 113 PREVIOUS STUDIES ...... 114 METAMORPHIC MINERAL ZONES IN THE KMA ...... 115 Introduction ...... 115 Metamorphic character of the KMA along traverses in the Ruby Range121 GEOTHERMOBAROMETRY OF THE KMA ...... 132 Introduction ...... 132 Estimation of metamarphic pressures and temperatures using computer generated equilibria reactions ...... 134 Results and discussion ...... 135 Regional metarnorphic temperature and pressure variations ...... 145 P-T-t PATH VARIATIONS OF THE KMA ...... 148 METAMORPHIC EVOLUTION MODEL OF THE SOUTHWEST YUKON 151 CONCLUSIONS ...... 154 CWPTER 5 - GEOCHEMICAL AND NEODYMIUM ISOTOPE SIGNATURES OF METAMORPHIC AND SEDIMENTARY ROCKS IN THE SOUTHVVEST YUKON ...... 157 INTRODUCTION ...... 158 WOLE ROCK GEOCHEMISTRY ...... 160 Major elements ...... 160 Rare earth elernents ...... 164 Traœelements ...... '...... 168 NEODYMIUM ISOTOPES ...... 170 PROTOLITH PROVENANCE AND REGIONAL CORRELATiON ...... 177 Aishihik Metamorphic Suite ...... 177 OezadeashFormation ...... 181 Kluane metamorphic assemblage ...... 181 CONCLUSIONS ...... 183 CHAPTER 6 .TECTONIC MODEL OF THE KLUANE METAMORPHIC ASSEMBLAGE ...... 185 MODEL OF TECTONIC WOLUTION ...... 186 Late Jurassic (?) - early Late Cretaceous (-95 Ma) ...... 186 Late Cretaceous (-95-70 Ma) ...... 190 Latest Cretaceous (-72 Ma) - Early Eocene (57 Ma) ...... 193 EarlyEocene(57-55Ma) ...... 194 Eocene (5540 Ma) ...... 195 Oligocene-Holocene ...... 196 DISCUSSION ...... 196 Evaluation of evidence for dextral strike-slip along the Denali fault zone in thecenozoic ...... 196 The Denali fautt zone in the southern Yukon - a Late Cretaceous suture zone with rninor Eocene dextral strike-slip displacement ...... 198 CONCLUSIONS ...... 203 REFERENCES ...... 204 APPENDICES ...... 223 Appendix 1-1: NTS rnap index of study area ...... 224 Appendix 2-1: Thin sedion sample localities and observed mineral phases . 225 Appendix 2-2: Electron microprobe analyses of Crmuscovite ultramafic layen of theKMA ...... 231 Appendix 2-3:Ca-Fe-Mg-rich layers in the Kluane metamorphic assemblage 232 Appendix 2-4: Aga determinations of the Ruby Range Batholith ...... 233 Appendk 2-5: Age deteminations of mica schists of the KMA and phyllites of the DF ...... 234 Appendix 2-6: Locality map of age deteminations of the RRB. KMA and DF 235 Appendb 2-7: %r-=Ar geochronology of cafcic schist 94-3 ...... 236 Appendix 2-8: Muscovite and whole rock RbSr isochrons of cafcic schists of the Kluane metamorphic assemblage ...... 237 Appendix 2-9: Location and 6% SMOW values of olivine serpentinfies of the KMA ...... 238 Appendk 2-10: Concordia plots of granitic dykes intniding the KMA ...... 240 Appendix 2-1 1: Felsic and mafic dykes intrusive in the KMA ...... 241 Appendix 3-1 :Shear sense indicaton deducted frorn field observations. oriented samples and oriented thin sedions ...... 243 Appendix 3-2: Mesoscopic folds in the Kluane metarnorphic assemblage ... 245 Appendix 33: Application of SpheriStat (version 2.0) ...... 248 Appendix 34: Station localities and rneasured structural data ...... 250 Appendix 3-5: Rotation of Iineation of the southern limb of the Ruby Range anticline around anticline fold axis ...... 264 Appendix 3-6: Restoration of lineation and shear-sense direction to pre-F,. folding and northeastward tilting ...... 265 Appendix 3-7: Structural data of phyllites of the DF and greenschist PMvs between Telluride Creek and Kathleen River ...... 266

Appendix 4-1 O Electron microprobe conditions and mineral standards ..... 267 Appendix 4-2 .Mineral assemblages and anaiyzed minerals of geothermobarometry samples ...... 268 Appendix 4-3 .Electron microprobe analyses and calculated endmembers of gamets ...... 270

Appendix 44O Electmn microprobe analyses of biotite ...... 274

Appendix 4-5 O Electron microprobe analyses of muscovite ...... 276

Appendix 4-6 O Electron microprobe analyses of plagioclase ...... 277

Appendix 4-7 O Electron microprobe analyses of cordierite ...... 280 Appendix 4-8 .Electron microprobe analyses of spinel ...... 281

Appendk 4-9 O Application of the cornputer program T\NQ 2.02 ...... 282 Appendix 41O .Equilibria reacüons calculated by TWQ 2.02 ...... 285 Appendix 4-1 l .Compositional zoning profiles of gamets ...... 295 Appendix 5-1 .Descriptions and locations of samples analyzed for geochemistry and Nd. Sr. 40Ar-39Arisotopes ...... 299 Appendk 5-2 .Analytïcal procedures for geodremistry and Nd and Sr isotope studies ...... 300 Appendix 53- Neodymium shidies in the North Amencan Cordillera ...... 303 Appendk 54- Generalized terrane map of the northern Canadian Cordillera with location of published neodymium studies ...... 306 LIST Of TABLES

Table 3-1 : Deformation events in the KMA with associated fabrics and metamorphism ...... 104 Table 4-1 : Mineral parageneses and reactions for micaquark schist of the KMA with increasing metamorphic grade ...... 119 Table $1 : Major and trace element abundances of KMA. AMS and DF .... 161 Table 5-2: Element ratios of micaquartz schists of the KMA. AMS and Nisling assemblage. and slates of the DF ...... 163 Table 5-3: Sm and Nd concentration and isotopic data for metamorphic and sedirnentary rocks of the SW Yukon ...... 173 LIST OF FIGURES

Figure 1-1 :Generalized terrane map of the Canadian Cordillera ...... 3 Figure 2-1: General gdogical rnap of the southwestern Yukon east of the Denali fauk zone with accornpanying legend ...... 9 Figure 2-2: Location map of detailed maps and cross-secüons ...... 11 Figure 23: Outcrop photograph of muscovite-chlorite schist ...... 14 Figure 24: Photomicrograph of muscovite-chlorite schist ...... 14 Figure 2-5: Photograph and map of Ca-Fe-Mg-rich layers in the KMA ...... 17 Figure 2-6:Photograph of intrusive contact between the Ruby Range Batholith and the Kluane metamorphic assemblage ...... 20 Figure 2-7: Outcrop photograph of siIlimanit-rdieritebiotequartr schist . . 25 Figure 2-8: Photomictograph of sillimanite-cordierite-biotitequartz schist .... 25 Figure 2-9: Detailed map of southern Dezadeash Range and Coast Mountains eastofDezadeashLake ...... 27 Figure 2-10: Detailed geological map of the JaMs River area. west of Haines Junction ...... 31 Figure 2-1 1 : Photograph of cordierite-biotitequarh schist xenolith in granodiorite in western Dezadeash Range ...... 32 Figure 2-1 2: Photograph of granodiorite intrusion into sillimanite-cordierite- biotitequartz schist of the Kluane metamorphic assemblage ...... 35 Figure 2-1 3: Geology of the Nasina assemblage at north end of Talbot Am. KluaneLake ...... 37 Figure 2-14: Geological map of the Klukshu Lake .Tatshenshini River area . . 40 Figure 2-15: Geological map of centml Kluane Lake area with schematic geological and total magnetic field cross-section ...... 45 Figure 2-16: Photograph of Swanson Creek ultramafic lens ...... 46 Figure 2-1 7: Outcrop photograph of tonalitic gneiss north of Doghead Point ultramafic ...... 51 Figure 2-1 8: Outcrop photograph of late-synkinematk fine grained biotite granite dyke intruding the KMA at Canyon Bridge. Alaska Highway ...... 53 Figure 2-1 9: Photog rap h of feldspar porphyry dyke intruding muscovite-chlorite- quartz schist of the KJuane metarnorphic assemblage, ...... 55 Figure 2-20: Photomicrograph of Dezadeash Formation slate ...... 58 Figure 2-21: Photornicrograph of Dezadeash Formation phyllite ...... 58 Figure 3-1: Structural map of the KMA ...... 63 Figure 3-2: Structural geology map of the area east of Kluane Lake ...... 64 Figure 3-3: Schematic geological .....sections through the KMA ...... 65 Figure 3-4: Photomicrograph of plagioclase porphymblast in aluminous mica- quartz schist of the KMA ...... 69 Figure 3-5: Photomicrograph of plagioclase porphyroblast of the calcic schist of theKMA ...... 69 Figure 3-6: Photomicrograph of .synkinematic gamet of the KMA ...... 71 Figure 3-7: Photomicrograph of CIS fabrics in olivine serpentinite of the Doghead Pointubamafic ...... 71 Figure 3-8: Outcrop sketch of S.. cleavage ...... 73 Figure 3-9: Photomicrograph of &type plagioclase porphyroblast in the KMA . 75 Figure 3-10: Photomicrograph of &type plagioclase porphyroblast in the KMA 77 Figure 3-1 1: Photornicrograph of mylonite of the KMA with C'-shear band ... 77 Figure 3-12: Map with obsenred shear-sense in the KMA. acaimpanied by two stereonetplots ...... 81 Figure 3-13: Block mode1 interpretation of shear-sense in the KMA ...... 82 Figure 3.1 4: Photornicrograph of crd-btqtz schist with undefomied crosscutting quartz vein overgrown by cordierite and fibrolite ...... 84 Figure 3-1 5: Outaop photograph of open F,,-f old ...... 86 Figure 3-16: Map displaying major lineaments, dykes and fautts in the KMA . . 90 Figure 3-17: Photograph of NNE-trending fault south of Killermun Lake ..... 92 Figure 3-1 8: Stereographic presentaüon of total schistosity , mineral stretching lineation and mesoscopic fold axes of the KMA ...... 95 Figure 3-1 9: Stereographic presentation of schistosity, mineral stretching lineation and mesoscopic fold axes of the noWestern and southeastern structural domains of the KMA ...... 96 Figure 3-20: Stereographic presentation of total schistosity. mineral stretching lineation and mesoswpic fold axes of the northem and southem limb of the southeastem structural domain of the KMA ...... 97 Figure 3-21 :Generaaed structural map of the souaiwest Yukon wiai regional fold axes in the KMA. Nasina and Nisling assemblages and the DF ..... 101 Figure 3-22: Blocking temperature .geochronological age plot of the KMA . . 109 Figure 4-1 : Index mineral and mineral isograd map of the KMA ...... 116 Figure 4-2: Detailed index mineral and mineral isograd map of the KMA in the centralRubyRange ...... 117 Figure 4-3: Natural scale metamorphic cross-sections through the KMA in the centralRubyRange ...... 118 Figure 44: Petrogenetic grid applied to the KMA ...... 120 Figure 4-5: Photomicrograph of a biotitequartz schist of the KMA ...... 124 Figure 4-6:Photomicrographs that show the effect of the appearance of cordierite on the texture of the biotite schist ...... 126 Figure 4-7: Photomicrograph of gitcrd-sil-bt schist near contact with RRB . . 129 Figure 4-8: Photomicrograph of grt-crd-$il-bt schist near contact with RRB . . 129 Figure 4-9: Backscatter images of K-feldspar-bearing cd-bt schist ...... 130 Figure 4-10: P-Tdiagrams of probed micaquartz schist of the KMA ...... 137 Figure 4-1 1: Geological map with calculateci P-T of analyzed samples ..... 138 Figure 4-1 2: Photomicrographs of gamets in grt-st-bt schist and crd-bt schist 142 Figure 4-1 3: Compositional cross-sections of gamets in the staurolite zone and Viecordientezone ...... 143 Figure 4-14: Regional tilt of the KMA, RRB and AMS after Eoœne thermal metamorphism ...... 147 Figure 415: P-T-t paths of the Kluane metamorphic assemblage ...... 149 Figure 5-1: &O/Na, O versus SiOJAl,O,, XREE (ppm), LacN,Eu/Eu8 plots.165 Figure 5-2: REE diagrams of the KMA, AMS, DF and average values ...... 167 Figure 5-3: LamN-WSc, La&-Th/Sc . Th-U. Zr-Th . La-Th, Ti-LalSc diagrams ...... 169 Figure 54: Tectonic setting discrimination diagrams ...... 171 Figure 5-5: €.(O ).values of the KMA. AMS and DF shown on geologiwl map.174 Figure 58: e, evolution diagram for the KMA. AMS and OF ...... 175

~igure5-7: ew(O) O 147SdUNddiagram ...... 176 Figure 58: ew(0) versus Th/Sc. WScand LamNdiag rams ...... 178 Figure 5-9: Blodc diagram of published neodymium studies in northern Canadian Cordillera ...... 179 Figure 5-1 0: Possible tedonic setüngs for the protolith of the KMA ...... 183 Figure 61: Model of tedonic evolution of the KMA ...... 187 Figure 6-2: Model of tedonic evolution of the western North American continental margin in the Late Cretaceous-Early Tertiary ...... 202 Abbreviations used in text and appendices

Mineral phases: PY PYroPe rt rutile ab albite qtz quartz alm almandine ser sericit aln allanite srp serpentine alt undefined alteration si1 sillimanite amp amphibole SP" sphene an anorthite SPS spessartine and andalusite st sburolite ann annite tlc talc al' apaüte tur tourmaline aQtz alphaquartz Xe xenotime bQtz betaquartz zrn zircon bt biotite cal calcite Cam clinoamphibole Anm denotes mol.% of anorhite end ch1 chlorite member in plagioclase. chr chromite crd cordierite X, denotes mol% of end member CZO clinozoisite component. 'a' can be expressed as do1 dolomite component (Le. gn) or as element (Le. en enstatite Mg). eP epidote fac fenoactinolite Fe-crd Fe-co rdierite Tectonic nomenclature: fsp undifferentiated feldspar grp graphite AMS Aishihik Metamorphic Suite w= grossular CPC Coast Plutonic Complex grt gamet DF Dezadeash Formation hbl homblende DFZ Denali huit zone hc hercynite INS lnsubr Superterrane idd iddingsite KMA Kluane metamorphic il1 illite assemblage ilm ilmenite MGMB Maclaren Glacier Metamorphic jar jarosite Beit kfs K-feldspa r NA North America ky kyanite NS Nisling terrane mag magnetite RRB Ruby Range Batholith ms muscovite O opaque O l olivine ph1 phlogopite PI plagioclase PX pyroxene Chapter 1

Introduction Statement of problem

The Kluane metarnorphic assemblage (KMA) is a 160 km long. northwest-striking, belt of graphitic micaquartz schist with interiayered serpentinireci dunite bodies, located at the northwestem margin of the Coast Beit of the Canadian Cordillera, in the souaiwest Yukon (Figure 1-1). The Coast Belt, comprised of granitic and medium to high grade metamorphic rocks, is interpreted to be the resul of Cretaceous subduction andior accretion of two volcanic arcs, the lnsular Superterrane (INS) to the west and the Intermontane Superterrane to the east (Gabrielse et al., 1991). The mica- quartz schists of the KMA are unique within the Coast Belt, since they comprise the most extensive homogeneous metamorphic assemblage and the only medium to high grade metamorphic rocks not of continental affinity. The lithology of the KMA is distinct from any other known metamorphic assemblage in the Cordillera. The KMA is situated at a major boundary in the Canadian Cordillera. To the east, it is bounded by rocks of continental affinity, that comprise the Nisling terrane (Wîheeler et al., 1991), thought to be part of the Yukon-Tanana terrane (Mortensen, 1992). To the west, the Denali fault zone separates the KMA from the INS, comprised mainly of the Alexander and Wrangellia terranes, Paleozoic to Cenozoic volcanic arc and oceanic assemblages that were amalgamated in Late Jurassic and accreted to the North American margin by mid-Cretaceous (GabrÏelse & Yorath, 1Ml). The accretion of the INS resulted in mid- Cretaceous to eariy Tertiary granitic intrusions of the Coast Plutonic Complex (CPC) that underiie the bulk of the Coast Belt woodsworth et al., 1991). Metamorphic rocks occur akng the western margin and as roof pendants in the CPC and are assigned to the Nisling terrane (Wheeler et al., 1991) or the Yukon-Tanana terrane (Samson et al., 1991a; Brew & Ford, 1993). The nature and the tectonic setting of the protolith of the KMA were unclear. Despite its location at one of the major fault zones in the Cordillera and the important dues for Cordilleran tectonism that the KMA holds, no au

CRATON

CA: ra*rrirr KO:Kao(snay nim

Figui. 14 :Generelized terrane map of the Canadian Cordillera with outline of geomorphdogical beiîs and location of study area. Post-accretionary overhip assemblages and intrusions are shown on enlarged map. Modifed a* Wheeler d McFeely (1 991) and Whasler et al. (1 991). detailed structural study of the KMA existed prior to this study. The relationship between deformation and peak metarnorphism was uncertain. Displacement estimates on bounding faults were primarily based on reconnaissance data. No geochemical or isotope data for the KMA were available to test the various models proposed. In order to fiIl these gaps in knowledge. and to develop the first tectonic mode1 of the evolution of the KMA in the framework of the Canadian Cordillera, I undertook a detailed study of the KMA.

Previous work

The temi 'Kluane metamorphic assemblagen was introduced by Mezger (1995) to emphasize the contemporaneous evoluüon of micaquartz schisk and ultramafic rocks in one assemblage. Older ternis, the "Kluane Schist" of McConnell (1905). widely used by Muller (1967), Eisbacher (1W6), Nokleberg et al. (1985), Erdmer (1MO), Dodds (1Wl), and Dodds 8 Campbell (1W2), "Ruby Range metamorphic belt" (Forbes et al. 1974, Turner et al. 1974), "Homfelsed Schist" (Tempelman-Kluit, 1974) and 'Kluane assemblage" (Erdrner, 1991; Erdrner & Mortensen, 1993), only referred to the schistose units. To avoid confusion, the older teninology will only be used in subsequent discussions if a specific point has to be made. Prior ta this study, work consisted of 1:250,000 scale regional mapping, localized structural mapping and themometry studies. as well as detailed geochronology studies. Early workers in the Aishihik Lake (Cockfield, 1Wi), Dezadeash (Kindle, 1952) and Kluane Lake (Muller, 1953a, 1953b, 1958,1967) map areas included the metamorphic rocks that comprise the KMA in the Precarnbrian Yukon Group (Cairnes, 1914) or Yukon Complex (Muller, l967), which were interpreted as metamorphosed geosy nclinal sediments. Tempelrnan-Kluit (1974) and Erdmer (1990, 1991) rewgnized the homogeneity of the micaquarh: schist of the KMA and the orientation of its schistosity. which distinguish it ftom more heterogeneous metamorphic assemblages of the Nisling tenane to the north and east. A single period of deformation and metamorphism has been obsenred in the KMA, related to the intrusion of the Ruby Range Batholith during the Eocene, compared to multiple phases of deformation and metamorphism in the Nisling terrane assemblages (Farrar et al. 1988; Erdrner, 1991 ; Mortensen & Erdmer, 1992). Forbes et al. (1974). Turner et al. (1974) and Nokleberg et al. (1 985) correlated metamorphic rocks and plutonic rocks of the Ruby Range with the Susitna batholith and the Maclaren glacier metamorphic belt (MGMB) in the eastem Alaska Range. Based on this correlation. a post-Eocene dextral offset of 400 km along the Denali fault was proposed. Subsequent worken questioned the amount of displacement (Stout 8 Chase, 1980; Csejtey et al.. 1982). Eisbacher (1976) interpreted the micaquartz schist of the KMA as rnetamorphosed equivalent of Late Jurassic-Early Cretaceous flysch sedirnents of the Dezadeash Formation (DF), which marks the amalgamation of the lnsular Superterrane (Monger et al., 1982). The DF is separated by an alluvium covered valley ftom the KMA in the east This correlation was questioned by Erdmer (1990).

Outline of present study

Mapping on a 1:50,000 scale was done in the 1993,1994 and 1995 field seasons. Map locations are shown in Appendix 1-1. Rock samples and structural measurements were collecteci for petrographic, metamorp hic, structural, geochemical and isotopic studies. First order interpretation of the KMA is established by a detailed description of rock types of the KMA and their contact relationships, with discussion of possible protolith ongin and comparison with adjacent assemblages. A cnücal evaluation of previously sWed comeIations with the KMA (Forbes et al.. 1974; Eisbacher, 1976; Nokleberg et a1.,1985) points out existing inconsistencies. Consequently, there is no geological evidence to support the postulated 400 km post-Early Eoœne offset along the Denali fault The following chapter on the structural geology of the KMA documents that one major ductile deformation event. which pre-dates peak metamorphism. has anected the KMA. Shear-sense indicators obsenred in the KMA record predominantly sinistral shear, an important implication for Cordilieran transcuncnt tectonics as the adjacent Denali fault is considered to be a Cenozoic dextral strike-slip huit. Next, the metamorphic character of the KMA is outJineci by mineral isograd maps and a detailed petrographic section across strike. Evidenœ for thermal metamorphic overprinüng of regional metamorphoseci rocks of the KMA is presented. Metamorphic pressures and temperatures are established by gamet-biotite-plagioc1ase-muscovite and gamet-biotite-plag ioclasecordierite geothennobarometry. The metamorphic and structural results provide evidence that the KMA cannot be correlated with the DF or the MGMB. Whole rock geochemistry and neodymium isotope studies of the KMA, the DF and the Aishihik Metamorphic Suite (Nisling tenane) are presented in Chapter 5. REE plots, discrimination diagrams, isotopic signatures and depleted mantle model ages indicate diiVerent tectonic settings for the protoliths of the three assemblages. A tectonic model of the Kluane metamorphic assemblage is presented in Chapter 6. The resuits from the previous chapters are incorporated with existing data to fom a new model of tectonic evoluüon of the North American continental margin in the Late Mesozoic and the evolution of the northwestem Coast Belt from the Late Cretaceous to the present. Chapter 2

Rock types and stratigraphic relationships This study presents the first detailed description of the lithology of one of the major metamorphic assemblages of the northern Coast Belt of the western North Amencan Cordillera. The petmgraphy. occurrence, and contact relationships of rock types that comprise the KMA and adjacent sedimentary and igneous assemblages are discussed in this chapter. The oceanic character of the KMA distinguishes it from other metamorphic assemblages in the Coast Belt, which have more heterogeneous iithologies that indicate an origin in the proximity of an ancient continental margin. The difference between the KMA and the Maclaren Glacier Metamorphic Beit (MGMB) of the eastem Alaska Range is outiined and it is concluded that a 400 km post-Eariy Eocene omet along the Denali fault, as proposed by Forbes et al. (1974) and Nokleberg et al. (1985). cannot be detennined by correlating these two different metamorphic assemblages. The general geology of the southwest Yukon east of the Denali fault is shown on Figure 2-1. Figure 2-2 shows the location of detailed maps and cross-sections used in this and following chapters. Locations referred to in the text (Le. 94-81) and mineral assemblages of sampled rocks are listed in Appendix 2-1.

THE KLUANE METAMORPHIC ASSEMBLAGE (KMA)

The KMA underlies approximately 3000 km2of the southem flank of the Ruby Range and the northem Dezadeash Range in the southwest Yukon. To the northeast and east it is in contact with the Ruby Range Batholith (RRB). the northwestem part of the Coast Plutonic Complex (CPC; Brew & Ford. 1993). To the southwest, the alluvium covered Shakwak valley obscures the contact between the KMA and weakly defonned volcanogenic rocks of the Wrangellia terrane, shales and phyllites of the Jurassic-Cretaceous Dezadeash Formation Figure 2-1 : Generalized geological map of the southwestern Yukon east of the Denali fault zone with accompanying legend on next page. The Kluane meta- morphic assemblage (KM)is highlighted in grey. Geology outside of KMA is rnodified after Kindle (1952). Muller (1 967). Tempelman-Kluit (1974). Wheeler 8 McFeely (1991), Dodds 8 Campbell (1992) and Johnston & Erdrner (1995). Index map shows the approximate se#ing of the study area in the tectonic framework of the northem Canadian Cordillera. Geology of the southwest Yukon east of the Denali fault zone Legend to accompany Fium 2-1

1 METAMORPHlC ROCKS

porphyMc augib diorHe and quarttdkrite- b- to blad

Nisling Range alaskite bmwnNisling watheiing, assemblage gametiferous siIlimanita- -q.-%eqiipnnu(sr. trliad* -ktitequB&ww kucocmtic granite. kyaniiktits-quartzschist, ndnorgameb- brous amphibolii. ma-, cakailkata. crebce0us Kluane metamorphic assemblage

Early - Mid (?) Jurassic M-Y -ml spldots-bearing graphiüc mtmwbch~wrtzsais4 Long Lake Plutonic Suite with gmphk Pm- porphVroMas& pink to white, leuaxralk, Mo- minor leruc#l of Wght gresn. epïâote- homblende quarh manzonite to granite, a~ibai~~iGa-plagiodase-quartzsdiist Early Jurassic -and massive adindWr-mica fois. Iight gmn, divine serpeniinite, massive or Aishihi k Batholith foliaW lenses minaie micaquartz schii. wrsecrystalline, equigranular, homblerick diorite and monzodhm Figure 2-2: Location of detailed maps and cross-sections of Figure 3-3. (DF) and greenschist (PMvs) that fom the Kluane Ranges. The KMA consists of three rock types that have undergone the same tectonic and metamorphic history, fomning an assemblage distinct from adjacent rocks in the northem Cordillera. The two major units are an aluminous biotitequartz schist and a calcic muscov~~hlorite-quartzschist Olivine serpentinite bodies of various ske ocair along strike near the contact of the hnro schist units. The KMA indudes the Kluane assemblage of Erdmer (1991).

Muscovite-chloritequartz schist (calcic schist)

The muscovite-chlontequartz schist (mschlqtz schist) can be traœd for 70 km ffom the south end of Talbot Am, Kluane Lake, along the EsEstriking ridge systern of the central Ruby Range to the McKinley Creek valley northeast of Kloo Lake. where it tapers out (Figure 2-1). Southeast of Kluane Lake the ms-chlqtz schist foms the northem part of the Kluane Hills, a lower ridge system parallelling the Ruby Range south of Cultus Creek. The maximum northeast-southwest extension of the msthlqtz schist is 15 km. It also underlies 4-6 km2 of an isolated hl12 km northwest of Haines Junction, 15 km south of its major occurrence in the Ruby Range. The ms-chlqtz schist is equivalent to the 'Kluane Schist" of McConnell(1905) and unit 2 on the Kluane Lake map area (Muller, 1967). The schist is characterized by elongated plagioclase porphyroblasts of 0.3 to 1.0 cm length, giving the foliation plane a "knottÿ surface. The porphyroblasts appear dark grey and striped, due to minute parallel graphitic inclusions (Figures 2-3,24). Twinning is not commonly observed. Two different plagioclase compositions, albite (An,,) and oligoclase (An,,), are observed. However, no systematic plagioclase analysis with the electron microprobe was undertaken, so that exact compositional variation is not known. A well developed schistosity and mineral stretching lineation is defined by 0.2 to 1.O mm long chlorite and muscovite grains. Muscovite and chlorite constitute for 2030 vol.% and form layers of 0.25 to 0.5 mm thickness. Figure 23: Fresh rodc face of the muscovite-chlorite schist of the KMA. The greenish appearance is due to abundant chlorite. Quartz-n'ch bands appear white. Dark grey spots with a diameter of 5 mm are plagioclase porphyroblasts with parallel layers of fine graphite (see photomicrograph of Figure 24), that are relics of an earlier slaty cieavage. Orientation of schistosiîy (S) is indicated by black line. Located at the east shore of Kluane Lake, 7 km east of Destruction Bay (93-1 1). Scale is in œntimeter.

Figure 24: Photomicrograph of mylonitic calcic schist of the KMA (95-22). The elongated grey porphyrobbst in the œnter is a plagiodese with inclusions of graphite. The foliation, defined by the platy muscovite grains (yellow interference cokur), is deflected around the plagiodase. The asymmetry of the porphyroblast indiates non-coaxial progressive deformation and can be used to determine a sense of shear. The &type shape of the crystal suggests top to the left sense of shear. The same asymmetric fabric shape with a top to the left sense of shear is seen in Figure 2-3. Chlorite, not as abundant as muscovite, is characterized by its brown to deep blue interference colour. Note the interîayered bands of almost pure quartz (white to grey). Scale bar: 0.5 mm. XPL (Cmssed Polan'zed Light)

Graphiac inclusions in chlorite and muscovite are common. Quartz (30-50 vol.%) occurs in lenses and layers of 0.5 to 1.O mm thickness. It fons mal1 (50 to 100 pm) grains with stable grain boundaries and unifom extinction and larger grains (250 to 500 pm) characterized by subgrains and undulous exünction. Stubby, subhedral ta euhedral, 0.25 to 1.0 mm long grains of clinozoisite and minor epidote are common in the schist and can make up to 10 vol.% of the rock. Clinozoisite overgrowth of epidote can be observed. Graphite inclusions are also common. Brown pleochroic biotite foms 0.2 to 1.O mm long platy grains. Replacement of chlorite and larger biotite grains that grow at random angle to foliation indicate postdefomational growth. Biotite is absent along Kluane Lake shore, but gradually increases in abundance towards the northeastem contact with the aluminous schist. Small(250-500 pm), anhedral to subhedral gamets coexist with clinozoisite within one kilometer from the contact with the aluminous schist in the Ruby Range and the Kluane Hills (Figure 4-1). Gamets from one sample (93-64) have a spessartine-almandine composition (&=30, &Im=60,see Appendix 4-3). Tourmaline, foming up to 1 mm long distinct tabular crystals. apatite, sphene, zircon and opaque rninerals, mainiy ilmenite, are common accessory rninerals. Calcite is abundant in schists on Jacquot Island. A well developed mylonitic fabric with a monoclinic symmetry and mineral stretching lineation, indicating noncoaxial progressive deformation is charadefistic for the calcic schist (Figure 2-3). The sig nificance of the asymmetric fabric shapes as shear-sense indicators is discussed in Chapter 3. A fresh surface of the schist has a silver grey to bluish green grey appearance (Figure 2-3). Weathered rock faces appear darker. Discontinuous, boudinaged, grass green layers of coarse grained actinolite fels, Crnica-actinolite schist and greenish grey Cr-ms-abact-ep-chl schist are interfoliated with the ms-chlqtz schist (Figure 2-5). Adinolite can Figure 2-5: Lake shore exposure of rn-l schist with boudinaged thin layers of massive green adnoliteCrmica fels and greenish grey Cr-ms-ab-adep-chl schist (thick white amow in foreground). The foliation of the schist dips to the northeast. Crosscutüng quartz veins (thin white amnius) are boudinaged. Scale bar is 50 cm (foreground). The observed occumnces of the adinolite-beanng rocks and olivine serpentinite bodies in the KMA are shown on the simplifieci map. Light grey lines indicate possible along-sûike correlation of the actinolite- bearing rocks. The divine serpentinites are located close to the contact between the ms-chlqtt schist and the btqtz schist. The location of the Denali fauk is taken from Dodds 8 Campbell (1 992). form radiating needles of 0.5 to 5 cm length. The green mica is a low AI-, high Cr-, Fmuscovite (Appendix 2-2). Quartz, calcite and sphene are minor phases. The Crms-ab-act-ep-chl schist has a texture that resembles that of the ms4lqtzschist. The thickness of these layers. which generally e~end laterally only a few meters, is less than one meter. An exception is a fie meter thick layer mat be traced for over 150 m north of Culhis Creek (93-1 59). Three separate layen are inferreci frorn along-strike occurrences of actinolite-bearing rocks on the southem slope of the Ruby Range (Figure 2-5 and Appendix 2-3). K-Ar muscovite and whole rock and *ArW3'Ar muscovite ages detemined by Stevens et al. (1982), Famr et al. (1988), Mortensen 8 Erdmer (1992) and this study range Rom 42.5 to 54.7 Ma (Appendices 2-5, 2-6.2-7). Kdr biotite ages of the Ruby Range Batholiai (RRB) are similar (50-57 Ma, Appendix 24. Fanar et al.. 1988), suggesting that the oldest ages of the KMA refiect peak metamorphism related to the intrusion of the RRB (Mortensen 8 Erdmer. 1992). Results of microtectonic and metamorphic studies discussed in Chapters 3 and 4 show that peak metamorphism postdates deformation. Rb- Sr dating of muscovites from samples along Kluane Lake shore did not produce reliable data to allow age constraint on the pre-peak metamorphic fabric (Appendix 2-8). Depleted mantle model ages of 1.29 and 1.42 Ga are calculated from Nd-isotope analyses of Mo samples (93-1 56, 94-36, see Chapter 5). These ages do not represent a formation age, but a possible age of the protolith or an intemiediate age resulting from mixing of dinerent source rocks. The ms-chlqtz schist is structurally overlain and undedain by a btqtz schist. The contact with the btqtz schist is exposed south of Gladstone Creek and in the Kluane Hills. Muller (1967) described the contact between the two schist units as a southerly verging thnist fault. Erdmer (1991) concluded that it is not a bnttle feature and the foliation of both units has a similar northeast dip. The abundance of biotite gradually increases over a few hundred meters, while chlorite and muscovite abundanœ decrease. In contrast, the transition from calcic clinozoisitelepidote-bearing schist to aluminous gamet-, staurolite-, andalusite- andlor siIlimanite-bearing schist is sharp. Both changes occur in the same area within the KM.but have difFerent origins. The calcic-aluminous contact is a change in bulk rock wmposiaon. It could be a primary sedimentary contact or a faulted contact Later thermal overprinting fiom the RRB intrusion caused an increase in metamorphic grade, resulting in the transition from muscovitelchlorite to biotite schist (see Chapter 4). Whole rock geochemistry did not reveal major differenœs between both schist types (Table 5-1). However, only two samples from the msthlqtz schist unit were analyzed and do not contain any Ca-rich mineral phase (epidote). and may not be representative for that unit. This suggests that aluminous-richer layen are also present in the predominantly calcic sequence. The eastem margin of the calcic schist is presumed to be a fault covered by overburden in the lowland sumunding Kloo Lake. Evidence for the existence of the fault is given by structural discontinuities, change of plunge of mesoscopic fold axes and presenœ of southdipping schistosity east of the fault. The informal name Kloo Lake fault is proposed and used throughout this thesis. Two olivine serpentinite bodies are located at or close to the contact between the calcic and aluminous schist at Doghead Point on Kluane Lake and in the Ruby Range south of Gladstone Creek (Figure 2-5). The exposed contact is parallel to the foliation of the schist No alteration of the schist, which would indicate an intrusive contact, has been observed. It is more Iikely that this contact is fault bounded, also implying a faulted contact between the aluminous and the calcic schist, pre-dating thennal overprinting in the Eocene. At its eastem margin the ms-chlqtz schist is in contact with a granodiorite that intrudes the schist diapir-like (Figure 2-6). The intrusive contact is parallel to the foliation of the schist Sills parallel to the intrusive contact can be observed 30 m away from the contact This suggests a primary intrusive origin of the contact and not a fault. The plug is interpreted as part of the major intrusion of the RRB, exposed 10 km further north. Graphite, residual organic matter, and calcium-rich mineral phases Figure 26: Foliation parallel intrusion of the granodiorite of the Ruby Range Batholith into the biotitequartz schist of the KMA. Several paralkl sills of the granodiorite, ranging from 0.5 to 2 rn in thickness, can be observed up to 30 m away frorn the main intrusive body. No foliation or flow banding has been observed in the granodiorite. Killermun Lake is seen in the background. Field assistant standing on plateau in the upper right corner for sale (93-60). suggest that the protolith of the ms-chlqtz schist was a calcic shale, depleted in aluminum, interbedded with more aluminous layers (see Chapter 5). The absence of larger sedimentary clasts implies deposition in a quiet basin, distal to the source region. The adinolite-rich layers have a more mafic protolith. They resernble epidoteadnolite schist of Yardley et al. (1990). which are hterpreted as greenschist grade metamorphoseci volcanogenic sediment or lava flow. Crenulation folds defineâ by small adnoMe needles and presewed in albite porphyroblasts suggest a sedimentary origin, rather than lava fiows. The minor occurrence of these rnafic layers suggests restricted and minor source.

Biotitequartz schist (aluminous schist)

The rnost cornmon rock type of the KMA is a biotite-quarb: schist which underlies approximately 75% of the study area shown on Figure 2-1. It can be traced over 160 km from the mouth of Kluane River, at the northwestern end of Kluane Lake, to the southem and eastem part of the Dezadeash Range. The biotitequarb: schist is equivalent to the rock types described as unit A by Kindle (1952) on the northem Dezadeash map area, unit 1 south of the RRB on the Kluane Lake map area (Muller, 1967). and PPsqr in the southem part of the Aishihik Lake map area (Tempelman-Kluit, 1974). The btqtz schist contains graphitic plagioclase porphyroblasts similar to those of the ms-chlqtz schist Biotite is the dominant sheet silicate and defines the main foliation. Muscovite and chlorite occur only as accessory minerals or are absent Alteration of plagioclase and biotite to sericite, a fine grained muscovite, and chlorite, respectively, is cornmon. Plagioclase also is present in the matrix. Plagioclase composlion does not Vary within a sample or behnreen porphyroblast and matrix grains. Throughout the btqtz schist the composition ranges fmm An, (oligoclase) to An, (andesine), as detemined by electmn microprobe (Appendix 4-6). Whereas the cakic schist contains Ca-rich mineral phases (dinozoisite, epidote and calcite), wmmon minerals of the btqtz schist are Al-rich mineral phases: gamet, staurolite, andalusite, sillimanite, cordierite, K-feldspar and spinel. Therefore the btqtz schist is also referred to as aluminous schist. The Al-rich minerals occur in zones that parallel the contact with the RRB. Their fi& appearances towards this contact can be traced as mineral isograds and describe increasing metamorphic grades that define a contact metamorphic aureole around the batholith (Chapter 4. Figure 4-1). Gamets are commonly subhedral to anhedral, poikilitic, ranging from 0.25 to 10 mm in diameter. They are purple red cdoured Fe- and Mn-rich, almandine-spessarüne gamets (Appendix 4-3). Zoning of the grains can be detennined by electron microprobe and provides important information on the pressure-temperature path during gamet growth. Rare preserved spiral shaped graphitic inclusion traïls indicate synkinematic growth (Figure 3-6). Gamet rims are commonly altered to chlorite, sericite and biotite. Replacement of the gamet core by biotite can also be observed. Staurolite uccurs as subhedral, rarely euhedral. porphyroblasts (0.5-3 mm) with graphitic inclusion trails in a narrow zone throughout the Ruby Range and in the Western Dezadeash Range. Andalusite forms anhedral to subhedral, poikilitic, colourless crystals. lnciusions of quartz and bioüte are common. The grains have an average size of 0.5 to 3 mm. Andalusite appean synchronous wîth biotite at the muscovite- biotite boundary. Overgrowth of staurolite indicates that andalusite is formed by the breakdown of staurolite (Figure 4-5). SiIlimanite occurs as fine needles of fibrolite with lengths of less than 200 pm and widths of a few tens of Pm. Fibrolite commonly nucleates in biotite and grows parallel to the cleavage of the bioüte crystal (epitaxial growth, Figure 44,as well as in plagioclase, quartz and cordierite. In rocks with abundant sillhanite, the fibrolite needles radiate away from the margin of biotite grains into the felsic layers. Coarse sillimanite was observed only at two locations, close ta the contact with the RRB (94-147c, 94174). In the eastem Ruby Range and the eastem and southem Dezadeash Range Fe-rich cordierite (Appendbc 4-7) forms porphyroblasts up to 3 mm in diameter (Figures 2-7.2-8.2-9). Inclusions of small cubes or woms of deep green coloured hercynite, a Fe-Alspinel (Appendix 44)and fibrolite needles are common. Hercynite is found in samples in close proximity (generally less than 1 km) to the intrus* contact with the RRB. K-feldspar has been identifid by electron microprobe as discrete grains in the order of 100 pm in certain cordierite-bearing samples (Figure 4-9). The paragenesis with airdierite and texhiral evidence that potassium-feldspar grows on the expense of biotÏte suggest a metamorphic origin. Estimation of modal abundanœ of K-feldspar is difficult, since it lacks twinning, and cannot be distinguished by optical petrology from the more abundant, but also commonly unhnn'nned, plagioclase. Due to abundant biotite the aluminous schist is darker than the ms-chl- qtz schist, and has a purplish grey to dark brown coloured rock face, depending on the state of weathering. Large plagioclase porphyroblasts give the foliation plane a "knotty" appearance. A well developed schistosity with a monoclinic symmetry and mineral stretching lineation, similar to the fabric of the calcic schist, is characteristic of aluminous schist in the western Ruby Range and Dezadeash Range. In the eastem Ruby Range and eastem Dezadeash Range, the schist is coarser, less well foliated and mineral lineations are absent. Quartz layers are cornpriseci of large single crystals instead of a multitude of smaller grains or subgrains. Biotite crystals are up to one millimeter in size and overgrow the foliation plane (Figure 2-8). The coarsening is related ta thermal recrystallization of qua-, plagioclase and biotite and new growth of cordierite near the contact with the RRB. A ligM bluish grey coloured orthoamp hibole-biotite-plagioclasequark schist occurs in the eastem Dezadeash Range. The oraioamphibole is Fe- and Mg-rich, a gedrite or anthophyllite, and forms poikilitic, anhedral grains, ranging in size hm0.25 to 0.75 mm. Although cordierite is abundant in the adjacent schist, it is absent in the orthoamphibole-bearing schist. The different mineral Figure 2-7: SiIlimanite-coidierite-biotite-qua* schist of the KMA in the eastern Dezadeash Range (94-275). Note the contrast in appearanœ to the muscovite- chlorite schist along Kluane Lake in Figure 2-3.The rock appean coarser. Compositional banding is more pronounced than in the schist of Figure 2-3. No asymmetry can be obsenred in the fabric. How8ver. geochemical and isotope studies ffom samples close to both localities (94-36 and 94-272) show that the rocks have had a similar protolith (Chapter 5), and the difkrent appearanœ is due to an increase in metamorphic grade cornpared to the rock in Figure 2-3.

Figure 24: Photomicrograph of a sillimanitecdrdkrite-biotite-~uartrschist 2.5 km east of the location of Figure 2-7 (90-33).The rock appears gneissic, almost granoblastic in thin sedion. Note the contrast to the well foliated ms-ch1 schist in Figure 24. Scale is the same in boai photographs. Scale bar= 0.5 mm. XPL

Figure 2-9: Detailed gedogical map of the southem Dezadeash Range and the Coast Mountains east of Dezadeash Lake. The area near Undie Creek was mapped by Erdmer (1990) and the metamorphic rocks assignecl to the Nisling assemblage. The gedogy a the 1798 m peak and norai of Undie Creek is adapted after Kindle (1952). Assumed contacts are shmas dashed lines. See Figure 2-2 for location. assemblage is also reflected in its geochemistry and neodymium isotope composition, indicating an andesitic composition and juveniie isotopic signature, cornpared to the pelitic btqtz schist with its more evolved signature (Chapter 5). The orthoamphibole-bearing schist has a texture similar to the a cordierite-bearing bt-qtz schist, and cannot be distinguished Rom the btqtz schist in hand sampies. The contact relationship with the cordierite-bearing schist and the exact edent of the orthoamphibole-bearnig schist are not known. It was observed at only one location in the eastern Dezadeash Range (94-297/1). Samples from locations 1-2 km away are cordierite-bearing btqtz schist. The orthoamphibole schist appears to be a local occurrence and is not shown as a separate unit on the map of Figure 2-1. The similarity of the texture with the cordiente schist and the lack of evidence for hydrothennal alteration (enrichment or depletion of mobile elements Sr, Ba, etc., see Table 5-1) suggest that the protolith of the orthoamphibole schist was a metamorphosed first cycle sedimentary rock derived from an andesitic source, rather than a rnetamorphosed and altered andesitic flow. Quartz bands, from a few centimeters to half a meter thick, crosscut the ms-ch1 schist along the eastem Kluane Lake shore. Deformed and boudinaged quartz layers may be transposed original quartz-rich sedimentary layers or late synkinematic veins relateâ to the early magmatic phase of the RRB (Figure 2- 5). Undeformed NNE-striking veins resemble tension gashes (93-9). compatible with NNE-SSW compression in the Early Tertiary (Engebretson et al., 1995; see Chapter 3). Undeformed quartz veins crosscut by granitic dykes at the northeastem margin of the KMA, east of Aishihik River indicate pre-RRB origin of the veins (S. Johnston, pers. comm., 1994). The contact of the aluminous with the calcic schist is described above and interpreted as a pre-peak metamorphic faulted contact between rock types of different sedimentary protoliths. The nature of the contact between the btqtz schist and the two olivine serpentinite bodies is the same as described for the calcic schist above. The btqtz schist overiies the olivine serpentinite south of Gladstone Creek, while it partially underlies the body at Doghead Point (Figure 2-1 5). Two smaller olivine serpentinites are interlayered with the btqtz schist. Their conta- are not exposed. Exposed contads of the btqtr schist with the main body of the RRB are parallel to the foliation of the schist. In the Ruby Range, the foliation of the schist dips north to northeast undermath the granodiorite intrusion. Similar dip of the schist undemeath the intrusion is observed in the western Dezadeash Range, while the RRB dips northward undemeath the btqtz schist in the eastem Dezadeash Range. A weak gneissic foliation can be observed in the granodiorite up to a hundred meters away from the contact (93-32). At diapirs and plugs of the RRB within the KMA, foliation parallel and crosscuttïng contacts are cornmon (Figure 2-6). Deflection of the foliation of the schist can occur near the contact (Figure 2-1 0). Xenoliths of the schist found the granodiorite in the southem Dezadeash Range confimi the intrusive nature of the contact (Figure 2-1 1). The age of the protolith of the btqtz schist is not known. No detrital zircon ages are recorded. Depleted mantle model ages calculated from neodymium isotope composition range from 1.22 to 1.45 Ga for the btqtr schist, similar to the ages for the ms-chlqtz schist (1-29 and 1.42 Ga). The similarities of the model ages and Ndisotope composition for both schist types suggest that their protoliths, although one more calcic and the other more aluminous, are of the same age. The orthoamphibole-bearing btqtz schist has a younger model age of 720 Ma, which may represent the actual age of its protolith, as it may not have been derived ftom sedimentary mixing as the other btqtz schist and ms-chlqtz schist samples. This is discussed fùrther in detail in Chapter 5. K-Ar biotite ages determined for the btqtt schist range from 45.4 to 61.7 Ma (Appendices 205.28;Stevens et al., 1982; Farrar et al., 1988; Mortensen 8 Erdmer, 1992). U-Pb monazite and xenotime ages of schist samples near the contact with the RRB yielded ages 2 to 5 Ma older than K-Ar biotite dates. suggesting rapid cooling of 40-165' ClMa of these rocks (Erdmer 8 Mortensen, Figure 2-10: Detailed geological map of the JaMs River ama, west of Haines Junction. Note the isolated plug of diorite north of Gamet Creek. The location of two samples anaiyzed for geothennobammetry (Chapter 4) is also shown. The geological contacts at Mt. ûecoeli are adapted from Dodds & Campbell (1992). Geology west of Kloo Lake is adapted from Muller (1 967).

Figure 2-11: LigM grey granodiorite of the Ruby Range Batholiai intruding dark cordierite-biotitequarh schist of the KMA. Note xenolith band of the schist next to the sale bar (8 cm).Southwestern slope of Dezadeash Range (9538). 1993). Mortensen & Erdmer (1992) interpret monazite and xenotime as metamorphic in origin and their U-Pb ages date peak metamorphkm of the KMA. Younger ages in the southwestern part are explained by slower cooling and/or slower rates of uplift. A K-Ar biotite age of 140 Ma as reported by Lowdon (1960) is regardeci as unreliable due to low K content (Erdmer & Mortensen, 1903). The btqtz schist of the KMA is derived from a homogeneow package of pelitic sediments. Abundant graphite preserved as thin layers in plagioclase porphyro blasts is residual org anic matter. Almandine-spessartine gamet, staurolite, sillimanitelandalusite and cordierite are typical minerals found in medium grade metamorphosed aluminous pelitic sediments. Trace elernent and neodymium isotope signatures of the btqtz schist indicate homogeneous mixing of sediments derived predominantly from a volcanic arc source with minor detrital input from ancient continental crust (see Chapter 5). Minor occurrences of orthoamphibole-bearing schists within the aluminous schist are interpreted as metamorphosed sediments directly derived frorn an andesitic source, without mixing wiüi continentderived matenal. The similarity of the appearanœ and major mineral assemblage of the calcic and alurninous rnica- quartz schist, implies similar depositional environment, with slightly different geochernical bulk composition of the source material. The KMA has been interpreted as the metamorphosed equivalent of the Dezadeash Formation (Eisbacher, 1976). Trace element and neodymium isotope data, discussed in Chapter 5, show that the DF has more juvenile signatures than the KMA, suggesting a volcanogenic source without mixing with continentderived material. Erdmer (1 991) proposed a faulted contact between bt-qtz schist of the KMA to the west and biotite schists of the Aishihik assemblage (equivalent to Nisling assemblage of Erdmer (1990)) to the east, east of Van Bibber Creek in the eastem Dezadeash Range. Aishihik assemblage rocks, describeci east of Dezadeash Lake and around Kusawa Lake, are more heterogeneous than the KMA and contain biotite schist, granitic gneiss, biotite granod iorite gneiss, amphibolite and minor quarbite, marble and calc-silicate (Erdmer, 1990, 1989). In light of recent field studies and detailed thin section analyses the existence of a contact between the KMA and the Aishihik assemblage in the Dezadeash Range cannot be supported: (1) The mineral assemblage of the KMA in the eastemmost Dezadeash Range is similar to cordierite-bearing KMA schists in the eastem Ruby Range, with the exception of orhoamphibole-bearing schist describd above. The rocks are brownish grey weatheflng aiarse grained sillimanite- cordierite-biotite schist, resembling cordierite-bioüte schist found in roof pendants in the southem Dezadeash Range (Figures 2-7,2-8). (2) Coanening of the schist towarâs the east is attributed to static recrystallization in proximity of the contact with the RRB and obscures foliation (see C hapter 4). (3) Quartzite, marble and calc-silicate described by Erdmer (1991), as typical of the east, were not found at this location. (4) A srnall(1 km2) strongly foliated granodiorite plug, not reported by Erdmer (1991), is found close to the proposed contact. Xenoliths of the crd- sil-bt schist are found at the margin of the intrusion. The intrusive contacts are sharp and no migmatization of the schist is obsewed. (Figure 2-1 2). (5) Mole rock geochernistry and neodymium studies do not indicate major lithological changes within the eastem Dezadeash Range (Chapter 5).

