(),.(o TGbÜEOTJS IhÜTTIIJSI\ZE ROCKS OF 1FHE PE^â,KE ^ã'I\ÜED DEITISODÜ FLATVGES WTTHI}Ü TtrHE .â.E'EI'ã.IDE GEOSYIÜCI-IìTE By: Robert sinclair llorrison B. Sc. (Acadia, 1981- ) B.Sc. Hons. (Adelaide, L982) The Department of Geology and Geophysics The UniversítY of Adelaide south Australia. This thesis is submitted as fulfilnent of the requirernents for the degree of Doctor of PhiIosoPhY in GeoIogY at The UniversitY of Adelaide South Australia. February 29Lr', i-988. Resubmitted March 31=È , L989 - C\,,.-,)r,f lrt,>c\ i';, ti 1_ Statement of OriginalitY: I hereby certify that this thesis does not incorporate, without acknowled-gernent, ãty material which has been previously submitted for a dégree or dÏ-ploma in any university, and, to the best of my knowledge ..tá b"Ii"f, it does not contain any written or published matãrial by another person, except where due reference is made in the text. Robert Sinclair llorrison- FebruarY 29Er', L988; March 3l-=È, l-989. 2 ,¿!tl Fronticepiece: Margi-n of a monzogabbro body of the Bungadillina suite in the Peake and Denison Ranges showj-ng an abundant felsic dyke network. The felsic dykes increase in size and density towards the contact, but are truncated with brecciated Burra Group sediments. Monzogabbro body is dominated by coarse grained euhedral arnphibole and smaller clinopyroxene. Dykes are thought to have originated by a fil-ter- pressínq mechanism where late-stage residual fel-sic rnelt is progressively squeezed out towards the margin of a ferromagnesian crystal-rich maqma. Location: Northeast of sample locality 17516l (Map E). 3 T.ã.BI-E OF CO¡UTEITTS Äbstract... 9 I2 Acknowledgements. llethodofogy and Scope of Research" ' " " "1-4 Terminology, Nonenclature and classification . ' 16 clrapter one: slmopsis of the Adelaide Geoslmcline. 1-.1 Introduction """L7 L.2 Pre-Adelaidean Crystalline Basement' r.2 . i-i;t;"duction " "2o I.2 .2 The Gawler Craton. "2o 1,.2 .3 curnamona Cratonic Nucteus" " '2I r.2 .4 The Inliers of the Mount Lofty Ranges " "22 L.2 .5 The Peake and Denj-son Ranges" " " "23 r.2 .6 The Flinders and Wiltouran Ranges " '24 1.3 Adelaidean and Cambrian Stratigraphy' l-. 3 .1 Callanna GrouP "25 l_. 3 .2 The Burra GrouP " " "28 1.3 .3 Umberatana Group. - "29 1.3 .4 WilPena GrouP " '30 1.3 .5 Moralana Supergroup.. " " '30 I.4 Structural Evolution of the Adelaide Geosyncline' L.4.L Introduction 32 Pre-Delamerian TecÈonism' ' 33 1-.4.2 ' 34 I.4 .3 The Del-amerian Orogeny ' ' t_.5 Diapirs and Diapirism in the Adelaide Geosyncline. l-.5 .1 Introduction 38 Work 40 1.5 .2 Previous 43 l_.5 :ã óiapiric Breccia of the Peake and Denison Ranges.. ' 1.5 .4 Discussion.. 48 Chapter Ttyo: Igmeous Intrusives of the Adelaide Geoslmcline: A Review' 2.L Introduction 5L 2.2 Granites of The Kanmantoo fiough and Padthaway Ridge 52 2.3 The Granites of the Nackara Arc' 2.3.L Introduction ""53 2.3.2 The Anabama Granite "54 2.3.3 The Bendigo Granite "60 4 2.4 Mount LoftY Ranges " " ' 61- 2.5 Intrusives Associated with Diapiric Breccia. 2 5 .1 Introduction ....62 2 5 .2 Blinman and OraParinna Region 63 2 5 .3 Worumba Anticline... ......66 2 5 .4 Northern Flinders Ranges . '67 2 5 .5 Southern Flinders Ranges . '68 2 5 .6 The Arkaba DiaPir ."'7o 2 5 .7 Northern Mount Lofty Ranqes ... '7L 2.6 Spalding Inlier and Burra... " " '7L 2.7 Mount Painter Region. 2.7.L Intrusives within Crystalline Basement 73 2.7.2 Intrusíves within Adetaidean Sediments 74 2.8 Will-ouran Ranges ' '78 2.9 Peake and Denison Ranges.. 82 2.1,o Jurassic Dolerites and Kinberl-ites ' ' ' 85 2.II Discussion.. ""'87 Cha¡rter Three: Field Geologry and Petrography of the Intrusives of tlre Peake and Denison Ranges. 3.1 Introduction """91- 3.2 Northwestern Zone, Maps A and A'.. " "95 3.3 Northern Zone, MaPS B and B' . 3.3.1 Si1l St^rarm, Maps B and B' .. " '1OO 3.3.2 Plutons, MaP B. ""'1-03 3.4 Central- Zone, Maps C and D... " 'l-05 3.5 Southeastern Plutons, MaP 8... "109 3.6 South-Central Plutons and Sills, Maps F and F' 110 3.7 The Southern Pluton, MâP G... " '11-4 3.8 Northeastern Area, MaP H... " " 'l-15 3 .9 Southeastern Area, MaP I. " " ' 11-5 Clrapter Fou¡: ltineralogryr of the Intrusives of tlre Peake and Denison Ranges- 4.L Introduction '""II7 5 4.2 Oxides .L1,7 4.3 Sphene 'L23 4-4 Garnets ""'L25 4.5 Pyroxenes. 4.5.I Introduction - PYroxenes.. r28 4.5.2 Pyroxene Zoning .. ' "I29 4.5.3 Pyroxene ChemistrY ' ' l-33 4.6 Amphiboles. 4.6.l- Introduction '''136 4.6.2 Arnphibole Zoning " "L37 4.6.3 Ã,mphibole ChemistrY 'L39 4.6.4 Coexisting Calcic Amphiboles: Hornblende-Actinolite ' ' "J'42 4 .6 .5 Arnphibole ComPositions : Geothermometry and Geobarometry " "L46 4.7 Biotite .....148 4.8 Feldspars. 4 .8 .1 Introduction ' ' '1'52 4.8.2 Zoning 4.8.3 Feldspar Geothermometry... ....L56 4.9 Epidote GrouP. 4.9.I Epidote and Clinozoisite . .1,57 4.9 .2 AIlanite. .160 4.1-o chroríte "'160 4.LL Synopsis "'1-61 clrapter Five: Geochemistry of the Intrusive Rocks of The Peake and Denison Ranges- 5.1 Introduction ""'1'