The micaquartz schists of the KMA are distinct from all other metamorphic assemblages norai and southeast of the RRB, and roof pendants within the RRB north of Kluane Lake. These assemblages are. from northwest to southeast, the White River Assemblage, Nasina Assemblage, Aishihik Metamorphic Suite (AMS), and the Nisling assemblage (Figure 2-1). These assemblages contain a variety of rock types, including micaquartz schist, micaceous quartzite, quartzite, calc-silicate, marble, amphibolite (Muller. 1967; Erdmer, 1990; Wheeler & McFeely, 1991; Johnston & Timmeman, 1993a). The AMS also includes metabasite and meta-igneous rocks and is correlated in Figure 2-1 2: Intrusive contact between siIlimanite-cordietite-biotitequa- schist of the KMA and medium grained bluish grey granodiorite in the eastem Dezadeash Range (94-276). The contact is generally sharp. The igneous intrusion occurred along existing foliation plane or along fractures. The host schist is not migmatized. Reacüon rîms in the host rock are not observed. The fold in the left hand corner apparently pre-dates the intrusion. Arrow points at flow banding, dark mafic layers and leucacratic bands in the granodiorite. part with the Nisling and the Nasina assemblages (Johnston & Timmeman, 1993a). Muller (1967) included the Nasina Assemblage, exposed north of the RRB, in the same une 1 with the btqtr schist of the KMA. lntercalated layen of micaquartz schist, micaceous quartziie. marble and calc-silicates were observed during mapping for this study, establishing the lithologic differences between the Nasina Assemblage and the KMA (Figure 2-13). The Nasina and Nisling assemblages and the AMS are interpreted as Late Proterozoic to Paleozoic continental margin and off-shelf sediments, associated with the pericratonic Nisling terrane (Erdmer, 1990; Wheeler 8 McFeely, 1991 ; Johnston & Timmerrnan. 1993a). Geochemical and neodymium isotope studies of micaquartz schists ftom the AMS confirm their mature provenance (Chapter 5). The White River Assemblage is associated with Paleozoic-Mesozoic oceanic assemblages meeler & McFeely. 1991 ). Metamorphic rocks exposed along the western part of the Coast Mountains, south of Dezadeash Lake and in northem British Columbia, are mapped as 'unl 1" by Kindle (1952) on the Dezadeash map area and "Msmn on the fatshenshini map area (Dodds & Campbell. 1992). These rnetarnorphic rocks are assigned to the "Kluane Schisr by Eisbacher (1976) and Dodds 8 Campbell (1 992). However, they differ in petrology from the btqtz schist of the KMA. Metamorphic rocks south and southeast of Dezadeash Lake are generally graphite-free gametiferous biotite quartzites. Feldspar occurs only as a minor phase. Kyanite-staurolite-gamet assemblages in biotite schists southeast of Dezadeash Lake indicate that these rocks experienced high P/high T conditions unlike the KMA (Chapter 4). 50 meter thick marble bands, interlayered with a biotiie schist, are observed south of Klukshu Lake (Figure 2- 14). Quartzite and marble are characteristic for the Nisling assemblage, but are absent in the KMA. Whole rock major element geochemistry of a gametiferous biotite quarbite east of Dezadeash Lake (94-358) also suggests a continental provenance for these rnetamorphic rocks (Chapter 5). The rnetamorphic assemblages south of Dezadeash Lake are part of the Nisling assemblage of Erdmer (1990) and not correlative with the KMA as Eisbacher (1976) proposed. 61'37' Cambrian Devonian Nasina assemblage aluvium - covered micaqwitL schist with miceamus qua* intapd-tife- with~wüirtgmaficdyke Eocene mi~œtmsau- ws

Figure 2-13: Geology of the Nasina Assemblage at the north end of Talbot Am. Kluane Lake. Location of biotite-gamet themometry sample is shown. See discussion in Chapter 4. Geology partly modified after Muller (1967). A ky-st-grt-bt schist structurally overiies phyllLs of the Dezadeash Formation east of Kiukshu Lake (Figure 2-14). Mineral stretching lineation and shear-sense indicators in the underlying DF phyllite imply a westward thrusting of the high grade assemblage over the DF (Figure 2-21). Detailed mapping and petrographic analyses show that a contad between the DF and the KMA, as inferred by Eisbacher (1976) does not exist south of Dezadeash Lake and his hypothesis that the KMA is metamorphosed DF, based on the lower metamorphic grade of the KMA in the south, cannot be supported by field evidence and geochemical and isotopic data (Chapter 5).

The KMA has been wrrelated with the Maclaren Glacier metamorphic belt (MGMB) in the eastem Alaska Range by Forbes et al. (1974), Turner et al. (1974) and Nokleberg et al. (1985). This correlation irnplies a dextral offset along the Denali fault of about 400 km. Cornparison between the KMA and the Maclaren Glacier metamorphic belt shows that rock types, and structural and metamorphic history of both assemblages are different and do not support a correlation: 1) The MGMB, which comprises three mappable belts of argillite and metagraywacke, phyllite, schist and amphibolite, is more heterogeneous than the KMA. 2) The East Susitna batholith, which is interpreted as the equivalent of the RRB by Nokleberg et al. (1985), north of the MGMB, has a pervasive schistosity of Eocene age. The RRB is undefomed, with the exception of an early stage sheared diorite near Doghead Point, and has developed flow banding near some contacts with the KMA. 3) The Meteor Peak fault, a faulted intrusive contact, between the East Suslna batholith and the MGMB, is truncated by the Denali fault to the east. No evidence of major faulang along the contact between the KMA and the RRB is obsenred in the Ruby Range. 4) Structural and metamorphic analyses of the KMA discussed in Chapten 3 and 4 show that deformation predates peak metamorphism, contrary to Figure 2-14: Geological map of the Klukshu Lake - Tatshenshini River area in the southem Yukon. The contact of the Coast Plutonic Complex (CPC) wïth the Dezadeash Formation west of the Haines Road, south of Klukshu Lake has been reported by Lowey (pers. comm., 1995). Location of the Shorty Creek pluton is from Dodds & Campbell (1902). K-Ar and Rb-Sr ages of the CPC are from Farrar et al. (1988) and LeCouteur & Ternpelman-KluR (1 Qï6), respectively. The K-Ar (whole rock) ages of the OF are from Lowey (pers. comm.. 1995). Location of Figure 2-21 is also shown.

Nokleberg et al.'s (1985) observations in the MGMB. 5) Deformation and metamorphism of the schists of the MGMB is related to synkinematic tonalite intrusions along localizeâ shear zones (Valdez Creek shear zone) of Late Cretaceous (68-74 Ma) age (Davidson, 1989; Davidson et al., 1992). No equivalent tonaiïïe bodies were observed within the KMA.

These points strongly suggest that the KMA in the southwest Yukon and the MGMB in south-central Alaska cannot be correlateci, removing a major evidence for 400 km dextral displacement along the Denali fautt during post- Eocene the, as proposed by Nokleberg et al. (1985). Alaiough major dextral offset along the Denali fault cannot be disproved, the lack of strong geological evidence requires reevaluation of the role of strike-slip along the Denali fault (see Chapter 6).

Metamorphic assemblages in southeast Alaska, located on the western margin of the Coast Belt and as roof pendants within the CPC are labelled "m - undivided metamorphic rocksn, just as the KMA,by Wheeler et al. (1991). Studies by Brew 8 Ford (1 984). Berg et al. (1W8), Brew 8 Gtybeck (1984). Himmelberg et al. (1984) and Brew et al. (1985) show that these assemblages are more hetemgeneous than the KMA. consisting of interlayered biotite schists, biotite gneiss, amphibolite, quarbite, calc-silicate and marble. Fossils found in lower grade carbonates southeast of Skagway were identiied as middle to upper Triassic in age (Brew et ai., 1985). Thick homogeneous mica- quartz schist assemblages and olivine serpentinites that characterize the KMA have not been observed. Brew et al. (1 991) included these metamorphic rocks in the 'Yukon prong" terrane, the equivalent of the Nisling terrane, to indicate that they are denved from ancestral North American margin. Neodymium isotope studies by Samson et al. (1991a) near Tracy Amsupport the idea of rocks derived from ancient crust on the western flank of the Coast Belt. Erdmer & Mortensen (1993) correlate the KMA btqtz schist with "distinctive graphitic phyllites, chloriteepidote-plag ioclase schist and phyllite" on Admiral Island, part of the Admiral Island metamorphic belt of Brew et al. (1992). The original mapping report by Loney (1964) list chlorite-epidote-caicite phyllite or schist with interbedded marble lenses and larger beds. phyllitic slate and greenschist as part of the Gambier Bay Formation. Graphiüc phyllite as mentioned by Brew et al. (1992) is not listed. A correlation of the KMA with the Gambier Bay Formation, basecl solely on lithology, is not strong, and should be regarded with caution. The micaquartz schists of the KMA are unique within the Coast Belt of the Canadian Cordillera. The KMA is the most extensive homogeneous metamorphic assemblage and the only medium to high grade assemblage allochthonous to a continental margin. It is distinguished by its lithology and isotopic signature from any other studied metamorphic assemblage in the Cordillera.

Olivine serpentinite

Four ultramafic bodies are observeci interiayered with the mica schists of the KMA. They occur for 60 km along strike in the Ruby Range from Doghead Point, northeast of Buiwash Landing, ta north of Kloo Lake. They Vary in size from a width of few tens of meten (Erdmer, 1990) to 15 km and a structural thickness of more than 1 km (Figure 2-5). The two larger bodies in the west forrn distinct positive magnetic anomalies on the aeromagnetic map (GSC, 1969). Muller (1967) and Erdmer (1990) recognized ultramafic bodies in the micaquartz schist, but did not map them as separate units. The ultramafics are serpentinized dunites consisting of varying amounts of Mg-rich olivine (Fo=90, determined by electron microprobe, 10-80 vol.%). serpentine (15-60 vol.%), talc (O40 vol.%), and iddingsite, magnetiie, chromite and pentIendt.de (5-10 vol.%), as well as traces of calcite. Olivine is preserved in rounded pods up to 1 cm long, with mesh-like inclusions of chromite overgrown by chromium-magnetite (Figure 3-7). Abundant serpentinite gives the rock a light greenish appearance and a soapy touch results from abundant talc. A well developed foliation defined by aligned serpentine grains characterizes the larger olivine serpentinite at Doghead Point. The foliation dips steeply to the north, parallel to the orientation of the underiying micaquartz schist. CIS fab tics that indicate progressive non-coaxial deformation and can be used as shear sense indicators are cornmon (Figure 3-7). Talc crystals are randomly oriented and postdate deformation. 0.5 m thick layers of boudinaged and aitered gabbronorite, parallelling the foliation of the serpentinite, were obsewed at one location (94-20). Orthopyroxene in the gabbronorite is partly replaœd by clinoamphibole. The foliated serpentinite at Doghead Point has an estimated structural thickness exceeding 1000 m and can be traced over 15 km along east-west strike (Figure 2-1 5). Steeper dipping foliation at its northem margin and the lack of a distinct magnetic low to the north of the ultramafic. suggest that the ultramafic body has a wedgdike shape not extending much into depth beyond its surface exposure to the north. The three srnaller olivine serpentinite lenses in the Ruby Range are not foliated. Talc is an abundant phase in the serpentinite at the margin of the body. The serpentinite at Swanson Creek appears as a 150-200 m thick and 1 km wide lens (Figure 2-16), which can be recognized as a positive magnetic anomaly (GSC, 1969). The other occurrences are much smaller, since they do not form noticeable anomalies on the aeromagnetic maps which are compiled from 750 m spaced flights. As described in the previous section, the olivine serpenthites are interfoliated within the micaquartz schists of the KMA. with the contact being parallel to the fabric of the schist. The similar orientation of the micaquartz schist and the serpentinite at Doghead Point suggests an emplaœment of the ultramafic prior to deformation. At the northem margin of the Doghead Point body, the ultramafic is in contact with gneissic quark diorite and tonalite associated with the RRB (Figure 2-15). The ultramafic is less serpentinized and olivine crystals appear fresh, implying new growth of olivine as a result of Figure 2-15: Detailed geological map with magnetic and geological cross- section of central Kluane Lake area. Cross-section AA-AA' shows the geology and total magnetic field of the Doghead Point olivine serpentine. Foliation of the schist and the serpentinite is indicated by the sketched lines. The wedge- shaped body of the ultramafic is inferred from the magnetic anomaly. See text for discussion.

Figure 816: Vew of the Swanson Creek divine serpentinite lens in the Ruby Range Rom a neaiby ridge. The ulbamafic (light grey) is situated at aie contact between the calcic schist of the KMA to the south and the aluminous schist to the north. The contact between serpentinite and schist is foliation parallel, as seen by the parallelism with the thin lines that trace the schistosity of the schist. The scale bar rebrs to the ridge wit h the ulbamafic. See map of Figure 2-5 for location. contact metarnorphism. The rock still has a foliation, but appears more massive in general. This supports a proposed postdefomiationalemplacement of the RRB. The ages of the olivine serpenthites are not known. The similar attitude of foliation in the micaquark schist and the Doghead Point ufframafic and new growth of olivine at the contact with the RRB suggest that the ultramafic and the schist were juxtaposeci prior to defornation that preceded the Early-Eocene intrusion of the RRB. Oxygen isotope studies of-theolivine serpentinite show that ol'O-values from the core zone of the two larger uhmafic bodies at Doghead Point and Swanson Creek range between 6.1-6.7%. similar to values ftom ophiolitic serpentinites (Appendix 2-9; Hoffhan et ai., 1986; Muehlenbachs, 1986). The pristine values indicate a small waterfrock ratio during serpentinization, but not necessarily an ophiolitic origin (K. Muehlenbachs, pers. comm., 1996). Oxygen isotope data obtained from the smaller serpentinite bodies have elevated 6180-valuesof +l1%0,indicating interaction with metamorphic fluids, that generally have a 8'0-range from +13 to +20%0. (Muehlenbachs, 1986). The juxtaposition of ultrarnafics and the sedimentary protolith of the KMA can be accomplished by intrusion of the ultramafic into the sedirnent ("Alaskan-type")r by interleaving of disnipted lower portions of oceanic crust ("Alpine-typen) Faylor, 1967; Patton et al., 1994). "Alaskan-typenultramafics are mncentn'cally zoned with a dunite core and pyroxenite shells. They are generally intnided into gabbros and interpreted as the result of magma fradionation (Taylor, 1967; Hirnmelberg et al., 1985; Patton et al., 1994). Zoned ultramafic bodies occur along a 560 km narrow belt southwest of the Coast Plutonic Complex (Patton et al., 1994). and are observed as Early Cretaceous intrusions into the DF (Pyroxenite Creek Ultramafic Complex; Sturrock et al., 1980). Similady, an unnamed massive serpentinized pyroxenite at the western slope of the Dezadeash Range, 10 km east of Haines Junction (95-13). may also be interpreted as an uAlaskan-typen ultramafic. In the central and eastem Alaska Range, fault-bounded nanow sliven of serpentinite, serpentinired dunite and peridotite are located north and south and parallel to the Denali fault zone (DFZ) (Patton et al., 1994). Some of those ultramafics are associateâ with flysch deposits and mica schists. Age canstraints for the uitramafics are vague and range from middle Paleozoic to Triassic (Patton et al., 1994). They are interpteted as "Alpine-type" ultramafics, remnants of an ocean basin, possibly the basement of Wrangellia, that collapsed during subsequent accretion (Nokleberg et al., 1985, Patton et al., 1994). Complete ophiolite sequences are only observed in the Chulitna terrane of the eastem Alaska Range, south of the DFZ, where a complete Upper Devonian ophiolite is disnipted by northdipping th~stfaults and serpentinite lenses occur as thin (4 km thick, 20-25 km wide) slivers (Jones et al., 1980), and on Admiral Island in southeastem Alaska (8erg 8 Jones, 1974). For most ultramafics in the Coast Belt or the Alaska Range, however, a distinctive origin cannot be determined (Patton et al., 1994). A number of small ultramafic bodies, ranging from tens of meters to eight kilometers in length, with a compositional variety of dunite, pyroxenite, pendotite, serpentinite and harzburgite, are reported within the CPC. These ultramafics are strongly foliated and situated in gneiss roof pendants of the CPC, predating its Late Cretaceous-Eocene intrusion. Grybeck et al. (1977) and Brew 8 Grybeck (1984) correlate them with the other uAlaskan-type"ultramafic intrusions in southeastern Alaska. Althwgh the serpentinized dunites of the KMA are not part of a complete ophiolitjc sequence, a tectonic "Alpine-typenemplacement of the ultramafic bodies into the micaquartz schist is supported by: 1) foliation parallel contact between schist and uhmafic; 2) lack of evidence of thermal overprinting of the schist at the contact; 3) location of the ultramafics along strike at or close to the boundary between the aluminous and the calcic schist; 4) homogeneous composition of the serpentinized dunites, indicating that they are deriveci Rom a similar magma and may be disrupted parts of one large body; 5) no zoning obsenred within the uitramafic bodies; 6) no intmsive relation with gabbros. 7) the gneissic quartz diorite and tonalite in contact with the Doghead point ultramafic are interpreted as an earlier more mafic phase of the RRB. instead of being genetically related to the ultramafics (see next section).

The tectonic setting and composition of the KMA ultramafics are very similar to that of the nAlpine-typenultramafics in the central and eastem Alaska Range. If their interpretation as remnants of oceanic cnist is correct, then the distribution of elongated fault-bounded ultramafic bodies near the DFZ strongl y suggests that it marks a major suture zone, characterized by the collapse of an oceanic basin, ranging from the Alaska Range in Alaska to the Ruby Range in the Yukon. Accretion of the sediments of the collapsing basins to the North American margin included divers of disrupted portions of the lower oceanic crust.

RUBY RANGE BATHOLITH (RRB)

The Ruby Range Batholith (RRB) (Muller, 1967) is a narrow. more than 200 km long, northwest-trending intrusion that underlies the Ruby Range in the southwest Yukon. It is the northemmost element of the CPC, which extends 1750 km from southem British Columbia to the Yukon-Alaska border (Brew 8 Ford, 1993). The RRB is equivalent to the Coast Intrusion of Kindle (1 952) and the Ruby Range Granodiorite of Tempelman-Kluit (1974). The RRB is composed of equigranular, fine to medium grained "salt and peppef granodiorite. Hornblende-biotite granodiorite is the most common type, with minor homblende granodiorite and biotite granodiorite. The major felsic minerals are quark and plagioclase. Pyrope-almandine gamets are present near the contact with the btqtz schist of the KMA a the Gamet Creek plug (Figure 2-10). Gamet grain size varies hm0.5 mm to 5 mm. Assimilation of some pelitic schist during the emplacement of the granodiorite may account for the presenœ of gamets. The texhire of the granodiorite is generally massive. At the contact with metamorphic rocks of the KMA and the Nasina assemblage, which is intrusive and generally parallel to the fabric of the country rock, a parallel alignment of biotite and homblende is present. This weak foliation W interpreted as a primary Row structure, where platy and elongated mafic minerais were aligned during the emplacement of the batholith. The width of the foliatd contact granodioiites ranges fiom a few metres up to 100 m. A 1 km2plug of massive medium grained porphyritic augb diorite is observed northwest of Haines Jundion (Figure 2-1 0). Fine grained, dark greenish grey to brown, equigranular, gneissic quartz diorite to tonalite with variable assemblage of mafic miner& (homblende and bioüte, diopside and biotite, and hornblende) is exposed along the western shore of Talbot Atm, north of Doghead Point (Figures 2-15,2-17). at the contact with the olivine serpentin&. Mafic minerals comprise 35-60 vol.% of these rocks. The felsic minerals are plagioclase (30-50 vol.%) and quartz (10- 20 vol.%). K-feldspar has not been observed. The rocks have a distinct foliation, mineral stretching lineation and cornpositional banding. The quartz diontenonalite is intruded by sills of massive medium to coarse-grained granodiorite. A genetic relation of these tonalitic gneisses with aie ubmafic, defining a mafic shell around the serpentinite, similar to mAlaskan-typenintrusions, is regarded unlikely, sinœ these shells are comprised by more mafic rocks (pyroxenite, gabbro) than the quartz dioritenonalite present. Also, the occurrence of a massive undeformed dioritic intrusion within the biotite schist of the KMA suggests that the diorite and the gneissic quartz dioritehonalite represent an earlier more mafic phase of the RRB. Biotïite and hornblende K-Ar and RbSr ages of the major body of the Figure 2-17: Well foliated, fine grained, blueish grey tonaliac gneiss with boudinaged quartz layers. A 2 cm thick granitic dyke, related to larger sills fifty meters away, cuts the diorite and the quartz boudins without any obvious deformation. The tonalite is interpreted as an eariier mafic phase that preceded the main felsic intrusion of the Ruby Range Batholith. Outcrop is located north of olivine serpentinite at Doghead Point (94-26). Rock hammer (32 cm) for scale. RRB range from 53 to 58 Ma (Appendices 24,2-6; LeCouteur & Tempelman- Kiuit, 1976; Farrar et al., 1988). Bioüte K-Ar geochronology of two smaller intrusions within the KMA, west of Kloo Lake and at Pine Lake, yield similar ages of 58 and 50.6 Ma, respectively. An undeformed granitic dyke, intruding the btqtz schist of the KMA at the Canyon Bridge along the Alaska Highway (94-81), has U-Pb zircon and monazite ages of 54.6 Ma (Appendices, 2-6,2- 10; Mortensen, unpublished data, 1996). U-Pb zircon ages of 71-8 Ma are obtained fiom a deformed fine grained biotite granite dyke in an outcrop less than one hundred meters away (Figure 2-18, Appendices 2-6,240; J. Mortensen. unpublished data, 1997). U-Pb zircon ages from homblende dionte at the northem margin of the RRB at the south end of Aishihik Lake and from hbl-bt granodiorite at the southem margin of the RRB south of Aishihik Lake range from 69-78 Ma and 70-90 Ma, respectively, while a granitic sample from the central part of the batholith yielded U-Pb zircon age of 55.8 Ma (Appendices 2-4, 2-6; Johnston, 1993). The two age groups suggest an eariy, more mafic (?), intrusive period in the Late Cretaceous, while the main granodiorite body of the RRB intruded in the Early Eocene. Magmatic activity fiom 55 to 70 Ma is also reported from the tonalites of the Great tonalite sill at the western margin of the CPC in southeastern Alaska (Gehrels et al., 1992). Latest Cretaceous ages are also reported from granodiorite of the Coast Plutonic Cornplex (CPC) near the Yukon-British Columbia border along the Haines Road (Rb-Sr and K-Ar biotite: 67 and 66.7 Ma, respectively, LeCouteur & Tempelman-Kluit. 1976; Farrar et al., 1988). The RRB dips northeastward undemeath the Nasina Assemblage and the AMS in the north, and is underiain to the southwest by the KMA. The RRB is interpreted as an Eocene (50-58 Ma) synmetamorphic and syntectonic sill by Erdrner & Mortensen (1993). The exposure of the smaller intrusions with similar composition and K-Ar ages at the southwestern margin of the KMA possibly trace a second siil, partly covered, parallel to the one underlying the Ruby Figum 2-18: Outcrop photogreph of a boudinaged fine grained biotite granite dyke (da& grey undemeath rock hammer) in the cordieritesillimanite-biot'ne- quartz schist near the eastem margin of the KMA. U-Pb zircon ages of 68-72 Ma and 55.6 Ma were obtained ftom zircon and monazite fractions, respectivefy (Mortensen, unpublished data, 1997). See text for discussion. Sample location is at the Aishihik River. near the Canyon Bridge on the Alaska Highway (9441). Rock hammer for scale. Photo courtesy of Jim Mortensen, University of British Columbia. Range to the north. Both sills anbe interpreted as large apophyses of the main body of the CPC south of the Dezadeash Range-

POSTZûCENE IGNEOUS INTRUSIONS

Felsic and maftc igneous intrusions are common in the KMA and the RRB (Figure 2-1, Appendix 2-1 1). Felsic dykes can be found on the eastern shore of Kluane Lake and on Jacquot Island, where they occur in ENE- and SSE- trendng swamis of two or thme parallel dykes, spaced tens or a few hundred meters apaR They are massive feldspar porphyries of dacitic composition. Centimeter-sized phenoayds of plagiodase, with minor homblende, biotite and miamMc quark occur in a fine grained groundmass of quark, plagioclase and biotite. Unaltered dyke rocks have a bluish grey appearance, while aitered dykes are light greenish brown. The dykes Vary in thickness from 10 cm to 7 m. They are undefomied, generally vertical, crosscutting the mschlqtz schist and the olivine serpentinite and deflecting the foliation of the schist during emplacement (Figure 2-1 9). Mafic dykes are fine grained hologrstalline, equigranular hornblende or hornblende-biotite diorites, mth minor porphyric andesites. The dykes are found predominantly along strike at the northern margin of the KM,trending N-NNE. The mafic dykes are generally vertical, crosscuttïng the biotite schist, and have a width of 2 to 7 meters. A swarrn of four parallel dykes, spaced 400 m apart, was observeci north of Cuitus Cr& (93-179,93-181). Daciüc and dioritic dykes also crosscut the RRB at Kluane Lake and in the Ruby Range east of Gladstone Creek- The mafic and felsic dykes postdate the Eocene emplacement of the RRB. They are the southem part of a north-trending set of rhyolitic, feldspar porphyry dyke swams that intnide metamorphic assemblages and Mesozoic and early Tertiary igneous rocks (Muller, 1967; Tempelman-Kluit, 1974; Johnston & Timmemian, 1993a), along 250 km, from the Shakwak Trench in Figure 2-19: Vertical, undefonned, altered feldspar porphyry dyke, intniding northeastdipping ms-chlqtz schist on the eastem Kluane Lake shore (94-38). Flow banding can be observecl in the lighter coloured dyke at the contact with the dark grey ms-chl schist The thickness of the dyke varies from 3 to 5 m along the outcrop (see dotted line of contact). the south to the Yukon River in the north. Geochronological data fw these dyîces is not available. Tempelman-Kluit (1974) and Johnston 8 Timmerman (1 993a) propose earîy Tertiary emplacement, related to the RRB and similar eariy Tertiary intrusions. North- trending rhyolitic to basaltic dykes are reported ftom the Kluane Ranges southwest of Kluane Lake, where they crosscut mid-Miocene conglomerates of the Amphitheater Formation (Eisbacher & Hopkins, 1977). K-Ar whole rock ages of 6-16 Ma are reported for several dykes (Stevens et al., 1982). Since the juxtapostion of the lnsular Supertenane with the KMA had happened by Early Oligocene (see Chapter 6), it is possible that the dykes crosscutting the Amphitheater Formation are coe.val with dykes in the KMA and the AMS. suggesting a Miocene age for these dykes. The predominantly north-trending orientation of the dykes intruding the metamorphic assemblages can be related to extensional ftactures resulting from northward movement of the Pacific plate relative to North Ameriw. which also caused dertial motion along the Denali fault zone (Eisbacher 8 Hopkins, 1977; see Chapter 3).

DEZADEASH FORMATION (Jb)

The late Jurassic-Earty Cretaceous Dezadeash Formation (DF) consists of generally undeforrned, interbedded sandstones and shales with minor conglomerates, limestone, interpreted as Rysch sediments of volcanogenic ongin (Eisbacher 1976). It is equivalent with the Dezadeash Group of Kindle (1952). At its northem and eastem margin of exposure the DF occurs as a fine to medium grained graphitic ms-bt-chlqtz phyllb. Euhedral spessartine-rich gamets and 'knotty schist" indicate low grade metamorphism (Figure 2-20). The width of that phylliüc zone varies ftom less than 100 rn at Klukshu Lake and Motherall Creek up to 3 km at Takhanne River (O. Lowey, pers. comm., Figure 2-20: Photomicrograph of a 'knotty schist", a date of the Dezadaesh Formation in the Takhanne river valley at Million Dollar Falls campground, along Haines Road in the southem Yukon (95-26). The porphyroblasts consist of fine grained muscovite. Biotite, quartz and muscovite make up the mat&. The contact of the DF with the Coast Plutonic Compkx is a kwhundred meters to the east. Scale bar 2 mm. XPL

Figure 2.21: Photomicrograph of coarse grained gameüferous homblende- biotite phyllite assigned to the Dezadeash Formation southeast of Dezadeash Lake (95-37). The phyllite is stnicturally ovedain by a kysnitestaurolite-gamet schist. Curved inclusions in the homblende porphyroblast (black arrow) and domino structures of the bioüte porphyroblast (white am)imply top to the left shear. See Figure 2-14 for loaction. Scale bar 2 mm. XPL

1995) to the south. The DF overlies a narrow band of chlonte-adinofite-schist (PMvs of Dodds & Campbell, 1992) (Figure 2-9). Andesioc clasts within the DF, and interbedded phyllite and chloriteactinolite schist suggest a pnmary sedimentary contact (Eisbacher, 1976; Bremner, 1990). East of Klukshu Lake the DF is in a presumed fauhed contact with the Nisling assemblage. as rnentioned above (Figures 2-1 5,2-21). South of Klukshu Lake the DF dips eastward undemeath the Coast Plutonic Cornplex. The contact is shown on the map by Kindle (1952) as a fault. A K-Ar whole rock age of 68.2 Ma of a DF phyllite at Takhanne River valley (G. Lowey, pers. cornm., 1995) is similar to K-Ar biotiie (66.7 Ma, Farrar et al., 1988) and Rb-Sr (67 Ma, LeCouteur & Tempehan-Kluit, 1976) ages of granodiorite of the CPC, suggesting an intrusive contact. However, the whole rock age of the phyllite has to be regarded with caution (J. Mortensen, pers. comrn., 1997). The interpretation of the DF as the immediate protolith of the KMA, as proposed by Eisbacher (1W6), cannot be accepted in Iight of the evidence presented in this chapter and Chapter 5.

GREENSCHIST (PMvs)

A fine grained greenschist of variable composition (pl-chl-epqtz. hbl-ep- qtz, hbl-plep-chlqtz), fonns a 100 km long and maximal 2 km wide discontinuous belt fmm the south end of UIuane Lake to Klukshu Lake (Figure 2-1). It crops out northeast and east of the DF. The greenschist is equivalent with unit PMvs of Dodds & Campbell (1992). Kindle (1 952) rnisinterpreted these rocks as peridotite or serpenthite (unit 5), west of Haines Junction, or assigned them to the 'Yukon Groupn, which also included the KMA btqtz schist. The greenschist has developed a foliation that parallels compositional layering. Distinct compositional layering with plagioclase and homblende clasts, obsenred in some sarnples, suggests that the protolith is a weakly metamorphosed andesitic tuf!f. A massive dark greenish grey andesite occurs 2 km east of Bear Creek Motel on the Alaska Highway (Figure 2-9). No radiometrie ages have been detennined for the greenschist. Since it underlies the DF north of Dezadeash Lake, and is presumably the depositional base of the DF (see above; Eisbacher, 1976). its minimum age is pre-late Ju rass ic. Chapter 3

Structural styles of the Kluane metamorphic assemblage INTRODUCTION

Well developed schistosity and mineral stretching Iineation in mica- quartz schist reflecüng ductile deformation of the KMA are described and their regional tedonic signkance is discussed in the first part of this chapter. Microtectonic analyses show that the KMA schists are mylonites characterized by a distinct monoclinic shape symmetry, indicative of intensive ductile defomation (Passchier 8 Trouw, 1996). Shear-sense obtained from &type porphyroclasts records consistent oblique slip with westwarddirected hangingwall up motion. This is the first report4 evidenœ of ductile deformation in the North American Cordillera indicaüng late Mesozoic sinistral motion along the North American continental margin as postulated by Monger et al. (1994). The structural geology of the KMA is shown on an overview map (Figure 3-l), a detailed map of the Kluane Lake region (Figure 3-2)and in several cross-sections (Figure 3-3). A proposed eariy Tertiary deep seated fault divides the KMA into a northwestem and southeastem domain. Computer aided stereographic analysis, presented in the second part of the chapter, documents that the orientation of mesoscopic folds is parallel to an ES€-plunging regional anticline. Sirnilady oriented local and regional folds are obsewed in adjacent metamorphic assemblages of the Nisling terrane (NS) and in unmetamorphosed shales and slates of the Dezadeash Formation (DF), suggesting a regional NNEdirected compression. The chapter concludes with a tectonic evoluüon model that incorporates previously unpublished geochronological data and metamorphic results from Chapter 4. The model proposes Late Cretaceous underplating of the KMA along a sinistral oblique slip faut underneath the North Arnerican continental margin. Non-coaxial progressive deformation coeval with high pressure-low temperature rnetamorphism is evident in rare synkinematic grossular-rich gamets. Latest Cretaceous emplacement age (72 Ma) of a late synkinematic granitic dyke provides a minimum age of deformation of the KMA.

3NN MSS 13

3NN MSS -lui*u - PREVIOUS WORK

Workers who previously studied the KMA northeast of Kluane Lake noted the unifotm northdipping schistosity (McConnell, 1905; Muller, 1967; Tempelman-Kluit, 1974; Erdmer, 1990). McConnell(1905) recognized that the schists dip more steeply and are in part overhirned near the eastem contact with the batholith. He assigned southdipping schists at the base of the St. Elias Mountains to the 'Kluane Schist" and suggested that the KMA foms a large anticline, whose hinge zone has been eroded dunng the formation of the Shakwak valley. Although fieid work camed out for this project did only find greenschist and phyllite of the DF, instead of KMA-type schists at McConnell's locality (Telluride Creek. see Figure 2-10), field observations and structural analysis presented below support McConneli's model that the orientation of schists of the KMA defines a regional anticline in the eastem part. Southwest-verging open to isoclinal folds, asymmetrical crenulation and small folds with an axial-planar northeastdipping cleavage were observed at the Kluane Lake shore and in the Kluane Hiils (Erdmer, 1990, 1991). Tempelman-Kluit (1 974) noted that schistosity is masked and Iinear elements are obliterated by thermal overpn'nting of regional metamorphosed rocks. &Pb, K-Ar, 'OAr-ja~rgeochronology of micaquartz schist record ages of 39-6 1 Ma, interpreted as peak metamorphic and cooling ages related to the intrusion of the RRB and constraining the development of the schistosity in the KMA to pre- Earty Eoœne (Erdmer 8 Mortensen, 1993).

DUCTILE FABRICS OF THE KLUANE METAMORPHIC ASSEMBLAGE

Planar fabfics

Parallel graphitic layers in plagioclase porphyroblasts are relics of an early slaty cleavage. Rare crenulation cleavage preserved in some porphyroblasts show that Viis cleavage was formed by transposition of an older foiiation, possibly bedding (Figure 34). Sinœ no primary sedirnentary structures are presenred to mnfirm that this older foliation represents original bedding, it is referreâ to as Sn, while the prominent parallel graphiac layers are called S,,. S,, S,, is cornmonly identifieci only in thin sections (Figures 34, 3-5), except when large porphyroblasts can be observed on unaltered rock faces along the Kluane Lake shore (Figure 2-3). The graphitic inclusion trails are generally curved, implying a synkinematic growth of the porphyroblasts (Figure 3-5; Passchier 8 Trouw, 1996). Continuation of S,, layen from plagioclase porphyroblasts into surrounding mica grains is observed in some samples. S,, in the mica grains is also parallel to the major schistosity S,, suggesting that S, has developed parallel to the eariier cleavage S,, (Figure 34). S,, is also observed in rare synkinematic gamets (Figure 38). The major fabric obsewed in the schists of the KMA is a spaced schistosity S, The cleavage domains which define the foliation plane S, are comprised of parallel aligned muscovite, chlorite and biotiie grains, ranging from 0.2 to 2 mm in length. Microlithons contain plagioclase porphyroblasts and quartz (Figure 2-4). Microlithons are generally thicker than cleavage domains, but individual thickness can Vary within a single sample from less than 200 Pm to more than 2 mm. The transition between microlithon to cleavage domain is discrete (domainal spaced foliation). Quark bands cornmonly appear lenticular, boudinaged. with thinning at the necks. Compositional layering can be observed with the unaided eye in some outcrops (Figure 2-7). Approaching the contact with the RRB, rocks of the KMA have a more gneissic appearance (Figure 2-8). This is due to coarsening of the grain size, overgrowth of the S, foliation plane and new growth of cordierite, a resuit of thermal recrystallization caused by the intrusion of the RRB. Sn, schistosity is also developed in the olivine serpentinite at Doghead Point, where it is defined by serpentine (Figure 3-7). Parallelism between the schistosity in the serpentinite and nearby ms-ch1 schist implies Figure 3.4: Photomicrograph of aluminous micaquartz schist from the northwestem part of the KMA (94446). Two foliation generations, oiiginal bedding (3) Sn and a slaty cleavage S,, are distinguished by graphitic layers in a plagioclase porphyroblast. SW,is approximately parallel to the schistosity in this sample, which is oriented parallel to the long axis of the picture. The continuation of fmm the plagioclase porphyroblast into the biotite grains suggests that the rock has not experienced significant deformation. Scale bac 0.5 mm. XPL

Figure 3.5: Photomicrograph of a plagiodase porphyroblast of the calcic schist of the KMA. The graphitic inclusions in the grain are wwed towards the rim of the plagioclase, indicaüng a counterclockwise rotation of the grain during growth. Sample location is from the eastem Kluane Hills (90-37). Scale bar: 0.5 mm. XPL

Figure 3-6: Photomicrograph of a gamet (center) of the aluminous schist near the contact with the calcic schist (93-1 83). Cuwed graphiac inclusion trails in the gamet crystal are remnants of an eariier foliation (S,,) and indicate a clockwise rotation of the gamet during growth. SW, does not continue outside the gamet. The gamet is rimmed and partly embayed by staurolite (st) and biotite (brown). Graphitic layers in the stawolite crystals do not show a preferred orientation and suggest a static overgrowth by staurolite. Scale bar 0.5 mm. PPL

Figure 3-7: Photomicrograph of an olivine serpentinite kmthe Doghead Point ultramafic body (W20b). The schistosity (C) is defined by platy alignment of serpentine (bluish grey to whitish needles) in the microlithons, parallel to the long ais of the photograph. Splanes are developed in the 3 mm wide zone between zones of more intense shearing. Sense of shear is top to the left. The light yellow mineral is talc. Olivine porphyrodasb are charaderirecl by bright yellow. red and green colours and a weMike alraüon to opaque minerais, magnetite and chromite (œnter of picture). Scale bar 2.0 mm. XPL

contemporaneous development of the fabric in both rock types (Figure 2-1 8). No planar fabric is developed in the smaller serpentinite bodies. The general attitude of S,, in the western Ruby Range remains unchanged over tens of kilometers. along and across strike, dipping moderately (1545") north to northeast (Figures 3-1, 3-2.3-3). East of Kloo Lake the attitude changes to easteriy dips and to steeper (55-85') southemly dips in the Dezadeash Range. A detailed discussion of the structural data is presented below. Locally, a secondary foliation S,, is developed in the micaquark schist and in the olivine serpentinite at Doghead Point. This foliation is axial planar to mesoscopic FW3-foldsand millimeter-scale F,,-crenulation folds. The cleavage is generally only observed in the irnmediate fold hinges. However, not al1 FW3- folds have developed a S,,-cleavage. The spacing of the cleavage ranges from 1 mm to several centimetem. Thin section analyses show the foliation is defined by preferred orientation of new mica crystals. The cleavage is generally better developed in the olivine serpentinite at Uoghead Point than in the mica- quartz schist. Rare good exposure at the Kluane Lake shore show that Sm, strikes subparallel to the main foliation SM,but dips steeper to the north. The outcrop sketch in Figure 3-8 shows the localized character of S,. indicating inhomogeneous defomation at outcrop scale. Due to its limited occurrence S, does not fom a pentrative foliation and is not mappable.

Linear fabrics

A distinct mineral stretching Iineation L2can be observed on the Sn+,- plane. It is defined by an elongated alignment of mica or chlorite minerals and is best developed in ms-ch1 schist along the Kluane Lake shore. At sample and outcrop scale the orientation of the mineral stretching lineation is consistent. Where observed in the KMA, the orientation of L, is homogeneous. generally plungïng gently (5.20") to NE-€SE or WNW (Figures 3-1, 3-2). L, is also developed in the foliated olivine serpentinite at Doghead Point. Figure 3-8: Outcrop sketch of a 10 centimeter-spaceâ crenulation cleavage S, in a north dipping muscovite-chlorite schist. The crenulation is developed irregularly and dies out at the top and the bottom of the sketch. The dip direction of both &and S,, is similar. The view plane is approximately perpendicular to the strike of the schist. Location of outcrop is at the eastem shore of Kluane Lake, south of Cultus Creek (94-33). Hand of field assistant for scale. L2is harder to distinguish in cordierite-bearing rocks, and non-existing near the contact with the RRB. It is obliterated by static growth of minerals during postdeformational thermal overprinting, concurrent with coarsening of grain size and gneissification. It can be observed that samples with well developed mineral stretching lineation generally have a distinct monodinic symmetry that can be used as a shear-sense indicator. Sinœ a mineral stretching lineation is regarded as indicator of progressive deformation (Hanmer & Passchier, 1991). L,, is contemporaneous with the asymmetrical fabrics described in the previous section. The distinct monoclinic fabric obsenred in sections parallel to L, and the lack of them in sections perpendicular to the lineation support this assumption. A second lineation L+3traces the fold hinges of small crenulation folds F, F, on the foliation plane. This lineation was developed concurrently with the crenulation cleavage S,. It occurs only locally and is not mappable.

Shear-sense indicators

A distinct asymmetry of the schistosity S, can be observed in thin section (Figures 24, 3-9, 3-10, 3-1 1) and outcrop (Figure 2-3), indicating progressive nontoaxial defonnation of the schist Alternating quartz- and mica- rich layers define a mylonitic foliation parallel to s,. The plagioclase porphyroblasts behaved as kinematic porphyroclasts, since they ceased growing in the early stage of metamorphism and actecl as passively rotated clasts during most of the major deformation period. Wfih a variable porphyroclast content of 15-35 vol.% in a fine grained micaquartz matrix, schists of the KMA are mylonites or mesomylonites, using the classifÏcation of Spry (1 969). Mica grains that define the Sn+,-foliation are deflected around plagioclase porphyroclasts with a &type shape. &type porphyroclasts are a special type of mantled porphyroclasts, where recrystallized plagioclase of the Figure 3-9: Elongated &type plagioclase porphyroclast (center) indicating non- coaxial progressive deformation with a top to the left sense of shear (Passchier & Trouw, 1996). Quartz grains are recrystallized in the pressure shadows. Thin section is cut parallel to mineral stretching lineation and perpendicular to schistosity. Scale bar: 2 mm. XPL Figure 340: Two Mype plagioclase porphyroclasts indicaüng top to the right (clockwise) sense of sheat. Deflection of the foliation between the two grains give local anüthetic shear. This shear is not penetrative, as it is restricted to the zone between two porphyrodast. The foliation to the right of the center grain is aligned to the main schistosity (paraliel to long axb of photograph) at the right margin, indicating th& the deflecüon is only causeâ by the porphymlast, and not by C'ahear bands. which would indicate opposite sense of shear. The upper part of the photograph is devoid of porphyrodast and no deflection of the foliation is notiœd. Pressure solution along the deflected foliation (white anow) forming stylolites, implies top left to lwer right maximum stress diredion, in agreement with a top to the right sense of shear. Sample is from the calcic schist on Jacquot Island (94-12). Thin sedion is cut parallel to mineral stretching lineation and perpendicular to schistosity. Scale ber= 2 mm. PPL

Figure 34:Fine grained mylonite of the calcic schist un@northwest of Haines Junction (95-22). Notice that a Cs-sheaiband is developed above the two center right &type plagioclase porphyrodasts (white anow). C'-shear bands are rarely observed in the KMA and probably resaicted to fine grained samples (compare the porphytoclasts in this sample to those in Figures 3-7 and 3-8, which have the same scale) and also indicate higher strain. Scale bar 2 mm. PPL clast foms wings with a monoclinic shape syrnmetry, that can be used as a shear-sense indicator (Figures 24. 3-9. 3-10). &type porphyroclasts are indicative of high strain rnylonites (Passchier & Trouw, 1996). Most analyzed KMA schist samples contain &type porphyrodasts. A large concentration of these clasts in a thin section give the impression that shear band cleavages are developed. The rotation of neighbouring clasts results in local antithetic shear near the contact of two clasts (Figure 3-10). However, the apparent shear bands are not penetrative on thin section scale and are not developed in porphyroclast-free zones. Figure 3-10 shows that Sw2 is being deflected around a single porphyroclast and the magnitude of deflection decreases with distance from the clast. Shear band cleavages. CIS fabrics (Berthé et al., 1979) and Cahear bands (Passchier & Trouw, 1996). are rarely observed and may be related to slightly higher strain andlor smalkr porphyroclasts (Figure 3-1 1). In cases where shear band cleavage is obsewed, the sense of shear is the same as indicated by &type clasts of that rock. Oblique foliation of quartz in mm-wide quartz layers distinguished in a few samples and rare spiral-shaped inclusion trails of SM in gamet porphyroblasts provide the sarne sense of shear. In any given sample the shear-sense obtained from porphyroclasts or shear bands is consistent on the scale of the thin section- Asymmetrical fabrics are also obsewed in the foliated olivine serpentinite at Doghead Point (Figure 3-7). Narrow shear zones, 0.254 mm wide, parallel to the dominant foliation S,, separate wider zones (1-3 mm) of oblique grain shape foliation defined by serpentine crystals. The angle between the foliation S, and the oblique serpentine grains is 3545". The orientation of foliation, lineation and the sense of shear is similar to that of the adjacent ms- ch1 schist. The described fabric resembles C/S fabrics reported by Norrell et al. (1989) from partly serpentinized peridotiies of the Josephine ophiolite in northem California. The formation of the CIS fabrics indicate a maximum T of 550°C, the upper stability limit of serpentine (Norrell et al., 1989). Geothermobarometry of a nearby sample (9447) yields a temperature 540°C (see Chapter 4). The sense of shear shown on Figure 312 and listed in Appendix 3-1 was primarily determined from thin section or polished rock slabs, along sections parallel to the mineral stretching lineation and perpendicular to the foliation (Passchier & Trouw, 1996). Only those samples which provided unambiguous sense of shear were consideted. Reliable kinematic indicators obsenred in outcrops are rare and include transposed quartz veins and centimeter-scale winged porphyroclasts.

Sense of shear observed in schists of the KMA is shown as direction of hangingwall motion on a map and as vectors and slip linears on stereonets on Figure 3-12. The motion of the hangingwall is similar in the western part of the KMA, generally towards west. At the southwestern Rank of the KMA, the orientation of the mineral stretching lineation is subparallel to the assurned strike of the Denali fault and hangingwall motion is to the WNW. Futther to the east and northeast, towards the contact with the RRB, the lineation changes to a NE-SW direction, with motion of hangingwall towards southwest. Shear- sense indicators are rare in the eastem Ruby Range and the Dezadeash Range, due to thermal overprinting caused by the intrusion of the RRB during the Early Tertiary (see Chapter 4). The stereonets show a consistent westwarddirected hangingwall up oblique slip. Oblique westward thnisting is in contrast with vertical right-lateral strike-slip assigned to the Denali fault to the southwest (Dodds, 1991). Absence of vertical slip planes in the KMA implies that no steep strike-slip faults or shear zones transect the KMA. Therefore westdirected ductile hangingwall motion obsenred in the KMA is not the result of right-lateral strike- slip along the Denali fault, but indicates oblique underplating of the KMA under the WNW-trending (in current referenœ frame) North American continental margin, as represented by the AMS, during eastward motion of the Kula plate in the Cretaceous (Figure 3-1 3; Engebretson et al., 1995). The consistent sense of shear and the lack of regional strain gradients in the KMA suggest Figure 3-12: Map of the KMA with observeci shear-sense indicators. Black arrows point in diwon of hangingwall motion, deduced hmoriented thin sections. Locaüon of samples and types of shear-sense indicators are listed in Appendix 3-1. Stereographic upper and lawer hemisphere projection of shear- sense indicators is show in upper right corner. Slip linears, which show hangingwall motion as arrows on pok of foliation containing the mineral stretching lineation (Hoeppner, 1955), are displayed in lower left corner. The trace of the Denali fault is after Dodds & Campbell (1992).

stretching iiraaîion M~@- n

of figure above depth

Figure 3-13: Tectonic interpretation of shearsense indicators in the KMA. Homogeneous hangingwall up sense of shear is compatible with underplating of the KMA undemeath the North Amencan continental margin, represented by the AMS. Schistosity of both assemblages cunently dip to the NNE. The mineral stretching lineation, which is assumed to lie in the direction of shear direction (Hanmer & Passchier, 1991). is at low angle wiai continental margin (- 30°), resulong in oblique slip with a left-lateral horizontal wmponent. Eastward motion of the Kula plate, between -80-95 Ma (Engebretson et al., 1995), resulted in the collapse and subduction of the oœanic basin onto which the KMA was deposM, and eastward underthrusting of the KMA underneath North America. The block diagram displays the presently exposed erosional surface. The actual accmtion to the upper plate (AMS) and ductile deformation of the KMA occuned at depths of 20 km (see small sketch). that the KMA was deformed as a whole. Local narrow high strain shear zones were not obsewed in the field. However, t is possible that some may exist that may not have been noticeci, sinœ sampling occurred on a kilometer scale and continuous outcrop exposure is not always realized. The magnitude of finite strain and the arnount of extension during defomation are hard to detemine, since no objeds of known shape exist on which defomation can be measured. AJso, the debrmed KMA schists do not represent a complete shear zone. since no undeforrned wall rocks exist from which a strain gradient could be detemined. Consistent strain of the mylonized schist and a possible depth of syndeformational metamorphism of approximately 20 km (see Chapter 4). suggest that the oœanic sedimentary protolith of the KMA was accreted to the base of an ovemding plate (AMS) during eastwards subduction, similar to models proposed by Karig (1 974,1982).

The age of the asymmetric fabric and thus the age of the deformation D, D, cannot be dated directly. The presence of synkinematic gamets (Figure 3- 6) and undeformed crosscutting quartz veins overgrown by sillimanite and cordierite (Figure 3-14) show that peak metamorphkm postdates peak defomation. K-Ar and 'OAr-jgAr ages of 39-60 Ma record cooling through the 280°C and 350°C blocking temperature for argon in biotite and muscovite, respectively (Erdmer & Mortensen, 1993). An 4oAr-)SArmuscovite age of 51.1 M.5 Ma was obtained from a sample of the lowest metamorphic grade on Jacquot Island (94-3, Appendix 2-7). A late-synkinematic boudinaged fine grained biotite granite dyke from the eastem part of the KMA recorded U-Pb zircon ages of 68.4iû.2 Ma and 71.8I0.2 Ma and U-Pb monazite age of 55.6I0.6 Ma (Figure 2-18; Appendix 2-10; Mortensen, unpublished data, 1997). The older age represents the emplacement age of the dyke, while the younger age reflects thermal overprinting in the Eocene. The blocking temperature of monazite (-700°C; Hearnan 8 Pamsh, 1991) is close to the peak temperature obtained fram a sample taken from an outcrop nearby (94- Figure 3-14: Photornicrograph of a cordierite-biotitequarz schist norai of Gamet Creek. A well defined schistosity, parallel to the long axis of the photograph, is crosscut by a small quartz vein. The vein does not appear to be defomed. In the center of the picture, the vein is overgrown by cordierite (black arrow), recognud by its higher relief and a yellowish brown altered rim. To the left fibrolitic sillimanite (white arrow) nucleates in the quartr vein. This indicates that peak metamorphism is postkinematic. (94-146). Scaie bar= 2 mm. PR 81,660°C). An undeformed graniüc dyke from an outcrop nearby yielded U-Pb zircon and monazite ages of 54.6I0.2 Ma and 54.7a.9 Ma, respectiveiy (Appendix 2-1 0; Mortensen, unpublished data, 1996). These ages indicate that ductile defomation of the KMA took place as late as Late Cretaceous, but had ceased by early Tertiary. No direct geological evidence is given for the maximum age of defomation. However, the la& of high PBigh f mineral assemblages suggests that defornation and associated high P metamorphism of presently exposed KMA schist did not occur over an exceedingly long period (20-30 Ma, see Chapter 4).

Folds

Crenulation folding of assumed original bedding Sn is preserved in some plagioclase porphyroblasts (Figure 34). Since these are found in thin sections of only a few samples, and the host grains were subject to deformation, the orientation of F,,-fold axes cannot be determined. Curvature of the graphite layers representing Sn+,in plagioclase porphyroblasts is interpreted as the result of synkinematic growth of the porphyroblast during non-coaxial progressive defomation, and does not reflect folding (Figure 3-5). In outcrop, SW2-foliationcan appear wavy, fonning gentle folds with amplitudes of 10 cm and wavelengths of 1-2 m. When more distinct folding is developed, open folds with wavelength ranging from several œntimeten to 10 m and amplitudes of a few œntimeters to 34m are most common (Figure 3- 15, Appendix 3-2). However, observed tightness of folds avers the whole spectrum from open to isoclinal. Fold shapes Vary from symrnetrical to slightly asymmetrical, upright to steeply inclined. Recumbent folds are less cummon and occur predominantly in the Dezadeash Range. Asymmetrical folds are often disharmonic, and their limbs sheared off. West to southwest vergence of the folds is slightly dominant. The majority of the folds can be classified as parallel or 1b type folds (Ramsey, 1967). Secondorder folds, from millimeter- Figure 3-15: Mesoscopic open Fm,-fold in muscovitechlorite schist of the KMA on a ridge east of Cultus Bay. Kluane Lake (93-23). The fold axis plunges rnoderately to the north (350425). The fold has an amplitude of 1 m and a wavelength of 3 m. S,,-schistosity in the area dips moderately to the north east. P. Erdmer for scale. scale crenulations to larger structures with amplihides of 5 cm and wavelengths of 10-15 cm are cornmonly developed on the Iimbs of upright open folds. Crenulation folding with the same ais orientation can also occur without larger folds. Locally, a crenulation cleavage S,, has fonned in the hinge zones of F,-folds (see previow section). Mesoscopic Fm,-folds effect only layers with thickness in the order of a few meters. These folds are not penetrative on a regional or even at outcrop scale. In the northwestem Dezadeash Range mesoscopic folding is common in an area of several square kilometers. The orientation of F,,-fold axes are similar, suggesting the same deformation event. Fold axes plunge shallowly towards southeast or northwest throughout the whole KMA (Figures 3-1, 3-2). In the southeastem part of the KMA. in the eastem Ruby Range and in the Dezadeash Range, Sn+,-schistosity is folded into a 20 km wide ESE- plunging anticline (Figures 3-1, 3-3). An along-strike change fmm generally north- to southdipping schistosity is observed east of Kloo Lake. Although there is no field evidence for faulting, the area being underiain by a 10 km wide lowland around Kloo Lake, the structural change from northdipping homocline west of Kloo Lake to an anticline east of the lake is best explained by a fault (Figure 3.1). However, near the Killermun plug to the norai, orientation seems to be continuous. The nature of the proposed fault is not known and the fault remains a conjecture. Stereographic analyses presented in the following section show thet the attitude of the regional fold axis, derived from foliation data east of the presumed fault, is virtually identical with that of mesoscopic fold axes (Figure 3- 19). It is therefore inferred that regional scale folding and local mesoscopic folds are part of the same deformation event. The MW-ES€ trend of the F fold axes indicates NEdirected compression. Although Fm,-folding cannot be dated directly by geochronology, folding of S,, and higher peak metamorphic pressures on the southem southdipping limb, suggest that F,+, occurred after peak deformation in the latest Cretaceous and before the emplacement of the RRB in the Eaily Eocene. Variations of the dip dimon of S, over several hundred meters to a few kilometers can be attributed to deflection near the contact with the RRB or associated plugs within the KMA (Figures 2-9.2-10).

BRITTLE STRUCTURES

The lithological homogeneity of the KMA and the absence of distinct marker horizons make identification of fauhs difficult. As a result most published maps show very few faults, if any. within the KMA (Kindle, 1952; Muller, 1967; Tempelman-Kluit, 1974). The faults shown on the Dezadeash map sheet are inferred Rom aerial photographs and are not supported by geological evidence (Kindle, 1952). Fieldwork camed out for this project did not find any evidence for faulting at the given locations. Faults are proposed by Muller (1967) at the contact between the calcic and aluminous schist in the Ruby Range and by Erdmer (1990) in the eastem Dezadeash Range, where the KMA is assumed to be in contact with the Nisling assemblage. The probability of those structures is discussed in Chapter 2. where it is concluded that the contact in the Ruby Range presents a syndeformational or primary sedimentary contact, while the contact in the Dezadeash Range does not exist. During work for this study only five faults within the UMA could be identified from geological evidenœ in the field (Figure 3-16). Two undeformed crosscutting dykes are offset by north-trending faults north of McKinley Creek valley in the northeastem Ruby Range (93-1 37, 94-1 19). The faults show apparent right-lateral stnke separation of 5 m and 20-25 m, respectively. The dip of the fault plane is not known. A right lateral north-trending fault with a strike separation of approximately one kilometer is infemd from omet of the Figure 3-16: Major lineaments in the Kluane Metamorphic Assemblage. Valleys are shown as thick grey lines, dykes as thin grey and black lines and Iines with anows represent faults with known along sûike disphcement. The major Iineaments in the Ruby Range Batholith are the Three Guardsmen (1) and the Dezadeash River (2) lineaments. The nature of the Thme Guardsmen lineament is not known. The ûezadeash River is thought to be the location of a tear fauH that juxtaposes rocks of the KMA, from Nisling assemblage rocks to the southeast that were at higher structural levels during Eocene metamorphisrn. Rose diagrams of the dykes are shown on the inset in the upper right corner. The relationship between conjugate Riedel shears (R, R'). P-shears, extension fractures with faulang and major stress direction a, is shown on the sketch in the lower left corner (modifiecl after Twiss 8 Moores, 1992). The strike of the majority of the observed dykes lies perpendicular to the extensional direction. The north-trending valleys and obsenred faults can be correlateci mth Riedel s hears that became active after the dyke emplacement in a more britUe environment. The southeast-trending linears are subparallel to the Oenali faut and may represent dextral faults with unknown omet. contact between the KMA and a granodiorite plug a the headwaten of Marl Creek (Figure 2-10). A more prominent huk, located south of Killemun Lake also dispiaœs the KMA-RRB contact (Figure 3-17). The fault strikes SSE and has an apparent right-lateral strike separation. The amount of displacement and the nature of the fault could not be detemined. A well preserved fault scarp can be traced along the slope of the ridge. Since the valley was fomied during the latest glaciation period, the McConnell glaciation (-1 0 ka; Bostock, 1966). the presence of fauk scarps suggests that the fault has been active during the Holacene. A north-striking steep dipping reverse (?) fault ofketting the muscovite- chlorite schist can be seen on a ridge at the eastem Kluane Lake shore. between Cultus and Thorsen Bay (94-33). A well preserved fault scarp indicates recent displaœment in the order of five meten. Two faults for which there is no direct field evidence are proposed on the basis of structural and metamorphic data. A norai-trending fault in the Kloo Lake area, dividing the KMA into a northwestem and southeastem structural domain, is inferred from structural discontinuW. Also, the apparent tapering of the calcic schist in the east may be caused by truncaüon along the proposed fault. East of the fault the calcic schist crops out just south of the Killemun Lake plug. In the eastem domain rnesoscopic F,-folds plunge to the ESE, while they plunge WMN in the western domain. Peak metamorphic pressures along the upper contact of the KMA do not show a signifiant gradient to support post-metamorphic tilüng of the eastem domain or large vertical displacement between the domains (Figure 4-1 1). This constricts the timing of faulting to the period immediately prior to the intrusion of the RRB. A NNE-striking tear fault is assumed to lie in the Dezadeash River valley. Indirect evidence for the presence of a fauk is given by the steep slope of the mountains Ranking the valley. The fault is necessary to juxtapose the KMA in the Dezadeash Range which record higher pressures during Eocene metamorphism with Nisling assemblage rocks east of Dezadeash Lake that Figure 3-17: One of few obseFIed bnttle faults. The contact between the granodiorite of the Ruby Range Bathoiiih and the biotitequartz schist of the KW(dottd line) south of Killermun Lake (93-67) does not continue to the foot of the mountain. A north-trending fauit can be traced along a little scarp (to the right of the dashed line). The apparent displacement and the fauit scarp suggests an oblique slip fault. The bush covered talus at the foot of the mountain hides any trace of the contact. Thin white lines indicate orientation of foliation of the schist. Scale bar equals 200 m. experienced only weak rnetamorphic overpnnting in the Eocene. The exhumed KMA rocks reflect greater depth. and were likely juxtaposed with the Nisling assemblage along a tear fault during more extensive uplift of the KMA compared to the Nisling assemblage (Figure 3-1). The strike of the fautts parallek major valleys in the Ruby Range and the undeformed mafic dykes (Figure 3-16). Narrow north-trending depressions are also occupied by Aishihik Lake, Sekulmun Lake. Talbot and Brooks amis of Kluane Lake, Aishihik Rivet and Brooks Creek. Compared to a stress pattern wiai a right-lateral Denali fault as a reference, north-trending structures are close to the orientation of a rig ht-lateral Riedel shear (Figure 3-1 6). The major compressional stress 0, would strike 15", as a result of noithward subduction of the Yakutat block underneath the St. Elias Mountains (Homer, 1983).

Jointing is common in the schist. although R is not a striking feature. Joint planes are generally vertical and perpendicular to the overall strike of the foliation of the schist. The spacing is irregular and in the range of tens of centimeten to a few meten. Well developed jointing can be observed on a ridge north of the McKinley Creek valley in the eastem Ruby Range (94-1 08,

109). There, vertical joint planes. striking 10 O and 10OU, spaced less than one meter, have developed in a shallow NNEdipping biotitequartz schist. A 20"- striking, vertical, fine grained granodiorite dyke cross-cuts the schist. Moderately (4040") southeast- and northdipping joint planes are also observed in the same outcrop. The ongin of jointing W probably related to the latest stage of uplift of the KMA. STRUCTURAL ANALYSIS OF THE KMA

Introduction

Statistical analysis of structural data can provide information on regional structural trends that may be overprinted by local variations. Structural data is planar or linear and is commonly representd by stereographic projections (Schmidt, 1925; Bucher, 1944). Foliation, lineation and fold axes data collected in the KMA was analyzed by using SpheriStat 2.0, a Wndows-based sofbvare program which produces stereoplots. circular rose diagrams and maps, calculates principle directions and provides a number of structural analyses (Pangaea Scientifc, 1995). Stemoplots shown in Figures 3-1 8, 3-1 9 and 3-20 are lower hemisphere projections using an equal area Schmidt net. Density contours are calculated by the Gausssian counting method. The statistical methods are described in Appendix 3-3 and the structural data are Iisted in Appendix 3-4. The following results are not intended to represent a quantitative structural analysis. The availabiliRy of structural data depends on outcrop density, which cm Vary throughout the area underlain by the KMA. Spatial averaging of the data was not attempted.

Results and discussion

Figure 3-1 8 represents the total structural data collected in the KMA: 583 Sn+,-foliation, 149 k+2-mineralstretching lineation and 143 F,+,-fold axes measurements. The foliation data forms a moderately developed cluster wÏth girdle (modified Flinn diagram analysis by SpheriStat). A major maximum coincides with the E,-eigenvedor. The E,-eigenvector, which represents regional fold axis, has an orientation of 10408. The trace of the fold axis shown on the regional map on Figure 3.1 and on cross section C-C' (Figure 3- 3). approximated from the location of the hinge zone. trends slightly more to the southeast (1 15 O). Fold axes data display two maxima, one shallowly SE- STRUCTURAL ANALYSE OF THE KLUANE METAMORPHIC ASSEMBLAGE, sw YUKON i

- -- contoui intervals: 2 sigma~ \\ I E3:89"l Ir standard devratiori: i sigma = 0.86

Figure 3-1 8: Stereographic presentation of total Se,-schistosity, L,,+i-mineral stretching lineation and F,, mesoscopic fold axes data of the KMA. STRUCTURAL ANALYSE

€3: 126f ts mndrddivlaon: 0s CI:- 4 JON eastem Ruby Range and Dezadeash Range

Figure 3-19: Stereographic presentation of S,,-schistosity, L.+2-mineral stretching lineation and F,, mesoscopic fold axes data of the northwestem and southeastem structural domains of the KMA. 8igm = 0.u limb cil4-

Figure 3-20: Stereogra p hic presentation of S,,-schistosity, i--mineral stretching lineation and F,, mesoscopic fold axes data for the northeastem and southwestern limb of the Ruby Range anticline. plonging, the other shallowly NWglunging. Mineral stretching lineation data ciuster at Iow angles in the east. east-northeast and west. It has been noted above that regional folding is observed only in the eastern part of the KMA The KMA is subdivided into a northwestem and a southeastem domain, on the assumption that a fauît is located in the Kloo Lake lowlands (see above). Schistosity of the northwestern domain foms a moderately developed cluster, presenting a NNEdipping homocline, as obsenred by the earliest workers (Figure 3-19; McConnell, 1905). A regional anticline in the southeastern domain is reflected in the moderately developed girddk with cluster. E, (1 14110) of the schistosity is close to the maximum eigenvalue E, (12811 5) of the mesoscopic fold axes. strongly suggesting that regional and local folding are related. This was not evident ftom field data. Fold axes of the northwestem domain plunge shallowly to the northwest or southeast. No regional variation is obsenred, as both orientations are represented in single outcrops. The difference between the maxima of both domains is minimal (E, northwest: 315/05. E3southeast: 128115) and data of both domains overiap. Mineral stretching lineation in the western domain has a well developed cluster, with a shallow east-plunging maximum (91113), coinciding with E, of the schistosity in that domain. This reReds the general observation in the field that strike of foliation and plunge of lineation are subparallel. But similar to the fold axis pattern, mineral stretching lineation does not Vary significantly between both domains, their maxima being virtually identical (E, northwest: 9411 2, E3 southeast: 89109). A minor northeastem maximum is observed in both domains, and especially in the northem Rank of the anticline (Figures 3-1 9, 3- 20). This is interpreted as an original regional deviation. since it sketches from the eastem Kluane Lake shore diagonal across the domain boundaries to the western margin of the KMA. Wider scattering of structural data in the eastem domain can be explained by several granodiorite plugs or diapirs of the RRB within the KMA that deflect the foliation locally. Except for the southemmost area in the Kluane Hills no RRB intrusions are observed in ttie western domain. Structural data of the northeastem and southwestem limb of the anticline in the eastem domain are show on Figure 3-20. The most notable difFerence, apart hmthe dip direction of the foliation, which defines the limbs, is the absence of westerly trending Iineation on the noithern limb. The influence of the regional folding on the orientation of the mineral stretching lineation on the southem limb was tested by clockwise rotation of the lineation of 60" around an axis of 115/10, the approximate attitude of the regional fold axis. The result after rotation does not dRer much from the original orientation. E, changes from 91/03 to 288/14 (Appendix 3-5). A similar test was made with shear-sense indicators on the southwestem lirnb. Generally, the sense of hangingwall motion does not change after the planes containing the mineral stretching lineation were rotated around the regional fold axes, so that they approach a northerly dip of approximately 30". The direction of motion, rneasured along the trend of the

mineral stretching lineation varies only by 10-20 O (Figure 3-20, Appendix 3-6). Therefore, it is not necessary to restore shear-sense direction on the southwestem limb to pre-folding orientation. The important conclusions of statistical analysis of structural data of the KMA can be surnrnarized: 1) A subdivision of the KMA into a northwestem and a southeastem domain along a presumed north-trending fault as suggested by structural discontinuity is supported by stereographic analysis. 2) In the southeastem domain & of mesoscopic FM-folds and E, of Sn+,- foliation have identical shallowly plunging ES€-trends, suggesting that both are results of the same defonnation event. 3) The trend of the regional fold axis, E, of Sm,-foliation. is similar to the trace of the hinge zone on the map. 4) Northeasterly trending mineral stretching lineation occun in al1 domains along Jarvis River-McKinley Creek and can be interpreted as regional deviation during underplating of the KMA. 5) The direction of shear-sense has not been changed significantly on the southern limb by folding and a'lang of the regional anticline.

Certain structures of the metarnorphic assemblages of Nisling terrane afFmity and the DF bear similarities to those of the KMA. providing important information on the tectonic evolutian of the Coast Beft-lnsular Belt boundary. The orientation of schistosity of the metamorphic assemblages east of the Denali fauit, the KMA and the AMS and Nisling assemblage define a large ESE-plunging anticline, with the KMA in its core zone (Figures 3-3. 3-21). The anticline can be traced from the north end of Kluane Lake to Kusawa Lake, 200 km to the southeast. Mesoscopic open folds and crenulation folds with moderately €SE-to SE-plunging fold axes are common in biotitequariz schist of the Nisling assemblage east of Dezadeash Lake and in the Kusawa Lake area, 40 Km further east. Regional folding in the same area has a similar orientation (Erdmer 1989. 1990). WNW-trending regional open folds are also reported in the Dezadeash Formation of the Auriol Range. where they are superimposed on northerly trending folds (Eisbacher, 1976). Mesoscopic southwest-verging open folding with wavelengths of a few meters and millimeter-scale crenulation folds in the DF and greenschist units in the Jarvis River area plunge shallowly to moderately southeast (Figure 2-1 0, Appendix 3-7). The similar orientation of regional folding and local mesoscopic folds within the KM,Nisling assemblage and the DF suggest a common origin in a NNE-directed stress field. In the metamorphic assemblages regional and mesoscopic folding overprint older penetrative foliation. Sinœ the metamorphic assemblages in the eastem part are found as roof pendants wlhin the generally undefomed granodiontes of the CPC, this folding event. F,, in the Figure 3-21 : Generalized structural map of the southwest Yukon with metamorphic assemblages outlined in grey. Regional trend of foliation. mesoscopic and regional fold axes are shown. The regional foliation in the metamorphic assemblages define a €SE-plunging regional anticline, the so called Ruby Range anticline with the KMA in its core. The area east of Dezadeash Lake and the Kusawa Lake region are indicated by (1) and (2), respectively. Geology modified after Wheeler 8 McFeely (1991). Nisling terrane structural data after Tempelman-Kluit (1974), Erdmer (1 989) and Johnston 8 Tïmmerman (1993b). Structural data from the DF after Eisbacher (1976). KMA, is older than the major magmaüc phase of the Coast Plutonic Cornplex. Mineral stretching Iineation in phyllitic rocks associated with the DF at the footwall of a west-verging thrust that puts high PBigh T kyanite-gamet- staurolite schist stnidurally over the OF (Chapter 2) plunges ES€. similar to the attitude of the lineation L2in the KM.Shear-sense obtained from synkinematic homblende porphyroblasts indicate hangingwall up motion or thrusüng towards MW,in agreement with the shear direction in the KMA. NNE-trending folds in the DF at Klukshu Lake (Figure 2-15) and in the Auriol Range (Eisbacher, 1976) are interpreted as having formed in response to westward directed stress, related to the thrusting of the Nisling assemblage ont0 the OF. The age of this event is pre-Early Paleocene (see Chapter 2). Northerly trending feldspar porphyry dyke swarms can be observed from the Shakwak vailey 250 km north towards the Yukon River crosscutting metamorphic assemblages and Mesozoic and eariy Tertiary igneous rocks (Chapter 2; Muller, 1967; Tempelman-Kluit, 1974; Johnston 8 Thmemian, 1993a). In the Kluane Ranges northeriy trending subvolcanic rhyolitic to basaltic dykes are interpreted as feeder dykes associated with the Miocene Wrangel1 Plutonic Suite (Eisbacher 8 Hopkins. 1977; Dodds 8 Campbell, 1992). The dykes crosscut the mid-Oligocene Arnphitheater Formation and yield K-Ar whole rock ages of 6-16 Ma (Eisbacher & Hopkins, 1977; Stevens et al., 1982). North-trending fractures in wnglomerates of the Arnphitheater Formation and a Holocene fault were reported by Eisbacher & Hopkins (1977). North-trending brime structures and dykes in the OF, KMA and the AMS are compatible with continuous north-south stress field from Oligocene to Holocene, related to northward motion of the Pacific plate relative to North America. EVOLUTlON MODEL OF THE KMA IN THE NORTHWESTERN COAST BELT

The deformation events observed in the KMA are summarized on Table 3-1 and in the following evoluüon mode1 of the northwestem Coast Belin the Yukon. The direction of plate motion and the orientation of continental margins mentionad below refer b present day reference frame.

D" Deposition and diagnesis of the protolith of the KMA occurred in a quiet backarc basin proximal to an island arc and distal to a mature source region (North Arnerica ?) (see Chapter 5). Crenulated graphite layers in plagioclase porphyroblasts are interpreted as original bedding Sn. The age of deposition and formation of Snis not known.

D,, A slaty cleavage Sn+,developed as a crenulation cleavage in the shale. Rare F,,crenulation folds are preserved in plagioclase porph yro blasts. Sn+,is defined by parallel graphitic layen in plagioclase and gamet porphyroblasts. Larger fold structures which may be related to S,, are not observed. Regional subgreenschist burial metamorphism accornpanies D,,.

DM Sn+2-schistosityoverpnnted the slaty cleavage Swl. Parallel S, and S, in Iess deformed schist suggest that D, and O,, are not completely separate events, but the result of a continuous deformation under increasing metamorphic pressures and temperatures. Well developed S,,-foliation in the large olivine serpentinite body at Doghead Point implies that the ultramafic bodies were stnicturally juxtaposed with the calcic and aluminous schists during the early stage of S, development. This juxtaposition was the resul of tectonical interleaving of the KMA during accretion and underplating underneath the North American continental Table 3-1: Deformation events in the KMA with associated fabrics and metamorphism

Eventl Foliation Lineation Folding Fabric / Structure Metamorphism Stress field2 Age O, Sn " - original beddlng (?) dlagenesis ? 3

Dntl Sn+l Fn+1 slaty cleavage M, subgreenschlst grade ?

&type porphyroclasts M, E-W Dn.2 Sn t2 Ln t2 - Late Cretaceous schistosity, mineral regional greenschlst grade stretching Iineation

Sn+3 ht3 Fn+3 local ~~SOSCO~~Cfolds, - NNE-SSW Latest Cretaceous regional ES€-plunglng to Eariy Tertiary anticline - - gnelssification M2 NNE-SSW Early Eocene contact metamorphlsm (57 Ma) amphibolite to granulite grade norlh-trending dykes, - N-S post-Early Eocene- north-trending steep (7) post-Plelstocene faults

1: Major deformation or metamorphic events are outlined in bold. 2: Motion of Kula plate relative to North American plate In current reference Arne (alter Engebretson et al., 1995). margin represented by the AMS. Fine grainecl basal sections of oceanic sediments can be underthrusted and accreted to the upper plate at greater depth than clastic trench fill. which is being removed by offscraping in the early phase of subduction (Karig, 1974,1982). As a resuit. the sediments experience high P metamorphism and dudile defonnation (Karig & Shaman, 1975; Moore, 1989). Topographic inegularioes in the downgoing slab may cause offshearing of slivers of oceanic cnist, which are then being added to the previously accreted oceanic sediments and are preserved as serpentinites (Karig & Shamian, 1975). Lack of foliation in the smaller olivine serpentinites is explained by strain defiedion around the more rigid massive ultramafic bodies, behaving as large boudins in the more plastic schistose mata. Wth continuous deformation the schist was moderately mylonized. As a result of progressive noncoaxial deformation a mineral stretching lineation L+2 and a monoclinic fa bric, defined by Mype plagioclase porph yroclasts, were developed (Passchier & Trouw. 1996). Curved graphiüc inclusion trails in plagioclase porphyroblasts indicate that the development of the mylonitic fabric began during early stage of metamorphism. Maximum depth of approximately 20-22 km attained during underplating is preserved in grossular-rich cores of synkinematic gamets (see Chapter 4). Consistent east-plunging 4, and hangingwall up sense of shear over 130 km along strike indicates homogeneous defonnation of the KMA across its total structural thickness of 12 km. Westward hangingwall up movement requires a eastward motion of the plate that carried the KMA, which is provided by the Kula plate from -95-80 Ma (Engebretson et al., 1995). Milethe KMA-AMS interaction resulted in left- lateral oblique slip along the WNW-trending North American continental margin, furthet south, the NA continental margin trends northerly, resulting in a straight convergence with westward thrusting of the North American Nisling assemblage ont0 the DF and the development of north-trending folding of the DF. The minimum age for deformation in the KMA and overthnisting of the DF is -70 Ma, the emplacement age of a late syndefonnationai biotite granite dyke intruding the KMA and cooling ages of the CPC at an intrusive contact (Figure 2-1 5). Late Eariy Cretaceous U-Pb titan& ages (109 Ma; Mortensen, pers. comm.. 1996) of the Shorty Creek Pluton which crosscuts NNE-trending regional folds in the DF, indicate that the folding event in the DF is as old as Early Cretaceous (Eisbacher, 1976; Evenchick, 1995). However, this does not neœssarily preclude a later thnistïng event at the eastem margin. The NNE- trending folds are inte~retedas outgrowth of syndepositional slump folds (Eisbacher, 1976), implying folding shortly after deposition of the OF (135 Ma), responding to ESE-WMN compression. This may have lasted until the latest Cretaceous and resulted in development of a WNW-directed thnist further east. The relative motion of the Kula plate to the southeast from 150 Ma, and to the east from 95-80 Ma allows prolonged ESE-WNW compression (Engebretsan et al., 1995). A maximum age for underplating of the KMA is given by Late Jurassic (-160 Ma) burial of the AMS (Johnston et al., 1996). Evidence from metamorphic studies suggests that presently exposed rocks of the KMA did not remain at high pressures for an extensive period, since no high Phigh T mineral assemblages are observed (see Chapter 4). However, it does not preclude earlier underplating of KMA-associated rocks, as these rocks may remain buried.

D"+3 ESE-SE-trending mesoscopic and regional folds are common south of the RRB, and can be observed in the KMA, Nkling assemblage schist east of Dezadeash Lake and in the DF (Figures 2-10,2-15, 2-18, 3-1, 3-21). Fn+,-folds are less wmmon in metamorphic assemblages nom of the RRB, and only observed in the Nasina Assemblage at the north end of Talbot Am(Figure 2- 14), and in the White River Assemblage along the Shakwak Valley. After correction for northeastward tilting of the KMA (see D, below), F,+, -folds verge to the southwest F,, developed in response to a change in the motion direction of the Kula plate from east to NNE. F,,-folds in the KMA are developed locally and affect only meter thick layers. Tight folds are wmmonly sheared off at their base. No penetrative dudile fabric is related with D,,,. This suggests that the amount of strain that was absorbed by the KMA schist was less than during DM,, and resulted mainly in the formation of a regional anticline. Timing of 0, is constncted by latest ductile deformation of the KMA at -70 Ma and the intrusion of the RRB at 57 Ma (Erdmer & Mortensen, 1993), slightly younger than the beginning of NNE motion of the Kula plate at -80 Ma (Engebretson et al., 1995). Presence of F,,-folds in roof pendents of the Nasina and Nisling assemblages in the undefomied RRB, defiection of F,+,-fold axes and brittle deformation of F,,-folds near the intrusive contact (Figure 2- 12) suggest that D,, preceded the intrusion of the RRB.

DM Continuation of N-NNE motion of the Kula plate resulted in faulting along the Kloo Lake fault with eastward tilting of the KMA and the metamorphic assemblages to the east, followed imrnediately by sill-Iike intrusion of the major body of the RRB along the suture between the KMA and the AMS. The resulting contact aureole is wide in the KMA, but relatively nanow in the Nisling tenane assemblages to the north and south, suggesting that the KMA was situated at greater structural depth. lncreasing metamorphic pressures and younger cooling ages of the KMA to the southwest also suggest that the KMA was at stnidurally lower levels than the AMS to the north. A post-metamorphic northeast tilt of 15" can be calculated from metamorphic pressure gradients (see Chapter 4). Assuming a similar NNE dip of 30" of the schistosity for the KMA and AMS and a foliation-parallel intrusion of the RRB, the batholith intruded at an angle of 15" dipping to the NNE (Figure 4-14; Johnston & Timmerman, 1993b). A second stnicturally lower sill, which is to a large extend covered, is situated at the base of the KMA on the northeast flank of the Shakwak valley. U-Pb geochronology of the KMA and intniding granlic dykes and K-Ar cooling ages of the RRB, indicate that the main body of the RRB was emplacad at 55-58 Ma (see Chapter 2; Erdmer & Mortensen, 1993). D, did not result in a major deformation.

DM Rapid cooling of the northem KMA (1 84 "ClMa) indicate that uplitt ensued immediately after the intrusion of the RRB (Figure 3-22). Cooling rates of the struchirally lower levels of the KMA in the southwest are much slower (24"C/Ma), reflecting slower uplii The uplR was the result of underplating of the lnsular Superterrane undemeath the KMA. The fault along which juxtaposition took place is covered by thick glacial till of the Shakwak Trench, so that the nature of the fault is not known. Similar metamorphic pressures along the northem margin of the KMA (see Chapter 4) imply that it was uplifted as a homogeneous block with an axis that parallels the strike of the schistosity 0.A NNE-trending tear fault, located in the steep Dezadeash River valley, juxtaposed deep level KMA rocks with Nisling assemblage rocks that were at higher structural level during early Tertiary metarnorphism. The amount and timing of right-lateral displacement along the Denali fault zone (DFZ) is a matter of conjecture (Chapter 2; Dodds, 1991). Southeast-striking steep shear zones, interpreted as strands of the Denali fault cut Pennsylvanian to Triassic strata of the Wrangellia terrane in the Kluane Ranges, but were not observed transecting the KMA (Eisbacher, 1976; Dodds & Campbell, 1985). A number of authors (Forbes et al., 1974; Turner et al., 1974; Eisbacher, 1976; Nokleberg et al., 1985) infer an offset of 300400 km in the Eoœne (40-55 Ma) during the rapid final subduction of the Kula plate underneath North America. These large omet estimates were besed on correlation of similar metamorphic and igneous assemblages on both sides of the fault, without existence of detailed geological data. Detailed studies along the McKinley strand of the DFZ in the eastem Alaska Range (Reed & Lanphere, 1974; Csejtey et al., 1982) and tectonic modelling (Stout & Chase, metamarphic T . - - -

K-Ar, Ar-Ar

lower middle

phase of Coast empbcemmtaf ~~utonicCornpieu granodkrite of and RRB Ruby Range Bathdith

Figure 3-22: Blocking temperature (Te)versus geochmnological age detemination of U-Pb zircon. monazite and xenotime, K-Ar (dark grey) and '"Ar-?4r (light grey) muscovite and biotite. Cooling rates are presented for various KMA samples from the upper and lower structural level of the KMA. Black bars represent uncertainties of Tc (after Heaman 8 Pamsh, 1991). Wic of ellipsoid reflects unceitainty of age detemination. Radiogenic data fmm Farrar et al. (1 988), Mortensen & Erdmer (1992) and this study. 1980) suggested that Cenozoic dextral offset along the DFZ mey amount to only 10-90 km. It is questionable that coeval rapid uplifk of the KMA, which requires northward underplathg or southward thnisting. could have been accomplished if a major steep strike-slip fault was located outboard the unroofing KMA. Current seismic activities are restricted to the Duke River and Totschunda fault zones to the southwest (Horner, 1983). Coinciding with post-Early Eocene uplift is the emplacement of hyollic to andesitic nom-trending dykes throughout the KMA and AMS in the Oligoœne to mid-Miocene (7) (Eisbacher & Hopkins, 1977; Stevens et al., 1982). The fault that juxtaposed high grade metamorphic rocks of the KMA against low grade rocks of the lnsular Supertenane and DF in the south may have been transformed into a steep southwestdipping reverse fault, as a result of NNW-ward subduction of the Pacific plate undemeath North America (Lowe et al., 1994). Altematively, the Shakwak valley is the site of a Pliocene graben, along which the southwall with the St. Elias Mountains continues to rise (Tempelman-Klul, 1980). North-trending brittle dextral (?) faulting in the KMA has been active into the Holocene, evident in well preserved fault scarps (Figure 3-17).

Mylonitic rocks of the Kluane metamorphic assemblage record two major deforrnation phases that can be related to the direction of motion of the Kula plate:

1) Late Mesozoic eashnrard movement of the Kula plate (Engebretson et al., 1995), relative to the North American craton, resulted in oblique left-lateral slip along the North American continental margin. represented by the AMS. During this period of oblique convergence the KMA was accteted ont0 North America by underplating the AMS. resulting in the development of a mylonitic fabric in the KMA with homogeneous westward hangingwall up sense of shear. Timing of accretion is confined by Middle Jurassic high pressure metamorphism of the AMS, eastward motion of the Kula plate (-95-80 Ma) and latest Cretaceous synkinematic graniüc dykes intniding the KMA. The existence of sinistral strike-slip along the North American continental margin, as postulat& by Rubin & Saleeby (1991) and Monger et al. (1994). at the time of accretion of the KMA is likely. However, since the KMA represents only the deep seated ductile part of a subduction zone. any evidence of brittle faulting was eroded during subsequent unroofing. Likewise, turbidites and mdanges, the upper portion of an associated accretionary prism. are also not preserved.

2) Change of relative motion of the Kula plate hmeast to NNE dunng the latest Cretaceous resulted in ESE-trending, predominantly southwest-verging folding in the metamorphic assemblages and sedimentary strata at the continental margin of North Amerka. Subsequent silClike intrusion of the RRB, a Late Cretaceous-eariy Tertiary apophysis of the CPC. overprinted the suture between the AMS and the KMA. Post-Early Eocene fast northward motion and consumption of the Kuia plate led to northerly underplating of the KMA by the DF and Alexander terrane to the south, resulting in differential uplift of the KMA with a relative northward tilting of the metamorphic assemblages. Right-lateral strike-slip faults may have developed in the lnsular Superterrane in front (outboard) of the late Cretaceous suture zone. Chapter 4

Metamorphic evolution of the Kluane metamorphic assemblage INTRODUCTION

The importance of mineral assemblages as indicators of metamorphism was first recognitad by Rosenbusch (1877), w ho observed distinct mineral parageneses in dates around granites in the European Vosges. The appearanœ of new minerals, designated as index minerals, towards an intrusive contact, first described by Barrow (1893). and the definition of metamorphic facies (Eskola. 19 15) and metamorphic grade (Tilley, 1924) allow qualitative statements on prevailing temperatures during metamorphism. The pressure (P) and temperature dependence of mineral equilibria reactions are determined by thermodynamics. and allow for the development of petrogenetic grîds, which show these reactions in P-T spaœ (e.g. Spear 8 Cheney, 1989; Powell & Holland, 1990), and provide more quantitative P-T estimations hmobserved mineral assemblages. Thus, the P-T conditions during metamorphism can be approximated by thorough petrographic studies. Geothermobarometry is the calculation of P and T by using electron microprobe chemical analyses of mineral phases in conjunction with cornputer software programs. such as TWQ 2.02 (Bernian, q996). The Crst part of this chapter summarizes previous studies on metamorphism in the Kluane metamorphic assemblage (KMA). Next. a detailed petrographic study along an exemplary section of the KMA describes textural relationships between mineral phases and help to define mineral isograds and metamorphic zones. The mineral isograds outline a contact metamorphic aureole parallel to the contact wîth the Ruby Range Batholith (RRB) wlh an inverted metamorp hic gradient. Geothemobatometric studies on 22 samples are presented in the third part of this chapter. As a result two major metarnorphic events can be distinguished in the KMA, an earlier syndefomiational low Tlhigh P metamorphism and a high Tllow P event, which can be conelated to the Late Cretaceous-Early Tertiary emplacement of the RRB. The P-T-t evolution of the KMA defines a clockwise path, characteristic of an underthrusting or underplating event, followed by relatively fast uplift and subsequent thermal overprinting in the PaleoceneEocene. Higher P and younger 'OArOSgArcooling ages in struchirally lower parts in the southwest indicate that the KMA expefienced northward tilong during post-Eariy Eoœne uplift. Comparison with adjacent pericratonic metamorphic assemblages of Nisling terrane affinity suggests that the KMA was acaeted to North America between post-Mid Jurassic to Late Cretaceous.

PREVIOUS STUDIES

Muller (1967) observed an increase of metamorphic grade in mica- quartz schists of the KMA from greenschist to amphibolite grade towards the contact with the Ruby Range batholith. Tempelman-Kluit (1974) recognized that regionally metamorphosed schists (homfels unit PPsqr) in the southem Ais hihik Lake area were themally overprinted. Whether this occurred during two distinct metamorphic events or was the result of regional metarnorphism with a late thermal event remained ambiguous. A prograde sillimanite-grade overprint of the btqtz schist, with temperatures of 530460°C. increasing towards the contact with the Ruby Range Batholith (RRB), was reported by Erdmer (1991). A decrease in metamorphic grade of the KMA towards the south was suggested by Eisbacher (1976), in agreement with his interpretation of the KMA as a metamorphosed equivalent of the Dezadeash Formation (OF). Eisbacher's descriptions are vague, however, and the lower grade schist, is more likely a coane-grained phyllite of the DF, as discussed in Chapter 2 (Figures 2-1 5, 2-21), instead of a biotitequartz schist with KMA affinity. K-Ar and 'OAr?'Ar ages obtained from micaquartz schists of the KMA range from Paleocene to Eoœne, and are interpreted as cooling ages related to the Late Pakoœne to Eoœne (5057 Ma) intrusion of the RRB (Erdmer 8 Mortensen, 1993; see Chapter 2). The oldest ages (50-55 Ma) were obtained in rocks close to the contact with the batholith to the north, and younger ages (39-43 Ma), at the eastem shore of Kluane Lake. indicating slower cooling in the souaiwest (Appendà 2-5, Erdmer 8 Mortensen, 1993). An earlier radiometric K-Ar age of 140 Ma (Lowdon, 1960) of the KMA is regarded as unreliable due to low K-content of the analyses (Erdmer & Mortensen, 1993). These studies date contact metamorphism at 50-55 Ma.

METAMORPHIC MINERAL ZONES IN THE KMA

Introduction

Mineral assemblages described in this study were obtained by optical microscopy and electron microprobe analyses of over 150 thin sections of samples collected by P. Erdmer and the author during field work from 1989 to 1995. Due to the small grain size, definitive identifcation of most diagnostic minerals in the field, with the occasional exception of gamet, was generally precluded. Mineral assemblages and sample location of al1 thin sections are listed in Appendix 2-1. Metamorphic indicator minerals and index mineral isograds for the whole KMA are shown on a regional map (Figure el),as well as a detailed rnap area in the Ruby Range (Figure 4-2), with accompanying cross-sections (Figure 4-3). Obsewed mineral assemblages and the appropriate reactions from one zone to another are Iisted on Table 4-1. The reactions are based on the petrogenetic grid of Spear & Cheney (1989) and Powell & Holland (1990) as quoted in Spear (1993) and Bucher & Frey (1994), respectively. It involves reactions in the CAS-HC (Cao, A1203,SiO, H20, CO&, FASH (FeO. A120,, SiO,, H,O), KFASH (b0,FeO, AI,O,, Si4, H,O), KFNASH (60,FeO, Na20, AI,O,, SiO,, H,O) and KFMASH (&O, FeO, MgO, A1203, SiO,, H,O) systems (Figure 4-4). AdditÎonaI components can change the location of individual equilibria on the petrogenetic grid. Sufficient Mn0 and Cao, which are not considered in the systems above, can significantly lower the first occurrence of

Figure 4-2: Oetailed index mineral and mineral isograd map of the KMA in the central Ruby Range (see Figura 4-1 for location). Dashad line marks the appmximate lithological ôoundary between calcic schists of the KMA to the south and aluminous schists to the north. Grey lines mark the locations of cross-sections of Figure 4-3. fe' Table 4.1 : Mineral1parageneses and reactions for micaquartz schist of the KMA with increasing metamorphic grade calcic sequence: reaction#: ms, chl, eplcro, cal, kfk (7) 1 (1) 8kfs+3chl=5ann+3ms+9qtz+4H,O bt. ms, chl, EO?#!a I (2) 2uo+3qtz+5cal=3grs+H20+C0, grt, bt, ms, chl, I epluo

aluminous sequence: grt, bt, ms, çhl I (3) ms + qtz + grt + ch1 = st + bt + H,O st grt, bt, ms 1 (4) 75 st + 312 qtz = 100 alm + 575 andlsil + 150H20 (5) st = grt + bt + andlsil silland, a, grt, bt i ms L (6) and = si1 sil, gnd, sf, grt, bt f ms (7) 2bt+6ms+15qtz=3crd+8kfs+8H20 L (8) 2alm + 4 andlsil + 5 qtz + n H20= 3 Fe-crd (9) 6 andlsil+2 bt+ 9 qtz= 3 Fe-crd +2 kfs + 2 H,O crd, m.&, kt*mgd, ms 1 (1 0) 2 si1 + alm = Fe-crd + hc spl (hc), crd, kfs, yl. M * ut 1 (1 1) bt + si1 = crd + grt grt, crd, kfs, spl (hc), sil, bt

Phases in bold afiar for the first time, phases underlined are king consumed. Reacbon (1) applies for the KFNASH system: K ,O. FeO. Na,O . SiO,, H20. Reaction (2) applies fa the CASHC system: Cao. Al ,O,. SiO,. H20. CO2 Reaction (4) applies for FASH system: FeO, Ai ,O3, SiO,, H,O. Reactions (8). (9) apply for the KFASH system: K ,O, FeO, AI&, SiO,, Hg. Reacüons (3). (5). (7). (10). (1 1) apply (br the KFMASH system: K ,O1 FeO. MgO. A12°31 SiO,. HzOc

1: Plagioclase and quark are present in al1 assemblages. 2: Reactions (1). (2). (4), (5), (6),(7), (8). (9) are taken hmBucher 8 Frey (1994); reactions (3) and (1 1) from Spear 8 Cheney (1989) are not balanced (see p. 345 in Spear (1993)), reaction (10) ftom Chacko (pers. comm., 1997).

119 Figure 44: Petrogenetic grid applied to micaquartz schist of the KMA. Equi- librium reactions are taken frorn Bucher 8 Frey (1994) and Spear & Cheney (1989). Note that Mn- and Ca-bearing phases are not included in the reactions. Reaction numbers refer to Table 4-1. Diamonds represent P-T estimates for samples analyzed in this study. Aluminosilicate triple point is taken from Holdaway & Mukhopadhyay (1993). Dashed line marks andalusite-sillimanite reaction after Richardson et al. (1969). H,Osaturated pelitic solidus cuwe after Spear (1993). Facies division is after Bucher 8 Frey (1994). gamet from -500°C in a Fe4ch system to 450°C (Bucher & Frey, 1994; Spear, 1993). At best these readons are valid as a general guide and have to be evaluated together with as many other equilibria as possible, especially if a substantial amount of additional components (Cao, MnO) is present. Tilley (1924) originally defined the term 'isograd" as a line joining points of similar P and T. Such a definition assumes detailed themodynamic knowledge of minerals and mineral reactions and is unrealistic given the scope of the present study. lnstead the term 'isograd", as used in this study, marks the first observance, in a prograde sense, of a new mineral or mineral assemblage, drawn as a line on the map to provide a general, if incomplete, overview of the mineral parageneses. In addition, the disappearance of a mineral phase due to a prograde readion can be shown on the map as an "upper stability" isograd.

Metamorphic character of the KMA along traverses in the Ruby Range

The metamorphic character of the KMA can best be descr-ibed along two SSW-NNE sections in the Ruby Range, that cover approximately 14 km of surface exposure of the KMA ecross strike, Rom the lowest grade rocks near the Kluane Lake shore to the highest grade assemblages near the contact with the RRB a Venus Creek (Figures 4-2,4-3). The schist of the KMA in that area has a homogeneous N-NNE dipping schistosity and strikes approximately parallel to the contact with the RRB. Although the intrusive contact is not exposed in that area, there is evidence elsewhere in the Ruby Range that the RRB overlies the KMA. Along the eastern Kluane Lake shore and on Jacquot Island, epidote- bearing chlorite-muscovite schist, as described in Chapter 2, represents the lowest metamorphic grade in the KMA. Prograde biotite fiist appears growing folioform on chlorite, and with decteasing distance to the intrusive contact of the RRB hcreases in abundance, growing more randomly. Biotite crystals overgrowing the foliation are cornmon, implying post-kinernatic growth. Biotiie is formed by the breakdown of potassium feldspar and chlorite at approximately 400 "C (reacüon (1 ), Table 4.1 ; Bucher 8 Frey, 1994). Simultaneous with biotite abundanœ increasing from 4 to 5 vol.%, 13 km away ftom the contact with the RRB, the chloriteImuscovite ratio decreases, as biotiite and muscovite are produas of the chlorite-consuming reacbion (1). In ACtich pelites, chloritoid would be the next mineral to fonn in a prograde metamorphic sequence. However, chloritoid is absent in the ms-chl schist, which can be attributed to the deficiency of aluminum in the calcic unl of the KMA. Coexisting clinozoisite and gamet are found in a narrow zone (-1 km) near the calcic-aluminous schist contact (Figure 4-2,4-3). Ca-rich gamet (grossular) can be produced by the breakdown of clinozoisite and calcite according to reaction (2). Gamet. clinozoisite, bioüte, muscovite, chlorite, plagioclase and quartz represent the highest grade mineral assemblage observed in the calcic schist of the KMA. The first mineral assemblage observed in the aluminous schist consists of gamet, biotite, chlorite, muscovite. plagioclase and quartz. Biotite overgrowth of the foliation plane results in a more gneissic appearance of the schist. The lrst prograde appearanœ of staurolite, 9 km away from the contact with the RRB, indicates that the lower amphibolite facies (-520°C) is reached. Abundant subhedral to euhedral, 0.25-1 mm long, stubby staurolite crystals, with common twinning and zoning, occur within a 2 km wide zone. Not far behind the first prograde occurrence of staurolite. the abundance of biotite increases, while muscovite is reduced to an accessory phase and chlorite disappears completely. Beyond the staurolite-isograd, chlorite occurs only as a retrograde alteration product of biotite. Staurolite and biotiite are formed by the breakdown of chlorite. muscovite and gamet, according to reaction (3). Andalusite and sillirnanite appear simultaneously on the western section of Figure 4-3. Andalusite foms large poikilitic porphyroblast, with abundant inclusions of biotite and graphite. SiIlimanite grows as small acicular fibrolite needles. Fibrolite generally nucleates in biotite and grows parallel to its cleavage (Figure Ma). Outside biotite grains the fibrolite needles generally fan out and display no prefened growth orientation. Concurrent.witha steep increase in the abundance of sillimanite and andalusite, from cl to 5-10 vol.%, over less than one kilometer along the section in Figure 4-3, the staurolite abundance experiences a sharp dedine. Over the next 34km staurolite is mantled by andalusite (Figure 4-5) and restricted to small (c 250 pm) anhedral and embayed relics within andalusb grains. This suggests that andalusite was formed as a product of staurolite breakdown (reactions (4) and (5)). P-T constraints cm be obtained hmthe breakdown of staurolite to fom andalusite and coexisting sillimanite, but depend on the A12Si0,-triple point chosen. This assemblage would plot at 2.5 kbar and 600°C. using the Holdaway 8 Mukhopadhyay (1993) mode1 and at 4.5 kbar and 630°C affer the Richardson et al. (1969) model (Figure 4-3). Spear (1993) suggested that the later model may represent the triple point for fibrolitic sillimanite. Estimated pressure of a nearby sample (4.5 kbar, 89-49a, see below) are similar to Richardson et al.'s (1969) triple point. Fibrolite growth at the rim of andalusite (Figure 4-5) indicates a replacement of andalusite by fibrolite due to increasing metamorphic temperature (reaction (6)). Coexisting andalusite and fibrolite are observed along 2.5 km on the western section. No andalusite was observed in the eastem section, where temperature andlor pressure exceeded the stability field of andalusite. Here, staumlite relics are commonly mantled by plagioclase or, at higher grade, by cordierite. The fint prograde cordierite appearance coincides with the breakdown of andalusite in the western section, and a decrease in biotite abundance from 30 to less than 5 vol.% along the next two kilometen. Biotite grains are embayed and do not form continuous bands along the foliation plane. These observations suggest that biotite is consumed in a cordierite-foming reaction (Figure 4-6). SiIlimanite abundanœ is also negatively correlatecl with the amount of cordierite in a sample. Some cordieriterich samples do not contain Figure 4-5: Photomiciograph of a biotitequartz schist of the KMA in the Ruby Range (89-341). 1.5 km after the fi& prograde appearanœ of andalusite and sillimanite (as acicular fibrolite) staurolite ocairs only as relics mantled by andalusite. This suggests that staurolite is being consurned by an andalusite foming reaction ((4) andlor (S), see text for discussion). In wntrast to the embayed crystals in this sample. staurolite is more abundant and forms euhedral porphyrobhsts in samples further away from the RRB. Fibrolite needles (arrow) growing at the rim of andalusite imply replacement of andalusite due to increasing temperature towards the contact with the RRB. Scale bar= 0.5 mm. XPL Figure 4-6: Photornicrographs that show the effed of aie appeannce of cordierite on the texture of the biotite schist of pelitic KMA schist of the Venus Creek section (Figure 4-3). a) Bioüte grains in this andalusite-sillimanite- staumlite-bearing bioütequartz scbist (89-Ma, sam as in Figure 4-5) are large and define th8 foliation (top nght to lower left). Fibrola nucîeates epitaxial in biotite in the upper left corner (arrow). b) In this sample (8945). which Es shown at the same scale, cordierite, recognizable by yehv alteration rirns, replaces biotite and sillimanite (reactions 0,(8), (9)). In the cordieriterich central portion of the sedion biotite grains are small and embayed. and do not define continuous layers as in the cordieriteabsent shown in a). Fibrolite is abundant in cordierite absent parts (top of section), but found only as inclusions in cordierite in the cordierite-rich amas. Scale bars,. 0.5 mm. PPL any sillimanite at all. Cordierite in contact with or enveloping gamets is common (Figure 4-7). According to these textural relations, cordierite can be the product of the breakdown of muscovite and biotite (reaction (ï)).almandine gamet and sillimanite (=action (8)),or sillimanite and biotite (reaction (9)). Reaction (8) probably has contributeci most of the cordierite. In the eastem Dezadeash Range, gamet, being consumed in reaction (8). is absent in a 8-1 0 km wide zone in the cordierite-bioüte schist (Figure 61). The absence of K-feldspar, a product of =actions (7) and (9). as a major phase in most cordierite-bearing samples suggests that these reactions are only minor contributors to wrdierite. K-feldspar, which has not developed twinning, can be distinguished from plagioclase by EDS (Energy Dispersive Spectrornetry) analyses with an electron microprobe. and was only obsenred as a major phase in the eastem Dezadeash Range (90-35, Figure 4-9) and the eastem Ruby Range (94-120). However, no systematic search for K-feldspar was undertaken for most samples, so that the extent of K-feldspar and thus the contributions of reactions O and (9) are not exactly known. Also, the scarcity of muscovite (~2vol.%), a major reactant in reaction (71, indicates that the reaction is only a minor contributor to cordierite, which makes up an average of 10 vol.% of the schist. Reactions (8) and (9), which include only the Fe-end member of cordierite, plot at lower P than the estimated P calculated for cordiente-bearing sarnples (Figure 4-4). However, the analyzed cordiente grains contain a substantial amount of Mg (XMg=60),which increases the stability field of cordierite towards higher P. P estimates of 44.5 kbar at 675°C (Figure 4-4) are close to the location of reaction (8) with &=60 according to Holdaway & Lee (1977). The cordierite-forrning reaction (7) consumes muscovite wmpletely so that primary muscovite is generally absent in cordierite-bearing schists. A muscovitesut isograd can be traceci close ta the cordiente-in isograd (Figures 4-2 and 4-3). Fine grained muscovite growing at the rim of cordierite is the produd of retrograde alteration of cordierite, known as pinitization. Poikilitic Figure 4-7: Photomicrograph of gametcordierite-sillimanite-biotite schist, within 2 km of the contact with the RRB at the Venus Creek section (8982a, Figure 43). The comâed and embayed rims of gamet (grey with da* inclusions). partly mantled by cordierite (am),suggest that gamet is being consumed by the cordierite producing reaction (8) (sec text). Scale bar 0.5 mm. PPL

Figure 4-8:P hotomicrograph of a sillimanitsgametcodieritebiotiteschist of the KMA within one kilometer of the contact with the RRB near Twetfth of July Creek (94-174). A gamet (tenter), dark green hercynite (black am)and colourless coarse sillimanb (white amw) are found mina large colourless, low relief cordierite porphyroblast, occupying most of the photomicrograph. The embayed nrn of the gamet crystal and the presenœ of sillimanite predominantly as inclusions in cordierite, indicate that both phases are being consumed by a cordierite-fonning reaction. See text for discussion. Scale bar 0.5 mm. PPL

Figure 4-9: Backscatter images of K-feldspar-bearing cordientebiotite schist of the Khiane metamorphic assemblage in the eastem Dezadeash Range (sample 90-35). a) K-feldspar (medium grey) grows at the expense of biotite (Iight grey), obvious in the ernbayments of K-feldspar in the biotite grain (white arrow). The black shading represents quartz. b) K-feldspar and cordierite (dark grey) are in contact with biotl. The white arrow indicates where cordierite is consuming biotiie. This textural evidence shows that cordierite and K-feldspar are fomed by the cansumption of biotite (and muscovite, not shown here), according to reacüon (6), implying T above 600°C. The redangular patterns in the images are due to reproduction limitations. texture of millimeter-sized muscovite crystals, cornmonly overgrowing cordierite and biotite, obsewed in cordierite-biotiterich rocks in the eastem Dezadeash Range, is also interpreted as indication of retrograde metamorphic growth. Close to the contact with the RRB, herqnite, a Fe-Al-spinel, can be obsewed in the wre of coidierite. It occurs first as equigranular, 10-20 prn euhedral cubes or Worms, and toms larger and more coherent grains doser to the intrusive contact (Figure 44). The presence of anhedral gamet inclusions in some cordierite crystals and fibrolite cornmonly suimunding hercynite within the cordierite suggest that the spinel is fonned by a gamet and sillimanite- consuming reaaion (IO) (T. Chacko, pers. comm., 1997):

2 si1 + alm = Fe-crd + hc.

For sample 90-35 TWQ calculates this reaction at 700°C and 4 kbar. This is in good agreement with the P-T estimates of 690°C and 4.6 kbar obtained from the grt-crdins-pl assemblage of the same sample (Figure 4-3). The highest grade assemblage realized in the KMA is found in the eastem Dezadeash Range, and consists of cordiente, sillimanite, K-feldspar, biotite, hercynite (nucleating in crd) and gamet (Figures 4-8, 4-9). This assemblage is characteristic of the lowermost granulite facies. The gamet, poikilitic and inclusion-free, is likely a prograde formation, possibly formed by the biotite- and sillimanite-consuming reaction (1 f ). Parallelisrn of mineral isograds with the exposed contact of the RRB and increasing metamorphic grade towards the contact strongly suggest that the above described rnetamorphic sequence is the mutof contact metamorphism related to the intrusion of the RRB during Paleocene-Eocene time. The individual isograds are generally parallel and do not cross each other, with the exception of the andalusiteout isograd. As coexisting andalusite and sillimanitefibrolite occur in several locations, a slight temperature variation has a large impact on the trace of the andalusite isograd. The increase in rnetamorphic grade from structurally Iower towards structurally higher rocks near the contact with the RRB indicates an inverted metamorphic gradient on the underside of the batholith. A normal metamorphic gradient can be obsenred at the southem end of Kluane Lake in the Kluane Hills. However, there the peak metamorphic grade (gamet zone) is less than in the Ruby Range (cordierite zone). From this is cm be deduced that metamorphism in the KMA is caused by an overiying batholith, the RRB, and by a smaller underlying sill. The thickness of the contact aureole. beginning with the staurolite isograd, measured perpendicular to the contact wiai the RRB, and assuming an average dip of 35" of the KMA to the north, and a northdipping sill-like RRB. is approximately 4-5 km at the Venus Creek section. The relative great depth of emplacement of the RRB (ca. 12 km, see next section) and a. prior to the intrusion, already hot KMA are major factors that cause the relative thick contact aureole. In the eastem Ruby Range and the Dezadeash Range. the minerai isograds are deflected by larger intrusions of the RRB within the KMA, effectively widening the high grade assemblages towards the southeast. The surface width of the cordierite zone of 10-20 km in the southeast is probably caused by igneous rocks of the RRB that underlie the KMA, but are not exposed, rather than representing the actual thickness of the contact aureole. In the western Ruby Range the surface of the mineral isograds is approximately parallel to schistosity of the KMA, as the KMA underlies the RRB. In the central Ruby Range and the Dezadeash Range, where isograds are deflected by intrusive plugs of the RRB, they probably cross structural fa brics.

GEOTHERMOBAROMETRY OF THE KMA

Introduction

The mineral parageneses described in the previous section are good indicators of the metamorphic grade of the KMA. Although metamorphic temperatures are well constrained by mineral equilibria, the steep slope of most equilibria readions does not provide good evaluation of metamorphic pressures (Figure 44). Quantiitive estimates of P and T can be obtai.ned by geothermobarometry. Geothermobarornetry utilùes the compositional changes of certain minerals with changing P-T conditions to calculate prevailing pressure and temperature during crystal formation (Spear, 1993). Geothermometen are based on exchange reactions, which involve cation exchange between coexisting minerals. without producing or consuming a new phase. These readions are pressure insensitive, due to negligible volume changes. The most comrnon geothermometer for metapelites is based on Fe-Mg exchange between gamet and biotite (reacüon (12); Thompson, 1976): ph1 + alm = ann + py.

Net-transfer reactions are used as geobarometers. These reactions produce and consume mineral phases, and are often associated with large volume changes, thus providing better barometers (Spear. 1993). A common barometer for metapelites involves the formation of Grossular, Aluminosilicates and quartz (S) from anorthite (P), known as GASP (reaction (14); Ghent. 1976):

grs + 2 sillandky + qtz = 3 an.

Uncertainties in pressures and temperatures calculated from these reactions result from uncertainties in the microprobe analyses, the P-T location of the end-rnember reacüon. and activity-composition models for rninerals showing solid solution. Kohn 8 Spear (l991a, b) provide a detailed discussion of the total P-T uncertainty expected from a combination of al1 these sources as well as the fraction of the total uncertainty attributable to each source. They estimate total unœrtainties of about 13 kbar and *75"C (la) for P-T estimates obtained using the gamet-biotite thennometer and GASP barometer. Importantly. only a small fraction (-540%) of this total uncertainty is attributsble to uncertainties in the microprobe analyses. This observation is significant, because it shows that P-T dfierences between samples are resolvable to about k300 bars and tlOUCprovided that the same set of thennometers and barometers, and a consistent set of calibrations and activity- composition models are used for al1 samples. 22 samples of gamet-beanng biotitequartz schist of the KMA and one rnicaceous quarbite of the AMS (PAW of Johnston 8 Timmennan, 1993a. b) were seleded for gsotherrnobarometry. In addition two phyllites of the OF and a micaceous quartrite of the Nasina Assemblage were analyzed for geothemometry. The criteria for the selection were based on a representative coverage of the KMA. the influence of the RRB intrusion on the country rock. the lack of retrograde alteration of minerals, and the presenœ of the appropriate mineral assemblage for geothemobarometry. The ideal mineral paragenesis in rnetapelitic rocks includes gamet, biotite, plagioclase and muscovite or cordierite. Coexisting staurolite and aluminosilicate phases help constrain P and T estimates. Quality and accuracy of geothermobarometric studies depend on a maximum mineral paragenesis. For that reason and due to field circumstances. the whole area underlain by the calcic schist, does not contain the essential gamet and is therefore not suitable for geothenobarometry. Once selected, the mineral composition of gamet, biotite, muscovite, cordierite and plagioclase of each sample was determined by eledmn microprobe (type ARL-SEMQ and JEOL JXA-8900R) at the University of Alberta. Descriptions of the equipment and the mineral standards, as well as the probed samples, are given in Appendices 4-1 and 4-2, respectively. Microprobe results of the probed minerals are listed in Appendices 4-3 through 4-8.

Estimation of metamorphic pressures and temperatures using cornputer generated equilibria reactions

Pressure and temperature were estirnated frorn intersections of mineral equilibria calculated by the computer program TWQ (version 2.02) (Beman, 1996). TWQ (Themiobarornetry With estimation of EQuilibrium state) calculates the P-T position of these equilibria using an intemally consistent set of thermodynarnic data for end member phases and adivity-composition relationships for minerals showhg solid solution. The convergence of al1 possible reaction curves in a single point in P-T spaœ is regarded as the equilibration point of al1 minerals involved (Berman, 1991). Therefore the tightness of the intersections can be regarded as an indicator of the quality of the state of equilibrium reached in the specific sample. It is not to be confused wlh the uncertainty. No specific uncertainhies are given for the intersections (see above for discussion on enors in geothermobarometry). Reproducibility and similar results with comparable samples as well as correlation with observed rnineral parageneses are regarded as an indication of the accuracy of the technique. Average pressures and temperatures for each sample are shown on a P-T grid on Figure 4.10 and in map fom on Figure 4-1 1. The application of the computer program TWQ 2.02 is described in Appendix 4-9.

Results and discussion

Equilibria reactions for gamet core and rim compositions in combination with average biotite or matrix biotite, were calculated for afl samples graphically, as shown in Appendix 4-10. According to the rnineral phases present, the gamet-biotitemuscovite-plagioclasegeothemobarorneter was applied on samples fram the staurolite zone, and a gamet-biotite-plagioclase- cordierite themiobarometer for cordierite-bearing samples that do not contain any pnmary muscovite. Gamet rim and matrix biotite values generally do not provide such tight intersections as do gamet rimantact biotiie points, which corne closest to an actual state of equilibrium within each sample. However, re- equilibration of biotite in contact with gamet during cooling will result in lower T than peak metarnorphic T. The generally wider scattered intersections of gamet core and average values suggest that these points are not in Figure 4-10: Pressures and temperatures of micaquark schist of the Kluane metamorphic assemblage and one granodiorite of the Ruby Range Batholith (94-147d) averaged from equilibria reaction internons, shown on the right diagram, calculated by TWQ 2.02 (Bennan. 1996). Sample syrnbols refer to mineral assemblage observed in thin sections of anaiyzed sampies. Staurolite was not considered in the calculations. but its presenœ in probed samples provides independent information on the acwracy of P-T data. Note that staurolite is cunstrained to its staôility field (after Spear, 1993) and cordierite is on ly present in higher temperature assemblages. See text for discussion on rnethodology and Appendk 4-9 for description of cornputer program. The rigM P-T diagram displays the triangles calculatd by TWQ 2.02 (Berman, 1996). that were used to estimate P and T for each sample. No triangles are shown for the samples shown in grey on the lefî diagram (03-77, 9340). as their spread is very large and exceeds the scale of the diagram. See Appendix 4-10 for their equilibria reaction diag rams. Aluminosilicate triple point, H,O-saturated pelitic solidus curve and facies division are after Holdaway 8 Mukhopadhyay (1993). Spear (1 993) and Bucher 8 Frey (1994), respectiveiy. Dashed grey Iine marks the location of the andalusite-sillimanite reaction after Richardson et al. (1969).

Figure 4-11: Geological map with pressure and temperature estimated from equilibria calcubted by TWQ (2.02) and displayed on P-1 diagrams on Figures 4-4 and 4-10. Only samples with good reaction intersections are shown. See text for detailed discussion. Geology is the same as on Figure 2-1. equilibrium, therefore P-T estimations for gamet core values are meaningless. The PTspread used in the followhg discussion describes the tightness of the equilibria reactions intersections and is not to be wnfused with error or uncertainty. Most samples of the btqtz schist of the KMA duster in two areas in P-T space (Figure 4-10). These clusters can be correlated with index mineral zones. gamet composition and geographic location. Samples that plot near the alurninosilicate triple point, at 4 kbar and 550°C. are from the staurolite zone. There is good agreement between P-T estimates presented in Figure 4-10 and observed mineral parageneses. All samples that plot in the staurolite stability field shown on Figure 44contain several weight percent staurolite. Andalusite and fibrolite are wmmon accessory phases. Outcrops in the vicinity of aluminosilicate-free samples contain either andalusite or fibrolite, or as in the case of 9447. both phases. The staurolite bearing samples have a P-T spread from M.7-1.9 kbar and î1540°C. Two of the samples (93-77and 93-80) that are shown in grey on Figure 4-4 have average P and T of 6.5 kbar and 575°C. which places them in the kyanite field. However. kyanite has not been observed, and a spread of 13 kbar and &75"C of the equilibria reactions. suggest that the probed mineral phases of these samples were not in equilibria. A second cluster of samples lies within the cordierite stability field at 4 kbar and 675°C. corresponding to a depth of 12 km (Figure 4-1 0). All samples are from the cordierite zone of the KMA, and most of them contain cordierite, as well as abundant sillimanite. The absence of staurolite is in agreement with the location of the samples outside the staurolite stability field. Reaction intersections obtained frorn cordiente-bearing samples are generally tighter than those from staurolite zone samples, with some intersecting at one spot (94-1 20,94283a. Appendix 4-1 O), suggesting that the probed phases in one sample come close to a chemical equilibrium. Sample 94-81 yields a tight intersection (3.3 kbar, 630°C) by using muscovite, while a wider scattered intersection (4.2 and 660°C) results from using cordiente instead (Appendix 4- 10). The cordierite P-T estimate is similar to other samples along strike and is thought to tepresent the peak metamorphic conditions, while the muscovite P-T is due to re-equilibration during uplift. The P-T estirnates fiom the cordierite-bearing samples plot at higher T than the solidus cuwe for water saturated metapelites. However, the samples do not show signs of migmatization, suggesting that these rocks were water undersaturated during peak metamorphism. The staurolite and cordierite zone samples have distinct gamet compositions. Photomicrographs. compositional zoning profiles of gamets and calculated equilibria reacüons for gamet rims from the staurolite and cordierite zone in the Dezadeash Range are shown on Figures 4-12 and 4-13. The gamet from a staurolite-bearing schist (9380) appean cloudy, due to minute graphitic inclusions. Its rim is corroded and embayments are abundant (Figure 4-1 2a). Biotite and staurolite in contact with the gamet suggest it is being consumed to form staurolite and bioüte according to reaction (3). An electron microprobe profile across the gamet shows distinct compositional zonation of the grain (Figure 4-1 3a, also see Appendix 4-1 1). Fe and Mg increase, while Ca, Mn and the Fel(Fe+Mg)-ratio decrease towards the rim. The compositional change reflects changing P-T conditions or a change in bulk composition during the growth of the gamet. This zoning pattern is known as growth zoning and is commonly observed in greenschist and amphibolite grade rocks (Spear, 1993). Preserved growth zoning indicates that the sample has not been heated long enough above 600°C, at which chemical diffusion is sufficiently rapid enough to homogenize the composition of gamets over hundreds of Pm. The "bell-shapedn profile with decreasing Ca towards the rim is typical of heating following decompression (Spear, 1993). In contrast, gamets from the cordierite zone often aie clear and poikilitic, with less altered nms (Figure 4-1 2b). Eledron microprobe cross-sections show no compositional zoning, implying either homogenization by diffusion at temperatures above 600°C or new crystal growth (Figure 4-1 3b and Appendix 4-1 1). Figure 4-12: a) Photomicrograph of a gamet-staumlitebiotiteschist from the western Dezadeash Range (93-80). The rim of the gamet (grey brown high relief mineral in the center) is conodecl. Embayments of biotite, obvious in the upper parts of the photograph, and staurolite (st) in contact with the gamet on the right side, suggest that the gamet is being consurned to form staurolite and biotite, according to reaction (2). As a result, the gamet rim is not in equilibria with other minerais. The calculated equilibria reactions have a wide spread (Figure 443a). Scale bar 0.5 mm. PPL b: Photomicrograph of a poikilitic, inclusion-fiee gamet of a cordierite-biotite- quartz schist in the eastern Dezadeash Range (9035). The gamet is clear, lacking the graphitic inclusions of the gamet in a). The margin is not embayed or corroded. To the right, the gamet is gWng into biotiie, apparently consuming it, according to readion (10). The same cm be observed in the lower part of the gamet, where it overgrows a biotiie crystal. This gamet is part of the highest T assemblage found in the KMA, which includes gamet, cordierite, K-feldspar (Figure 49), biotits and sillimanite, es well as hercynite- nuclei in cordierite. The resulting equilibria teaction intersection is relatively tight (Figure 4-13b). Scale bar 0.2 mm. PPL

Figure 4-13: Cornpilional cross-sections of gamets and equilibria reactions cumcalculated by TWQ for two samples in the Deradeash Range. a) 93-80 is hma staumiiiring bmtite schist Aitered rims, embayments in the crystal and staurolite in contact with gamet (Figure 4- 12a) indmthat the grain is consumed by the staurolite producing reaction (2). As it is consumed, the gamet rim does not represent the current P-T conditions, and resulting equilibria reaction cunres (right diagram) show a w'de spread. The mbell-shaped"curve of grossular indicates heating following decompression. The preserved growth zoning pattern implies that the gamet was not sunicientfy heated above 600°C for diffusion to homogenüe the grain. b) The gamet of sampie 9035, a siIlimanitecardierite-biotite schist, shows a homogeneous gamet composition, implying temperatures above 600°C. The gamet is either totatly hornogenized due to diffusion or, as in this case, a second generaüon gamet (see Figure 4-12b and text for discussion). The low grossular- and spessartine-components are also indicative of high temperature gamets- The tighter intersecüon of the equilibria =action curves suggests that the analyzed mineral phases were in a better equilibrium than in the sample of the staurolite zone. Note that in a), the compositional cross-Secfion is fmm mie to rim, while in b) it is from rim to nm. Also note the diirent scale of the P-T diagrarns. Staurolite zone gamet cores have a higher Ca-content (-&=15-30) compared to &=3-5 for the airdierite zone gamets. indicating higher metamorphic pressures or lower temperatures during the formation of the core (Spear. 1993). A higher Mncontent &=15-30 versus %=5-15), and higher Fel(Fe+Mg) ratio of the same gamet cores also indicate lower temperature condlions than cordierite zone gamets. Gamets of the staurolite zone were being consurned by the formation of staurolite, whereas in the cordierite zone renewed gamet growth occuned due to the breakdown of staurolite or gamet compositions were homogenized by diffusion. As a result, it is to be expected that equilibria reactions of cordierite zone gamets have in general tighter intersections. Their rim composition is believed to be closer to peak metamorphic conditions than the partly corroded rims of the staurolite zone gamets. This explains in part the temperature gap between the staurolite and cordierite zone samples. Calculated temperatures of aluminosilicate-bearing samples of the staurolite zone are 50-1 00°C lower than the peak T indicated by the aluminosilicates. which fom by the breakdown of staurolite, as described in the previous section. The cores of staurolite zone gamets preserve earlier high Pllow T conditions, while the homogenized cordierite zone gamets represent peak metamorphic conditions. However, as the gamet cores are not in equilibriurn wth the other phases (plagiochse. biotite and muscovite), which re-equilibrate much faster than gamet, calculation of reaction equilibria using gamet core values result in widely scattered intersections (Appendix 4-10). P-T estimates based on the location of these equilibria would be meaningless. The highest P and T, 6 kbar and ilO°C, were obtained from a grt-crd-bt- qtz schist and a gametiferous granadiarite of the RRB plug near Gamet Creek. Both samples (94-147c and 147d) are located close to the intrusive contact (Figure 2-10). The gamets are exceptionally large (13-2 mm), euhedral. clear, and relatively Fe-rich. The schist sample also contains coarse sillimanite, which is othemise uncommon in the KMA. Cordierite from the schist sample has the highest Mgcontent (hg=68)of al1 probed KMA samples. Readion equilibria intersections of both samples are similar. The high P and T of these samples imply a crystallization at greater depth (-1 8 km) than those of other cordierite zone samples, at the contact with the top of the structurally deeper sill (see Chapter 2). Assimilation of some pelitic schist during the emplacement of the granocfionte may account for the presence of gamets in the granodiorite. Mn-rich (&=25-30). clear, small(l50-300 pm), euhedral gamets, with low P (1.4-2.3 kbar) and low to medium T (460-565°C) were found east of the Killermun Lake plug of the RRB (93-64,93426II) and in the western Kluane Hills (95-71). The Killemun Lake samples lie in the staurolite field, but gamets are small and, unlike other staurolite zone gamets described above, have no zonation. They indicate formation at higher stmctural levels during uplift. The western Kluane Hills sample (95-71) cuntains a small euhedral, Mn- n'ch (&m=25), gamet that crystallized a relative lower P and T of 2.3 kbar and 460°C, respectively (Appendix 4-10). The gamets in these three samples cannot be related to any known metamorphic event and may refiect local thermal events or anomalies during uplR In contrast. a sample near the Kluane Lake shore (89-85a), 2.5 km west of 95-71. contains gamets that are similar to the staurolite zone gamets. The grains appear corroded. display growth zoning and have Ca-rich (&=24) cores (Appendix 4-1 1). The P and T obtained from this sample, 5.5 kbar and 525°C. have to be regarded with some caution, since they are derived from only twa independent reactions, which do not constrain P very well (Appendix 4.8). However, the intersection of reactions (12) and (14) is in the same P range as those of other staurolite zone gamets. suggesting formation at similar high Pnow T conditions.

Regional metamorphic temperature and prossure variations

The confinement of the probed samples to gamet-bearing staurolite and cordierite zones within the aluminous portion of the KMA. generally limits cornparison to samples along strike. Sinœ the rnetamorphic character of the KMA is dominated by a large contact aureole, T estimates obtained through thermometry can be conelated with mapped mineral isograds. T increases from 525°C at Kluane Lake (8945a) to 680°C near the intrusive contact (89- 49a). The highest T of 710 OC were recorded in samples immediately near an intnisive contact (94-147c, d). Along stike, an increase Rom 580°C at the north end of Kluane Lake (94-346) to 690°C in the eastem Dezadeash Range (90-35) can be obsenred. A southeastward increase in T can be explained by the massive nature of the Coast Plutonic Complex (CPC) east of the Dezadeash Range, which provided a larger heat source than the comparably thin sill-iike body of the RRB in the Ruby Range. There is little variation between P estimates along stnke (Figure 4-1 1). Although equilibria intersections of staurolite samples are more scattered, the intersection triangles al1 overiap in the 3.5-5 kbar range. Although P-T conditions during gamet core growth cannot be calculated, the similarity in core composition may indicate similar P-T ranges of the samples. Cordierite zone samples that reflect peak metamorphic conditions, show no variation in P along strike. Samples 100 km apart (8949 and 90-35) were equilibrated at the same P and T. These samples are at the northeastern exposed margin of the KMA, close to the contact with the RRB. A P-gradient across strike can be obtained from 94-120 (3.9 kbar) near the northeastem contact with the RRB, and 94-147c (5.8 kbar) and 94-147d (6.1 kbar), 20 km to the southwest. closer to the structural base of the KM. Tne difference of approximately 2 kbar across strike indicates that the samples in the southwest represent rocks mat were equilibrated at 6 km greater depth than those near the intnisive contact to the northeast. The resulting P-gradient of 0.1 kbarlkm W equivalent to a depth gradient of O.3kmkm and requires post- peak metarnorphic northward tilb'ng of the assemblage in that area of 15" (Figure 4-1 4). The apparent lack of P-variation along strike indicates that the present erosional surface was at the same depth during peak metamorphism. The KMA behaved as a rigid block in during subsequent uplift and northward tilting. 94-147 KYA 94-120 RRB WS 6 kbar (18 bn) 4 Kbar (1 2 km) -2 kbar (6 km)

-. + L .r +

Earîy Eocene

'i- % +

Figure 4-14: Peak metamorphic pressures of samples of the KMA and the RRB in the Ruby Range suggest that samples from the exposed structural base of the KMA were equilibrated at greater depth Vian samples near the intrusive contact with the RRB in the north. The original structural levels during the emplacement of the RRB can be restored by calculating a pressure gradient. See text for discussion. P-T-t PATH VARIATIONS OF THE KMA

The different P and T ranges record4 in the KMA document two major metamorphic events, an older regional high Pnow T event Ml, and a younger contact metamorphic low Phigh T event M, Possible P-T-t paths for samples representative of the high T assemblage near the contact with the RRB, and samples of the low grade schists along the Kluane Lake shore are shown in Figure 4-1 5. The first metamorphic event Ml is -val with deformation D, resulting in the development of the Sn+,- and L&abrics and regional upper greenschist grade metamorphism that reached the gamet zone in the aluminous sequence. The maximum T is given by the first prograde appearance of staurolite at approximately 525 OC at 4-5 kbar (Figure 44). Prevailing P-T during growth of cores of staurolite zone gamets can be approximated by the composition of the gamet cores. An average gamet core composition of 5==20, %=5, Gm=60 and &=IO is located at 7 kbar and 500°C on P-T composition diagrams for gamets in pelitic schist (Figure 17-10 in Spear, 1993). However. this is just an approximation and should not be considered as accurate as P-T estimates from reaction equilibria calculations. 7 kbar equals a depth of approximately 21 km. A high Pllow T metamorphism is typical for accreted rocks during underplating, resulting in a defiedion of the geothemi towards depth (Platt, 1986). The timing of M, is unclear, since radiometric dates show that the cooling ages of the KMA were reset by the intrusion of the RRB, or the KMA did not undergo cooling below 280-350°C the dosure temperatures of argon in biotite and muscovite, before Eocene. Rb-Sr dating of muscovite, which provides higher closure temperatures (500°C) proves to be inconclusive. An isochron calculated for muscovite and whole rock samples of lower grade ms- ch1 schist yield an age of 57.5 * 7.2 Ma, with a large deviation (MSWD 67.2) and therefore cannot be regarded as reliable (Appendix 2-7). Concordant zircons of a late-synkinematic granitic dyke (location of 94-81) yield an age of Figure 615: P-T-t paths with observed metamorphic events for the KMA close to the contact with the Ruby Range Batholith (black line) and further away from it (grey line). The periods of major deformation are shown. Ages represent time at which rocks have undergone cooling through blocking temperature (after Erdmer 8 Mortensen, 1993). Minimum age of 70 Ma is from late synkinematic granitic dyke intniding the KMA (Mortensen, unpublished data, 1997). The staurolite stability field is shown in grey. 71.8 Ma, which can be regarded as a minimum aga for Dm and Mt (Appendices 2-5. 2-6; Mortensen. unpublished data, 1.997). The absence of high PIhigh T mineral assemblages in the KMA implies mat the assemblage did not stay long enough at this depth for the geotherm to relax and T to increase. However, quantification of the duration at higher P cannot be made without geochronological evidence. sinœ too many unknown factors, such as the rate of heat flow and the nature of the geotherm prior to underplating, as well as the thickness of the material that was underplated and the duration of subduction and underplating of cooler material, al1 influence the perturbation of the geotherm. Estimates for the duration of the presently exposed KMA at depths in excess of 20 km are in the order of 10-30 Ma, from comparison with studies in the Alps (Rubie, 1984) and models (England & Thompson, 1984). Shortly af€erreaching peak P during Mt isothermal(7) decompression is followed by an apparent isobaric heating event M, at 44.5 kbar, corresponding to a depth of 12-13 km, at the northern margin of the KMA. Replacement of andalusite by sillimanite. observed in samples along the Venus Creek sections discussed above indicate an apparent isobaric heating path preserved at the current erosional surface. The above mentioned pressure gradient of 0.1 kbarlkm across strike further to the east, would imply an increase of 1 kbar towards the south end of the Venus Creek transect. This ditference is too small to be distinguished by petrographic methods. Radiometric and petrographic studies discussed above strongly suggest that M, is the result of the intrusion of the RRB in the Late Cretaceous to early Tertiary. Overprinting of earlier schistosity and lineation indicates that no significant deformation was related with the M,-event. As the thermal effect of M, decreases with distance to the intrusive contact. so is M, less evident in the mineral assemblages. The grey anow in Figure 4-15 outlines a decompression path for lower grade rocks of the KMA. Absence of staurolite in samples of the aluminous schist near Kluane Lake (89- 85a) suggests that these rocks did not experience substantial T increase after peak P conditions. Chlorite overgrowing foliation in the lowest grade ms-ch1 schists along Kluane Lake may indicate retrograde formation of chlorite from biotite. Younger4Ar?Ar ages of 40 Ma, reported by Mortensen & Erdmer (1 992) for the lower grade rocks, are interpreted as slower cooling of the rocks near Kluane Lake, which would provide more time for retrograde reactions to take place.

METAMORPHIC EVOLUTION MOOEL OF THE SOUTHWEST YUKON

The metamorphic evoluüon of the former continental margin is preserved in the pericratonic assemblages associated with the Nisling terrane, the Aishihik Metamorphic Suite (AMS), the Nasina assemblage and the Nisling assemblage. Triassic (?) greenschist grade regional syndeformational metamorphosed rocks of the AMS were thermally overprinted by the Early Jurassic (1 86 i2.8 Ma) intrusion of the Aishihik Batholith (Johnston et al., 1996). High pressure assemblages (staurolite-kyanite) and geobarometry in the AMS indicate pressures of 8-10 kbar, corresponding to a depth of emplacement of the Aishihik Batholith at 30 km. Similar high P assemblages are common in Nisling assemblage schists east and southeast of Dezadeash Lake (Figures 2-9 and 2-1 5). Gamets of the AMS and Nasina Assemblage (93- 42, 95.5313) have distinct compositional zoning, with 'bell-shaped" Mn- and Ca- profiles, and grossular- and spessartinarich (&==25, &p=lO-l 5) wres similar to gamets of the staurolite zone of the KMA (Appendix 4-1 1). Gamets of the AMS and the Nasina Assemblage are larger (up to 1 cm) than those in the KMA and display usnowball" inclusion trails, indicating synkinematic growth. Calculated P of 5.2 kbar for one AMS sample (93-42) is comparable to staurolite zone KMA samples (4-5 kbar, Appendix 4-1 0). However, this P is much lower than the 8-10 kbar reported by Johnston & Erdmer (1995a), and may reflect re-equilibration during uplift. A direct correlation between this sarnple and the staurolite zone samples of the KMA should be cautioned. Likewise. the relatively low gamet nm T of 500°C recorded in the micaœous quarttite of the Nasina Assemblage is interpreted as a result of re-equilibration in cooler conditions during exhumation of the assemblage (Appendix 4-1 0). It is possible that the KMA was already accreted to the continental margin represented by Nisling tenane assemblages. The contact aureole of the Aishihik Batholith is only 10 km wide (Johnston 8 Erdmer, 1995a) and the intrusion may have thermally effecZed only the AMS and not the KMA. However, recorded pressures in the AMS increase towards south, away from the contact with the Aishihik Bathoiiih, implying that the KMA, if underlying the AMS at that time, would be at greater depth. and should record greater pressures. P-T results available for the KMA suggest that this was not the case. Johnston et al. (1996) report that the AMS experisnœd rapid uplift after the intrusion of the Aishihik Batholith, as evident in the low level(e6 km) emplacement of the Long Lake plutonic suite (185.6S2 Ma), followed by another period of burial in the Middle Jurassic, es indicated by K-Ar ages of 165 Ma. It is after this late Middle Jurassic burial that the KMA was likely accreted to the continental margin. An earlier accretion can be ruled out for the following reasons: 1) the KMA records only one deformational and hornetamorphic events, compared to two and four, respectively, for the AMS (Johnston et al., 1996); 2) there is no indication of repeated uplift and burial in the KMA as in AMS; 3) geochronology and petrography records oniy one high T event, related to the intrusion of the RRB (Mortensen 8 Erdmer, 1992); 4) no pre-late Cretaceow intrusive events have been observed in the KMA.

The accretion of the KMA onto the continental margin of NoNi America must have taken place before the latest Cretaceous (71.8 Ma) intrusion of the syndeformational dyke, and possibly already during mid-Late Cretaceous, as indicated by U-Pb zircon ages of 78-87 Ma from marginal phases of the RRB in the Aishihik Lake area (Johnston, 1993). High T andalusite-cordierite-sillimanite assemblages are found near contacts with the RRB in the KMA and the pericratonic AMS, Nisling and Nasina assemblages, identifying the RRB as a "stitching pluton" (Figures 2-1 4,291 5). The relative thidc (-5 km) contact aureole observed in the Ruby Range, compared to thinner aureoles in the AMS (cl km, S. Johnston, pers. wmm., 1996) and in the Nisling assemblage east of Dezadeash Lake, indicates that the KMA was at greater crustal depth, probably in part underlying the pericratonic tenanes to the north and east. Depth of emplacement for the RRB at the exposed contact with the AMS is believed to be 2-3 kbar (S. Johnston, pers. comrn., 1996). The intrusive contacts of the DF and Nisling assemblage with the CPC south of Dezadeash Lake are shallow level, as indicated by the lack of thermal overprinting of kyanite-staurolitegamet assemblages in the Nisling assemblage, and by the presence of 'knotty schist" (Figure 2-20) and low T gamets (>1,=50), recording T of 490 OC (94-204b, 94-237; Appendices 4-1 0,4- 11) in phyllites of the OF at Million Dollar Falls campground (Figure 2-1 5). K-Ar ages of 66-68 Ma, obtained from the phyllite and hmgranodiorites of the CPC (LeCouteur & Tempelman-Kluit, 1976; G. Lowey, pers. comm., 1995). suggest that the DF was already attacheci ont0 North America by the latest Cretaceous. Since the KMA is situated between the pericratonic metamorphic assemblages in the east and northeast and the DF in the southwest, the minimum age for the accretion of the KMA ont0 the continental margin is 68 Ma, unless the spatial relations between assemblages east of aie Denali fauit have changed significantly since the emplacement of the RRB and CPC.

No major metamorphic event postdating the Late Cretaceous-Early Tertiary intrusion of the RRBICPC is observed in the plutonic and metamorphic assemblages of the southwest Yukon. Cooling ages from 68 to 40 Ma record final uplif€of these assemblages through the 280-350°C geothem range (LeCouteur 8 Tempelman-Kluit, 1976, Mortensen & Erdmer, 1992). The juxtaposition of low-grade DF to the southwest with medium to high-grade KMA north and northeast occuned along a southwest-verging thrust or reverse fault, coeval with the relative northward tilting that brought structural lower levels of the KMA to the present surface.

CONCLUSIONS

1) Two major metamorphic events are recorded in aluminous schists of the KMA: M,: Syndeformational high Pllow T regional metamorphism, which is preserved in Ca-rich cores of gamets that display compositional zoning. Inclusion trails in some gamets indicate synkinematic growth. No staurolite is identified with M,, limiting the maximum T to approximately 525°C. equivalent to upper g reenschist grade. M,: A thermal event that overprinted existing foliation and lineation and resulted in coarsening of the grain sire. Mineral assemblages associated with M, define a metamorphic aureole with an inverted rnetamorphic grade around the exposed contact with the RRB, suggesting that the emplacement of the RRB resulted in the thermal metamorphism. The thickness of the rnetamorphic aureole is estimated to exceed 5 km in the Ruby Range. Peak assemblages of cordiente-K-feldspar-sillimanitegarnet near the contact indicate thaï the lower granulite grade was reached. Gamets in high T assemblages have no composlional zoning, which is caused by diffusional homogenization at T over 600°C. No major deformation is associated with M,

2) Geothemobarometry of the KMA distinguishes two P-T ranges, related to the twa metamorphic events. P and T of 4-5 kbar and 550°C are recorded in samples that contain gamets equilibrated under peak P conditions. Actual peak P is thought to be in the order of 7 kbar, as implied by grossular-nch gamet cores. However, since gamet cores are not in equilibrium with other phases. reliable P-T calcufations are not possible. P-T estimates of high T assemblages record 4-4.5 kbar and 635490°C. in good agreement with observed mineral assemblages.

3) A clockwise P-T-t path can be reconstructed for the KMA. The high P event Ml represents burial of a relative cool pelitic assemblage. This burial was likely related to underthnisting or underplating of the KMA undemeath the North Amencan continental marg in, represented by Nisling terrane assemblages. Minimum dspth of burial was 20 km, but grossular-rich gamet cores suggest that the actual depth could have been greater. The lack of distinct P gradients suggests that the present erosional surface exposes rocks from the same depth. Timing of Ml is constrained by late-Middle Jurassic (165 Ma) metamorphism of the AMS and beginning of the igneous activity of the RRB in Late Cretaceous (70-90 Ma; Johnston, 1993) marks the stitching the KMA and DF ont0 the continental margin. Absence of high Phigh T mineral assemblages in the KMA suggests that Ml is not older than latest Early Cretaceous. The propased clockwise P-T-t path of the KMA is similar to Alpinetype P-T-t paths, where isothemal decompression is interpreted as rapid exhumation due to underplating (Platt, 1986) or as a change ftom subduction of oceanic cnist to collision of island arcs or continental crust (Ernst, 1988). Beginning of underplating of the INS (7) undemeath the KMA, resulting from a change in plate motion of the Kula plate from east to NNE in the latest Cretaceous, provide a rnean for a rapid Paleocene uplift prior to the intrusion of the RRB (see Chapter 3). Geochronology yields cooling ages for the KMA (39-61 Ma) similar to the assumed crystallization age of the RRB (50-57 Ma) indicating that M, occurred in the Late Paleocene to Early Eocene. Maximum depth of emplacement of the RRB, as recorded in structural lower units of the KMA, is 18 km. The main portion of the RRB intruded the KMA at depth of 12 km.

4) Wider RRB-reIated contact aureoles in the KMA compared to the AMS indicate a greater cnistal depth of the KMA at the time of emplacement of the RRB. An approximated Pgradient of 0.4 kbat/km, from the southem contact of the AMS (2 kbar) to the structural lower levels of the KMA (6 kbar) is obtained from geotherobarometry. Therefore, a post-peak metamorphic northward tilting of 15" is requked to bring these rocks to the present erosional sutface. The RRB was emplaced along the contact between the KMA and the AMS, at a shallower angle (15") than observed at the presently exposed contacts (-30"). Younger argon cooling ages (-40 Ma) reporteci for structurally lower schists of the KMA at the Kluane Lake shore, mrnpared to schist near the contact with the RRB in the north (-55 Ma) are compatible with the tilt.

5) The KMA has been correlated with the Maclaren Glacier Metamorphic Belt (MGMB) in the eastem Alaska Range, which has led several authors to suggest a post-Eocene dextral offset of 400 km along the Denali fault (Forbes et al., 1974; Nokleberg et al., 1985). Peak metamorphism in the MGMB is only up to middle amphibolite facies and coeval with defornation. The deformation, dated to the eariy Eocene (57 Ma), ais0 resulted in the development of a penetrative foliation in the East Susitna Batholith (70 Ma), which was previously correlated with the RRB (Forbes et al., 1974; Nokleberg et al. 1985). Deformation and metamorphism in the eastem Alaska Range is interpreted to have occurred dunng faulting along the Denali fault (Nokleberg et al., 1985). Together with stratigraphie differences discussed in Chapter 2, the different deformation-metamorphism histories, post-defomational peak metarnorphism in the KMA venus lower grade syndeformational peak metarnorphism in the MGMB, suggest that a correlation between these metamorphic assemblages in eastem Alaska and in the southwest Yukon is not justified. Consequently, it cannot be used as geological evidence to support the postulated 400 km right- lateral offset along the Denali fault. Chapter 5

Geochemical and neodymium isotope signatures of metamorphic and sedirnentary rocks of the southwest Yukon Establishment of the tedonic aninity and protolith provenance of metamorphosed sedimentary rocks are important aspects in the development of a tectonic model for the northwestern Coast Beit, which marks the boundary between terranes with North American affinity to the east and accreted suspect terranes to the west The distinct lithology and metamorphic and deformational history of the KMA, that set 1 apart ftom the NislingMT-assemblages to the east and the Insular Superterrane (INS) and associated overbp assemblages (DF) to the west, has been discussed in detail in the previous chapters. However, as metamorphism and deformation have obliterated any primary minerai assemblages, sedimentary features or fossils, a correlation of protoliths of the KMA with North American temnes or volcanic arc temnes can neither be concluded nor exduded on basis of the results presented in the previous chapters alone. The difficulty of distinguishing between different medium to high grade metasedirnentary rocks was clear in the earlier part of geological exploration in the southwest Yukon when al1 metamorphic rocks were assigned to the 'Yukon Group" (see Caimes, 1914; Kindle, 1952; Muller, 1967; Tempelman-Kluit, 1974). Geochemical and isotopic studies can help distinguish protolith provenances of sedimentary and metasedirnentary rocks and place constraints on the depositional tectonic setüng. Major element geochemistry as source rock indication is limiteâ due to mobility of Na, Ca and K during weathering and metamorphism (Taylor & McLennan, 1985). Rare earth elements (REE: La-Lu) and other traœ elements, such as Y, Th, Zr, Hf, Nb, Ti, Sc and Co, are best suited for provenance determination, since they are considered immobile during sedimentation and metamorphism, and are transported quantitatively into clastic sedirnentary rocks (Bhatia, 1985; Taylor & McLennan, 1985; Bhatia 8 Crook, 1986). They are also good provenance indicators for medium grade metamorphic rocks like the KMA and AMS, since mobility of these traœ

158 elements and REE does not appear to be increased until granulite grade metamorphism (Bhatia, 1985). The ratios between elements that are compatible (V, Sc, Co) and incompatible (LREE: La-Sm and Th) during differential crystallizaüon can be used to fu rther distinguish sedimentary protolith provenance (Bhatia 8 Crook, 1986). lncreasing abundance of trace elements that are conœntratd in heavy minerals, such as Zr, indicate multiple recycling phases and increasing sedimentary matunty of the protolith (Bhatia 8 Crook, 1986). Nomalized REE plots, La-Th, La-Th-Sc, Tir-WSc and Th-Sc- Z rl1O diagrams are good discriminatory plots to distinguish different tectonic settings (Taylor 8 McLennan, 1985; Bhatia & Crook, 1986). The nature of the source region and terrane relationships can be further constrained by Nd isotope analyses, which yield average cnistal residence ages, also called depleted mantle mode1 ages CT,,), of the various protolith components involved (McLennan & Hemming, 1992). Nd isotope studies also provide information on the isotopic evolution of the protolith (DePaolo, 1988), as well as on the homogeneity of mMng during sedimentation (Frost & Coombs, 1989). Model ages obtained from Nd isotope signatures do not reflect the depositional age of the protolith (Faure, 1986). but the average cnistal residenœ age of the provenance. Cornbined geochernical and Nd isotope studies are important tools to constrain tectonic setting and possible protolith provenance of metamorphic assemblages, as demonstrated by Creaser et al. (1997), in the Teslin tectonic zone (TL)of the southem central Yukon. This chapter presents the first detailed geochemical and Nd isotope study of metamorphic and sedimentary rocks of the northwestem Coast Belt of the Canadian Cordillera. Previous studies by Eisbacher (1976) and Tempelman-Kluit & Cunie (1 978) analyzed only selected major element distribution in the KMA and DF and precious metal content in the KMA, respectively. For this study 11 samples of btqtr schist of the KMA (for 3 samples only major elements), two slates of the DF and four samples of mica- quartz schist of the AMS correlated with the Nisling assemblage (units PAMqb and PAMfs of Johnston 8 Timmennan, 1993a, b), piovided by Steve Johnston from the Yukon Geoscience ûffïce, one biotite-quartr schist sample (major elements only) of the Nisling assemblage (NS) were selected. Sample descriptions and locations are listed in Appendix 5-1. Analytical procedures are described in Appendix 5-2. Major and trace element abundanœ and element ratios of the analyzed samples are shown on Tabks 5-1 and 5-2. Neodymium isotopic data is listed on Table 5-3. Trace element and Nd isotope signatures of the KMA, AMS and DF show .bat they have distinct protolith provenances. The DF has juvenile signatures and young cmstal residence ages corresponding to an origin a or near an volcanic island arc, while evolved signatures and Late Archean crustal residence ages of the AMS suggest an ancient cratonic source. Geochernical and isotopic signatures of the KMA are intermediate between the DF and AMS, indicating relatiiely homogeneous mixing of predorninantly juvenile with minor evolved sedimentary sources. Local occurrence of orthoamphibole schist within the KMA displaying strongly juvenile character suggests relative proximity to a volcanic arc. The overall intemediate signatures of the KMA imply the existence of a backarc basin outboard the North American continental margin in the Cretaceous, that collapsed during the accretion of the INS ont0 NA in the Late Cretaceous.

WHOLE ROCK GEOCHEMISTRY

Major elements

KMA and AMS sarnples show a similar range of SiO, content fmm 59 to 75 wt.%, which also includes the DF (63 %) and NS (65 %) samples (Table 5- 1). The range in Si4content in the AMS and KMA is due to quartz-rich layers of variable thickness that are commonly obsenred in the schists (Chapter 2). The four assemblages are indistinguishable by their SiOJAI,O, ratio, ranging Table 5-1: Major and trace element abundances of mica-quartz schists of the KMA, AMS and Nisling assemblage and slates of the DF Kluane motamorphic assemblage Major elements: (weight %) SIO, &O, Tk, Fe0 Mn0 Cao Mg0Ka Na,O e,o, Totel Trace ebnmnt8 (ppm): Ba Rb c8 sr Pb Th U Zr Nb Hf Ta Y ta Cs f'r Nd Sm Eu Gd ovTb Ho Er Tm Yb Lu Sc' \P Cr" Ni' Cu' Zn" Gaa Major ebment analyses perfarmed by m-.Analyses were made a! Washington State Mnivenity. Table 54 (continued):

Major elementa: KUA AMS (welght %) 94-190 SiOa 82.84 04.28 6S.10 AbOs 17.01 17,22 17.60 Tba 0.65 0,88 0.89 Fa 5,18 645 S.8Q Mn0 0.09 0.10 0.00 Ca0 3,13 2,18 1,14 Mg0 2,22 283 2,07 KiO 4.01 2.28 4.68 Nsp 2.70 2.71 1A7 P,O, 0.13 0.21 0,12 Total 07,M 89.10 88.03 Trace bkmenb (ppm): Ba 1112 Rb 88.9 CI 2.78 SP 320 Pb 13.16 ni 1.63 U 1.13 Zf 62 Nb 4.83 HI 2.00 Ta 0,61 Y 18 Le 8.76 Ce 18.63 Pr 2,60 Nd 11.68 Sm 2,73 Eu 0,67 Gd 2.95 Tb 0.61 4( 230 Ho O,BO Er 1.72 Tm 0.23 Yb 1.61 Cu 0.24 Sc' 16 V' 127 Cf 65 Ni' 47 Cu' BO Zn' 75 Ga* 16

a ore men ana ses pe O raceeemen s enoe w orme y ,a o ers na yses wem ma s aaa ng on a s nvem , Fl'up& corliine#ai w JmiadaM Table 5-2: Element ratios of micaquartz schists of the KMA, AMS and Nlsllng assemblage, and slates of the DF 8

~WAW, K,OMa,O MgO+FeO CIA' RblSr Total RE€ LREUHREE LaNb Laflb; EulEu' = ?$1 TWU Lam MNb wsc TîùSc crm a W 04-366 KMA SIO~A~O, 4,08 3.73 K,OINa,O 1,49 0.92 MgO+FeO 11,79 9,28 CIA' 73,s 70,6 RWSl 0,23 Total REE 114,83 LREEIHREE 5,71 Wb 9.21 ~~flh2 6,22 EuiEu* ' 0.86 154 ?Gd" 0.24 ThIU 2.65 LaKh 4 $04 HfMb 1.66 LalSc 1,40 ThlSc 035 CriTh 21 .O5

1: CIA (Chernical Inden of Alteration): AhO,l(AI,O,+ slllcate CaO+Na,O+K,O)n100; 2: nonnalked to chondriîic valuets La,=LalO.367, YbN=Yb10.248 ; 3: EuEu*: Eu~sqrt(Sm,,xGd,J,EuN=Eu/0.087, SrnN=Sm/0.231, GdN=Gd10,306 (chondrltic nomalizlng factors) (Taylor & Mctennan, 1985), from 3 to 6 (Table 5-2). K20/Na20ratios of 2 to 4.5 for the AMS and NS and 0.45 to 1.8 for the KMA and OF sarnples assign them to the Iithic arenite field and greywacke field of Petüjohn et al. (1987). respectively (Figure 5-1 a). This may indicate a higher sedimentary maturity of AMS and NS samples compared to the KMA and DF. The weathering index CIA and the combinecl MgO+FeO% of individual samples overlap for al1 four assemblages and cannot be used to discriminate between them (Table 5-2). Although major element geochemistry is able to distinguish the pericratonic assemblages (AMS, NS) from the KMA and DF, 1 cannot discriminate between KMA and DF. This fact may be one reason why Eisbacher (1976) correlated the KMA with the DF. However. trace element and isotopic data described below clearly establishes distinct protoliths for both rock types-

Rare earth elements

Geochemical differentiation of the protolith of a sedimentary rock is reflected by its REE characteristics. Sediments derived from a highly differentiated protolith will have higher total REE abundance, a stronger enrichment of LREE (LaSm) over HREE (Gd-Yb). as expressed in the HREERREE or Laflb, ratios, and a more negative Eusnomaly, expressed in the EuEu' ratio (see footnotes in Table 5-2 for definitions). compared to sediments derived from a more primitive, less differentiated source (Taylor & McLennan, 1985). The rnaturity of AMS, KMA and DF samples can be correlated with these three RE€ characteristics, as shown on bO/Na,O versus total REE abundance, Laflb, and EuEu* ratios (Figures 5-1 b, 5-1 c). Normalized RE€ plots are shown for individual samples of each assemblage (Figures 5-2a-c) and wmbined averages for cornparison with the upper and bulk continental crust models (Figure 5-2d). DF sarnples have moderate Eu-anomalies (0.72 and 0.82). the least *uppr continental crust Kluane metamarphic assemblage 0 bulk wntinental cnist A Aishihik Metarnorphic Suite 0 oceanic cnist + Dezadeash Formation + Nisring assembbge

Figure 5-1: a) SiOJAl,O, versus iC,O/Na,O diagram for KMA, AMS, Nisling assemblage metasedimentary rocks and Dezadeash Formation sediments. Greywacke, lithic arenite and arene fields ftom Pettijohn et al. (1987). bc) A weak positive correlation between &O/Na20 versus LaJYb, and total REE can be observed, with AMS samples plotb'ng in the evolved corner. KMA and DF samples occupy a similar &0/iUa20field and are indistinguishable. d) &0/Na20 versus EuEu* plot has a negative correlation. AM$ samples plot at the higher &0/Na20 and the lower EuEu' ratio end, indicative for more evolved cnistal rocks. Note tha one AMS sample (93-14) is near the KMA field. The arrow points in the direction of increasing differentiation. Upper continental and bulk continental crust, oceanic crust and post-Archean average shale values are from Taylor & McLennan (1985). Figure 5-2: a) RE€ plot of DF slates. 60th samples are sirnilar to the bulk continental composition, but show a slightly negative Eu-anomaîy. b) REE plot of AMS biotitequartz schists. The samples have similar patterns as the upper continental cnist average. c) RE€ plot of KMA micaquartz schists. Except for sample 94-29711, which displays positive Eu-anomaly and shallow dope, they display an intemediate signature between upper continental cnist (solid black line) and bulk continental crust composlion (solid gray line). d) Average RE€ values of KMA, ARAS and OF show that each assemblage can be distinguished by its REE pattern. Upper continental and bulk continental crust, as well as chondritic normalizing factors are from Taylor & McLennan (1985). Note the change in logarithmic scale.

LREEenridiment (LamN-3.6) and total REE abundances close to the bulk continental cmst average (Table 5-2; Taylor 8 Mclennan, 1985). REE patterns of the DF are similar to the bulk continental cnist, with the exception of a moderately negative Eu-anomaly (Figure 5-2a). Phanerozoic first-cycle volcanogenic sediments derived fram andesites or basalts of magmatic island arcs do not display a negative Euanomaly (Taylor & McLennan, 1985). The modest negative Eu-anomalies obsenred in the DF indicate a slightly more felsic source. The most evolved characteristics are displayed by three AMS samples with a strong negative Eu-anomaly (-0.6-0.7), Wb, of 12 to 13 and high RE€ totals (120-280 ppm). Sample 93-14 has more juvenile signatures than other AMS samples with a less pronounced Eu-anomaly (0.87) and less enrichment in LREE (Laflb,: 5.6). Their RE€ pattern is sirnilar to post- Archean sediments derived from a felsic upper continental crust (Figure 5-Zb, Taylor & McLennan, 1985). KMA samples show patterns and characteristics that are intermediate between the evolved AMS and the more primitive DF (Figures 5-1, 5-2c). EulEu* ranges from 0.69 to 1.09 and LREE are rnoderately enriched over HREE (Laab,: 4.4-7.3) (Figure 5-2c). REE abundanœ ranges from 63-160 ppm. The lowest REE abundance. the least LREE enrichment of the KMA sarnples and a positive Eu-anomaly is obtained from the orthoamphibole-rich schist 94-29711.

Trace elements

Trace elements that are cansidered good provenance indicaton, Th, Zr, Ti and Sc (Bhatia 8 Crook, 1986), combined with REE, generally display a linear correlation between relative primitive DF and strongly evolved AMS samples. The KMA samples occupy the field between the AMS and OF (Figure 5.3). AMS samples have LaiSc 1.3-5.6 and ThISc 0.8-2 near or above the upper continental cnist average, while lower ratios of the DF (LaISc 0.6, ThlSc Figure 5-3: Relationship between REE and Sc, Th, U, Ti and Zi. The three assemblages are easily distinguished in the various plots. DF samples plot close to the bulk continental cmst composition on the LaiSc versus Laflb, (a) and ThlSc (b) diagrams. Note that KMA sample 9429711 plots close to the DF. AMS samples lie near the average upper continental crust, except 93-14, which is either off a linear carrelation trend (b, d, e) or in the KMA field (a, f). Symbols and source are the same as in previous figures. 0.1 2) are similar to the bulk continental cnist. KMA samples have ratios between upper and bulk continental c~st(Lac 1-3-2.1, ThlSc 0.3-0.5) Fable 5-2, Figure 5-3). Exceptions are the orthoamphibole schist of the KMA (94- 29711). which falls in the DF field and AMS sampk 93-14 which plots close to the KMA in several diagrams (Figure 53) . On LaSc-Th and Th-Zr11 0-Sc temary diagrams DF samples and KMA sample 94-29711 plot near the bulk continental crust or within the 'oceanic arcf field of Bhatia & Crook (1986). AMS samples near the upper continental crust average, within the 'continental margin' and 'continental arc' fields, while the KMA samples plot between both averages within the 'continental arc' field (Figure 54). REE and trace element signatures may then recognize two geochemical end members, an evolved felsic continental cnist source of the AMS and a more juvenile, basaltic to andesitic source of the OF. The possibility of mixing of both sources to fom the intemediate KMA will be discussed with Nd isotope signatures below. The data presented above clearly shows that the KMA is not simply higher metamorphosed DF as suggested by Eisbacher (1976), but derived from a different sedimentary protolith. The two samples of the calcic schist of the KMA (93-1 56, 94-36) are geochemically indistinguishable ftom samples of the aluminous schist, suggesting that the two samples which do not contain epidote, the typical calcic mineral phase of the calcic schist, may be more aluminous portions within the calcic schist. and not representative of that sequence (see Chapter 2).

NEOOYMIUM ISOTOPES

Neodymium isotope analyses stress the distinct protolith provenances of the KMA, AMS and DF, that is already suggested by their geochemical characteristics and help to further constrain possible source regions. Nd- *upper mntinmtd ast 0 bu~kcontinental crust Q oceanic wst

Kluane rnetamorphic assemblage

+ Dezadeash Formation

A Aishihik Metamorphic Suite

Figure 54: a, b) Tedonic setting discrimination diagrams for clastic sediments after Bhatia 8 Crook (1986) plot the DF samples and KMA sample 94-29711 in the oceanic arc field (A) near the bulk continental crust composition, KMA in the continental arc (6) and AMS in both the continental arc (8) and continental margin fields (C). Upper continental, bulk continental and oceanic crust values are from Taylor 8 McLennan (1985). isotope charaderistics are reported as present day uepsilonparameter" ~~(0) (DePaolo & Wasserburg. 1976), sinœ the depositional ages of the KMA and the AMS are not known. Nd isotopic signatures are Iisted on Table 5-3 and shown on a map on Figure 5-5. Their isotopic evoluüon through time is plotted on Figure 5-6. The four AMS samples have strongly negative €,(O) ranging from -20.5 to -27.9 and latest Archean model ages of 2.52 to 2.69 Ga, indicating an ancient cmst source. Similar rnodel ages and c,(O) are reported from the Precambrian basement of the Canadian shield in Alberta and British Columbia (Frost 8 O'Nions, 1984; Thériault 8 Ross, 1991). The DF slates are characterized by higher s,(O)-values of +1.6 and +2.2, suggesting a relative juvenile protolith, and younger Late Protetozoic model ages (l,,0.92 and 0.94 Ga). Initial e,-values for the üme of the deposition of the DF (- 140 Ma; Eisbacher, 1976) are +2.6 and +3.0. These values are similar to those observed in sediments of Wrangellia and Alexander terranes to the west (Samson et al., 1989; Samson et al., 1990b). Micaquartz schists of the KMA record little cNd(0)-variation,rang ing from 5 -6 to -1 -4, unrelated to geographic location (Figure 5.5). These values may imply a mixture between a juvenile and an ancient source. TOMvaries Rom 1.45 to 1.1 7 Ga, intermediate between AMS and DF values, with the exception of the orthoamphibole schist 94-297/1, which has the most juvenile signature of al1 analyzed samples, e,(O) of +3.9, and the youngest TDMof 0.72 Ga. Its distinct geochemical character is described in the previous section. The '47Sm/'UNd ratio is negatively correlated with ew(0). The most evolved AMS samples have '47Sm/'uNd ratios ranging from 0.104 to 0.1 19, while the DF slates have ratios of 0.142 and 0.148. 147Sm/'uNd ratios of KMA samples Vary ftom 0.123 to 0.144 (Figure 5-7). Although sample 93-14 has a negative c,-value of -20.5 and Late Archean T, of 2.52 Ga, comparable with other AMS samples, it has a high '47Sm/"'Nd ratio, close to KMA samples with more evolved signatures. Its anornalous position within the AMS L also obvious in the relationship between c, and the LaflbN ratio, which reflects the

172

white filling: Kluane metarnorphic assemblage light grey filling: Aishihik Metamorphic Suite dark grey fifling: Dezadeash Formation- O Kilometen lo 13a0 13B0

Figure 5-5: Neodymium signatures of the KMA (white). DF (dark grey) and AMS (Ilght grey). lsotopic data are listed in detail on Table 5-3. Locations of samples analyzed for major element geochemistry only are also shown. Geology is the same as on Figure 2-1. Figure 5-6: Evolution of o, through time for analyzed samples of the KMA, AMS and DF. The depleted mantle model is after Goldstein et al. (1 984). Note that the orthoamphibole schist sample of the KMA (94-297f1) plots above the DF samples. AMS samples are characterized by their Late Archean model ages. Plutons: Overîap assemblages: Metamorphie assemblages: @ Eacene a Triassic X GlavinaBeit 0 faku Pabogne Mississippian Dezadeash Formation A AMs fERP El ~retaœous Nisling C Nisutlin

Figure 5-7: e,(O) versus '"SmPUNd of the KMA, DF and AMS samples in cornparison with previously published data of the northem Canadian Cordillera. The DF samples fall in the field for sediments and igneous rocks of the Alexander, Wrangellia and Stikine terranes (Samson et al., 1989, l99Ob). The AMS plot in the same field as Archean igneous rocks of the Alberta basement flhériault 8 Ross, 1991) and similar to some Archean igneous rocks of the Wopmay Orogen (Bowring 8 Podosek, 1989). Plutons are from the Coast Plutonic Complex (Samson et al., 1991a). Other metamorphic assemblages are from Creaser et al. (1997) (Nisutlin, YT), Jackson et al. (1 991) (Nisling) and Samson et al. (1991b) (Taku, TERP: Tracy Am, Endiwtt Am, Ruth and Port Hughton terranes). Gravina Bek data are fmm Samson et al. (1991b). See text for discussion and Appendix 54for location. steepness of the REE curve and is therefore an indication how evolved a certain sample is (Figure 5-8a). Negatïve conelations of c, with ThlSc and LalSc plot AMS near the Precambrian continental cnist and DF close to average island arc volcanics, while the KMA foms a cluster in an intemediate field close to the DF (Figures S-ûb, 54~).The location of the KMA samples on or near a line that conneds AMS and DF may indicate formation of the KMA by mixing AMS with DF or their protoliths (Figure 5-8).

PROTOLITH PROVENANCE AND REGIONAL CORRELATION

The study of neodymium isotope system is a fairly young field, pioneered among othen by McCulloch and Wasserburg (1978), who presented the first comprehensiw study of rocks from the major cratonic provinces in the world. Although studies in the North American Cordillera are still in an incipient state, available data is sufficient to establish first order relationships. The published work is summarized in Figures 5-7 and 5-9, Appendix 5-3 and shown in geographic relation on the terrane map of the northem Canadian Cordillera (Appendix 5-4).

Aishihik Metamorphic Suite

Trace element geochemistry, strongly negadive s,(O)-values and depleted mantle model ages of Late Archean age suggest an ancient cratonic protolith for the analyzed biotitequark schists of the AMS. The AMS has been conelated with continent marginal sediments of the Nisling assemblage. part of the Nisling Terrane (Wheeler 8 McFeely. 1991 ; Mortensen, 1992; Johnston & Erdmer, 1995). Plutonic and volcanic rocks from the Precambrian basement of the Canadian shield in Alberta and British Columbia yield model ages of 2.46 to 2.83 Ga and recalculated s,(O) of -27 (Frost & O'Nions, 1984; Thériault & Ross, 1991). Volcanic and plutonic rocks of the Wopmay Orogen in the Figure 5.8: ac) cw(0) versus ThSc, LalSc and Laab,,,. AMS samples plot near the Precambrian upper continental cnist field, while DF samples plot close to the island arc volcanics. KMA orthoamphibole schist (94-297/1) plots in the DF field. KMA samples lie on a line that joins DF and AMS, implying a possible origin of the KMA by mixing protoliths of the DF and AMS. The symbok are the same as in previous figures. Average present day volcanic island arc Nd signature is after Faure (1986). Precambnan upper continental crust range is adapted from Taylor & Mclennan (1985) and Mclennan & Hemming (1992). Coast Plutonic Complex ' , El

southvuest Yukon (this study)

metamarphic assemblages Alaska O: metamorphic assemblages in Cordillera in SE N N'autlin assemblage 0 ~~iitenane~

Gravina Belt SA

Volcanic arc terranes

stikine a Aîiin Lake a central Bdüsh Cdmbia Refbmncm: 1 1: Andrew et al. (1 991) 2: Cmaser et al. (1997) mvokanks and intniskns' 3: Jackson et al, (1991) inafidultramafic intrusions4 4: Marcantonio et al. (1 993) 5: Samson et al. (1989) I 6: Samson et al. (1WOb) 7: Samson et al, (1991a) 8: Samson et al. (1991b)

Figum 5-9: Block diagram of previously published Nd isotopic studies of metamorphic, igneous and and sedimentary rocks of the Canadian Cordillera in cornparison with the KMA, DF and AMS of this study. See Appendices 5-3 and 5-4 for detailed description. Northwest Territories have an average ~~(0)of -25 and model ages between 2.4 and 2.0 Ga (Bowring 8 Podosek, 1989). fhese results are generally similar with AMS and therefore represent possible source regions on the North Amencan continent. AMS and basement rocks ovedap in the same field on a €,(O)- '''Sm/lUNd diag ram (Figure 5-7). Studies of plutonic and metamorphic rocks the Yukon Tanana terrane 0 of eastem Alaska are few, but also report negative ~~(0)of -27 to -16 and model ages of 1.9 to 2.3 Ga, similar to AMS values (McCulloch & Wasserburg, 1978; Aleinikoff et al., 1981; Bennett 8 Hansen, 1988). Elsewhere, metamorphic assemblages assigned to the YYT, the Tracy Am, Endicott Am, Port Houghton and Ruth assemblages (TERP, informal terminology) at the western margin of the Coast Plutonic Complex in southeastem Alaska, and the Nisutlin assemblage in the TT2 in southem central Yukon, have yielded ~~(0)-valuesof -28 to +2 and model ages of -0.6 to 2.8 Ga (Figures 5-7, 5-9; Appendices 5-3, 54; Samson et al., 1991 b; Creaser et al., 1997). The range of isotopic signatures and model ages is interpreted as mixing of Late Archean to Cambrian sources, supported by 0.5- 3.0 Ga detrital zircon ages for the TERP assemblages (Gehrels et al., 1991a; Samson et al., 1991b) or mixing of magmatic arc and ancient NA continental crust in the Nisutlin assemblage (Creaser et al., 1997). Nd isotopic and RE€ signatures and model ages of the most evolved Nisutlin and TERP samples are very similar to the AMS (Figures 5-7, 5-9; Appendix 5-3). suggesting a cornmon protolith source. However, this does not necessanly imply the same depositional age for these metamorphic assemblages, as a multiple recycling and depositional phases cannot be distinguished in medium grade metamorphic rocks. Taking the limited number and spatial distribution of the analyzed AMS samples into consideration, it can be concluded that, unlike in other metamorphic assemblages of the YIT, the AMS may have derived its detritus from an ancient continental crust source, without mwng of more primitive or post-Late Archean sources. Oezadeash Formation

The DF has been correlateci wiVi the Late Jurassic-Early Cretaceous Gravina-Nutzotin Bel, wnsisting of flysch sediments derived from an oceanic island arc that mark the amalgamation of the Wrangellia and Alexander terranes to fomi the INS during the Jurassic (Monger et al., 1991). eNd(0)- values of shak and phyllite samples of the Gravina Belt in southeastern Alaska are slightly negative (-2), but yield the same T, of 900 Ma as the DF samples (Samson et al., 1991b). Figures 5-7 and 5-9 show that the isotopic signature of the DF is indistinguishable ftom sedimentary and igneous rocks of Wrangellia and Alexander terranes, which range in age from Cambrian to Cretaceous in age and have €,(O) values of 4 to +IO, and are interpreted as derived from a juvenile mantle source (Samson et al, 1989,199Ob; Andrew et al., 1991). The isotopic compatibility of the DF with Wrangellia and Alexander tenanes and other Gravina-Nutzotin Belt assemblages suggests that the DF was derived wmpletely from the INS. The positive e,-values indicate that little or no sediment from an ancient cratonal source was incorporated sufficiently enough to affect the isotopic signature of the DF.

Kluane metamorphic assemblage

Geochemical and isotopic signatures of the micaquartz schists of the KMA show that it is a very homogeneous sequence, compared to other metamorphic assemblages associated with the Nisling tenane and the Yukon- Tanana terrane in the Yukon and southeast Alaska described above. The present location of the KM,between juvenile rocks of the DF in the west and highly evolved metamorphic rocks of the AMS to the east, may suggest deposition in a basin behind a volcanic island arc to the west, but not isolated from an ancient continental source to the east, to account for the slightly negative values. Altematively, the KMA could have been com pletely derived from older, more mature parts of the INS. However, the oldest known rocks of the Alexander terrane (upper Precambrian; Souther, 1991) and TDMmodel ages of -900 Ma (Samson et al., 1991b) are much younger than model ages of the KMA (1.2-1-5 Ga), which does not support a single volcanic arc source region for the KMA. The relative juvenile signature of the orthoamp hibole schist 94-29711 , with ç,(O) of +3.9 and T, of 720 Ma, compatible with those from igneous rocks of Wrangellia and Alexander (Samson et al.. 1989,1990b). can be interpreted as metamorphosed sediment derived from an andesitic source. Andesioc volcanism is common in the adjacent Alexander terrane, and occurs as andesitic fiows southwest of Oezadeash Lake (Cambrian Field Creek Volcanics, Dodds 8 Campbell, 1992). As shown on the diagrams of Figure 5-8, it is possible to derive the KMA by mùing of the DF with the AMS. However. given the distinct metamorphic and deformation histories of these three assemblages (see Chapters 3 and 4). the location of the KMA along a major cnistal boundary, and unknown pre-Late Cretaceous history of the KMA, such a simple correlation should be cautioned. Nevertheless, the isotopic and REE signatures imply the possibility that the UMA has derived its detntus from sources similar, if not the same, to that of the AMS (NA) and the DF (INS). Several tectonic settings can be envisioned that would allow mixing of material from juvenile and ancient crustal sources (Figure 5-1 0). A model where detntus from a volcanic arc to the west and an ancient continent to the east were transported into a backarc basin and thoroughly mixed best represents the present geological setting (Figure 5-1 Oa). Altematively, the protolith of the KMA could have been deposited in a forean basin west of a volcanic arc with continental detritus transported trench-parallei Rom a source north or south of the volcanic arc (Figure 5-lob). However, the KMA is accreted directly ont0 North America and no remnants of the intervening volcanic arc can be observed. The missing arc is difficult ta explain with any tectonic processes. A third possibility would be a forearc basin setting where the volcanic arc is situated in the west and the continent in the east, similar to the first model, except that a westward subduction undemeath the volcanic arc

3) Trace and RE€ elernent signatures, juvenile c,(O)-values (2.5-3 .O) and late- Middle Proterozoic model ages (950 Ma) of the weakly metamorphosed slates of the DF suggest a juvenile volcanic island arc protolith, most likely the INS. which has compatible isotopic signatures (Samson et al. 1989. 1991b).

4) The KMA, situated between the AMS to the northeast and the DF to the south, has intermediate isotopic signatures (cw(0) -1 -3 to -5.6, T, 1.2-1 -5 Ga), that cannot be correlated to any single source region, and are interpreted as mixing of ancient Archean (7) continental cnist with more juvenile sources. Possible sources include the AMS and DF. However, the unknown spatial relations between the three assemblages prior to the accretion of the KMA and DF ont0 the North American continental margin make a direct correlation very speculative. It is more likely that the KMA has similar, if not necessarily the same, protoliths as the DF and AMS. Restridad occurrence of an orthoamphibole schist with distinct primitive geochemical and isotopic signatures indicates a single andesitic source, possibly derived from the INS. The homogeneity of trace element and Nd isotope charaderistics of the KMA suggest that the original sediments reœived a constant ratio of juvenile and mature detritus throughout the duration of the deposition, prior to the accretion of the KMA ont0 NA in the Late Cretaceous (see Chapter 3). A possible tectonic setting of the sedimentary protolith of the KMA is a backarc basin distal to a continental source and in the proximity of a volcanic island arc.

5) The distinct protolith provenances prove that the KMA is not simply the metamorphosed equivalent of the OF as suggested by Eisbacher (1976).

6) The juvenile character of sample 94-297/1 from the eastem Dezadeash Range support the suggestion brought forward in Chapters 2 and 4 that a contact between the KMA and peflcratonic rocks of the Nisling terrane does not exist in the eastem Dezadeash Range, as proposed by Erdmer (1991). Chapter 6

Model of tectonic evolution of the Kluane metamorphic assemblage MODEL OF TECTONIC -LUT ION

The geology and the structural, metamorphic, geochemical and isotope charaderistics of the Kluane metamorphic assemblage (KMA) are incorporated into a model of evoluüon for the northwestern Coast 8elt of the Canadian Cordillera. The rnodel is illustrateci in Figure 6-1.

Late Jurassic (3)- early Late Cmtaceous (-100 Ma) Geochemical and petrological studies indicate that the rocks of the KMA (graphiüc quartzose pelites (aluminous sequence) and graphitic calcareous clays (calcic sequence)), are predorninantly of sedimentary origin. The lack of recognizable liaiic fragments and the presence of fine graphitic layers in feldspar porphyroblasts, interpreted as original bedding, suggest that the protolith was a fine grained sediment. Consistent c,,-values throughout the KMA imply hornogeneous mixing between juvenile volcanic arc and ancient continental sediment sources (Figure 6-la). Schists with more juvenile signatures indicate a protolith derived directly from an andesitic source. The mixing of sediments derived ftom a juvenile and ancient continental source is interpreted to have taken place in a backarc basin setting. Other possible tectonic settings, such as deposition in a forearc basin are considered less likely, since no evidenœ for a remnant arc between KMA and NA exists. Olivine serpentinite bodies interlayered with the schists in the KMA support a backarc basin model, the serpentinites derived from oceanic crust. The occurrence of ultramafic rocks along a contact between calcic and aluminous schists, similar fabrics developed in schist and serpentinites, and the lack of compositional zoning within ultramafic rocks support a tectonic ('Alpine-type") instead of an intrusive ("Alaskan-typen) origin for the serpentinites. lsotopic charader of the KMA and presence of minor rnetamorphosed volcanoclastic layers within the schist indicate proximity of the depositional basin to an active volcanic arc, but also indicate contribution of sediment from 1 a Late Jurassic (?) - Late Cretaceous (-95 Ma)

CI Late Cretaceous (-95 - 70 Ma)

Figure 6-1 : Schematic model of tectonic evolution of the Kluane rnetamorphic assemblage and adjacent terranes in the southwestern Yukon. See text for discussion. Paleocene (-70 Ma - 57 Ma)

157 - 55 Ma)

Figure 6-1 (continued): Schematic mode1 of tectonic evolution of the Kluane metamorphic assemblage and adjacent termes in the southwestern Yukon. See text for discussion. e Eocene (-55 - 40 Ma)

NNE relative amount of uglii

t Oligocene - Holocene

Figure 6-1 (continued): Schernatic model of tectonic evoluüon of the Kluane metamorphic assemblage and adjacent terranes in the southwestern Yukon. See text for discussion. an ancient continental margin. Several authon (Csejtey et al., 9982; Plafker et al., 1989) have postulateci an oœanic basin of uncertain width between the lnsular Superterrane (INS) and North Arnerica (NA) in the Jurassic-Cretaœous, into which the Late Jurassic-Eady Cretaceous flysch derived from the Gravina- Nutrotin arc of the INS were deposited eastward into the basin. Workers in southeast Alaska and British Columbia have questioncd the existence of oceanic crust in the basin and suggested intra-arc rifüng instead (McClelland et al., 1992; van der Heyden, 1992). The schists and uiûamafic rocks of the KMA provide evidence for the existence of an extensive andlor long-lived backarc basin between NA and the INS. A small basin. as proposed for the southem Cordillera (McClelland et al.. 1992), would have resulted in a greater lithological and isotopic variety. reflecting varied detrital input from ancient and juvenile sources, such as reported from the Nisutlin assemblage of the Teslin tectonic zone (Creaser et al.. 1997). The amount of exposed KMA, with a structural thickness of q2 km and an along-strike extent of approximately 160 km, requires a basin of a few hundred kilometers width to allow consistent long- term sedimentation of homogeneously mixed detritus. A precise estimate cannot be made, since the necessary width of the basin to allow homogeneous mking depends on the amount of clastic input, which is a factor of the age of the continental rnargin, the sire of the magmatic arc and the depth of the basin. Modem analogues may be the Japan basin or the Aleutian basin. The flysch of the DF may be arc-proximal sediments deposited in the same basin (Eisbacher, 1976).

Late Cretaceous (-95-70 Ma)

Southeast motion of the Kula plate during the Early Cretaceous (Engebretson et al., 1995) resulted in sinistral striks-slip along the Wrangellia- Alexander terrane boundary in the INS (Plafker et al., 1989), while the marginal basin between the INS and NA remained stable. The collapse of the basin started when the Kula plate changed from southeastward to eastward motion at around 95 Ma (Engebretson et al., 1995). Eastward subduction of the oceanic crust undemeath AMS at the North American continental margin began (Figure 6.1 b, section 1). 84-05 Ma old andesites and rhyolitas of the Montana Mountain volcanic complex near Carcross (Hart, 1993) may be part of the magmatic arc that developed in response to the eastward subduction of the backarc basin. Alternatively, Late Cretaceous magmatic arc plutons could have been eroded during subsequent uplR or assimilated by the extensive Early Eocene plutonism of the Coast Plutonic Complex (CPC; Woodsworth et al., 1991) east of the KMA. The fine grained sediments of the proto-KMA entered the subduction zone and were transported to a depth of at least 20 km where they were accreted to the upper plate represented by the AMS. Several authors (Karig, 1974,1982; Karig & Sharman, 1975; Moore, 1989) have suggested that fine grained pelagic sediments, forming the lower sedimentary layers on the oceanic crust, can be transported on the downgoing plate and added to the base of the upper plate. Meanwhile overiying clastic trench fiil is being removed before entering the subduction zone and is added to the accretionary prism (Figure 6-1 b, section 2). This observation is compatible with the homogeneous isotopic character of the KMA. The proto-KMA was covered by younger sediments and did not receive any detritus when it entered the subduction zone. Topographic inegulariües on the downgoing plate, such as horst and graben structures, or sea mounts, provide the means of shearing off parts of the oceanic cnist and adding them to the accreted oœanic sediments (Karig & Sharman, 1975). This can explain the presenœ of the disnipted lens-shaped ultrarnafic bodies within the schists of the KMA. The present 12 km thickness of the KMA is probably the resut of structural stacking due to addition of newly underplated material. During subduction and underplating at the base of NA, the KMA experienœd ductile deformation and high PAow T metamorphism. The parallel alignrnent of slaty cleavage with schistosity suggests that both developed during continuous deformation under increasing strain and pressure. Distinct mineral stretching lineations and mylonization of the schist indicate progressive non-coaxial defornation. The consistent westward hangingwall up sense of shear at a small angle with the strike of the foliation, and the general northeast- dipping foliation of the KMA and the AMS north of the RRB indicate oblique eastward underplathg of the KMA undemeath the AMS (Figure 6-1 b). This resulted in left-lateral displacement along the WNWtrending ancestral NA continental margin. However, sinœ the exposed suture between the AMS and KMA represents the deep seated part of a subduction zone, evidence for coeval sinist ral strike-slip faults at higher structural levels, as proposed by Mezger & Creaser (1996), is unlikely to have been preserved as it would have been destroyed by erosion dunng uplift. Underplating of the KMA is constrained by early Middle Jurassic (-1 87 Ma) high Pthigh T metamorphism of the AMS (Johnston et al., 1996), which has not been observed in the KMA, and a latest Cretaceous (72 Ma) late synkinematic dyke intnided into the KMA (Mortensen, unpublished data, 1997). Absence of high T minerais, such as kyanite, which would indicate isobaric heating of the originally cool KMA slab, indicates that maximum age of deformation of the exposed rocks of the KMA is not older than 90-1 00 Ma. The absence of Late Jurassic to pre-Late Cretaceous plutons on ancestral NA in the southwest Yukon predudes signifiant eastward subduction undemeath NA during that tjme (Woodsworth et al., 1991). Shear-sense indicaton in phyllites on the eastem margin of the OF record similar WNW hangingwall up motion as the mylonitic schist in the KMA to the norai and suggest westwarâ thnisting of high Plhigh T schists of the NS ont0 the OF (Figure 6-1, section 3). South of the KMA, eastward motion resulted in orthogonal plate convergence, as the ancestral NA margin strikes south. While schists of the KMA reWductile deformation at a depth of -20- 22 km, the exposed eastem thnist fault of the low grade slaty and phyllitic OF implies a contact at higher structural levels at a depth of a few kilometer. The time window for accretion of DF ont0 NA is restricted by the youngest deposlional age of 135 Ma for the DF (Eariy Cretaœous; Eisbacher. 1976) and by radiometrk ages of 68 Ma for the intrusive contact of the DF with the plutons of the CPC (LeCouteur 8 Tempelman-Nuit, 1976; Lowey, pers. comm., 1995). NNE-trending folds cut by a late Early Cretaceous pluton (108 Ma, Mortensen, pers. comrn., 1996) suggest that thnisting of the NS rnay have happened as early as late Earîy Cretaceous (Eisbacher, 1976). Mid-Cretaceous westward thnisting of NA ont0 the INS is proposed along 1200 km in southeastem Alaska and Briüsh Columbia causing high PAow T metamorphism of Gravina belt sediments (Rubin et al., 1990; McClelland et al., 1992). Crosscutang plutons constrain deformation and metamorphism to the intenral90-115 Ma (McClelland et al., 1991, 1992). McClelland et al. (1992) and van der Heyden (1992) interpreted midCretaceous thnisting as intra-plate shortening, rather than collapse and subduction of a marginal basin between INS and the Sükine terrane, along the NA continental margin during the Cretaceous. The implications of these two different tectonic settings for the evolution of the North Amencan margin are discussed below. Paleomagnetic studies in southem British Columbia suggest 2000 km of Late Cretaceous-Early Tertiary dextral motion has taken place between the eastem Coast Belt and the Intemontane Belt (Wî'ynne et al., 1995; Irving et al., 1996). Late Cretaceous eastward subduction beneath NA in the southem Yukon (this study) and lack of dextral northwest-trending faults or shear zones in the-Coast Belt of the southem Yukon (Tempelman-Kluit, 1974; Johnston & Timmerman, 1993a; this study) do not support large amount of dextral motion within the Coast Belt or at its eastem margin in the southem Yukon during the Late Cretaceous.

Latest Cmtaceous (-72 Ma) - Eaily Eocene (57 Ma) A change from east to NNE-motion of the Kula plate in the latest Cretaceous resulted in ESE-trending regional folding of the metamorphic assemblages and the DF (Figure 6-1 c). Locally developed WSW-verging mesoscopic FM-folds are interpreted as contemporaneous with uplift of the KMA. UpliR was accomplished by underplating of the remaining backarc basin and the approaching DF and INS underneath the KMA. The first magmatic phase is marked by the late synkinematic dyke crosscutting the KMA (70 Ma) and the intrusion of the CPC into the DF at Million Dollar Falk campground at -68 Ma. A small undated tonalitic gneiss at the northem margin of the KMA at Kluane Lake (Doghead Point) is cut by undeformed granodiorites of the RRB. The tonalite is interpreted as a mafic precursor of the RRB, possibly related to a 69-78 Ma old quartz diohte at the northem margin of the RRB near Aishihik Lake (Johnston, 1993) and similar to tonalite bodies along the western margin of the CPC in southeastem Alaska. These tonalite bodies, referred to as the Great Tonalite Sill (Gehrels et al., 1991b), are interpreted as deep (15-20 km) sill-like intrusions along a steep dipping shear zone, the Leconte Bay shear zone, which has developed along the former suture zone between INS and NA (McClelland et al., 1991). The tonalites range in age from 57-83 Ma, and are sucœeded by undefomed granodiorites of the CPC (Gehrels et al., 1991).

Early Eocene (5766 Ma)

Continuing NNE-compressive motion along the Kloo Lake fault resulted in eastward tilting of the KMA, immediately followed by emplacement of the granodiontes that comprise the major portÏon of the RRB along the suture between the KMA and the AMS (Figure 6-Id). FabricgaraIlel intrusive contacts with the northeastdipping KMA and AMS suggest that the batholith intruded in a silblike fashion (Erdmer & Mortensen, 1993) dipping 15" to the NNE. The batholith has a minimum thickness of 5 km and can be traced for 200 km to the WNW. A shorter, 70 km long structurally lower sill is infened fnxn several granodiorite exposures at the base of the KMA. The sill is only partially exhumed and was probably emplaced along the faulted contact of the KMA with the DF to the south. The RRB and the unnamed sill to the south are northemmost portions of the granodiorites of the CPC, intruded at shallow levels (6-1 2 km) as a result of increased speed of subduction of the Kula plate in the late Paleoœne (Erdmer & Mortensen, 1993; Engebretson et al., 1995). The Eariy Eoœne crystaliizaüon of the RRB resuited in a 5 km thick contact aureole in the KMA. Thermal overprinting was strong enough to reset radiometric ages and partiy anneal existing fabrics. Peak metamorphic temperatures reached 650-700°C, uppermost amphibolite grade to lower granulite grade. Gamet, sillirnanite, cordierite, K-feldspar and spinel charaderire the highest grade metamorphic mineral assemblage. The metamorphic gradient is inverted, as it decreases to upp»r greenschist grade in the stnidurally lower section of the KMA. In the overlying AMS. contact metamorphism related to the RRB resulted only in a few hundred meter wide contact aureole, which did not reset radiometric age dates (Johnston et al., 1996). Geothermobarometry hdicates depths of 12 and 18 km for the top and the base of the KMA during the emplacement of the RRB. No major deformation of the KMA or the AMS resulted from the emplacement of the RRB.

Eocene (5540 Ma)

The upper structural panel of the KMA was exhumed rapidly after the emplacement of the RRB by northward underplating by the DF/INS (Figure 6- le). In the southwest, where the KMA was 6 km deeper than near the contact with the RRB, the schist cooled through the 280°C isothem at 40 Ma, 16 Ma later than at the northem contact A relative northward tilting of the KMA by 15" is necessary to account for the current levels of exposure. Similar peak metamorphic pressures along strike of the KMA imply that the tilt axis is parallel to the strike of the schistosity. The rapid uplift of the KMA was enhanced by increased speed in the northward motion of the Kula plate, which was finally consumed at 40 Ma (Engebretson et al., 1995). Major southeast-striking strike-slip faults are not observed cutting the KMA. Shear zones of unknown age, interpreted as strands of the Denali fault, are observed within Pennsylvanian-Triassic strata of the Wrangellia terrane in the Kluane Ranges (Dodds & Campbell, 1992; T. Bremner, pers. comm., 1993; White, 1997). Together with the lack of compatible metamorphic assemblages west of the Denali fauit, this observation strongly suggests that the KMA is not truncated to the southwest by strike-slip faults, but by dip-slip faults.

Oligocene - Holocene The disappearanœ of the Kula plate by the end of the Eocene led to new plate configurations. Oblique convergence of the northwest moving Pacific plate, resulted in novth-trending dykes of (possible) Miocene age that intrude the INS, KMA and AMS (Tempelman-Kluit, 1974: Eisbacher 8 Hopkins, 1977; Stevens et al., 1982, Johnston & Timmenan, 1993a). The cessation of exhumation of the KMA can be atbibuted to reduced north-south compression and northward tilting of the KMA. rotating the overtumed southem Iimb of the Ruby Range anticline to normal upright position (Figure 6-76). Steep southward dipping foliation of the KMA and the DF enabled to change motion along the fault plane from a south-verging thnist into a steep north-verging reverse fault with the southem hangingwall moving up (White, 1997).

DISCUSSION

Evaluation of evidence for dexbrl strike-slip along the Denali fault zone in the Cenozoic

Based upon correlation of similar assemblages along the Denali fault zone (DFZ), major Cenozoic dextral displacement along the DFZ, ranging ftom 150400 km, has been postulated by several authon (Forbes et al., 1974; Turner et al., 1974; Eisbacher, 1976; Hudson et al., 1982; Nokleberg et al., 1985). Others have interpreted the DFZ as a major Late Cretaœous collision zone with only minor (-1 0 km) dextral offset (Csejtey et al., 1982). This study has shown that the Maclaren Glacier Metamorphic Belt (MGMB) of the eastem Alaska Range can not be correlated with the KMA. Although these results do not disprove a 400 km dextral displacement along the DFZ as proposed by Nokleberg et al., (1985), they do remove a major evidence. Based on correlation of Late Jurassic-Eariy Cretaœous flysch sediments of the Nutzotin Mountains sequenœ with the Dezadeash Formation, and Upper Triassic strata of the Chilkat Peninsula, southeast Alaska. with simibr strata in the Wmngell Mountains. Eisbacher (1976) and Plafker et al. (1989) proposed 300-350 km dextral offset along the DFZ. Along the southern continuation of the DFZ. the Chatham Strait fault. Hudson et al., (1982) only inferred 150 km of dextral offset. It is beyond the sape of this study to evaiuate the validity of these wrrelations, but they should be regarded with extreme caution. Detailed studies of assemblages on both sides of the fault are necessary to determine possible tectonic correlations. Also, the discrepancy in the apparent omet dong the same fault zone (350 and 150 km), shows the weakness of fault displacement determinations based on correlation of similar assemblages on opposite sides of a fault zone. Even if these assemblages were part of one unit that was disrupied by the fault, only the apparent strike-slip offset can be observed. The amount of offset is dependent on outcrop exposure, vertical motion along the fault, which can resuit in differential erosion, and independent faulting within one fault block. In the case of the Denali fault and the Chatham Strait fault none of these factors can be estimated since the faults are covered by glacial till or water, respectively. Based on similar Late Jurassic-Eady Cretaceous stratigraphy and mid- Cretaceous granodiorite intrusions, Eisbacher (1976) correlated the DF with the Nutroün Mountain sequence. However, subsequent authors (Plafker et al., 1989; Stanley et al., 1990) have postulated a -1 500 km long flysch basin dong the western margin of North America in the mid-Cretaceous. Mid-Cretaceous granodiorite intrusions were also observed in the flysch strata of southeastem Alaska (McClelland et al., 1992). Considering the length of this flysch basin and the similarity of its Late Jurassic-Eariy Cretaceous strata, a correlation between two preserved flysch sequences has to be regarded with caution. Further evidenœ that question major dextral displaœment along the DFZ are: 1) hck of Pleistocene to Holocene lateral disphcement on the DFZ east of the Totschunda fauit (Richter 8 Matson, 1971; Clague. 1979), 2) minor (-10 km) right-lateral omet of metamorphic minera1 isograds in the MGMB along the McKinley segment of the DFZ (Csejtey et al., 1982). 3) only 38 km offset along the McKinley segment since earfy Oligoœne (38 Ma, Reed & Lanphere, 1974), 4) no activi along the Hines Creek segment of the DFZ since the Late Cretaceous (95 Ma. Wahrhaftig et al., 1975) and 5) uplift of Mt. Denali south of the McKinley segment in exœss of 8 km in the last 6 Ma as detennined by apatite fission-track analyses (Fitzgerald et al., 1993).

The Denali fault zone in the southern Yukon - a Late Cretaceous suture zone with minor Eocene dextal strike-arlip displacement

A tectonic model is proposed which incorporates the tectonic and metamorphic evolution of the KMA described in this study with new plate motion estimates for the Kula plate (Engebretson et al., 1995) and previously published data. This model postulates northward motion of the INS along a mid-Cretaceous suture and the closure of an oceanic basin in the southern Yukon and south-central Alaska without evoking major Cenozoic dextral motion along the DFZ. The model is illustrated in Figure 6-2. Mid-Cretaœous (90-100 Ma) collision of the INS with NA resulted in the collapse of an intervening marginal basin and westward thrusting of NA ont0 the INS along a 1200 km long zone (Rubin et al., 1990; McClelland et al., 19923. Lack of evidenœ for underiying oceanic crust may imply that the collapsed basin was associated with intra-arc rifting (Rubin et al.. 1990). Syndeformational tonalite bodies were emplaced along the shear zone (Rubin et al., 1990). This study has shown that, contemporaneous with westward thrusting in the southeastem Alaska and British Columbia, easîward oblique subduction of the backarc basin. into which the KMA was deposited, undemeath NA occurred in the souaiern Yukon (Figure 6-2a). Both eastward subduction in the southern Yukon. and westward thnisting of NA ont0 the INS, are compatible wiai eastward motion of the Kula plate in the eariy Late Cretaceous (Engebretson et al., 1995). Sinœ the eastward subduction of the backarc basin continued until the latest Cretaceous, the INS either remained outboard of the subduction zone at that time or was located further south. Sinistral strike-slip faults were likely developed at strucfurally higher levels of overrÏding NA plate as a result of oblique subduction. Due to subsequent unroofing of the subduction zone, no evidence of sinistral faulting is presewed. Earlier sinistral faulting is postulated for the south-central Coast Belt in southern British Columbia during Middle Jurassic-Eariy Cretaceous (Monger et al., 1994). It is unclear if strike-slip faulting along the North American continental margin in the southem Yukon was active at that time or if it occurred outboard the volcanic arc that enclosed the backarc basin. Change of motion of the Kula plate from east to NNE in the latest Cretaceous (Engebretson et al.. 1995) juxtaposed the INS and DF with the KMA (Figure 6-2b).The backarc basin finally collapsed when the INS and the DF were underthrust beneath the KMA. causing uplift of the KMA by >5 km. Northward motion of the already accreted INS occurred along the Coast shear zone, the former suture between the INS and NA (Hollister et al., 1997). Coeval collapse of an oceanic basin in south-central Alaska. evident in underplated mesozoic flysch beneath NA (Stanley et al., 1990) and "Alpine-type" ultramafics along the suture (Patton et al., 1994), suggest that a single backarc basin may have existed along the southem continental margin of souaicentral Alaska and the southern Yukon. Rapid subduction of the Kula plate in the Early Eocene (Engebretson et al., 1995) resulted in the emplacement of the granodiorites of the CPC along the suture zone between INS and the North American continental margin (McClelland et al., 1992; Erdmer & Mortensen, 1993). Early Tertiary granites are also observed along the INS-NA suture in south-central Alaska (Csejtey et al.. 1982). Subduction of successively younger. and therefore more buoyant, Kula plate underneath the INS resulted in rapid removing of 12-18 km of crustal material overiying the KMA, exhuming the Late Cretaceous subduction zone. The youngest K-Ar cooling ages in the KMA (739 Ma; Erdmer & Mortensen, 1993) are coeval with the final subduction of the Kula plate a -40 Ma (Engebretson et al., 1995), suggesting that exhumation of the KMA ended with the disappearance of the Kula plate. Evidenœ for right-lateral strike-slip has neither been found at the southem rnargin of the KMA, nor along the contact between the KMA and the INS and DF. Shear zones within the INS and at the basal contact of the DF suggest only minor dexbal (?) strike-slip displacement (White, 1997). Eocene- Oligocene clastic sediments of the Amphitheatre Formation, deposited in small pull-apart basins near the trace of the DFZ and the Duke River fauk in the INS (Ridgway et al., 1992), may indicate dextral strike-slip motion of 10-35 km during Eocene-Oligocene time. Rearrangement of plate configuration and NNWdirected motion of the Paciiic plate resulted in underplating of the Yakutat terrane beneath the INS (Engebretson et al., 1995) and rapid uplift of the St Elias Mountains in the INS (Homer, 1983). Vertical normal or reverse fault motion of the Shakwak fault overprints earlier strike-slip movement along the Denali fault (White, 1997). The lack of post-Eariy Oligocene evidence for strike-slip displacement along the INS-NA suture suggests that dextral displacement has to be accommodated by faults to the west, e.g. the Fairweather fault (Dodds, 1991) or the Totschunda fault, which joins the DFZ in eastem Alaska (Homer, 1983). On the base of northeast-trending linearnents and sinistral faults Page et al. (1995) proposed a 300 km wide dextral shear zone between the DFZ and the Tintina fault. The faults are interpreted as boundaries of individual blocks which are inferred to rotate clockwise during dextral motion along the Denali and Tintina faults. However, northeast-striking sinistral faults are not observed between the DFZ and Tintina fault in the Yukon (Tempelman-Kluit, 1974; this study), suggesting that very little dextral motion is taking place along the DFZ east of the Totschunda fault. The continuation of Iineaments south of the Denali fault in central Alaska (see figure 2 of Page et al., 1995) rnay imply that the observed seismicity can be explaineci without evoking a dextral shear zone between the DFZ and the Tintina fault.

The tectonic model presented here describes two different tectonic settings for the western North American continental margin in Cretaceous. In the southem Cordillera a relatively narrow flysch basin deposited in an intra-arc setting (?) collapsed during the eariy Late Cretaceous when NA was thrust westward over the INS (Rubin et al., 1990). In the southem Yukon and south- central Alaska, a large (-200-400 km) backarc basin with oceanic cmst existed and was subducted underneath NA. The Late Cretaceous change of Kula plate motion resulted in dextral strike-slip of the already accreted INS along the Coast shear zone (Hollister et al., 1997) resulting in the collapse of the backarc basin. No dextral strike-slip dong the Denali fault in the Yukon is necessary to explain tectonic configurations. Small amount of dextral omet (10-35 km) is possible dunng the time of rapid northward motion of the Kula plate (5540 Ma). The model provides two important constraints on the fault displacement in the Coast Belof the North American margin: 1) Latest Cretaceous dextral displacement and northward motion of the INS along the Coast shear zone is necessary to explain the collapse of a larger backarc basin and the exhumation of the KMA in the southem Yukon. The amount of motion is uncertain, and can Vary from less than 100 km to several hundred kilometen (Hollister et al., 1997). 2) Dextral motion along the Denali fault in the Yukon is restricted to the Late Eocene-Early Oligocene and did not exceed 30 km. This model proposes that the Denali fault in the Yukon is a major Late Cretaœous continent-volcanic arc suture zone with only minor strike-slip motion, as suggested by previous studies (Csejtey et al., 1982). a? Yukon Tanana

Kula- plate

ate Cretaceaus

Figure 6-2: Speculative tectonic evolution model of the North American continental margin in the Late Cretaceous (a) and the Early Tertiary (b), based on plate motion model of Engebretsen et al. (1995). and work by Rubin et al. (9 WO), McClelland et al. (1 992) and Hollister et al. (1 997) in southeastem Alaska, and Csejtey et al. (1 982) and Plafker et al. (1989) in south-central Alaska, as well as this study. See text for discussion. CONCLUSIONS

The Kluane metamorphic assemblage is distinct in its lithology and rnetamorphic history from any other metarnorphic assemblage in the Western North American Cordilkra. Structural, petrograp hic. isotopic, geochemical and therrnobaromettic studies show that:

1) The sedimentary protolith of the KMA was derived ft~mthe mixing and homogenization of juvenile and ancient continental cmst sources and, most likely, was deposited in a backarc basin between North America and the lnsular Superterrane.

2) The KMA experienced syndeformational high Pnow T metamorphism resulting from eastward subduction and underplating undemeath the Aishihik Metamorphic Suite of the North American continental margin in the Late Cretaceous.

3) The change in plate motion of the Kula plate during the latest Cretaceous resulted in underplating of the KMA by the lnsular Supertenane and the Dezadeash Formation.

4) Contact metamorphism, due to the Early Eocene intrusion of the RRB at a depth of 12 km. resulted in high T thermal overprinting producing a wide contact aureole and resetting radiogenic ages in the whole KMA.

5) The distinct lithologic and metamorphic character of the KMA does not support correlation with other metamorphic assemblages west of the Denali fault. Previous estimates of dextral strike-slip displacement based on such correlations are not supported by geological evidence. It is concluded that the Denali faul developed along an earlier suture zone between island arc tenanes and the ancient American continental margin, possibly without any major dextral strike-slip movement. Aieinikoff, J- N.. Dusel-Bacon, C., Foster, HL& Futa, K. (1981): Pmterozoic zircon from augen gneiss, Yukon-Tanana Upland, east-central Alaska.- Geology9, pp. 469473.

Andrew, A. Armstrong, R. L & Runkle, O. (1991): Neadymium-strantium-lead isotopic study of Vancouver Island igneous rocks.- Cari-J-EarthSci, 28, pp, 1744-1 782

Aranovich, L. Y. & Beman, R. G. (1996): Optimized standard state and mixing prope- of minerais: II. Cornparison, predictions, and applications.- Contn'b-Min.PetroI. 126, pp. 25- 38,

Arth, J. G., Barker, F. 8 Stem, T. W. (1 988): Coast batholith and Taku plutons near Ketchikan, Afaska: Petrography, Geochronology, Geochemistry and Isotopic charactec- Amer. J-Sci 288 A, pp. 461-489-

Barrow, G. (1893): On an intrusion of muscovite biotite gneiss in the S.E. Highlands of Scotland and -ts accompanying rnetamorphism.- Q.J.Geol.Soc.Lond. 49, pp. 330-358.

Bennett, V- C. & Hansen, V. 1. (1988): Neodymium isotope similarities between the Yukon- Tanana terrane, Yukon Territory and continental North America.- Geai-Soc.Am.Abstr, Pmgrams 20, p. A1 11.

Berckhemer, HI (1990): Grundlagen der Geophysik- WSssenschaMiche Buchgesellschaft, Darmstadt, 201 p.

Berg, H.C. 8 Jones, D.L. (1974): Ophiolite in southeastem Alaska.-Geol.Sm.Am.Absfr. Pmgrams 6, p. 144.

Berg, H. C., Elliott, R. L, Smith, J. G. 8 Koch, R. O. (1978): New Geological Map of Ketchikan and Prince Rupert quadrangles, southeastern Alaska- in: Johnson, K. M. (ed.): The United States Geological Survey in Aiaska. Accamplishments during 1977.- U. S. Geol.Sunr. CimuIar 772-BI pp. 82-83.

Bennan, R- G- (1991): Therrnobarometry using multiequilibrium calculations: a new technique, with petrologic applications.- CanMheraL 29, pp. 833-855.

Beman, R, G. (1996): TWW (version 2.02).

Bennan, R, G, & Aranovich, L Y- (1996): Optimired standard state and mixing properties of minerais: 1, Model calibraüon br olivine, orthopyroxene, cardierite, gamet, and ilmenite in the system Fe0-Mgû-CaO-AI ,O,-TiO,SiO,- Condn'b,Min.Pebol. 126, pp. 1-24.

Berthé, D., Chouiwune, P-1L Jegouro, P. (1979): Orthogneiss, rnylonite and non coaxial deformation of granites: the example of the South Annorican Shear Zone.- JStnrct,Geol- 1, pp. 31-42.

Bhatia, M. R- (1985): Rare earth elements geochernistry of Australian Paleozoic graywackes and rnudrocks: Provenance and tectonic control.- Sediment Geol. 45, pp. 97-1 13-

Bhatia, M- R-8 Crook, K A. W. (1986): Trace element characteristics of graywackes and tectonic setting discrimination of sedimentary basins.. Contnb. Miner.Petmi. 92, pp. 181 - 193.

Bostock, H- S. (1966): Notes on glaciation in central Yukon Territory.- Geol. Surv- Can. Paper 6546,18p.

Bowring, S. A & Podosek, F. A (1989): Nd isotopic evidence from the Woprnay Orogen for 2.0 - 2-4 Ga cnist in western North Ameflca.-EarthPlanetSciLet, 94, pp. 217-230.

Brernner, T. (1990): Oezadeash rnap-area (NTS 115 A).- in: Morison, S. R. (ed.): Yukon Exploration i 989.- indian and Norfnem AMis Canada, pp. 97-99.

Brew, D. A. & Drew, L. J., Schmidt, L. M., Root, O, H. 8 Huber, D. Ç. (1991): Undiscovered locatable mineral resources of the Tongass National Forest and adjacent areas, southeastem Alaska- U.S-Geol. Surv, Open-çile Report 94-11 0,370 p.

Brew, O. A- 8 Ford, A B. (1984): The northem Coast plutonic metamorphic cornplex, southeastern Alaska and noraiwestern British Columbia.- rin Conrad, W. L. 8 Elliott, R. L- (ed.): The United States Geolagical Suwey in Alaska. Accomplishments during 1981-- U.S. Geol.SUN. Cimuiar 886, pp. 120-124. Brew, D. A. 8 Ford, A. 8, (1993): ïhe Coast Plutonic-Metamorphic Complex between Skagway, Alaska, and Fraser, British Columbia - Geologic sketch and road log.- in: Johnstan, S. T., Hart, C. 3- R-, Mihalynuk, M. G-, Brew, D- A & Ford, A B- (ed.): The Northem Intermontane Superterrane.- fieldguide to 1993 NUNA conference, Lakeview Marina, Marsh Lake, Yukon, August 22-28,1993, pp. 1-19-

Brew, 0. A, Ford, A 8- & Garwin, S- L (1985): Fossiliimus middle and (or) upper Triassic rocks within the Coast Plutonic Complex, southeast of Skagway.- in: Bartsch-Mnkler, S. (ed.): The United States Geological Survey in Alaska, Acearnplishrnents during 1984.- U-S- Geol-SUN. Circular 967, pp- 86-89.

Brew, D. A & Grybeck, D. (1984): Geology of the Tracy Arm - Ford Terror Wildemess Study Area and Vicinity, Alaska-- in: Mineral Resources of the Tracy Arrn - Ford Terros Wildemess Study Area and Vicinity, Alaska-- U.S.GeoLSun/-Bull- 1525-A, pp. 23-52.

Brew, DA, Hirnrnelberg, G-R., Loney, RA& Ford, AB. (1992): Distribution and characteristics of metamorphic belts in the south-eastem Alaska part of the North Arnerican Cordillera- J.metamorphic Geol. 10, pp, 465482-

Bucher, W. H- (1 944): the stereographic projection, a handy tool for the practical geologist- J.Geol- 52, pp. 191-212-

Bucher, K 8 Frey, M. (1994): Petrogenesis of Metamorphic Rocks- 318 p., Springer-Verlag.

Cairnes, D. D. (1914): Geology of a portion of the Yukon-Alaska boundary, between Porcupine and Yukon rivets.- Geologkal Survey Department of Mines Summary RepoR 1912, pp. 9- 11.

Chatteqee, N. D. & Froese, E. F. (1975): A themodynamic study of the pseudobinary join muscovite-paragonite in the system KAISi ,O,-NaAlSi,O,-AIO,-SiOZ-HtOO- Am.Mineral.60, pp- 985-993.

Clague, J.J. (1979): The Denali Fault system in southwest Yukon Temitory - a geologic hazard?- Cunent Resea~h,Part A, GeoLSurv-Can. Paper 79-1 A, pp. 169 - 178. Clague, J. J. (1991): Structural Styles, Chapter 17.- in: Gabrielse, H., Yorath, C. J. (eds.): Geology of the Cordilleran Orogen in Canada, The Geology of Canada, n0.4,- Geol,Sur.Can,,pp. 571475.

Cackfield, W. E. (1927): Aishihik Lake District, Yukon-- Ged.Suw.Can- Summary Repot 1926 A, pp. 1A-1 34with accompanying map 2124.

Csejtey, B., Cox, D.P & Evarts, RC. (1982): The Cenozoic Denali Fauit System and ihe Cretaceous Accretionary Development of Southem Alaska- J.GeophysRes. 87, pp- 3741- 3754.

Creaser, R. A, Erdmer, P., Stevens, R. A. 8 Grant, S. L (1997): Tectonic affmity of Nisutlin and Anvil assemblage strata from the Teslin Tectonic Zone, northern Canadian Cordillera: constraints from Neody mium isotope and geochemical evidence- Tectonie 16, pp. 10% 121.

Oavidson, C. (1989): The Maclaren Glacier metamorphic belt, south-central Alaska: a tectonometamorphic signature of the accretion of Wrangellia to the North Amencan continent- Geol.Soc.Am.Abstr.Pmgmms 21, p. A1 81-

Oavidson, C., Hollister, L S. 6 Schmid, S- M- (1992): Rote of melt in the formation of a deep- crustal shear zone: the Maclaren metamorphic belt, south central Alaska-- Tectonics 11, pp. 348-359.

DePaolo, O, J. (1981): Neodymium isotopes in the Colorado Front Range and crust mantie evolution in the Proterozoic.- Nature 291, pp. 193-196.

DePaoIo, D. JI (1988): Neodymium Isotope Geochernistry.- Springer-Verlag , Berf in, 187 p.

DePaolo, D. J. 8 Wasserburg, G.J. (1976): Neodymium isotopic variations and pettogenetic models.- GeophysRes.Letters 3, pp. 249-252.

Dodds, C. J. (1991): Denali FauIt System.- in Gabrielse, H. (Cornp.): Structural Styles. Chapter 17.- in: Gabrielse, H., Yorath, C.J. (eds.): Geology of the Cordilleran Orogen in Canada, The Geology of Canada, no.4.- GeoLSur.Can., pp. 573-674. Dodds, C. J- 8 Campbell, R- B. (q 992): Geology of NE Yakutat (1 140) and Tatshenshini River (114P) map areas, British Columbia-- Geel-Sur,Çan.Open File 2191.

Eisbacher, G. H- (1976): Sedimentology of the Dezadeash flysch and I& implications for strike- slip faulting along the Denali Fault, Yukon Tenitory and Alaska- Can.J.EartnSci- q3, pp. l49Sl513-

Eisbacher, G- H. & Hopkins, S. L (1977): Mid-Cenozoic Pafeogeornorphology and tectonic setting of the St Elias Mountains, Yukon Tenibry.- Geol.Sur~Can. Paper 77-1 b, pp- 319- 335.

Engebretson, O. C., Kelley, K. P., Bumester, R- F., Russell, R. & Blake, M. C- (1995): North American Plate Interactions Re-revisited.-Geol.~ssoc-Can.Min.AssocCan.Abstr.Programs 20, p. A 28.

England, P- C. 8 Thompson, A B. (1984): Pressure-Temperaturefime Paths of Regional Metamorphism 1. Heat Transfer dunng the Evolution of Regions of Thickened Continental Crust- J-PetroI. 25, pp. 894928-

Erdmer, P. (1989): The Nisling Schist in eastem Dezadeash rnap area. Yukon-- Cunent Research, Pafl E, Geological Sutvey of Canada, Paper 89-1 E, pp. 139-144.

Erdrner, P. (1990): Studies of the Kiuane and Nisling assemblages in Kluane and Dezadeash map areas, Yukon,- Cumnt Research, Part E, Geological Survey of Canada, Paper 90- 1E, pp. 107-111.

Erdmer, PI(1 991 ): Metamorphic terrane east of Denali fault between Kluane Lake and Kusawa Lake, Yukon Territdry.- Cunent Research, Part A, Geological Survey of Canada, Paper 91-l A, pp. 37-42.

Erdrner, P. & Mortensen, J. K. (1993): A 1200-km-long Eocene metamorphic-plutonic belt in the northwestem Cordillera: Evidence from southwest Yukon.- GeoIogy 21, pp. 1039- 1042.

Ernst, W. G. (1988): Tectonic history of subduction zones infened from retrograde blueschist P-T path.- Geology 16, pp. 1081-1084. Eskola, P. (1915): On the relation between chemical and mineralagical composition in the metamorphic mIcs in the Oniavi region-- Bull.Comm-Geol. de Finlande 44, pp, 67-225.

Evenchick, CI A. (1 995): Structurai evidence of Early Cretaceous sinistral displacement in the Northem Canadian Cordil1era.- GACIMAC Pmgram wifh Abstracts 20, p A 30.

Farmer, G. LI Baker, F. & Platker, G- (198f): A Nd and Sr isotopic study of Mesozoic and eariy Tertiary Granitic rocks in southcentral Alaska- Geol,SocAm.Absb.P/ograms19, p. 376.

Farrar, E., Clark, A H., Arctiibald, D- A. 8 Way, 0. C, (1988): Potassium-Argon age of granitoid plutonic rocks, southwest Yukon Temitory, Canada- IsochmMest 51, pp- 19-23.

Faure, G. (1986): Princîples of isotope geology (2nd dition): John Wiley 8 Sons, New York, 589 p.

Feng, R,, Kemch, R. & Maas, R. (1993): Geochernical, oxygen, and neodyrnium isotope compositions of metasediments from the Abatibi greenstone belt and Pontiac Subprovince, Canada: Evidenœ for ancient cnist and Archean temane juxtaposition.- Geochim.Cosmochrni.Acta 57, pp- 641-658,

Ferry, J. M. 8 Spear, F. S. (1978): Experimental Calibration of ParMionhg of Fe and Mg between Biotite and Gamet- Confrib.Mineral. Petmi. 66, pp. 113-1 17.

Fitzgerald, PG., Stump, E, & Redfield, T-F. (1993): Late Cenozoic Uplift of Denali and Its Relation to Relative Plate Motion and Fault Morpho1ogy.- Science 259, pp. 497 - 499.

Flinn, D. (1962): On folding during three-dimensional progressive defortnation-- Geol.Soc. London Quart Jour. 118, pp. 385433.

Forbes, R. B., Smith, T. E. & Turner, D.L (1974): Comparative petrology and structure of the Maclaren, Ruby Range and Coast Range belts: lmplicaüons for offset along the Denali fauk system.-Geol.Soc.Am.Abstr.Pmgrams 6, p. 1?ï.

Frost, C, D. 8 Coombs, O. S. (1989): Nd isotope character of New Zealand sediments: Implication for terrane concepts and crustal evo1ution.- Am.J.Sci. 289, pp. 744-770. Frost, C. D. 8 O'Nions, R- K (1984): Nd evidence for Proterozoic cnistal devetopment the Belt-Purcell Supergroup,- Nakm 312, pp- 53-56,

Fuhnan, M, L- 8 Lindsley, D. H. (1988): Ternary feldspar modelling and thermometry.- Am-Mineral, 73, pp. 201-216.

Gabrielse, H., Monger, J. HI W., Wheeler, J. 0.8 Yorath, CcJ- (1991): Part A. Morphogeological belts, tectonic assemblages and terranes- in: Chapter 2 of Gabrielse, H., Yotath, C. J. (eds.): Geology of the Cordilleran Owen in Canada, The Geology of Canada, No. 4- Ged-Su~Can.,pp- 15-28-

Gabrielse, H. 8 Yorath, C. J. (1991): Tectonic Synthesis, Chapter 18.- in: Gabrielse, H-, Yorath, C- J. (eds,): Geology of the Cordilleran Orogen in Canada, The Geology of Canada, No. 4- Geel-Sur.Can., pp- 679-705-

Gehrels, G- E-, McClelland, W. C., Samson, S. 0, 8 Patchett, J. P. (1991a): U-Pb geochronology of detntal zircons from a continental margin assemblage in the northem Coast Mountains, southeastem Alaska.- CanJEarfh Sci 28, pp. 1285-1 300.

Gehrels, G. E-, McCleIland, W. C-, Samson, S, D, Patchett, 3. P, 8 Brew, O, A (1991b): U-Pb geochronology of Late Cretaceous and early Tertiary plutons in the northem Coast Mountains batholith.- Can.J. Earth Sci. 28, pp. 899-91 1.

Gehrels, G. E., McClelland, W. C., Samson, S- D,, Patchett, J. P. 8 Orchard, M. J. (1992): Geology of the western flank of the Coast Mountains between Cape Fanshaw and Taku Inlet, southeastern Alaska.- T;ectonics 11, pp, 567-585.

Geological Suwey of Canada (1969): Kluane Lake, Yukon Terntary.- Can-Geol,Suru,Geophys. Paper 7827.

Ghent, E. O. (1976): Plagioclasegamet-Al,SiO,quarfz: a potential geobarometer- geothemometer.- Am. Mineral. 61, pp. 710-714.

Goldstein, S. L., O'Nios, R. K & Hamilton, P. J. (1984): A Sm-Nd isotopic study of atmosphenc dus& and particles from major river systems.- Earth. Planet SciLet. 70, pp. 221-236. - - Grybeck, O-, Brew, D. A, Johnson, B. R. 8 Nutt, C, J. (19n): Ultramafic rocks in part of the Coast Range batholitic cornplex, southeastem Alaska- rir: Accornplishment in Alaska 1976, US GeoLSurv. Ci~ular7SiB, pp, 88245.

Hanmer, S. 8 Passchier, C- W. (1991): Shear-sense indiators: a review.- Geol,SuwCan. Pap. 90-17.72 p.

Hart, C. J. R- (1993): 0.C- -Yukon Border to Carcross to Alaska Highway.- Nuna '93 filed log, Day One, Leg C.- in: Johnston, S- T., Hart, C. J. R., Mihafynuk, M. G., Brew, D- A 8 Ford, A. B. (ed-): The Northern Intemiontane Supertenane.- fieldguide to 1993 NUNA conference, Lakeview Marina, Marsh Lake, Yukon, August 22-28.1993, pp. 3141.

Heaman, L. & ParrÏsh, R, (1991): U-Pb geochronology of accessory rninerals- in: Heaman L 8 Ludden, J. N. (ed.): Short course handbook on applications of radiogenic isotope systerns to problems in geology.- Min.Assoc.Can 19, pp. 103-166.

Himmelberg, G. R,, Ford, A B. 8 Brew, D. A. (1984): Progressive rnetamorphism of pelite rocks in the Juneau area, southeastem Alaska- Iir: Conrad, W. L- & Elliott, R, L (ed-): The United States Geological Sunrey in Alaska. Accomplishments during 1981.- U.S.Geol.Sun/.Cimuiar886, pp. 131-134.

Himrnelberg, G. R., Brew, D, A 8 Ford, A B. (1985): Ultramafic bodies in the Coast plutonic- rnetarnorphic cornplex near Skagway , southeastem Alaska- in: Accomplis hment in Alaska 1984, US Gml. Sum. Cimuiar 967, pp. 92-93.

Hoeppener, R. (1955): Tektonik im Rheinischen Schiefergebirge: Eine Einfûhning.-

Hoffman, S. E., Wilson, M. & Stakes, D.S. (1986): lnferred oxygen isotope profile of Archaean oceanic crust, Onverdacht Group, South A-.- Nature 321, pp. 55-58.

Holdaway, M. J. & Lee, S. M. (1977): Fe-Mg Cordierite Stability in High Grade Pelitic Rocks Based on Experimental, Theoretical, and Natutal Observations.- Contrib.Mineral. PetroI- 63, pp. 175-198.

Haldaway, M. J. & Mukhopadhyay, B. (1993): A reevaluation of the stabilii relations of andalusite: thermochernicai data and phase diagram for the aluminium silicates- AmMineral, 78, pp. 298-31 5,

Hollister, L SI,Andronicos, C., Crawford, M., L. Davidson, C. M., Klepeis, K A 8 Rusmore, M. E (1997): Geological data cannot rule out large scale (>IO00 km) transcurrent motion across aie Coast orogem- in: Cook, F. 8 Erdmer, P. (cornp.): 1997, Slave-Northem Cordillera Liiospheric Evolution (SNORCLE) Transect and Cordilleran Tectonics Workshop Meeting (March 7-9), University of Calgary, Lidhopmbe RepoR No. 56, pp. 155-1 59.

Hooper, P- R., Johnson, O. M. & Conrey, R- M. (1993): Major and trace element analyses of rocks and minerais by automated X-ray spectmrnetry.- Washington State University, Open File Report, 36 p.

Homer, R, B. (1983): Seismicity in the St. Elias region of northwestem Canada and southeastem Aiaska- Bulletin ofthe Seismo/ogical Society of America 73, pp. 11 17-1 137.

Hudson, T., Plafker, G. & Dixon, K (1982): Horizontal offset history of the Chatham Strait fault- US Geoi-Surv-Cricuar834, pp- 128 - 132.

Irving, E., Wynne, P. J., Thorkelsen, O- J. 81 Schiarizza, P. (1996): Large (1000 to 4000 km) northward movements of tectonic domains in the northem Cordillera, 8345 Ma.- J-Geoph-Res.101, pp. 17901-17916.

Jackson, J, L, Gehrels, G. El Patchett, P- 3.8 Mihafynuk, M. G. (1991): Straügraphic and isotopic link between the northem Stikine terrane and an ancient continental margin assemblage, Canadian Cordillera- GeoIogy 19, p. 1177-1 180.

Jones, DL, Silberfing, N. J., Csejtey, Jr., B., Nelson, W. H. 8 Blome, C.D. (1980): Age and Structural SignifÏcance of Ophiolite and Adjoining Rocks in The Upper Chulitna District, South-central Alaska- US Geol.Surv. Pmf Pap 1121-A, 21 p.

Johnston, S. T. (7993): The geologic evolution of Nisling assemblage and Stikine terrane in the Aishihik Lake atea, southwest Yukon-- Ph-D. dissertation, Univ. of Alberta, Edmonton, 270 p.

Johnston, S. T- & Erdmer, P. (1995a): Hot-side-up aumole in southwest Yukon and limits on terrane assembly of the nofthem Canadian Cordillera- Geology 23, pp. 419-422-

Johnston, S. T. & Erdmer, P. (1995b): Magmatic Flow and Emplacement Foliations in the Eariy Jurassic Aishihik Batholith, Southwest Yukon.- i& Miller, D. M. 8 Busby, C.: Jurassic Magmatism and Tectonics of the North Amencan Cordillera- Geol.Soc. Amer. Spec.Pap. 299, pp. 65-82.

Johnston, S. T., Mortensen, J. K & Erdrner, P. (1996): lgneous and metaigneous age co nstraints for the Aishihik metamorphie suite, southwest Yukon.- CanJEarthSci- 33, pp- 1543-1 555-

Johnston, S. T- & Timmerman, J. R- (1993a): Geology of the Aishihik Lake and Hopkins Lake Map areas (115 H6/7), southwestern Yukon.- Yukon fiploration & Geology 1993, pp. 93- 110.

Johnston, S- T. 8 Timmerman, J. R, (1993b): Geological Map of the Aishihik Lake area (115 H6),- Bploration and Geologïcal Services Division, Yukon, Indian and Northem Arnim Canada, Open File 19961 (G).

Kindle, ED. (1952): Dezadeash map-area, Yukon Territorp Geological Survey of Canada Memoir 268,68 p.

Karig, O. E. (1974): Evoiution of arc systems in the western Pacific. - Ann-Rev. Earth PlanetW. 2, pp. 51-76.

Karig, O. E. (1982): Deformation in the forearc: implications for mountain belts- in: HsO, K. J. (ed,): Mountain Building Processes.- pp. 59-71. Acacfemic Press, London-

Karig, D. E. & Sharman, G. f. (1975): Subduction and acctetion in trenches- BulLGeoi.Soc. Am. 86, pp. 377-389.

Kohn, J. M. & Spear, F. S. (1991a): Error propagation for barometers: 1. Accuracy and precision of expenmentally located end-mernber reactions.- Amen'can Mineralogist 76, pp- 128-137-

Kohn, J. M. 4% Spear, F. S. (1991b): Error propagation for barometers: 2. Application to rocks.- Le Couteur, P. C. & Tempelman-Nuit, D. J. (1976): RblSr Ages and a profile of initial Sr =/Sr" ratios for plutonic racks acmss the Yukon Crystalline Terme,- Can-JEarViScL13, pp. 319-330.

Loney, R. A. (1964): Stratigraphy and petrography of the Pybus-Gambier area, Adrniralii Island, Alaska- US Geol.Sunr.Bull. 1779, 17 p.

Lowdon, J, A (ed.) (1960): Age deteminations by the Geological Survey of Canada, report 1- lsotopic Ages.- Geolugical Survey of Canada, Paper 60-l7,51 p.

Lowe, C., Homer, R- B., Mortensen, J- K., Johnston, S- T. & Roots, CI F. (1994): New geophysical data frorn the northern Cordillera: prelirninary interpretations and implications for the tectonics and deep geo1ogy.- CanJ.EarthSci, 31, pp. 891-904-

Lowey, G. W. (1992): Vanation in bed thickness in a turbidite succession, Oezadeash Formation (Jurassic-Cretaceous), Yukon, Canada: evidence of aiinning-upward and th ickening-upward cycles- Sedimenfary Geology 78, pp. 217-232-

Makashima, A. 8 Nakamura, E, (1991): Calibration of Farady cup efkiency in a rnulticollector mass spectrometer.- Chem-GeoL 94, pp. 105-1 10.

Marcantonio, F., Reisberg, L, Zindler, A, Vliyman, D. & Hulbert, L. J. (1993): An isotopic study of the Ni-Cu-PGE-rich Wellgreen intrusion of the Wrangellia terrane: evidence for hydrothennal mobilization of Re and Os.- Geochrm.Cosmochim. Acta 55, pp. 1007-1017.

McConnell, R. G. (1905): The Kluane Mining District- GeoLSurv.Can, Annual RepoR 16, pp. 1A-1 8A

McClelland, W. C., Anowib, L M. & Gehrels, G. El (1991): Thermobaromeüic constraints on the structural evolutian of the Coast Mountains batholith, central southeastem Alaska.- CmJ.EarthSci 28, pp. 912-928.

McClelland, Gehrels, G. E., Samson, S. D. 8 Patchett, P. J. (1992): Structural and geochronologic relations along the western Rank of the Coast Mountains batholith: Stikine River to Cape Fanshaw, central southeastem Alaska- J-StnrctGeoL 14, pp. 475489.

McCulloch, M. T. & Wasserburg, G. J. (1978): Sm-Nd and Rb-Sr ctironology of continental crust formation.- Science 200, pp. 1003-1011.

McLennan, S. M. CIt Hemming, S- (1992): Sarnafiumlneodyrniurn elemental and isotopic systematics in sedirnentary rocks.- Geochïm~CosmochimmActa 56, pp. 887-898.

Mezger, J. E. (1995): The Kluane Metamo~hicAssemblage, SW Yukon - first steps towards developing a tectonic model.- CordiIIeran Tectonii Workshop Meeting 7995, Ottawa- Carleton Geoscience Centre, Febmary 10-12, 1995, p 11.

Mezger, J. E. 8 Creaser, R, A (1996): Backatc basin setting of the Kfuane Metarnorphic Assemblage and sinistral strike-slip along a proto-Denali faut Evidence from isotope and microtectonic studies in the SW Yukon.- Geol.Soc.Amer.Abstr.PrograrnsS28 (7). p- A 312.

Monger, J. W. H., Price, R. A 8 Templeman-Kluit, D. J. (1982): Tectonic accretion and the ongin of the two major metamorphic and plutonic welts in the Canadian Cordil1era.- Geology 10, pp. 70-75.

Monger, J. W. H., Wheeler, J. O., Tipper, H. W., Gabrielse, H., Harms, T., Stniik, L C., Campbell, R. B., Dodds, C. J., Gehrels, G. E 8 O'Brien, J. (1991): Part B. Cordilleran termes.- in: Upper Devonian to Middle Jurassic assemblages, Chapter 8 in: Gabrielse, H., Yorath, C. J. (eds.): Geology of the Cordilleran Orogen in Canada, The Geology of Canada, no-4.- Geol,Sur. Can, , pp. 28 1-327.

Monger, J. W. H., van der Heyden, P., Joumeay. J. M., Evenchick, C. A & Mahoney, J. B. (1994): Jurassic-Cretaceous basins along the Canadian Coast Belt: Their bearing on pre- mid-Cretaceous sinistral displacements.- Geology 22, pp. 175-1 78.

Moore, J. C. (1 989): Tectonics and hydrogeology of accretionary prisms: role of décollement zone.- J-StmctGeol. 11, pp. 95-106.

Mortensen, J. K. (1992): Premid-mesozoic tectonic evolution of the Yukon-Tanana tenane, Yukon and Alaska. Tectonics Il,No.4, pp. 836-853. Mortensen, J. K & Erdmer, P. (1992): U-Pb, APA~and K-Ar Ages for Metamorphism of the KIuane and Aishihik Assemblages in Southestem Yukon-- Radr'ogenic Age and Isotopic Studies; Report 6; Geologicai Survey of Canada, Paper 92-2, pp. 135-139-

Muehlenbachs, K (1986): Aiteration of the Oceanic Cnist and the "0 History of Seawater-- in: Valley et al, (ed.): Stable Isotopes in High Temperature Geological Processes.- Min-SocAm. Revr'ews in Mineraiogy 16, pp. 425-444.

Muller, J. E, (1953a): Preliminary map Kluane Lake (Wst Half), Yukon Territory (Descriptive Notes).. Geological Sumy of Canada, Paper 53-20, pp- 1-9.

Muller, J. E. (1953b): Kluane Lake map-area, Yukon Territorp Geologiical Suwey of Canada, Paper 58-9, pp, 7-9, with accompanying map 19-1958.

Muller, J. E. (1958): Tectonics of the Shakwak lineament, southwest Yukon and eastern Aias ka.- Bu//.Ged SocAm. 69, pp. 16 19-1620.

Muller, J. E. (1967): fûuane lake map-area, Yukon Temtory (11 SG, 115F E112). Geological Survey of Canada Mernori 340,137 p.

Nokleberg, W.J., Foster, H. L 8 Aleinikoff, J.N. (1989): Geology Of The Northern Copper River Basin, Eastern Alaska Range, and Southem Yukon-Tanana Upland.- in: Sedimentation and Tectonics of Western Nom America, Vol.1. Proceedings ftom the 28th International Geological Congress.

Nokieberg, W. J., Jones, D. L. 8 Silberling, N. J. (1985): Origin and tectonic evolution of the Maclaren and Wrangellia tertanes, eastern Alaska, Alaska.- Buil.geoLSoc.Am, 96, pp. 1251-1270,

Norrell, G. T., Teixell, A & Harper, G. D- (1989): Microsbuchire of serpentine mylonites from the Josephine ophiolite and serperrtinization in rebogressbe shear zones, California.- Geoi.Soc- Am. BuiL 101, pp. 673-682,

Page, R. A & Plafker, G. & Puplan, H. (1995): Block rotation in eastcentral Alaska: A framework for evaluating earthquake potential? - Geology 23, pp. 629-632. Pangaea Scientific (1995): SpheriStat 2.0 for Mndows 3.1 manual.- 198 p-

Passchier, C. W 8 Trouw, R. A- J- (1996): Microtecbnics- Springer, Berfin, 289 p.

Patton, W. W., Box, S.E. 8 Grybecû, 0.3. (1994): Ophiolites and other mafic-ultramafic complexes in Alaska- h: Plafker, G- 8 Berg, H- C. (ed.): The Geology of Alaska.- GeoLSocAmer. 7he Geology of Nom Amen'ca G-1, pp- 671-686.

Pettijohn, F. J,, Potter, P. E 8 Siever, R. (1987): Sand and sandstone, 2nd &ion.- Springer Verlag, 553 p,

Plafker, G., Nokleberg, W.J. 8 Lull, J.S. (1989): Bedrock geology and tectonic evolution of Wrangellia, Peninsular, and Chugach terranes along the Trans-Alaska Crustal Transect in the Chugach Mountains and Southem Copper River Basin, Alaska..J.Geophys.Res. 94, pp. 4255 - 4295-

Platt, J. P. (1986): Dynamics of omgenic wedgen and uplii of high-pressure metamorphic rocks- Geol,Soc.Amer. Bull. 97, pp- 1037-1 053,

Powell, RI & Holland, T- (1990): Calculated mineral equilibria in the pelite system, KFMASH (&O - Fe0 - Mg0 - AiA SiO, - H20).- AmMineral. 72. pp. 255-272.

Ramsey, J. G. (1967): Folding and fracturing of rocks.- McGraw-Hill, New York, 568 p.

Red, B. L & Lanphere, M. A (1974): Offset Plutons and History of Movernent along the McKinley Segment of the Denali Fault System, Alaska- Bull,Geol.Soc.Am. 85, pp. 1883- 1892.

Richardson, S.W., Gilbert, M, C. 8 Bell, P.M. (1869): Expenmental detemination of kyanite- andalusite and andalusite and siIlimanite equilibria: the aluminium silicate triple point- Amer.J.Sci. 266, pp. 259-272-

Richter, D.H. 8 Matson, N.A. (1971): Quartemary Faulting in the Eastern Alaska Range.- Bull. Geol.SocAm. 82, pp. 1529 - 1540.

Ridgway, K. O., DeCeIles, P. G., Cameron, A R. 8 Sweet, A R. (1992): Cenozoic syntectonic sedimentation and stn'ke-slip basin development along the Denali fault system, Yukon Territorp Yukon Geobgy 3, fiploration and Geological ServrCes Division, Yukon, lndian and Northem Afiits Canada, pp. 1-26.

Rosenbuscfi, H. (1877): Die Steger Schiefer und ihre Contactrone an den Graniten von Barr- Andlau und Hohwa1d.- Abh-Ged Specialkarte Elsass-Lodhr. 1, pp. 79 - 393.

Ross, G. M., Boghossian, N- D-, Patcheît, P. J. 8 Gehrels, G. E. (1995): \Mie@ did al1 that mud corne from? Provenance evoluüon of the Cordilleran miogeocline from neodymium isotope system studies- Cordrllemn Workshop, Carleton University, Program wifh Abstracfs?p. 12.

Rubie, O. C. (1984): A thermal-tectonic rnodel for high-pressure metamorphism and deformation in the Sesia Zone, Western Alps.- J.GeoL 92, pp. 21-36.

Rubin, CM., Saaleby, J.B., Cowan, DS, Brandon, M.T. & McGroder, M-F. (1990): Regionally extensive mid-cretaceous west-vergent thrust system in the northwestem CordiIlen: Implications for continent-rnargin tectonism,- Geology 18, pp. 276 - 280.

Samson, S. O., McCtelland, W.C., Patchett, P. J., Gehrels, G. E. 8 Anderson, R, G- (1989): Evidence from neodymuim isotopes for mande contributions to Phanerozoic cnistal genesis in the Canadian Cordillera- Nature 337, pp. 705-709.

Samson, S- O., McClelland, W-C., Patchett, P- J., Gehrels, G. El 8 Anderson, R. G. (1990a): A detailed isotope investigation of the Taku and Yukon Crystalline terranes SE Alaska: Ancient continental material between juvenile crust of the Canadian Cordillera- Geol.Assoc.Can, Min.Assoc- Can-Abstr. Programs 15, p. 11 7.

Samson, S. O., Patchett, P. J., Gehrels, G. E. &Anderson, R. G. (1990b): Nd and Sr isotopic characterïzation of the Vkangellia Tenane and implications for crusbl growth of the Canadian Cordi1lera.- J-GeoL 98, pp. 749-762-

Samson, S. D., Patchett, P. J., McCtelland, W.C. & Gehrels, G. E, (1991a): Nd and Sr isotopic constraints on the petmgenesis of the West side of the northem Coast Mountains batholith, Alaskan and Canadian Cordil1era.- Can.J.EarthSci 28, pp. 939-946.

Samson, S. O., McClelland, W-CI, Patchett, P. J. & Gehrels, G. E. (1991b): Nd isotopic characterkation of metamorphie rocks in the Coast Mountains, Alaskan and Canadian Cordillera: ancient crust bounded by juvenile terranes- Tecfonics 10, pp. 770-780.

Schmidt, W- (1925): Geftlgestab'stik- Tschennaks miner,pefmgr.Mitf, 30, pp. 392423.

Souther, J- G. (1991): Volcanic Regimes- Chapter 14 in: Gabrielse, H., Yoraai, C. J. (eds.): Geology of the Cordilleran Orogen in Canada, The Geology of Canada, n0.4,- Geol,Sur.Can., pp. 47-90.

Spear, F. S. (1993): Metamorphic Phase Equilibria and PressureTemperahire-Time Paths.- Mineraf.Soc.Amer. Monograph, 799 p.

Spear, F. S & Cheney, J. T. (1989): A petragenitic grid for pelitic schists in the system Si0 ,- AI&, - Fe0 - Mg0 - b0 - Hg.- Contnb-MineraI.Pebol.101, pp. 149-164-

Spry, A (1969): Metamorphic Textures.- Pergamon (Oxford), 350 p.

Stanley, W.D., Labson, V.F., Nokleberg, W.J., Csejtey, B. & Fisher, MA(1990): The Denali fault system and Alaska Range of Alaska: Evidence for underplated Mesozoic flysch from rnagnetotelluric surveys- Bull.GeolSoc.Am~ 102, pp. 160-173.

Stevens, R. A (1994): Structural and tectonic evolution of the Teslin tectonic zone, Yukon: a doubly-vergent transpressive shear zone.- Ph.D. dissertation, Univ. of Alberta, Edmonton, 252 p.

Stevens, R, A, Delabio, R, N. 8 Lachance, G. R. (1982): Age deteminations and geologicaf studies - K-Ar lsotopic Ages, Report 16.- Geological Survey of Canada, Paper 82-2, pp. 15-26.

Stout, J.H. & Chase, CG. (1980): Plate Kinematics of the Denali fault system.- Can.J.EarthScL 17, pp. 1527 - 1537-

Stumck, D. L, Armstrong, R. L & Maxwell, R. B. (1980): Age and Sr isotopic composÎtion of the Pyroxenite Creeb Ultramafic Cornplex, southwestern Yukon Territory: An Alaskan-type ultramafic intrusion.- Geol. Sun/. Can-, Paper 80-1 8, pp. 185-188. Taylor, H.P. (1967): The zoned ultramafic complexes of southeastem Alaska- h: wllie, P. J. (ed.): Ultramafic and related rocks- John Wley and sons, New York, p. 96-1 16-

Taylor, S. R- 8 McLennan, S. M. (1 985): The Continental Cnist: its Composition and €volution.- Blackwell ScieriMc Publications, Oxf&d, 312 p,

Tempehan-Kluit, O. J. (1974): Reconaissance geology of Aishihik Lake, Snag and part of Stewart River map-areas, west-central Yukon (1154 115F. 115G and 115K)-- Geulogical Suwey of Canada, Paper 7341,97 p.

Tempelman-Kluit, O. J. (1980): Evolutian of physiagraphy and drainage in southem Yukon-- CanJ.EarütScL 17, pp. 1189-1203.

Ternpelman-Kluit, D. J. 8 Cume, R, (1978): Reconnaissance rock geochemistry of Aishihik Lake, Snag and Stewart River map-areas in the Yukon crystalline terrane.- GeoLSurv,Can. PaperTt-û, 72 p.

Tempelman-iauit, D.J. & Wanless, .K. (1975): Potassium-Argen Age Determinations of Metamorphic and Plutonic Rocks in the Yukon Cfystalline Terrane.- CanJ-EarthSci 12, pp. 1895-1909-

Thériault, R, J. & Ross, G. M. (1991): Nd -isotopic evidence for crustal recycling in tfie 2.0 Ga subsurface of western Canada.. Can.J.EartnSci. 28, pp. 1140-1 147.

Thirfwall, M. F. (1982): A triple-filament method for rapid and precise analyses of rare-earth elements by isotope dilution.- Chem. GeoL 35, pp- 155-1 66.

ThirîwaH, M- F. (1991): Long-term reproducibility of multicollector Sr and Nd isotope ratio analyses- Chem.Geol. 94, pp. 85-1 04.

Thompson, A. 6- (1976): Mineral reactions in pelitic rocks II: Calculations of some P-T-X (Fe- Mg) phase relations.- Arn.J.Sci. 276, pp. 425454.

Tilley. C. E. (1924): The facies classification of metamorphic rocks.- Geol-Mag. 61, pp. 167-171. Turner, D. L, Smith. T- E 8 Forbes, R. 0- (1974): Geochrcrnology of offset along the Oenali fault system in Alaska- GSA abstracts wiff~program 6, pp- 268-269-

Twiss, R, J, 8 Moores, E, M- (1992): Structural Geology.- 532 p-, WH- Freeman and Company, New York van Heyden, P. (1992): A middle Jurassic to Eary Tertiary Andean-sierran arc mode1 for the Coast belt of British Columbia,- T~toni'cs11, pp. 82 - 97-

Wahrhaftig, C., Turner, D.L, Weber, FR8 Smith, T.E. (1975): Nature and timing of movements on Hines Creek Strand of Denali fault system, Alaska- Geology 3, pp- 463 - 466.

Wasserburg. G. J-, Jacobsen, S. B., DePaolo, D. J., McCulloch, M. T. 8 Wen, T. (1981): Precise detemination of SmlNd ratios, Sm and Nd isotopic abundances in standard soluüons.- Geochim. Cosmochim. Acta 45, pp. 2311-2323-

Watson, G. S. (1966): The statistics of orientation data.- Jou~Geoi-74,786-797.

Wheeler, J. 0. & McFeely, P. (comp,) (1991): Tectonic Assemblage Map of the Canadian Cordillera, Geo/ogica/ Suwey of Canada, Map 1712A, scale 1:2,000,000c

Wheeler, J. O., Brookfield, A J., Gabrielse, H., Monger, J- H, W., Tipper, H. W- & Woodsworth, G. J. (comp.) (1991 ): Terrane Map of the Canadian Cordillera, Geological Survey of Canada, Map l713A, scale 1:2,000,000-

White, J. C. (1997): Deformation Processes Along the Denali Fault System.- in: Cook, F. & Erdmer, P. (comp.): 1997, Slave-Northem Cordillera Lithospheric Evolution (SNORCLE) Transect and Cordilleran Tectonics Workshop Meeting (March 7-9), University of Calgary, tifhoprobe Report No. 56, pp. 143-145.

Woodcock, N. H. (1977): Specifcation of fabric shapes using an eigenvalue methad.- Geo/.Soc.Amer-Bull-88, pp. 1231-1 236.

Woodsworth, G. J., Anderson, R. G. & Armstrong, R. L. (1991): Plutonic Regimes. Chapter 8 in: Gabrielse, H. & Yorath, C. J- (ed.): Geology of the Cordilieran Omgen in Canada-. Geological Suwey of Canada, Geology of Canada, N0.4, pp. 491-531 -

Wynne, P. J,, Irving, E, , Maxson, J- A & Klehsphen, *KL (1995): Paleomagnetism of the Upper Cretaceous sbata of Mount Tatim Evidence for 3000 km of northward displaœment of the eastem Coast Belt, British Columbia-- J-Geoph-Res-160, pp. 6703-6091 -

Yardley, B. W- D. MacKenzie, W. S. & Guilbrâ, CI(1990): Atlas of metamorphic rocks and their textures.- Longman Scientific 8 Technical, Hariow, 120 p. APPENDICES Appendix 1-1: NTS map index of study area

,Whiihorse

Yukon

British Columbia 0' * \ \

1:250,000 115 A17 Kluhini Riier 115 G12 Congdon Creek 115 G16 Duke River 114 P Tatshenshini River 115 A18 Sandpiper Creek 115 GR Buwash Landing 115 A Dezadeash 115N9 Jojo Lake 115 Gl8 Gladstone Creek 11 5 B Kaskawulsh 115 Al1O Mount Bratnokr 115 G/10 Serpenthead Lake 115 G&F Kluane Lake 115 Ail 1 Kathleen Lakes 115 Gll1 Nuntaea Creek 115 H Aishihik Lake 115N13 Kloa Lake 11 5 Gi12 Lynx Creek 115K&J Snag 11 5 A/14 Canyon 115 Hl3 Ifflemit Lake 115 A11 5 Cracker Creek 115 Hl4 McKinley Creek 1:50,000 11 5 6/16 Jarvis River 115 Hl5 Sekulmun Lake 114 Pi15 Parton River 115 Fi15 Canyon Mountanr 115 Hl6 Aishihik Lake 115 A12 Takhanne River 115 Fi16 Koidem 115 KI2 Dry Creek 115 A16 Mush Lake 115GIl CultusCreek Appendix 2-1 :Thin section sarnple localities and obsenred mineral phases

Sample rock type Long ON) 1 bt (N) major phases (>5 vol%) minor phases (4vol%) 138"Oirl On, 61"1 3'20" rns, grt, CM, tuf, sil, grp 138"06'40n, 61"1 3'50' st, sil, ms, tur, and, grp, O 138°06'1 Sn, 61'14'1 0" st, grt, grp, tur, ms 138°06'15n, 61014'10n - 138"OirSOn, 61O1 3'00" chi, bt, grt, grp, O, tur 138008'3Sn, 61012'40n bt, grp, grt, =O, o 138"09'30n, 61"12'1 On bt, m ap, grp, 0 138009'40n, 61O1 1'50" gQ, b& furI aP, SPn 138'1 0'1O", 61'1 1'35" bt grp, m 0, =O, ep 138'1 0'35", 61"1 1'20" bt, ap, O, czo, ep 138"0Q4On, 61"10'55" bt, grp, tw0, spn 138°08'20n, 61 "1 0'57" bt, ap, tur, grp, ao, 0, ep 138°07'20", 6 1"1 3'05' rns, st, chi, grt, gtp, O, ap l38"06'3O'', 61"14'40" st grt, and, crd, ap, mr, grp 138"06'30", 61O14'4OW ap* gr% 0 138°06'OOw, 61"15'1 0" - 138°06'00", 6 t OISIO" sil, grt, grp, crd, ms, 0 138"06'OOW, 61 "15'40" ms, grp, crd, tur, st, sil, grt 138°06'00, 61"1 5'55" sil, ms, chl, grt, grp, O 138"06'l5", 61"16'30" chi, cd, grt, ms, ap, grp, o 138"06'1Sn, 61"16'30" chl, O 138°07'10", 61"1725" msker, sil, grp, O, crd 138OO3'4Sn, 61"1 1'50w O l38"O3'45", 61"1 1'50" bt, ms, grt, ao,tur, grp 138"03'OOn, 61"12'20" grt, aP l38"03'00", 61Ol2'40" cal 138"O3'OOI 61"12'40 chi, grt, ap, tur, ms 138°02'35', 61"12'55" grt, grPl st, tur 138°01'40", 61"13'1 5" sil, grt st, grp. 0, ms, ap l38"Oî'l 0,61 "1 3'1 5" =Pl aP 138°02'00", 61O1 3'40" ms, st, grp. grt 0, tur, ap 138°04'00", 61'1 5'1 5' ms, st, cd, ch1 l38"02'45", 61 "13'40" crd, sil, grp, ms, ap, tur 138"OTW, 61"1 5'1 5" grt, ms, ch1 138"OT30n, 61"1 5'45" hc, tur, ms, chl, crd, grt 138"02'OOn, 61"14'55" ms, chIl grp, grt, ap, crd, hir 138°0TOOn, 61"14'30" crd, grt, O, grp 138°02'00n, 61"14'10" cd, grt st, grpl ap, tur 138O45'24', 61 "1 5'05" grp, w aln 138O44'5OU,61 O19'50" grp, tur, ap, czo l38O45'l Sn, 61020'25" grp, cal 138"46'OOn, 6 1"20'20" ep, tuf, cal 138°4T20", 6 1019'00" grp, =O, tur,d 2 138°4T40, 61"18'48" qtt, pl, ms, chi, grp, cal 2 138O43'03", 61"1 6'35' qtz, pl, ms, ch1 2 138042'50m, 61 "1 6'0s" qtz, pl, ms, ch1 2 138042'2Sn, 61O15'55" qtr, cal, pl, ms, ch1 3 138°38'10", 61O14'30" act, chl, pl 3 138O38'10", 61 O14'30" act, Cr-mica 3 138036'30n, 61"14'1 0" chl, fsp, cal

Appendix 2-1 (continued):

Sample rock type Long (W) / Lat (N) major phases 05vol%) minor phases (<5 vol%) 137O39'30", 61"0555" qtz, chi, pl, bt, grp ap, grt, ms, tur, ao,zrn 137"63'4SW, 60°43'00" @z, pl, bt grt, a grp, ap, ms, tut, ml 137O05'55", 60'44'1 5" pl, bC st grt, ms, gV, aP, ch1 137O0555", 60°46'45" se PI,bt, St, grp ms, chl, ap, grt, ilm, tur 137O08'1 su, 6û04s30n 9at bt, pl, ms, ch1 grt, st, grp, ilm, tuf, ap, o i36°59'30u, 61041'30n qb, pl, ch1 cal 136°5f'36u, 60°42'15" mebt, pl, si1 grt, grP, msl tur 136°58'20", 60°40'25" qlz, bt, pl hc, cd, ap, grp, ms, zm, si1 137'1 l'Wu, 60°54'55"qtz, pl, bt, sil, rns, gr, crd ilm, spn, zm 137O12'3OU, 60°54'00" qtr, bt, pl, and sil, ap, grp, gR, ms, st, tur 137 O1 7WU, 60°S6'30" qk, bt, pl cd, sil, grp, ap, ms, tur 13721 '1OW, 6O05ïO0" qkl bt, pl, sil, grp crd, ap, ms, zm 137O35'17", 60V555" qb, pl, bt, ms st, chl,grp,and,ap,~l,grt,iim,tur 137°35'35n, 60°04'20" qe, plt chi, bt ap, ms, grp, ap, tur 137033'20"~ 61 003'3~ qtz, pl, bt, ch1 st, ms, grp, ap, tur 137°30'50", 61004'20n qe, pl, bt, ms chl, gr, grt, and, st, ap, hrr 137O31'00", 61"03'42" qw, pl, bt, ms, st grt, grp, sil, and, tur, jar 138"26'SOn, 61"1 8'00" qtz, bt, pl, chi, ms and, crd, grp, cal, ap, st 138°2T00n, 61"17'35" qtz, pl, chi, ms grp, bt, rt, tut, spn 138971 5", 61 016'05" chi, pl, qtz, grp, ms ap, bt, tur 138"22'55", 61 "14'00" ml ms, pl, ch1 gW, bt, aP 138'1 755", 61 "11'35" qtz, Pl, chi, ms gtP, eP, aPl tur, SPn 138°16'00, 61 012'20n qtr, pl, chi, ms ap, spn, 138°14'3û", 61 "1300" qtz, pl, chl, ms bt, gr^, tur, ap 138°14'00", 61 O12'35" qtz, chl, ms, cro, pl, pl hbl, spn, O 138°12'30", 61°11'1S" qtz, bt, chl, ao ms, O 138°18'00", 61 012'50n pl, qtz, chl, ms grp, bt, ap, a0 138'18'05", 61 010'55" pl, qtz, chl, ms gW* a0 138'1 1100,61"14'25" qtz, pl, bt, st, chl, grt and, grp, ap, ms, tur 138°14'4S, 61 "14'35" pl, hbl, cal chl, O 138°15'00", 61 "14'45" qtz, pl, bt, st ms, grp, ap, chl, tur 138°15'30", 61 O15'10 qe, PI,bt, stl grp grt, and, ms, ap, tur 138a25'5OU, 61 "1 5'20" SrPl 01 chr, mag, cal 139°03'35', 61 026'00" qtz, pl, bt, ms, gv grt, st, ap, chi, tur 138O49'35', 61 23'05" SV, ~c,ol,mg idd, ch1 138°09'00", 60°56'00 chl, qtz, O, hbl, ep, pl ah, set 138"43'40", 6 1"38'45" qe, PI,bt, hbl aP, 0, eP 138O43'4OU, 61'38'45" qtz, bt, ms, sil, pl O, ch1 138O41'1 Sn, 61 "40'40 qk, ms, chl Ph gf't gV*0 139°14'00", 61"24'25" alt, qtr, chi, gtp cal, O 140°08'20", 61O52'2S' qk, rns, bt grt 0 140°08'20", 6 1"53'1 5" qtz, pl, ms, bt, crd O 140°15'00", 6 1"54'25" act, PI,eP -1, 0, qk 136'59'1 O", 60°1T40" cal, qtz, chl, bt, grp, pl eP 136°57'15", 60°1û'00" qE, ms, gW 0, SPn 136"58'3OU, 60°54'15" qk, bt pl, si1 i38048'00n, 6 1"1 9'00" qtz, ms, chl, cal aln, grp, PI i38°4T45w, 61 "1 9'05" cal, qb, PI O, chi, ap, zm 138O47'45", 61O1 9'05" qk, cal, pl rt t38O45'1Sn, 61020'30" qk, ms, chl, pl grp, al, bt, ap Appendix 2-1 (continued):

Sample rock type Long (W) 1 Lat (N) major phases (>5 vol%) minor phases (es vol%) 94-1 7a 2 138°49'30", 61"23'30" pl. qtz, ms, ch1 bt, ep, czo, aln, ab, grp, ilm, tur 94-20a 138'49'1 Sn, 6 1"23'20" 94-20b 138°49'lS', 6 1a23'20" 94-26b i 38"43'SO", 61"23'50" 94-36 138"M'3O", 61 "14'1O" 94-39 138"43'03", 61'16'3P 94-41b 138°43'OOn, 6101620" 9445 138039'10", 61"20'00" 94-47 138"37'20m, 61 020'55" 94-5 1 138"33'20m, 61 "19'50" 94-58 138?3'20N, 61 "16'50" 94-60a 138"24'25", 61 016'10)( =Ob 138024'25", 61016'10" woc l38'%'25", 61 016'10" 94-60e l38"24'2û", 61 "16'20" 94-62 13821'00", 61"15'50" 9443 138020'30n, 61"1 5'40" 94-72 138"30'2Sn, 61 "16'40" 94-76 l38"2ir50", 61"15'50" 94-8 1 137"O#l 0",60'51 '35" 94-84 13f0S6'l 5', 60a51'50" 94-87 13ï059'30", 60°51'4S 94-89 b 137"57'20", 61"51 '1 0 94-94 137Y0'20", 60a58'40" 94-98 137'1 8'30N,61 "00'1O" 94-105 137"25'45", 61 O04'50" 94-108 1370î8'20n, 61 '03'1 O 94-1 15 13702î'30n, 61 O0305 94-1 18 l37O2O'OO",61 O0440 94-1 20 137"17'30n,61 '03'20 94-1 23 137"43'OON, 61 O03'55" 94-1 30 137O34'40", 61001'05" 94-1 33 137O31'30", 60°58'05" 94-1 45 137"34'00, 60°Sf 30" 94-1 46 13i0M'O0", 6O057'0OU 94-1 47a 137"34'00", 60°56'45" 94-147c 137"34'00", 60°56'45" 94-1 474 137"34'00", 60°56'45' 94-1 53 137°37'30", 60°57'30" 94-1 72 137"55'10, 61"10'40" 94-173 137"54'40", 61"09'55" 94-174 l37"53'1O", 61"1 2'50" 94-185a 137°50'4î", 6 1 "10'40" 94-191 a 136"58'20", 60'1 7'35" 94-1 92 136°58'20", 60a17'20" 94-1 95 136"58'00", 60°12'35' 94-1 97a 136°58'00", 60 '1 1'49 94-204a 1W0S6'30", 60°W30" 94-204b 137"56'30N, 60°06'30" 94-2 14 136"4î'OO", 59°56'ST' Appendix 2-1 (continued):

Sample rock type Long / Lat (N) major phases (>5 vol%) minor phases (<5 vol%) 94-235a 5 136°5330m, 60°04'55" chl, ap, cal, zrn grt,pl ap, zm,cal - grt, ser- kfs, hc, chi, ilm- hc, ch1 grp, rndser, chl, tur ill, chl, ms, ap hbl, ap, zm chi, O, grt, zm grt ms, se?, grp, zn, O crd, grp, ms, zm ser, O, grt, sil, chl, kfs chl, zm ms, sil, chi, hc, ap, zm 0, aP- ms, grp, grt, aP chi, tur, grp bt, ms, chi, grp, grt, czo, tur O, pl, ms rnslser, chl, crd, si1 ms, cd, and, O - st, gr4 tur, ms pl, crd, grt, hc, ser, O grt, aP grt, tur, ch1- O, cal aP and, rns, grp, chi, tuf, ap bt cal, O bt, hbl, O qe grp. 0

01 9"P hbl, =O, grt, pl ms

grtl kY1 PI grt, st, QI chf grt, 0, hbl, pl crd, gQ, O, m, ms PL bt chl, czo bt, O, chi Appendix 2-1 (continueâ):

Sarnple rock type Long (W) I Lat (N) major phases (~5vois) minor phases (4vol%) * PI, ch11 ms. qtr, pl, chl, ms cal, act m,chl, pl, ms Qtz, ep, =O, pl, ch1 qb, uo, ms, ch1 stzl pi, bt qb, bt, pl, mslser, crd qfz,cal, O, ms, ch1 chl, pl ep, ao, cal, O, hbl

sil, tur, O tur, st, 0

Samples collected by P. Erdmer (8% go-), J. Mezger (93-,94-,95-) J.R, Timmeman (JRT), S.T. Johnston (STJ); first number denotes year of collection. rock types listeci above:

1: btqtz schist (aluminous) of KMA 2: ms-chl-qtz schist (calcic) of KMA 3: Ca-Mg-Fe-tich layers of KMA 4: olivine serpentinite of KMA 5: Ruby Range Batholith granodiarite, Sa: amphibolïte, 5d: diorite 6: Dezadeash Formation slate, phyllite 7: epidote-chlorite schist 8: felsic dykes 9: mafic dykes 10: Nasina Assemblage mica schist 1Oq: quartzite 11 : White River Assemblage mica schist 12: Nisling assemblage schist 12m: marble 13: Aishihik Metamorphic Suite mica schist

Appendir 23: Ca-Fe-Mg-rich layers in the Kluane metamorphic assemblage t i Sample location rock type field relation 89-52a 138O03'35" epidote-bearing hornblende-plagioclase foliated layer in garnetiferous 61'1 1'50" schist biotite-muscovite schist epidote-bearing hbl-pl-qtz schist within biotite-muscovite schist epidote is being replaced by opaque mineral plagioclase-epidote-actinolite-Cr-biotit schist

fuchsite-actinolite schist and boudinaged layers within muscovite- plagioclase-epidote-actinolite-Cr-biotitschist chlorite schist plagioclase-hornblende schist float sample in biotite schist

Cr-biotite-actinolite schist 5x1 0 cm lense within muscovite- chlorite schist Cr-biotite-actinolite schist and large layer (>lm thickness, 150111 plagioclasespidote-actindte-Cr-biotiteschist width) Cr-biotite-actinolite schist layer within (thickness 7) muscovlte- chlorite schist Cr-biotite-actinolite schist boudinaged 10 cm thick layers in muscovite-chlorite schist altered epidote-bearing hbl-bt-pl-qtz schist near lower contact of Swanson Creek olivine serpenthite lense biotite bearing epidote-hornblende schist foliated layer within zoisite-bearing contains no Cr-biotite biotite-muscovite schist altered zoisite-bearing actinolite schist (7) 50 cm thick, 15 m wide boudinaged layer within muscovite-chlorite schist epidote-chlorite-plagioclaseschist 10-15 m thick layer epidote-bearing muscovite-chlorite schist quartz rich white layer (no plagioclase) B e V cl) % -E B Elt EEZ WWW Appendix 24: Localities of radkmeûic age deteminations of micaquark schist of the KMA and phyilii of the Dezadeesh Formation (whii fiIl) and igneous rocks of the Ruby Range Batholith and the Coast Plutonlc Cornplex (grey fill). The nurnbers in parentheses tefer to references listed in ADpendic8.s 24 and 2-5. Note that the localitfes of sampks 37.38 and 41 are show inconedly in the original papers by Mortensen & Erdmer (1 992) and Erdmer & MorlcHisen (1993). The geology is the sarne as in Figure 2-1. Appendix 2-7: aAr-39Ar geochronology of calcic schist of the KMA

1 Plateau age 51 -14 +/- 0.56 Ma

Y I 83.2 % of "Ar

Fraction =Ar Appendix 24: Muscovit~and whole rock RbSr bochmns of calcic schists of the Kluane metamorphic assemblage

muscovite

O whole rock

Muscovite: JM 93-1 56 JM 94-17 JM 94-33 JM 94-36 JM 94-51 JM 94-173 Whole rock: JM 93-156 JM 94-36

-- - errors are given as 20

Appendix 2-9: Location and 6l8OSMOW values' of olivine serpentinites of the Kluane Metamophic Assemblage

* Sampte Location field relationship Modal mineral composition2 o"0 SMOW

93-2* Doghead Pt, eastern margin of large lense olivine, serpentine, magnetite, east shore (>1 km stratigtaphtc thickness); chromite Talbot Am, distance to contact with Ruby (estimate from polished section) Kluane Lake Range Betholith not precisely known (few 100 m) 93-44' Oaghead Pt, northern margin of large lense; olivine (80%) Kluane Lake close to Intrusive contact serpentine (20%) magnetite, chromite (5%), - 93-185 Swanson 150 - 200 m thick lense within olivine (30%) Crwk, mica-quartz schist of KMA; serpentine (66%) Ruby Range locaiion within lense noi known magnetite, chromite (S%), caldte 93-1Wb' Doghead Fi, central part of large lense at olivine (1045%) Kluane Lake Doghead Point; farther away from serpentlm (60-70%) intrusive contact of Ruby Range talc (10%) Batholith than JM 93-44 iddingsite (2-3%), pentlandlite, chrornite, magnetite (5%) 94- l85a Ruby Creek, resislive rocks on Ilat plateau; olivine (2040%) Ruby Range contact with biotite-quartz schist serpentine (10-20%) of KMA exposed; size of lense talc (50%) unknown, but apparently small chromite, magnetite (few tens of meters) Cr-enstatite (-5%) 89-55b Snyder small ultramafic body (400 m) olivine (15%) Creek, withln blotite-quartz schlst of KMA serpentine (3M0%) Ruby Range talc (50%) calcite (tr) magnetite, chromite

* samples are from the same ultrarnafic body 1: O~ygenisotope analyses done by F. Longstaffe at the Unlvenlty of Western Ontario. Reproducabitity of quartz standards * 0.03 Xi. 2: modal mineral composition detemined by thin section estimates, except for sample 3M 93-2, where no thin section is avallable. b 1.19 Gâ Undafomied ms-grt granite pegmab (JK-PE-1) / cm-ng cordiierite-biotiteschist of the KMA 0 A -

A B: zircon hadoru OD. El=MirPdta-

t

0.012 - Deformed biotite granite intruding cordiente-biotite schist of the KMA

9

0.011 -

3 0~010 - criCD LY \ 9 A 0. c: zirton fra&ms M. 86: manaziîe liaCoans

zkmAco~ordrntl68AU-01YI xîman Bcacicardrnt1716 U-02- manul(ragm=S5.ü+I-ObIY.

I I 0.007 1 I I 1 . 0.05 0.06 0.07 0.08 207Pb 1

Appendix 2-10: Concordia plots of dykes intruding the KMA. Analyses by J. Mortensen, University of British Columbia, (unpublished data, 1996.1997) Appendix 2-1 1: Dykes intrusive in the KMA

- - Sample cadinates rocktype thickness strike field relationship

93-7b 138°43'00" fine grained greenish 54 rn 100" cro-ng ms-ch1 schisi 9441b 61°16'20" PWhYrV 138°41'10" fine grained greenish 5-7 m 4 50° cmsscutting ms-ch1 schist 6101 5'35" POQ~Y~V 138°41'30" fine grained greenish fioat sample, continuation of dyke as 93-10 61'1 550" POQ~YV 138°34'SO" fine grained greenish ? 70" crosscuts Ruby Range 61"23'40" porphyry, less aitered Bathol'm 136°59'30" fine grained blueish-gray 3-5 m 10" crosscuts ms-ch1 schist 61"41'30" PO~P~YW 138O4T45" fine grained greenish 3 m 40/45 parallel ms-ch1 schist foliation 6101 9'05" POQ~YW 138'4T45" fine grained greenish 3 m 45" deflects rns-ch1 schist foliation 61'1 9'05" porphyry and aphanite Noparallel dykes 50 m apart 138'47'25" greenish aphanite 4 m 45" deflects ms-ch1 schist foliation 61'1 9'05" 138O4T10" greenish aphanite ? float sample, continuation of 94-6 61°19'10" 138°4T10" greenish aphanite ? float sample, continuation of 94-4c 61'1 9'20" 138°45'00" fine grained greenish 1-2m 90' crosscuts ms-shl schist 61"20'00" PO~P~YV continuation of 94-4 or 94-6 138°41'35' fine grained blueish-gray lm 160" crosscuts uitramafic 61022'50" P~Q~Y~Y 138°33'15" greenish aphanite 20 cm 40135 parallels ms-chi 6 1'1 3'00" schist foliation 138°38'05" fine grained greenish 4 m 60" crosscuts rns-ch1 schist 61°14'30" PW~Y~Y 138O38'45" greenish aphanite 4 m 50" crosscuts ms-ch1 schist 6I0i4'35' 138O40'20" fine grained greenish 1-2m 160° crosscuts ms-ch1 schist 61O1 5'30" POV~YW 138039'50n fine grained greenish 1 m 80/30 parallels ms-ch1 schist foliation 6 1'1 5'35" ~orphy~ 138°38'40" fine grained greenish 4 m 150/20 parallels ms-ch1 schist foliation 61°15'10" ~OrlJhyv 136O59'30" fine grained grey ? ? C~OSSCU~Sms-~hl schist 60°34'35" p0rPh~r~ 139"04'35" fine grained greenish 2-3 m 90" crosscuts ms-chl schist 61"29'20" POQ~YW 138°44'50" fine grained greenish ? ? float sample, continuation 61'1 9'50 POQhYV of 94-6 ? Appendix 2-1 1 (continuad):

Sample cardinates rock type thickness -ke field reiationship fine grained diorite crosscuts biotite schist vertical 93-1 12 fine grained dark green float sample in biotite schist diorite 93-1 15 diorite crosscuts biotite schist

93-1 33 fine grained diorite crosscuts biotite schist

93-1 34 porphyritic andesite float sample in biotite schist (hW 93-1 45 fine grained diorite crosscuts biotite schist

93-1 48 fine grained diorite crosscuts biotite schist

93-1 79 fine grained diorite th ree parallel dy kes 200m spaced in biotite schist 93-1 81 fine grained diorite 20" cmsscuts biotite schist

94-53 diorite ? float sampie in biotite schist

94-108 fine grained hbl 20" crosscuts biotite schist granodionte 94-1O9 fine grained hbl 20" crosscuts biotite schist granodiorite continuation of 94-108 94-113 fine grained diorite ? float in biotite schist

94-1 16 diorite ? fioat sample in biotite schist 117 94-1 27 fine grained rnafic ? float sample in muscovite- biotite schist 94-128 fine grained mafic ? float sample in muscovite- biotite schist 94-1 58 fine grained mafic 30" crosscuts biotite schist

94-1 70 fine grained mafic 90" cmsscuts RRB

94-1 77 fine grained mafic O" crosscuts RRB

94-277 fine grained dark 330125 parallel to strike of KMA grey mafic 94-285 twa greyish black O" crosscuts biotite schist fine grained mafic 130150 parallel to strike of KMA 89-34 porphyritic andesite ? biotite schist

STJ 94-2 dark mafic 20" crosscuts cordierite-biotite schist and granitic dyke Appendix 3-1 :Shear-sense indiators deducted from field observations, oriented sam ples and oriented thinsections

Location Orientation hangingwall Station (longitudeîlatitude) (foIiation/lineation) lndicators motion

Kiuane metamorphie assemblage

Field observation: 94-3 138048'OOn 61"1 9'00" a-qtt boudin UP 94-1 5 138044'40n 61"1 9'45" PQ~- UP 94-36 138"36'30n 61°14'10" sheared qb boudin UP 94-281 136050'Wn 60°41'1On folded qb vein down 94-348 1390W3On 6157'00" a down 95-66 138'4 7'36" 61'1 0'45" cl-shear bands down

Thin section: 94-3 l38O48'OO" a UP 94-1 2 138°r)S'l5" a down 94-20c l38"49'l5" c/s UP 94-36 138"36'30" a UP 94-39 138O43'04" O UP 9445 138"39'10" a down 94-47 138'37'20" c'-shear bands 'JP 94-5 1 138'33'20" cl-shear bands UP 94-58 13823'20" a UP 94-60e 138024'20" b, CIS down 94-62 138"îl'OO" a 'JP 94-63 138020'30m 6 'JP 94-72 138O3O'2Sm 6 down 94-76 138027'45" a. C/S UP 94-1 23 137"43'00" O, c/s 'JP 94-1 30 1373440" 6 UP 94-1 33 137031'30" a, c/s 'JP 94-1 46 137034'00" a, CIS OP 94-1 53 137037'30" O down 94-172 l37"SSl On a UP 94-1 73 137054'40n a, CJS UP 94-266 137OOSOO" a down 95-22 137040'00" 6, C'-shear bands down 95-58 13824'47" a 'JP 95-64 138"17'55" a UP 95-67 138O47'25" a UP

Hand sample: 94-68 138"3S40n 61"1 5'1 O O 94-74 138028'SSn 6 1"1 6'1 O" a 94-1 O8 l37"28'20" 61O031 0" CIS 94-1 25 l37"40'l0" 61°03'25" 6 94-1 73 137'54'20" 6 1009'50n a 94-263 l37OO3'l2" 60°36'20" a 94-305 138°07'45" 61°05'20" O Appendix 3-1 (continued):

Location Orientation hangingwall Station (longitudellatitude) (foliationliineation) lndicators motion

6 UP 6 UP 6 'JP a UP O down c'-shear bands down O down 6 UP

Ruby Range Batholith

Fieid obsewation: 94-26 138O43'3OU 6 l"23'55' 350140 7011 0 rotated qtz boudin down Hand sample: 94-26~ 138O43'25" 6123'40" 25/70 11 1/09 C/S down

Thin section: 94-84 137056'15" 60'5 1'45" 21 0145 165135 O UP domino str. in epidote 94-1 91 136"58'3OW 60'1 7'30" 11 O185 196140 a-PX po~h- down

Dezadeash Formation

Thin section: 94-237 136'55'40" 60°04'38" 75/35 155/07 rotated grt 94-242 138O06'20 60°53'54" 220188 220188 rotated grt 9429312 13741 '20" 60a06'5S 220/75 293148 CJS 95-26 136O56'30" 60°06'55' 95/27 73/25 rotated porph 95-37 136'54'56" 6021'15" 85132 114/29 rotated grt, bt Appendix 3-2: Mesoscopic folds in the Kluane metamorphic assemblage

Station Mdtype' incfination2vergence fotd mis wavelength ampliaide

Western Ruby Range: open, symmetn'cal - open, asymmetncal mP tight, disharmonic recumbent with parasitic fdds open, syrnmebical upright open, syrnmebical upright open, symmetrical uprÎght dose, dishamnic gentfe kink bld moderate close, asymmebical moderate open upright open upright open upright open, syrnmetical upright open * open * asymmetrical isoclinal steep anticline with parasitic fdds 93-168 open, syrnmetrical upright - 93-169 asymrnetrical, various - tig ht-open 93-1 72 asymmetrical open moderate W S-ward thnist 93-1 73 ptygrnatic adnoMe - - mm-cm 93-1 74 open gentle SW 10 cm 94-2 asymmetncal tight steep NE 5 cm open NE 10 cm 94-4 asymmetrical, open O N contact with altered dyke 94-9 asymrnetrical open-tight steep NW asymrnetrical, open steep 1.5 m 10-20 cm parasitic fûlds 10 cm 2-3 cm crenulation folds mm mm close, asyrnmetrical steep 10-20 cm 10 cm asymmetrical, tight moderate 2 cm 1.5 cm asymmetrical, close steep few cm cm with parasitic fdds mm mm asymmetrical, open steep 0.3-1 m 10-30 cm with parasitic folds syrnmetrical, open uprïght - - asy mmetrical 0.1-1 m cm open-dose crenulation 1 cm 5 mm open rnoderate 10-15 cm 3-5 cm open upright 20-30 cm 5-1 0 cm with crenulation folds open uprïght - - with crenulation folds cm mm-cm open uprÏght 10-20 cm 10 cm Appendix 3-2(continued):

Station fdd type' inclination2 vergence fou &s wavelength ampliide 94-68 crenulation blds open to close moderate E 160125 94-69 isoclinal - - Wt30 94-70 a~yrnmet~cal,tight modefate SW 360105 SW thnisting symmetncal, open upright - 11OllO 94-72 asymmetrical, tight moderate SW 330125 94-79 symmetrical, open steep SE 14/25 94-173 symmetn'cal, open steep SW 360125 94-300 isoclinal - NE 300125 94-301 asy mrnetnkai, steep S 120150 dose-tight 290115, 110/10 94-302 asy mmetrical, tig ht steep S 110/20 94-303 open - NE 310115 94-304 open steep SW 310130 94-305 symmeûical, open upright - 320/25 94-306 symmetrkal, open upright - 310110 crenulation folds - - 110110 94-307 asymmetncal, open - 315120 95-58 asymmetricaf, open moderate SW 320124 crenulation - - 310120 95-59 asymmetical, open moderate SW 325120 95-60 asymmeûical, open moderate SW 310105 crenulation - 310105 95-62 crenulation - 315111 95-66 asymrnetrical, open steep W 345135 95-67 asyrnmetrical, close gentle SW 310130 95-72 isoclinal recumbent - 315115 Olivine serpentinite nwr ûoghead Point: 93-1 90 crenulation folds - - 50140 93-1 9 1 crenulation folds - - 130118 93-192 asymmetrical open moderate NW 105130 94-20 crenulation fold gentie S 50130 tight W - 94-21 symmetncal, open moderate W 150R5

94-23 crenulation O - 190125 95-43 crenulation - - 115116 9547 asymmetn'cal, dose steep N 265140 wiai crenulation 95-49 crenulation - - 255135 Eastern and soudhem Ruby Range: 93-63 asymmetical, close rnoderate SW 330112 open - - 330112 93-65 kink fold moderate - 350118 93-122 symmetical, open upright - 290106 93-123 crenulation - 300111 94-92 asymrnetrical, open moderate SW 125/20 94-93 symmetrical, open steep NE 300118 94-98 symrnetrical, open upright - 70125 94-91 asymrnetn'cal, open moderate SW 135/30 94-101 symmetrical, open upright - Il0145 Appendix 3-2 (continued):

------Station fold type1 incJination2 vergence Bld axis wavelength ampiiide 94-1 02 symrnetrical, open upright - 80125 50 cm 5 cm 94-1 17 symmetrical, open upmht - 0/15 20 cm 3 cm 94-1 18 open modemte W 35011 5 fewm 0.5-lm kink folds, ciose moderate W 350/1 0 10-1 5 cm 2-5 cm with stiear zones (40130) indiing hw dom 94-1 19 syrnmetrical, open up@ht - 35WlO 10-50 cm 2-1 0 cm with parasitic crenulation symmetrical, open upmht asymmetn'cal kink -P asymmetrical, open -P asymmetncal, moderate open-close open recumbent symrnetrical, open upaht asymrnetrical, open moderate with parasitic folds asymmetrical, close gentie crenulation in hinges symrnetrical, open SteeP syrnrnetrical, open upright symmetn'cal, open upright open moderate crenulation - open maderate Dezadeash Range: 93-81 symmetrical, open recumbent 93-82 asymmetncal, kink moderate 93-84 asymmetrical, open gentie 93-86 asymmetrical, open gentfe 93-87 asymmetrical, open gentie with parasitic crenulation 93-88 asymmetfical, open gentie - 93-90 asymmetrical, open gentle 1-1.5 m 93-99 asyrnrnetncal, close recumbent 1.5 m symmetrical, open upright 20 cm 94-252 symmetrical, open gentie 20 cm 94-263 symrnetrical, open S-P 10 cm 94-265 symmetrical, open s-P 10-1 5 cm with crenulation œ mm 94-270 crenulation mm 94-274 crenulation mm 94-275 open SmP few cm 94-276 asymmetrical, open -P 20-30 cm 94-279 asymmetn'cal recumbent cm 94-280 asymmetrical, open -P 20-30 cm 94-283 asymrnetrical,isaclinal genîie 94-297-1 open -P

1: interfimb angle: open:120°-71 O ;close:70°-31 O ; tight30°-1 ; isoclinal: 0"; 2: recumbent 0"-IO0;gentle: 11"-30"; maderate: 31 "-60"; steep: 61 -80"; upright: 81 O-90"; (after Twiss 8 Moores 1992). Appendh 33

Application of SpheriStat (version 2.0)

SpheriStat 2.0 (Pangaea Scientific, 1995) is a \111Sndowsbased program able to produœ stereoplots, circular rose diagrams and maps, calculate principle directions and provide a number of structural analyses. SpheRStat graphics can be imported into any graphics software for further enhancement. The SpheriStat data base consists of station identification, group identification, azimuth and inclination. Optional are station coordinates, weighing of points and additional text information. Stereoplots of structural data presented in this thesis are equal area (Schmidt) lower hemisphere projections, unless noted othennrise. Point density distribution was calculated using the Gaussian counting method. Compared to the fixed-circle counting methods (Schmidt, Starkey, Kamb), which have sharp cut-off points. the Gaussian method includes al1 data points weighted by the function of the cosine of the angular distance from the counting station. As a result the contours calculated with the Gaussian rnethod are smoother than fixedcircle contours. The counting function used by the Gaussian method is a Fisher fundion: w=exp[k(cos(0)-11, where 0 is the angular distance and k is the kurtosis. SpheriStat calculates the expected count E=N/k, representing an uniform distribution of N points, and the standard deviation a as the square root of the variance (integral of (w-E)~over the half sphere). A value of k=100, as applied in this study, represents a counting area of 1%. Contour intervals are shown as multitudes of o. Principle directions or eigenvedors, which measure the clustering of the whole data set, are calculated independently from the counting method. The eigenvedors are three orthogonal vectors with a certain magnitude, the so- called eigenvalues. The smallest eigenvector represents the normal to the best fit plane through the data points. The largest eigenvedor is the direction of the statistically largest clustering. Eigenvecton are calculated by summing the matnx of the products and cross-products of the direction cosines of ea~hdata point. The eigenvector of the resulang matm is calculated by the Jacobi method. The diagonal cornponents of the matm are the eigenvalues. The sum of the eigenvalues is N, the total number of data points (Watson, 1966). A method to analyse the fabric shape of stereographic projections was developed Woodcock (1977). Two ratios of the natural logarithms of nonnalized eigenvalues S,, S,, S, of the eigenvectors E,, E, E3,respectively, are plotted on a 'modifiecl Flinn diagram', named after Ramsay's (1967) modification of the Flinn strain diagram. which describes strain shapes (Flinn, 1962). SpheriStat uses the modified Flinn diagram and calculates the Woodcodc ratios K and C. The K-ratio, K=[ln(S,/SJfln(SJS3)], describes the pattern (girdle or cluster), while the C-ratio, C=ln(S,IS3, describes the pattern strength (weakly ta strong developed). Appendix 34: Station localities and stnidural data '

Sample rock Long ON) 1 Lat (N) foliation lineation fold axes NTS map 89-39 2 138°09'40m, 61 "1 1'50" 0135 138°10'10m,61 "1 1'38' 33011O, 65110 l38"l0'35", 61"1 1'20" 011 6 138"09'40m, 61 "1 0'55 l38"û8'2Ou, 6101û'5ï" 138"W3Om, 61 O14'40" 138"û6'00*, 61"1 5'40" 738aû6'00ws61 "15'55" 138°û6'lSw, 61 "1 6'30" 138"06'SOU, 61 "1 7'1 0" 250105 l38"O3'45", 61"1 1'50" 138"O3'OOW, 61 "12'20" 138"03'OOm, 61 "12'30 1 511 5 138"03'OOU, 61 O12'40" l38"02'35", 61"12'55" 138"01140",61 "1 3'1 5" 138"O2'1Ow,61 "13'15" 138°02'00", 61"13'40 138"04'OOm,61 "1515" 138°0î'45*, 61 "13'40 138OO2'3OW, 61 "1 5'1 5" 138OOZ'3OW, 61 "1 5'45" 138"OZ'OO", 61"14'55" 138°0î'OO", 61"14'30" 138°02'00", 61"l4'10" 138O45'20", 61O1 5'05" 138°44'50, 61'1 9'50 138'45'1 S', 6190'25' l38"46'00", 61 "20'20" 138"4û'3On, 61"20'00 138"46'50", 6 1 O1 9'20" 13804T20n, 6 1"1 9'00" 350/15 (SW) 138O47'40, 61"18'48" 138°43'03", 61 O1 6'35" 138O42'5OU, 61 016'05' 135130 (Cr) 1 38O42'25", 6 1"1 5'55" 320/25 lW48'lS", 61"1 5'30" 35011 0 l38O38'1On, 61"14'30" l4OllO 138"3712", 61"14'22" 138"36'30m, 61 "1 4'1 O" 138"34'2Su, 61 "1 3'25" 310105 (SW) l38O32'l Sn, 61"1 3'55" 340120 138028'4SW, 61 "1 0'55" 32011 0 (SW) 13855'4SU, 61 "07'50" 75/15 l37026'3O,6Oo49'35" l37"25'OO", 60°50'00 89-97 12m 136033'OOU, 60a30'l5" 89-98 12 1W33'2SW, 60°30'07" 11 0150 89-99 12 136"34'OOn, 60°30'01" 110140 (cr) 89-1 O0 12 l36"35'lO*, 60029'55" 89-1 O1 12 136'36'1 7",60'29'55' Appendix 34(continued):

Sampk rock Long ON)/ Lat(N) foliation Fneation fdd axes NTç map 89-1 02 12 l36"37OS', 60029'45" 115Ai7 115 An 115an 13603~30"; 60"31*05" 110130 115A/10 136°31'30nl 60°31'10" 150150 115A/lO l36O33'lO", 60031'20" 115 Al10 136°35'13"16OWl 5" 115AIlO 136"33'50n, 60°3û'38" 115AI10 l37OO3'l O", 60°42'55" il5Al11 136°49'0û", 60°49'00" 20110 115AI15 13i0Ol'3On, 60°54'25" 115 AI14 l37"ûl'5O", 60°58'1O" t 15 A114 136°51'30", 60°42'05" 115 AI10 136O50'45", 60°40'55" 115 NI0 136°49'35', 60°41'00" 115 NI0 136O48'40", 60°41'30" Il5Al10 136O47'l O", 60'41 '40" 115 A/10 136°46'SO", 60'41 '45" lisAI10 136°52'00",60°41'1 0" 115 MO l36"53'30",60°41'25" 115A/10 136053'30n, 60°41'25" 115 A/10 136"54'50", 60°41'35" 115N10 136"54'00", 60°42'35" 115 AI10 138Oi 5'O0",61 008'0û" 90130 115 Gf1 138'1 7'20", 61'Oi'05" 115 G/1 l38Ol 7'20", 61'06'45" 115 Gfl 138°16'20", 61"O6i 0" 115 G/1 138'1 1'1O", 6 1"05'40" Il5 G/1 138'1 0'00", 6 1"OS35" 115 G/1 138OO7'lOn, 6 1'1 320" 115 G/1 138°06'15",61 '14'10" 115 G/1 138'06'1 Sn, 61 '1 4'20" 115 G/1 138"OirSOW, 61 '1 3'00" il5G/1 138OO8'35", 61 '1 2'40" 115 Glf 138°09'30", 61 olTiO" il5 Gl1 138°42'55w,61 '1 6'35" 115 GU l38O38'lO", 61O14'30" 115 G12 138029'4Sn, 61 014'45" 115 G/1 138028'5On, 6 1"1 525' 115 G18 138027'48",61 "1S50" 115 Gl8 138"27'00", 61 01S15" 115 G18 138026'16",61 OISOO" 115 G18 138024'50n,61 O1S16" 115 GI8 13853'30n, 61 "14'30" 115 G11 138022'00",61 "13'50" 115 G/1 138"21'00", 61°12'15" 115 GI1 t 38022'Oû", 61'1 1'58" 11OIlO 115GM 138aî3'30', 61 '1 1'50" 350125 115 G/1 138"24'15,61°11'50" 115 G/1 138"25'0016101 1'45" 115 Gll 138O37'29, 61'24'20" 115 GU Sample rock Long (W) / Lat (N) foliation lineation fold axes NTS map 93-32 138~33'50".61 22'05" 280/55,340/50 115 GU 138033'40n, 61 "21 '45" 1W33'5ON, 61 "21'28" 138°34'50", 61O21 '28" 138'35'5On, 61021 '40" 138'36'1 On, 6122'00" 138'38'1 On, 61022'20" 138"38'Wn,61 "22'40" 138OWOO", 6123'40" 138O4428", 6123'25" 138*44'4O", 6102320" 137'05'05", 60'5202" 137"05'2On, 60'52'20" 137 '06'1 Sn, 60°52'20" 1W'OTW, 60'52'1 8" 137"08'20", 6O052'l9" 136O47'OOn, 60 '49'35" 136O47'20", 60'49'45' 136045'30m, 60 '49'40" 'I36'3T30", 61009'00" 137'39'30n, 61 "08'30 137O39'3OW, 61 "08'1 O" 137"38'50", 61 '07'27' 137"38'55", 6 1OO7'0O" 137°40'50", 6 1'06'55" 137°40'50", 61°06'17" 137°40'00", 61O05'56 137'39'50", 61 "05'57" 137"39'30", 61 '05'55" 137"39'30",61 '06'20 1W038'20", 61"06'35" 137"41'5Y, 61 "07'45' 137"41'5S', 61 '08'00" 137"40'55", 6 1'07'1 8 137"43'00", 61"09'45" 137"0225', 60°44'50" 137'01'50n, 60'44'25' 137'O113S', 60'44'20" 13TO3'l O", 60°42'55" 137'03'45", 60°43'00" 137'04'25", 60'43'00" 137O05'25", 60'4420" 137°05'55", 60'44'15" 137"07'05", 60'4335" 137"06'40n, 60'431 Sn 137'05'55', 60'46'45" 137°06'1 5", 60'46'20" l37"Of'lû", 60'45'50" 137'08'20t', 60'46'00" 1W008'f 5',60°45'30" 137"08'3SW, 60'45'1 0" A ppendix 34(continueâ):

Sample rock Long (W) / Lat (N) kîiin lineatmn fold axes NTS map 137°07'35w16O04S25" 215/75 13?003'4p, 60°4515" 137003'20u, 60°41'20" 137"02'4S', 60'41'1 7" 137"Ol'25", 60°41'1 5" 136'59'45", 60'41 '05" 136O59'3OU, 61 041'30" 136'57'36", 60°42'1 5" 136°57'45", 60'41 '30" 136"S8'OOU, 60°40'50' 136'58'20". 60°40'25" l37"l0'55", 60°5S3û" 137'1 1'OOn, 60'54'55" 137'1 1'40u, 60"54'30" 137"12'3OU, 60°54'00" 137Yî'5OU, 60°53'45' 137"1445", 60'53'55" 137'1 5'00". 60'54'1 O" 137°14'45", 60°57'00 137"14'40", 60°56'1 0" 137°14'00", 6O055'52' 137Ol4'50, 60'55'1 5" 13?016'lO", 60"54'30" 137°1745w, 60°56@30" 137'1 8'35", 60°56'00" 137'1 9'00, 60°55'53* 137O19'3OU, 60°56'00" 137'1 9'40", 6O056'08" 13702O'5On, 60°56'07" 13?a20'40",60'56'50 137021 '1O", 60°57'00 137021'00". 60°57'10" 137'1 8'50, 60°56'40" 137"35'17", 60°05'55" 137"35'25", 61"05'00" 137'35'35", 60°04'20" 137'35'10, 61"04'18 137'34'lSn, 61 "04'15" 137'32'OOn, 61 "03'40" 137'31'10, 61003'15' 137'31 '30". 61"02'55" 137"32'50", 6 1 "03'1 5" 137'33'20n, 6 1'03'30 137"3O'5OW, 6 1 "04'20" 138026'50", 61O1800 f38W'O0", 61O17'05" 138026'20", 61'16'38 138026'10". 61O16'28" 138"26'1O", 61"16'20 13827'15", 61°16'05" 13827'40,61O15'Or' Sample rock Long 0 1 Lat (N) fMatÏon Iineation fold axes ' NTS map 100102 165106 11 5 Gl1 115 Gfl 115 Gf1 15/55 115 G/l 115 Gl1 14117 115 GI1 115 GI1 335iïO ?15 Gl1 115 Gf1 115 Gl1 340140 115 G/1 355140 115 Gl1 355150 115 Gll 85/06 115 Gli 115 Gl1 20150 115 Gl1 115 Gl1 40150 115 Gl1 40150 115 G11 115 Gf1 115 Gl1 25138 115 GI1 340/20 115 Gl1 25/20 115 GI1 55/25 115 Gll 0125 il5G11 10143 115 Gl1 50130 115 GI1 0135 115 G18 200150 115 Gi6 0180 115 Gff 355160 115 Gff 30150 115 Gff 240165 115Gl7 145150 115 Gn 355170 115 G/7 240150 115 BI16 l6OI9O 115 BI16 195f75 115 8/16 115 GR 1SOI70 115 GIIO 16920 115 GIIO 140155 115 G110 40130 115 GI10 45145 115 Gl10 30125 115 GIlO 40130 115 G/10 190185 (b) 115 G16 190UO (b) 115 G16 115 Gi6 180135 (b) 115 G16

254 Sample rock Long (W) / Lat (N) foliation lineation fold axes NTS rnap 93-225 1S 1392555", 61"29'05' 210185 tsom 60MO 60/30

28W30 250155 230170

65/80 40180 345180 80150 95150 1SOI65 180135 l8OlSS 180140 260/80 (b)

340160 70160 136'58'00, 60'1 8.1 2" 136°57'1î", 60al7'40 136'58'1 S, 60 O1 1'07" 220185 (b) 136°!Y'S0, 60°10'40 0185 (b) 136°W'20, 60°10'12" 270ffO (b) 136°57'lS', 6Oa10'00 280ff5 (b) 136O41'20, 5g05î'55 250160 (b) 136"41140, 60°46'35' 1801 50 (b) 13ô044'lO", 60a45'05' 24550 13ô045'301 60'45'20" 320140 (b) i37°01'lSu, 6Oo54'l0 200185 137°00'35"1 60°54'20" 0165 136°S8'30, 60°54'15" 30145 137"58'45", 60 ?W00" O60 138"45'30",61 019'1T' 30140 100115 138"47'2OW, 6 1 "1 842" 40135 350125 (NE) 138°48'00", 61O1900 60J40 105f15 l38"4T45', 61 "19'05" 50140 100135 138"47'3OU, 61 "19'0s" 0160 l38O47'lO, 61 "19'OT S5/lO l38"41'OS', 61O19'08" 54/50 138"47'O0", 61O1 9'20" 138°46'50,61"19'3On 60RO l38"46'OO, 61"20'1 0 75130 138"45'15, 61 020'30" 340120 138°46'0û", 61 20'15" 30160 138OU'l O, 61"1 9'45" 15/45 138°45'00", 61 O19'20" 60127

255

Appendix 3-4 (continueâ):

Sample rock Long ON) 1 Lat (N) foliation Iineation fold axes NTS map 94-76 2 138027@50",61 "1 SSO" 10115 138°29'S5", 61"1 SI 0" 65130 138°31'20n,61 "15'42" 50135 t38"33'30n, 61 "14'55" 45/40 i38"35'25", 61"14'05" 40155 137°04'1On, 60'5 1'35" l8Ol6O 137Vl'l On, 60°S4'l 5" 30185 137Vl'50m, 60'58'1 0" 15/75 137"56@15",60°5t'S0" 21OMS 137"SïSOn, 60°51'40" 210135 145/20 (cr) l37"38'1O", 60°St '30" 195/60 137"59'30", 60°51'45" 21 O185 138°00'03n, 60°51'50" 25/75 137°5ï@20",61°S1YO" 180155 1 1O120 137029'40", 60°08'30" 200180 13729'30". 60°08'30" l35/3O (SW) 137°27'40n, 60°08'30" 220185 125/20 (SW) 137"î1100", 60°08'30'@ ORO 300/18 (NE) 137"20120",60°58'40" 35/30 137"l 9'30". 60°58'38'@ 0140 13iol 8'40n, 60°59'30" lOl6O d 37"l8'30". 61 OOû@lO" f 15/30 70125 137"lû@45"' 61 "00'45" 90/30 1Vol 8'1 Sn, 61 "01'37 45/60 137"17'1 O", 61 000'05" 11 Of45 11 Of45 137"l 6'OO,6l 000'35" 50130 80QS 137025'50'@,61 006@10" 300145 137025@4Sn, 6 1 "04'50" 35130 137"26@40n, 61 OW30" 50/30 137Wl Sn, 61 O04'02" 60130 137028'20n, 61 "03'1O" 2011 5 137°29@20", 6 1 '02'1 5" 4011 5 137"28'3Sn, 61 002'00" 4511 5 137"26'4S", 61"02'1 On 55120 137024'30",61 "03'00" 35135 137a22'15, 6l004'06" 3011 5 137"22'30n, 61 O03'30" 30125 137022'3O", 61 003'05" 30122 137020'37@@,61 "03'25" 31 O11 O 137a20'25', 6 1"03i4û" 290122 011 5 137°20'00n, 6 1'04'40" 325120 35011 0 (N) 137'1 7@30",61 "03'20" 150/20 13011 5 137"22'50n, 61 *02@45' 30125 1W044'10", 61 "W'1 5" 100/15 137O43'OO", 61"03'55" 90/20 137"40'55'@, 6 1 003@40" 100140 137O40'l 0,61O03'25" 130135 175/15 13f039@0ü@,61"03'15" 100130 l37"38@lOn, 61 003'05" 120no 137"36'30", 61 "02'25' 125/30 140125 (SW) 137"35'10", 61"0114û@' 1ZS/ZO

257 Appendix 34(continued):

Sample rock Long 01 Lat (N) foliation linestion fdd axes * NTS map 1 137"34'4ûn,61 O01'05" 140115 115 Hf4 l37034'25", 6100û'30" 15011 5 137O33'1OU,61 000'05n 1W15 137"31'30N, 60°58'05" 140120 137"34'ûûn, 60°57'45" 100135 137"3û'OO", 6O05ï3O" 13i03û'2O", 60°56'55 145145 137'29'4SW, 60°56'30" l4O/3S 137a28'25u, 60°55'50" 145/70 137"2ï'l2", 6O05S4û" 15/80 13603î'40N, 60 "58'00" 100140 136"WOOn, 60°57'50" 140135 137"34'OOn, 600W30n 200180 137O34'00", 6O0WO0" 115/20 137"34'OOn, 60'56'45" 1SOI60 137aW'l 8", 60°56'22" 150145 137"35'l 5", 6O05S5O" 136/40 137°36'35n, 60°5S30 11 0130 137"38'40n, 60°5S45" l8O/25 137"3750", 60°56'40" 150115 137"3ï'30n, 60°57g0 220130 137"33'55", 60°58Y 3" 1sol25 137"3O'2On, 60°5920 55/35 137"31130'@, 60°59'50" 130/40 13f031'45",61°00'18 90130 137a32'îO",61 O0 1'10" 115/25 137°31'10", 61001'00" 1lOQ5 137"î9'OOn, 61000'05" 11 OIX 13728'1 O", 61OOO'l8" 170150 137"28'20n, 60"59'55" l8O/88 137O52'45", 61'1 2'55" 60ff5 137O39'30". 61"08'30' 60135 137"39'30n, 61 008'30 320145 137"55'l On, 61"1 0'40" 350145 137"54'4O", 61'09'55'' on5 137°5310", 61012'S0 30160 137O53'30, 61O1318 l2Ol3O 137"54'50n,61 "12'55" 0125 137°5S10, 61O14'45' 0155 137"56'îSn, 61O1 4'45" 90120 137"57'40", 61'1 503" 13011 O 137°S7'40n, 61 "1 605" 180120 1370W40n, 61'1 5'1 O 18O/5O 13f059'40n, 61 '1 6'50" 170150 137"54'10", 61O14'48" 30135 137"5OB42", 61 "1 0'40 O125 137"04'30n, 60'1 9'1 9" 150135 (b) 137°04'W, 60°19'20" 140145 (b) 137°03'00n, 6002111 O" 270185 (b) 137°03'00, 60'22'52" 60188 (b) 137°02'40", 60023'20" 55/75

258 Appendùr 34(continued):

Sample rock Long (W) 1 Lat (N) foliation Iineation fold axes NTS map 136"58'20n, 60°1f 35" 30145 11SM 136058'20n, 60°1720" 1ion0 30/40 115M 136"W40n, 60'38'45" 80175 70ffO 115M 136"5T45", 60°16'35" SOI60 (SW) 115M 136"58'15", 60 "11'07" 40180 115 Al2 136°S8'OOu, 60'1 1'45" 260180 115 Ai2 136°Sï'20u, 6O0lû'l2" 270160 350135 115 Al2 136058'20n, 60'1 1'37" 240145 115m 136O59'lOn, 60009'50" 70185 (b) 115m 136"58'45", 6OWl~" 70185 (b) 115N2 136"57'40N, 60°0738" 250/80 115 Al2 136OS6'3O", 60006'22" lOOl3O 115 A/2 137"56'30", 60'06'30" 120145 160/20 (cr) 115 A/2 136039'50n, 59'53'30 30140 80130 (cr) 114 Pl15 136039'30a, 59'53'45" 45/45 Il4Pl15 136040'20m, 59O54'07" 40135 114 Pl15 136°40'40", 59'54'1 0" 30160 114 PM5 136'41 '15"' 59 "54'27" 40165 114 Pl15 136O41'3OW, 59'54'45" 20135 320130 114 Pl15 136'41'20", W'SSl5" 100165 114 Pl15 136°42'00", 59'56'57" l2Ol5O 114 Pl15 136"39'4OW, 59O43'05' l4OMO 114 Pl15 136'39'1 Sn, 59"43'0Sw 20135 114 Pl15 136'41'1 O", 59O43'05 20155 114 Pl15 136°41'12n,59O43'05" 230170 114 Pl15 l36"41'12", 59'43'05" 70170 3011 5 (E) 114 Pl15 136'41'1 5",59'43'05' 30165 114 Pl15 136"41rl 2"' 59'43'05" 55/60 150130 (cr) 114 Pl15 l36"39'1O", 59'43'05' 45/50 9011 5 (S) il4Pl1 5 136a38'45w, 59°43'05" 50165 114 Pl15 136"53'00",60'03'00" 350130 115 A/2 136055'40m, 60'04'40" 70135 115N2 138°07'25", 60'55'48" 230160 240155 (cr) 115 6/16 138'07'45', 60'55'20" 200180 115 BI16 138°0ir40, 60°54'15 200155 115 8/16 l38"Of00"' 60'55'35" 230155 175150 ON) 115 8/16 138°û6'20", 60'53'54'' 220188 115 6/16 138°0535", 6Oo53'4On 35/88 110/10 115 8/16 l38OO5'lS', 60'53'30 10185 115 6/16 138"04'30", 60'53'25" 20185 115 BI16 138O03'55", 60'53'20 1OR5 120165 (cr) 115 8116 138'04'2S, 60'54'00 180î75 115 8/16 138'05'OOn, 60°WlO 200/75 il58/16 1 38'06'3Sa, 60°54'45" 20185 115 8/16 136'56'1 0,60'34'05" 260145 115AI10 136°55'25", 60°34@10" 230155 11 5 A/10 136°W30n, 60'34'35" 145135 Il5A/10 l37OO3'12", 60a36'20" 125/70 lïOl6O 115AI11 137°03'35,60036@35'@ 125/50 115 Nll 137"03'50", 60'36'40" 18O/Z 110/10 0 115AIl1 137°05'00", 60'36'1 O" 180115 l15N11

259

Sample rock Long (W) 1 Lat (N) foliation lineation fold axes NTS map

139'1 4'20n, 6123'1 O" 200185 . 139'1 4'20n, 6123'05" 139'1 4'O5", 6 12420" 138"59'40n, 61 O33'3OW 138"59'58", 61"351 0" l39"Ol'30n, 61 35'20" 13QOO2'3On, 61 "3520" 139002@35",61 "3522" 13Q002'40", 61 "34'1 5" 300150 (S) 13Q002'40", 6 1"3505" 300145 (SW) 139"0l'3SW, 61 "34'50" 139°02'40", 61 W45" 139"03'00n,61034'15" 139"02'0O", 61"34'50" l39"02'40", 61'34'45" 13S001'25', 6 1'34'42" t39°01'l Sm,6 1'34'42" t 39°04'OOu16 1026'12" 139a04'lO", 6126'45" 139"04'25", 61 27'02" 139°05'3S', 61 027'38" 139°06'1O", 6 127'38 139O06'15", 61 27'12' 139"25'55, 61 "29'05' l39"26'3O",61 "29'25" 130J20 (N) 136O52'35", 60°30i40" 136'51 '50n160°30'02" 136O50'55", 60'29'48" 136O48'50", 60°30'10" 110/40 (cr) 136059'30n, 60°34'35" 136048'2în, 6029'48 150135 136048'Zn, 6029'32" 13604520n, 6028'40 136"44(40", 6028'55" 136°45'00", 60 WOO" 136O45'4SW1 6029'40 125115 136°5û'00", 60a30'2S 136°51'0û", 6O03û'5S' 120145 (cr) 136°54'50"160aû4'09" 136"55'25', 60aû4'30" 136°57'25", 60a05'30" 136O59'40", 60'1 1'00 136O59'5Ol 60'1 1'15" 137"O6'45', 60°18'30" 137"01'00", 60al8'55' 13i0Ol'20", 60'1 9'08" 137°01'05n, 60°19'22" 137"00'50", 60°19'25" 137°01'00", 60al9'40" 137°00'4T, 60°19'52" 160/55 (cr) 137"00'40", 60'19'57' crl

3crl Sample rock Long (W) 1Lat (N) Miabon Iineaüon fold axes MSmap 95-57 2 138~6'OOn, 61 "1 1'00" 90114 95-58 138"24'47", 61'1 1'35" 45/55 310120 (cr) 95-59 138"23'3OW, 61 O1 1'50" 50145,65150 (al) 325120 (SW) 95-60 138"22'25", 61'1 1'53" 25120 310105 (SW) 95-61 138021'45", 6101T05" 50/29 95-62 13851'0OW,61°1T15" 25/25 315Ill (cr) 95-63 138'1 9'3OW,61'1 1'45" 40155 95-64 138"1T55", 61'1 1'35" 20150 95-65 138'1 8'1O", 61O1 1'1 0" 35/35 9546 138°17'30", 61°1 0'45" 20130, 55160 (cd) 345135 0 95-67 138'1f 03", 61010'10" 330132 310130 (SW) 95-68 138'1 7'58", 61'09'35" 30140 3 10130 95-69 138'1 840n, 6 1"09'25" loi60 95-70 13854'20n, 61007'23" 30130 95-71 138"23'00", 61O071 8" 18/~7,~~~/68(ccl) 95-72 138022'23", 61°07@18" 55/46 31SI1 5 95-73 136°50'57", 60033'40" 245168 95-74 136050'3SD, 60°33'44" 235150 95-76 136°59'50", 60°19'48" 105/25 STJ 94-1 13i007'S0", 61000'1 5" 28/81,24/?4 STJ 94-1 b 137°07'5û", 61"OO'lS1 54/72 STJ 94-2 137e08'40", 6 1000'30" 3718 1,30/74 STJ 94-3 137"08'4!Y', 61"00'35 63/79 STJ 94-4 7 3i009'30", 6 1"00'37" 68/44,34/56 STJ 94-5 137O1 0'1 5,61000'30 70164 STJ 94-5b 137'1 0'1 S, 6 1000'30 56144 STJ 94-6 137'1 û'45', 6 1'00'50" 50168 STJ 94-7 137'1 lb10,61001'00" 47158 STJ 94-8 137'1 1'55', 6 1000'00" 35141,29147 STJ 94-9 137°12'4û", 6 1"00'3Sn 58157,49145 STJ 94-1 O 13i014'12", 61 000'30" 73/46, 53137 STJ 94-1 1 137"14'45", 61"00'20" 6 1(47

Structural data collecteci by P. Erdmer (SS, go-), J. E. Mezger (930, 94, 954, S. Johnston (STJ); first number denotes year of collection. 1: Foliation data are Iisted as dip direcb'onldip of schistosity, unless noted (b) or (cd), indicating bedding and crenulation cleavage, respectively. Lineation, fold axes and crenulation fold axes (ct) data are noted as trendlplunge. 2: The quadrant in parenthesis denotes direction of vergence of axial plane, if known. 3: NTS map number of 1:50,000 scale topographical maps; see map index in Append'i 1-1 for location. Rock types: 1: KMA: btqk schist 8: felsic dykes 12: Nisling assemblage: 2: KMA: ms-chlqtz schist 9: mafic dykes bt-qtz schist 3: KMA: Ca-Mg-Fe layers 10: Nasina Assemblage: 12m: marble 4: KMA: olivine serpentinite mica schist 14: Hasen Creek Formation: 5: RRB: granodiorite, 1Oq: quartzite, mud-, silt-, sandstone 5a: amphibolite, 1Om: marble 15: Station Creek Formation: 5d: quartz diorite 11 : White River Assemblage: me tavo Ican ics 6: OF: shale, slate, phyllite mica schist 16: Nicolai Greenstone 7: PMvs 11 m: made, calc-silicate 17: Hydrotunnel orthogneiss original lineation data

original &: 91/03

Iineation data after clockwise rotation

new %: 288114

Appendix 36: 60" clockwise rotation of lineation from the southwestem limb of the eastem structural dornain of the KMA around an axis of Il5/10, the approximate trend and plunge of the regional F,,-fold axis. Appendix 3-6: Restoration of Iineation and shear-sense indicators of southwestern Iimb in the eastem domain of the KMA to pre-Ff,folding and northward tilting'.

Location measured lineation shear-sense lineation after rotation new sheaFsense

1: Lineation and sense of shear of southdippng planes on southwestern lirnb are rotated around a fold axis of 115/10, until plane containing the Iineation dips approximately 2040" ta north-northeast Foliation

N =37 El: 120M8 €2: 255/65 €3: 2511 7 8 Dezadeash Formation\\/ CI: 4 sigma - Greenschist (PMvs)

Oszademh Formation Fold axes N = 22 openfdd A crsnulation fdd GreensGhist (PMVS) + opanfold A wnulation fold

Appandix 3-7: Foliation. mineral stretching lineation and fold axes orientation of phyllites if the Dezadeash Formation and the greenschist (PMvs) between Telluride Creek and Kathleen River- Equal area (Schmidt) projedion of lower hemisphere. Appendix 44

Elecbon microprobe conditions and mineral standards

Ail geothembarometric studies were undertaken at the University of Alberta microprobe lab using nNo microprobe modds, an ARLSEMQ and a JEOL JMSOQR. Operaüon conditions for both microprobes induded an accelerabion voltage of 15 kV, a beam cunent of 15 nA, measured at a Farraday Cup, a peak count of 20 sec, with 10 sec high background and 10 sec low background- The precision of oxides with several weight percent is approximately -1 % of measurement, while oxides with less than one weight percent o=lt0-20% (P. Wgner, pers. comm., 1997)- For data reduction the programs phi-ttio-3 by Tracor Northem (ARL-SEMQ) and Z-A-F by JEOL (JEOL JXM900R) were useci, The composition of the probed minerais was determined by using me following standards:

Biotite Muscovite: Ai Muscovite Rhodonite Ca Rhodonite Scapolïte Cl Scapolite Biotite F Bioitite Kakanui Kaersuitite Fe Kakanui Kaersuitite and high Fe Biotite K Muscovite Biotite Mn Wllemite Kakanui Kaersuitite Na Kakanui Kaersuitite Willemite Si Muscovite Kakanui Kaersuitite Ti Kakanui Kaersuitite Biotite Kakanui Kaersuitite Plagioclase: Al Plagioclase Ca Plagioclase/Anorthite Cordierite: Al Anorth ite Fe Osumilite Fe Kakanui Kaersuitite K Anorthoclase/Sanidine Na Anorthoclase Mn Willernite K Anorthoclase Na Anorthoclase Mg Osumilite Si Plagioclase Mn Willernite Si Plagioclase Spinel: Al Chrornite Ti Kakanui Kaersuitite Cr Chromite Fe llmenite Gamet: Al Roberts Victor Gamets Mg Chromite Ca Roberts Victor Gamets Mn Ilmenite Fe Fayalite Si f ayaiite Mg Roberts Victor Gamets Ti llmenite Mn Wiliemite Zn Gahnite Si Roberts Victor Gamets Ti KakanuiKaersuitite

Reference number of standards: Kakanui Kaersutite USNM 11O752 Anorthite USNM 137041 Muscovite not available Anorthoclase USNM 13868 Osurnilite USNM 143967 Biotite not available Plagioclase USNM 115900 Chromite USNM 117175 Rhodonite not available Fayalite USNM 143965 Roberts Victor Gamets USNM 87375 Gahnite USNM 145883 Sca polite USNM R-6600-1 llmenite USNM 96189 Willemite not availa ble - bt4l17 mss4I14 gamet, gnins are I pl: 5 / 13 dmbPydd, tims altsred- bt6/24 anhadnl to subhedral. pl: 4 / 16 graphite indusion-free- I crd:4/12 &3/ 16 gnphitic indusions in pl: 3 112 garnct, grains are hW- I - - bt4 1 22 spi: 12 / 12 subheûtal, üear, ad:3115 indus ion^. I pl: 3 1 10 I bt7ll2 inclusions of graphite mS:4/10 and plagiodase in I pl: 3 1 14 gamet 1. qtz. Ph al. M. grp 3. ms. grt tur, ab.ap. trn, O

bt7110 anheâral, embayed rns:3/6 gamet l pl: 3 / 21 graphitic indusions in gamet. grains are embayed, rims altered ------1.- bt. PI gamets are subhedral, 2. m. ch1 rninor indusions. 3. grt. st, $il,ilm.ap,tur.(

bt: 7/13 indusion-frae m:5/8 subhedral gamet I pl: 2 / 10 200 - 700 bt7112 graphitic indusions in 2/18 ms: 7 12 gamet. grains an 2 pl: 3 / 15 mbayed, rims altered 500-1100 bt9114 graphitic indusions in 2/ 10 ms:6/8 gdmet, grains are 2 pl:3/ 17 mbayad, Rms altered

1.qtz. bt, PI graphitic indusions in 2st.9w game!, grains an 3. QR. and. op, m, tur ernbaysd. rim altered - bt5121 subhadral, partly ms: S/ 18 poikilitic, char gamet DI:8 / 3t graina 500 - 2000 bt 6 / 24 ad: 6 1 12 gmghitic indusions in 2 / 20 ms:2/8 gamet. grains am 2 pl: 4 / 8 mbayed, rims aftered Appendix 4-2 (continuai): I I I 1

bt5131 dear, poikiigamets ad:4/12 pl: 6 123 I - - 94-147~ t-qiz,kpl o00-2800 bt10140 dcar, mpkteiy 2 ad, gR, sil, grp 3/29 pt8132 indusion-fme, poikiiiic 2 crd:6/12 QI- se~n .r.qt~.bt.p~ 500-2000 ~8132 anMial, embayed. 2. SC 9iP. m*gR 3/27 m~:6/21 corn raplacsd by 3. dl, 0 3 pl:8/4a biotîte

Se277d l.qt~.pl.bt 700 -800 bt 16/59 duar, anhadral 2 gR 2 / 21 pl: 3 / 15 ebngated po~kilin'c 3. grp, un,m. O 2 grains L 94-283a 1- qtz. pl. bt, ad 500 - 1500 bt13/59 rslativsly indusion- 2 gQ 4/20 crd:4/12 fiea, daar gamets 3. grt, sil, ser. chi, O 2 pl:3 115 btSI30 dear. indusion-fiee, m: 8 124 subhedral pl: 311s

1. pf, bt bt4 128 indusion-free. Z ms, al. grp. gR m: 5/23 subhedtal gamet 3. tur, O I pl: 3 / 15 Ruby Range BatholHh (granodiort&) 94-147d 1-qffbtpl 650 - 1000 bt 10 / 40 clear, indusion-free. 2 gfl 2M7 ms:4/16 3- ms, ch1 2 pl: 10 148

bt 9 126 quartz inclusions ms: 2/20 pl: 5 120 1 NaimArcmblaqa (N of Talbot Am. Kkom LW) quartz inclusions indicate rotation dunng growth, snowball gamet

anhadral, nlaüve indusion-fias. aitered nms

W2Wb 1. gtp. qt~,bt 30-80 &Si30 euhadral. unaiterad 3. grt 3/11 3

94-242 1. qtt, M. gv 1300 - 1500 bt4/18 subhedral to euhedral 2. grt 2/ 19 3. rn 1 Appandix 4-3: Ehctron micmprak aiulyaes and akulaidrd mdmemkn of grme -14 se-@ 2- oddi. Rm Ca8 Ernw Opal am (lsm «PO am) sa2 36s 3125 37.00 S1.1S J7.N no2 a ai1 a10 am 0.m a03 21s 21- 21-41 nm am Fa0 3222 27- =O) a47 2sa YnO 5s 4.74 IQa as a12 woo U5 1 lm 1.84 1-77 Cao id0 7.77 am 2.37 4-45 NPO am o.m a05 aoi aoi CRO~ am o.a~ am iiri nh 1- IOOS lW.71 lW.40 10417 101.07 Plioinin -51 MZmron 297 tom ~i am aaw aom aQz a- Al 2.011 2029 2023 r05 2m6 Fit* t.m Zltl 1-7 1s 2213 un 0.321 Ofts 0.339 439 a315 uo atm m am 0.24 a263 u am am om an ai= ~i am O.OOB am aot am O am am am nm 0.0(# TO

2- Rim Cam A- BB)

rOlb 2977 2970 2- am1 ami am ami 2017 2063 2073 ual 2178 2201 2.223 2211 aut 4363 02û2 0316 0.2üS a335 0.314 0.114- atm aria 0.10~ nh nhnnNi. a012 7- ?.Sm 7.m 299 aw 201 223 0.34 0.20 0.16 aoi

*zua a4448 4- ZOnn Wd# Rim Cas Av Cas A- (W%) (5PW Opal (20pts) PPUI (2OOCII Si 3591 36.00 3a19 3-72 37.19 Ti02 0.00 4-03 A01 0.06 0.04 A003 21.76 21.86 21-84 21.49 21.42 F& 34.90 34-17 34.29 30.83 31.63 Mn0 231 1.94 213 6.67 5.90 Mo0 297 3-44 325 1.91 224 Ca0 1.05 1.14 1.M 257 209 TOM 9ô.91 98.57 9ü-73 101.30 101-12 PrlZ-YWn -Si ZSZ 2933 2944 Ti 0.000 am 0.001 AI 2094 2100 2095 Fez+ 2383 2329 2333 ~n ara ais a147 MO 0.362 0.417 034 Ca 0.031 0.099 0.094 Tatal: 6.021 a015 6.m bid mmkr(niol%) Gmaaifœ 3.W 3.33 3.11 12ûô 14.a 13.26 Ahicndir# 13-53 7814 70.59 sfnmswhe a34 4-50 4.94 Ume WûIa 4- 2- Rbn Cm AHRQI Rirn Corn ri- 0*ld# (4Pw (llpa) 6Pa) (SPI 01-) 5102 37.42 37.3 37.36 37.44 3728 37.38 Tioz am am 0.02 Ut1 0.13 0.13 APL03 21.74 21.62 21-60 21.74 21.67 21.68 Fe0 27-74 n.58 27-72 2û.45 la46 19.S Mn0 1213 1219 1214 lS.12 21.m m.40 1.51 1.ü2 1.61 1.21 1.1 1-36 Cn) 1.w 1.45 1.49 1.M 1.72 1.87 Tot& l02.M 101.83 10202 101.94 101.911 102.15 ~wl2arirga Si- 211 2geZ 2m n o.aai ami ami AI 2041 2034 2037 Fe+ 1.- 1.841 1.w Mn 0.818 0.824 Am Mo aim o.raz aisi CO 0.120 0.124 am Taai: 7.987 7.998 aOQ2 End nirmkr: 4.31 117 42B pyrOg. 6.05 b45 6.40 Umindn 6213 61.74 6l.a sp88adlm , n.s1 27.m 27.4 8um un 3- 8- 8anm Coinia Man Aurigi carma Avrigi (16 Pi) (8 ml (16 PW ml (13 Pb) 34.85 3476 3823 3537 3560 2.9 270 1.66 3.93 1-92 1641 18.05 iam 17.I 19.16 n.30 22.02 19.0s 2234 19.90 A19 0.18 a19 020 0.10 0.71 8.56 la67 7-63 $10 aoi a00 aoi 0.01 0.02 a17 [123 0.14 0.12 ais 9.57 9.07 9-16 9.32 b99 aao am am a00 aao 0.02 aoi 0.01 am o.ot 95-00 9561 95.41 m.St 94.99

5377 533s 5353 5.- 5.34s 5.430 ais 0299 4312 0.189 0.447 0.229 3.472 3.327 3.275 3.265 3.203 3.450 2495 2750 2836 2412 2- 2539 0.015 0.025 a023 0.024 0.025 a012 2230 2m 1.971 2469 1.720 2071 0.m 0.Wl QOQO 0.002 A002 a004 0.055 0.051 0.070 0.040 0.034 aou 1.745 1.079 1.702 1.769 t.796 1.750 15.568 156a 15.623 15.597 rs.sa 75.522

#It -128 u.110 sin Ulm wim fgaru 6- 9- tlgfah sgnnr Avrrg, A- AHnOs Avag. A- Avarag. (13 Pu) (13 PW (32 Pw (14 plt) (16 Pt1 (31 ptr) 34.77 33.49 3392 34-17 35.22 3s4a 1-37 1.52 1.63 1.45 1.a3 b70 19.13 1873 la62 1852 19.43 187î 19.68 20.09 19.62 19.51 16.47 Zû.98 a10 024 0.13 0.10 ais a17 922 0.73 9.02 9.35 9.80 7.64 a03 am 0.03 0.03 nh aoi A14 0.13 0.19 0.20 02 a18 b53 a94 8.96 a39 a42 9.18 0.00 a01 0.00 0.00 rila 0.00 aoi 0.01 0.01 0.01 n/a Am 9299 91.89 9212 9i.n 93.41 %.O9

5.330 5385 54û1 5416 axa 4182 0.144 0.172 0.189 0.423 1514 5471 1451 3.521 3.354 2674 2595 298 2375 2.667 a032 a017 û.014 0.020 am1 2071 2128 22(W 2247 1.M 0.003 O-ocw 0.005 0.000 o.mi 0.040 0.057 0.081 0.- 0.054 f -814 1.m 1.691 1.652 1.780 15.659 15.m 15-97 15.504 15424

274 )C34( 5- CaiPd Mmk A- [3t Pa) (32 Pb) m W) 35.37 35.14 sr6 2m 3.3 1.55 la69 17-75 19.59 iam 19.34 19% acs a36 am ian 934 as aoi ais aoi ai8 0.22 0.17 an 9.16 am a00 1.10 0.00 am 0.13 0.00 93.32 96.06 95.09

5.414 6393 5404 0.307 a390 o.in 3.372 3310 ami 2155 2482 2523 0.006 0-047 0.012 2457 2138 2031 0.002 a024 a002 0.054 a064 0.051 1.703 1.193 1.669 15471 15.541 15449

Appendîx 4-6: Elenmicroprobe rnriyses of plagioclase

8943 mu sonhr 2- AHnOI A- (W%)- (13 Pb) @ *) Sa2 !%.FI 57.35 Al203 25.54 25-96 Fe0 0.1 1 oa Mn0 0.01 0.01 Ci0 5.m 7.51 NU0 8-10 7.0 K20 0.W 0.00 Tari 99.63 98-19 ~OIEIpl 0- Si 2675 2611 Al 1.342 1.393 Fe 0.W 0.01 1 Mn 0.000 0.000 Ca 0279 0.386 Na 0.701 0-625 K 0.005 ORO0 Total 5.006 5.005 End mrmkr(mol X) Albile 71.24 sa03 An- 2e.30 36.97 Orlliodole 0.46 0.00

sw7 U4t 2- Wdu Avangs A- (wtw (10 ml m pt) si02 6261 61.95 A1203 24.S 24.73 Fe0 0.12 0.01 Mn0 0.00 o. 00 -0 5-87 5.31 Na20 8.M 9.61 K20 0.07 0.09 Total 1O1 -33 101.73 c8tt~pn00ryglii Si 2738 2712 Al 1267 1.276 Fe 0.W 0.001 Mn 0.000 0.000 Ca 0275 0249 N8 0-685 0.816 K 0.004 0.- TaEiI 4.973 5.m End mrmblr (mol %) Albita 71 .O7 7623 Aii4(ViL 2851 23.m OrlhOCbsa 0.42 0.47 AHnOI (wm)- (aPa) SI02 60.22 Al203 25.54 fs0 0.07 mo 0.01 Ca0 6.0 WO 7.80 KZO 0.1 7 Tarol 99-90 Cations par8 osyg~~ si 26n Al 1-33 Fe O.= Mn 0.000 Ca 0.305 Na 0.655 K 0.m Total 4.%7 End mmnkr(moi %) Albite 67.59 Anwthi 31-44 Orn~ 0.90

OCIffd Zuwisdgnnr Oxldan Rh (*%) (6 PW Si02 59.25 A1203 26.10 Fa0 0.12 Mn0 0.01 Cao 7.1 3 NP20 7.26 K20 0.œ Total 99.94 won+para 0xyg.n Si 2641 W 1.371 Fe 0.- Mn 0.000 Ca 0.340 N. 0.627 K 0.005 ToW 4.m9 End mamkr (moi %) Albh 64.51 Anoraib 35.02 Orihoclase 0.47 Appendix 4-6 (continuecl):

KMA AMS

94-2838 %442 3 grains 5 gmh Olidu A-m Avsnga (W%) (15 pts) (20 pCs) Si02 60.76 61.34 Ai203 24.90 24.79 Fe0 0.03 0.08 Mn0 0.00 0.00 Cao 5.78 5.45 Na20 8.19 8.33 K20 O23 0.1 3 Total 99.90 100.1 1 Cations pot 8 oxygmn Si Z703 2718 Al 1.305 1.295 Fe 0.001 0.002 Mn 0.000 0.000 Ca 0276 0259 Na 0.706 0.71 5 K 0.01 3 0.007 Total 5.004 4.9% End nmmkr (mol %) Al bite 70.97 7285 Anorthite 27.71 26.41 Orthodase 1.33 0.75 Appndlx Cf: Electron microprobe analyses of cordierite

oxu.8 4gnVII (*%) 12 Pb Si02 46-07 Ti02 0.02 AU03 33-98 FsO 9.20 Mn0 0.42 Mg0 7.81 Na20 0.51 K20 0.02 Total: 100.01 Cation8 par 18 oaygmn 90-36 nudeaüng in cordiem 1 cordiefite 2 Total (6 ptt) Recalc Recaic Recalc Si02 0.01 0.01 0.16 Ti02 0.01 0.00 0-05 Ai203 56.37 56.29 55.32 Cr203 0.08 0.08 0.15 Fe0 34.16 3229 35.21 Fe203 217 297 Mn0 0.40 0-41 0.36 Mg0 285 281 235 Ni0 0.00 0.01 0.09 Zn0 3.53 3.38 1.17 Total 97.41 97-45 97.84 Cations per 4 oxygan Si 0.000 0.000 0.005 Ti 0.000 0.000 0.001 Al 1.961 1-950 1.919 Cr 0.002 0.002 0.004 Fez+ 0.843 0.794 0.866 Fe3+ 0.048 0.066 Mn 0.010 0.010 0.009 Mg 0-126 0.123 0.103 Ni 0.000 0.000 0.002 zn o.on 0.073 0.025 Total 3.018 3.000 3.000

Recalculation after Oroop (1 987): Fe3+ = 8 x (1 - 3 1 total cation); Appendix 44

Application of the cornputer program lWQ 2.02

TWQ 2.02 (Thennobarometry Wth estimation of EQuilibrium state) is a DOS-based cornputer program (Beman, 1996). To calculate a P-T intersection, the user selects end-member components of al1 mineral phases involved in the various equilibria (e.g., almandine, pyrope, grossular, annite, phlogopite, muscovite, anorthite, Feardierite, andalusite andlor sillimanite). Themodynamic data (molar enthalpy, entropy, volume and heat capacity) for end member phases are taken from Aranovich & Beman (1996) and Berman & Aranovich (1 996). Compositional files must then be created for phases showing significant solid solution. In the case of the present study, these files contain data on gamet, plagioclase, muscovite, biotite and cordierite, obtained through electron microprobe analyses (Appendices 4-3 through 4-8). The mineral compositions are converted to activities using the activity-composition models of Beman 8 Aranovich (1 996) for gamet and cordierite, Berman (in prep.) for bioüte, Chatterjee & Froese (1975) for muscovite and Fuhman & Lindsley (1988) for feldspar. Using these themodynamic and compositional data, the TWQ program then calculates the location of al1 possible equilibria within a selected P-T window (Appendix 4-1 0). Some or al1 the following equilibria wete considered for each sample: (12) ph1 + alm = ann + py (13) py+ms+grs=3an+phl (14) 2 siiland + qtr + grs = 3 an (15) py + ms = ph1 + qtz + 2 siiiand (16) ms + grs + alm = ann + 3 an (17) alm + ms = 2 siiland + qtz + ann (18) and = si1 (19) 4sil+5qtz+2alrn=3Feixd (20) 4 si1 + 5 qtz + 2 py + 2 ann = 3 Fe-crd + 2 ph1 (21) 6sil+5gn+3Fe-~rd=2alm+15an (22) 3Fe-~rd+5grs+2phl+6sil=2py+15an+2ann (23) 3qtz+2py+6an+2ann=3Feçrd+2grs+2phI (24) 2 alm + 6 an + 3 qtz = 2 grs + 3 Fe-crd

Reacüon (12) is the biotite-gamet thennometer (Ferry 8 Spear, 1978). reacüon (14) is the GASP readion. Readion (19) is a version of reaction (8). Reactions (12) - (1 8) can be calculated for staurohte zone samples, while for cordierite zone samples bcking primary muscovite reactions (12), (14) and (19) to (24) are calculated. If no aluminosilicates are chosen only reactions (1Z), (13) and (16) are computed and al1 three intersect at one point. This occun because only two of these reactions are independent, the third being a Iinear combination of the other two. As such, the intersection does not provide any information on how well constrained the P-T estimate is. Wth the choice of an aluminosilicate the six equilibria define three independent reactions, which allow for the qualitative evaluation of the state of equilibrium of the sample. The tig htness of the intenections is displayed on the diagram by a triangle, defined by the intersections of reactions (12), (14) and (15) for staurolite zone samples (Bernian, 1991) and reactions (12), (21) and (23) for cordierite zone samples. In the case where andalusite and sillimanite are both present in the rock. ten equilibria can be calculated, four of which are linearly independent The resulting intenections do not dner much fiom the ones calculated with only one aluminosilicate, since the equilibria using andalusite are in the same position as those for sillimanite, but have a slightly shallower dope. It should be noted calculations for al1 samples assume the presence of andalusite or sillimanite even if no aluminosilicate mineral is actually present in the sample. In effect, this procedure calculates the position equilibria (14), (15) and (17) assuming amsio5=leven though the absence of any aluminosilicate mineral in the rock necessadly indicates amsi&. The validity of the resulting P-T estimates can be evaluated by considering the tightness of intersections obtained in the aluminosiiicatefree samples and the agreement between these intersections and independent P-T estimates. RelativeIy tight intersections of * 1 kbar and I 30°C are in fact obtained for several aluminosilicate-fiee samples (93-64, 93-87,934 77 and 94-47, see Appendix 410). In al1 these cases, nearby rocks contain eiaier andalusite (samples 93-64.87, 1n) or both andalusite and sillirnanite (94-47). Thus, with the exception of sample 93-1 7?, the P-T estimates obtained for the aluminosilicate-free samples are in. or within error of, the appropriate aluminosilicate stability field. Sample 94-47 is a particulerly interesting case. Althoug h no aluminosilicates are found in this rock, a sample from an outcrop 1 km away contains coexisting fibrolite and andalusite. The pressure and temperature calculation for 94-47 correctly places it close to the sillimanite-andalusite reaction curve. These results suggest that a,& for al1 samples considered in this study and in tum that even the aluminosilicatefree samples provide valid P-T estimates. Appendix 4-1 0

Equilibria reacüons calculated by TWQ 2.02 for gamet-biotiternuscuvite- plagioclase and gamet-bioüteplagioclase-cordierite assemblages of the KMA. For each sample the reactions using gamet core and gamet rim values along with average biotite values. and if available. contact biotite values are plotted. Gamet rim readÏon equilibria curves were used for P-T estimation and are summarized in Figure 610. Note that the scale varies between samples. IR denotes number of independent reactions. loft gamet rim, average biotite rlght gamet cote. average bîotite

I.lt: gamet dm, 2 average bblite dght gametoors, average MotRa

Appndix 4.10: Equilibria reacüons cakulatad by TWQ 2.02 for KMA biotitequarh schist of the staurolite zone. loft gamet rim, average bioüte z HgM: gamtm. average Motite

Appendix 4.1 O (continud): Equilibria reacüons calculated by TWQ 2.02 for KMA biititequarh schist of the staurolite zone. Iofk gamet dm. average bioüte rlgm gamet m. average Motite

1.- 1.- gamet dm. average bioüb right gamet m. average bioh

Appndix 4.10 (eontlnued): Equilibria reactions calculatecl by TWQ 2.02 for KWbiootequartz schist of the staurolite zone. lait gamet rim, maûix biobite rtght: gamet cm, matruc biotib 2

Idt gamet rim, matruc bioüte 3 muscovite right gamet rim, maîrix bioüta, coidiefite 2 5QQam6smom 3 independent reacbkrw T cc)

Appendix 4.10 (continuad): Equilibria maclions calculatecl by TWQ 2.02 for cordierite-bean'ng biotite-quartz schist of the KMA. Iofk gamet rim. matrix blolite rlght: gamet m. mat& bioüte 4

94447d

IdC gamet rim. contact biow rlght gamet core, matrix biatite 4 g00rn~Km 3 independent miadbns T cc,

AppondIx 4.10 (continued): Equilibria reaca'ons calculated by TWQ 2.02 for coidierite-bearing biotitequartz schist of the KMA. 1aik gamet rim, maûix biotite dg- gamet-. maûix biotite 2

Appendix 4.10 (cantlnued): Equilibria Monscalculateci by TWQ 2.02 for cordierite-bearing biotite-quartz scfiist of the KMA 291 loft gamet rim, average biilite 1 right: gamet cors, average bioIftib

Appendix ClO (continud): Equilibria reactions calailated by TWQ 2.02 for staurolite bearing KMA biotitequartz schist of the western Dezadeash Range (93-87) and the Killermun Lake area (93-64 and 93-1 26). 292 let: gamet rim, contad bioiite 1 right: gamet cm, average ûii

squan: gamet rim, average Mate ci-: average gamet, amrage biom uppor dgM coni.r: gamet cors, average b&üb

Appendix 4.10 (continuad): Equilibria reactions calculatecl by TWQ 2.02 KMA biotitequartz schist (staurolite-bearing. 94-47) of Gladstone Cmkarea and the western Kluane Hills (95-71, 89-85a).

293 a) gamet amand average Moüte. muscovite and plagbdass: b) gamet rim, contact bktite and average rntBcotW end ph-: c) gamet values from gii~asularpoor rons doss Io M. contact biotits, awage muscmita and plagbd~~~.

95-53b (lower left) ma: ma* bbüte values, averag?3gamet mc: mat& bklbMkw#, cmgamet ri. R. r3: spedRc gamet iim and contac! bklb valucw K gamet rim and contact bbtb rim values

Appemdix 4-10 (continueci): Equilibria reacüons calculated by TWQ 2.02 for micaquartz schist of the AMS (93-42) and the Nasina Assefmblage (9553b) and phyllites of the OF (962046.94-242). 294 Appndix 4-11 :Compositional ming profiles of gamets staurolite-free KMA bioütequartz schist

a o. e nn O.? $ - g 0.6 - ,,l ...... 10.5 o1 ...... Los 500 1000 1500 2ma 2500 2004006008001OOO dm diameter (micron) rim rim diameter (micron) rim

o1 ...... -los o1 ...... 'los a)(I4(10600a#lOOO 200 4w soo rn tao0 rim diamter (micran) rim rim dhmstsr (micron) rim s'O

-9'0 g L'O v 9 8"

"O

O' L Appendix 4-11 (continued): KMA biotitequarh schist

Ob..... 1.0

.....'05 50 100 lm 2w 250 ml low P schist from mie radius (micron) rim Killermun Lake intrusion

CQlb radius (micron) dm

western Kluane Hills

oL ...... los 100 2(1(1 3[14 rim diamater(miaori) rirn rim diameter (micron) rim Appendix 4.1 1 (continued):

Pericratonic assem Mages

...... las QI0 Io00 19#1 2mo rim dïmetar(m#wi) rim

9342: micaquartz schist, Aishihik Metamorphic Suite, Aishihik Lake

94-3-68:micaceous quarbite, Nisling assemblage, east of Dezadesh Lake 95-53b: micaceous quartzite,Nasina Assemblage, norîh end of Talbot Am, Kluane Lake

Island arc overiap assemblage: Dezadeash Formation

94-237a: date, Tatshenshini River

94-2W: date, Million Dallar Falls provincial campground

5. 94-242: phyllite, Tdluride Creek 2 0.1 : * 0.0

--...... %Y --S.--- * 2m 500 750 lm 1250 t5m rim dlameior(miei#i) ihi Appendix 5-1 :Descriptions and locations of samples analyted for geochemistry and Nd. Sr, 40Ar-3gArisotopes gsample longitude (W) latitude (N) major element geochemistry: Kluane metamorphic assemblage: 90-39 graphioc ms-bt-qtz schist (al) 138°17'30" 60°06'15" 94-1 15 sil-bearing crd-btqk schist (al) 137O22'30" 61"03'05" 94-387 graphitic and-bt-msqtz schist (al) 137O2S225" 60'50'1 0" Nisling assemblage: 94-358 crd-beanng kygrt-btqtz schist 136"48'54' 60'30'1 O"

SfTtmd: Kluane metamorphic assemblage: 93-96 graphiac silqrtqtz schist (al) 13656'36" 93-1 36 graphitic grt-st-chl-ms-btqtz schist (al) 137"33"2OW 93-1 56* graphitic ms-chlqtz schist (ca) 138' 1600 94-36' graphiac ms-chlqtz schist (ca) 138"36'30" 94-82 sil-beaflng crd-btqtz schist (al) 137"0111 0" 94-272 bt-qtz schist (al) 136"46'20" 94297f 1 arthoamphibole-bt-plqtz schist 136"42'00" 94-346 grt-st-btqtz schist (al) 139"04'00" Dezadeash Formation: 94-1 90 graphitic date 137 "02'40" 94-204 b graphitic date 136 '56'30" Aishihik Metamorphic Suite: 93-1 4 bt-msqtz schist (PAMqb) 137O29'00" 93-1 6 sil-grt-bt-msqtz schist (PAMqb) 137"27'3OW

9342 st-btgrtmsqtz schist (PAMfs) 137 O 10'40" 93-67 bt-msqtz schist (PAMqb) 137028'20m

RblSr muscovite: 94-1 7a graphioc ep-bt-ms-chlqtz schist (ca) 138"49'4SB 61 "23'30 94-33 graphitic ms-chlqtz schist (ca) 138O27'45" 61 " 10'40 94-5 1 uo-ms-chlqtz schist (ca) 138'33'1 5" 61 O 19'00" 94-1 73 and-ms-chl-btqtz schist (al) 137'53'50 61"09'50"

ccms-chlqtz schist (ca) 138 "48'00" 6 1O 19'00"

denotes mpksthat wmalso analyzed for whok rock and muscovite RbSr. 1: 'ai' and 'a'denates aluminous and cakk schist of the KMA. 'PWand 'PAMqb' am un& of the AMS altar Johnston & Timmfman (1 993a. b). Appendix 5-2

Analytical procedures for geochemistry and Nd and Sr isotope studies

A suite of 11 samples of graphitic micaquartz schist of the KMA. 2 date samples of the DF, 4 micaquark schist sarnples of the AMS and one mica- quartz schist of the Nisling assemblage were selected for whole rock geochemical analyses. The DF and AMS samples along wïth 8 of the KMA sarnples were also analyzed for their Nd isotopic signature. Two KMA samples were analyzed for their Sr whole rock and muscovite signatures. Sr isotopes were also analyzed on two additional KMA samples. The samples are described in Appendix 5-1 and are shown on map on Figure 5-5.

Werock geochemisfry: The samples were crushed to grave1 sire avoiding contact with rnetal and subsequently grinded to -35 micron using a tungsten carbide swing miil and an agate grinder. Major and trace elements were detemined at the Washington State Univenity by x-ray fluorescence (XRF) and inductively coupled plasma mass spedrometry (ICPMS), respectively, as descnbed by Hooper et al. (1993).

Neodymium isotopic analyses: Neodymium isotopic analyses were perfomied by the author at the University of Alberta. The following analytical procedure description is modified after Creaser et al. (1997). Sample powders were weighed, totally spiked with a 1MNd-14QSrntracer solution, and dissolved in 12 ml of a 5:i mix of 24N HF and 16N HNO, in sealed tefion vessels at 160°C for -120 hours. The solution was evaporated to dryness, IOml of 6N HCI was added to the residue heated at 160°C for 24 hours to dissolve fluorides. This solution was evaporated to dryness and dissolved in 6 ml of O.75N HCI. After filtering to remove graphite the solution was centrifuged at 5000 rpm for 5 minutes. The REE were separated as a group using standard cation chromatography. Borosilicate glass and polypropylene Bio-Rad Econo-Colurnns, containing 4.4 ml of a wet Bio- Rad AG50W-X8 cation minwith a mesh süe of 200-400, were used. Subsequent separation of Nd Rom Sm was done by Di(2ethylhexyl phosphate) chromatography (HDEHP), ushg heat-shrink FE4: 1 (Zeus #164SS3,7/8") columns with Bio-Rad BioBeads SX-û (200400 mesh) resin. The purified Nd and Sm fiactions were analyzed for isotopic composition using VG354 and Micromass MM30 mass spedrometers, respedively. Total procedural blanks for Nd and Sm are 0.5 ng. The 150Nd-"gSmtracer solution consists of highly purified (97.62 at%) and "'Sm (97.22 at.%). as determinecl by direct calibraüon in triplicate against a mixd SmNd normal solution (Wasserburg et al., 1981) with a reproducibility of better than kO.011 for lMNd and I0.03% for ldgSmconcentrations. lsotopic analyses of Nd used a dynamic multicollector routine, correcting raw ratios both for variable mass- discrimination to laNd/""Nd = 0.7219 using an exponential law after Wasserburg et al. (1981) and for the effects of low abundance. n~n-'~~Nd. tracer Nd isotopes. Sm was analyzed in static multicollector mode and corrections made both for variable mass-discrimination to lSzSrn/'YSrn= 1.1 7537 using the exponential law of Wasserburg et al. (1981), and for the effects of low abundance, n~n-'~'Srn,tracer Sm isotopes on '%n/lYSm. During the couse of this study a dissolution of the spiked standard rock BCR-1 yielded lUNd/"'Nd = 0.512634 i9 (e,= -0.1) and 147Sm11UNd= 0.1378 and a spiked aliquot of the La Jolla Nd isotopic standard had a 'UNd/'UNd value of 0.51 1848 * 8 after separation of Nd from spike Sm by HDEHP chromatography. These values are in good agreement with previous deteminations of BCR-1 and La Jolla (Thihall, 1982. 1991; Makashima & Nakamura, 1991). Multiple analyses of an unspiked in-house Nd isotopic standard yielded an extemal reproducibility of * 0.000016 (20). which is taken as the minimum uncertainty estimate of lUNdl'uNd for the analyzed samples of this study. As an additional check of accuracy for Nd isotopic analyses, al1 totally spiked samples were monitored for recovered lQNdrUNd, which was detennined to be 0.348407 for the average of analyzed samples here. This value is also in good agreement with previous unspiked determinations of '*NdfUNd, as reported in Thiriwall(l991).

Strontium isotopic analyses: The samples that were also analyzed for Sr were spiked with a highquality SRM988 spike with a 'Sr/% value >1700. Rb and Sr were extracted separately from the sarnple during REE separation using the cation chromatography, as described in Nd analyses above, and evaporated to dryness. The resïdues containing Rb and Sr were taken up in an oxalic acidBlCI mix solutions. loaded on heat-shrink TF€ 4: 1 (Zeus #164553, 718'7 coiumns with wet Bio-Rad AG50W48 cation resin (mesh site: 200400) and cleaned from oxalic acid by using HCI. The purified Rb and Sr fractions were analyzed for isotopic composition using Micromass MS30 and VG354 mass spectrometers, respectively. Muscovite separation was done separately fiom the above described procedures for whole rock samples. The sample material was cnished to grain size (0.5-1 mm) in a manual metal cnisher and agate mill. Mineral separation was done by shaking sample material over filter paper, followed by using a Frantz magnetic separator and subsequently by heavy Iiquid fractionation with Sodiumpolytungstate (STP). The resuiting fraction was highly enriched in muscovite (>98 vol.%). X-ray difftactionation (XRD) recorded minute amounts of chlorite, quartz and graphite. Rb and Sr were separated from muscovite by using the same analytical procedures as described above, except that the spike used was a ORNL spike with a %,Sr value of -460. Apprndlx 5-3: Neodymium studles In the North Amerlcan Cordlllera

Rock type'

Alaska Range Birch Creek schlst (qtz-serkite schlst) I (1) greenschist f. Abinikoff et al. YïT 1 Yukon Tanana Upland augengnelss (1) (1W Famret al. central-southcentral (1987) Alaska (TACT route) bkic contlnrntal mst - Adh et al. (1988) Taku, Ketchikan, SE Alaska Taku tonalites (3) Taku and CMB have ditfaml CM6 granites (2) int~8bnhbbry prlor to Mid CMB granodlorites Tefllaty (4)

Bennett 6i Hansen MT eastem Alaska Dsvonian- (1988) southetri Yukon Misdslppian aourm; Mf ha6 wrnalmd same position relative

Samson et al. ST, AX SE Alaska Ax (28) ST and AX wst am compkteiy (1989) igneous rocks juvenlk, montk dsrivsd material, sediments

ST (22) igneous rocks sediments

- - Samson et al. YCT Taku Inlet - Pemlan- as low as tel-2,45 YCT more evoived (199w Taku Prince Ruprî Trlasslc Ga than ST, \MI and AX r rn I (SE Alaska) -4.6 to +4 (modem arc) Samson et al. Vancouver and Quien igneous rocks 340.860 WR compbtely (199Ob) Charl~tbIslands clastic sediments Ma juvenlb, mantb I (3)) derhred material,

Appendix 53(continued):

Location

Jackson et al, Nisling Wlson Bay, Atlin Lake Nisling Terrane (3) older wdal (1991) ST (N British Columbia) a) Boundary Range material in basal b) Florence Range unit Indicetes uppr Tdasuic Northern Stikins (7) link btween ST Laberge Group Jurassic and Nisllng Stuhini Group Triasdc torranes basal clastic unit

+4.0 Io t6.Q grandlorite (5) Cretaceous -18 to -1,3 -2,1 to -2.6

- -- Marcantonlo et al. Quill Creek Intrusive ultramafic (3) mofidultnmfio (1993) Compiew (Kluane Lake gabbro (5) intrusions piirtly SW Yukon) contamlnateâ by Parmian shaks and sand8toner

-- - Creaser et al, Teslln Tectonic Zone, Nleutiln assemblage pre-Earfy -7,2 to +O3 -3.9 to +3,4 dotrital input (19W south central Yukon (metasediments) (14) Missippian 49to - -3,7 to -143 tram proximal (350 Ma) 17,9 -20 to -24.3 arcs and dimtat -24 to -28,4 W craton, TTZ rocks locrld on outamntmargln of

ancknt W a: numben in ~arenthedsindicate numbers of analyd samples A%: ~kxande;terrane; CC: Cache Creek terrane; CMB: ~oastMountaln Batholllh; ST: Stikine terrane; WR: Wrangellla terrane; YCT: Yukon Crystalllne Temns; YTT: Yukon Tenana Terrane Appendix 5-4: Generalized tenane map (modified after Wheeler et al., 1991) with the location of al1 published neodyrnium data including this study. The numben refer to e,,(O)-values. Smaller numbers Niling indicate references. i: Arth et al. (1 988). 2: Taku Bowring & Podosek (1989), 3: Creaser et Yukon-Tanana Alexander al. (1 997), 4: Jackson et al. (1990), 5: Jackson et al. (1991). 6: Marcantonio et al. SiMountain Wrangellia

(1 993). 7: Ross et al. (1995). 8: Samson et Dorsey Chugach al. (1 989), 9:Samson et al. (1 WOa), 10: Samson et al. (1WOb), 1 1 : Samson et al. Quesirellia Yakutat (1 991a), 12: Samson et al. (1991 b). 13: cade Creek undivided Thériault & Ross (1991), 14: this study. meiîmorphic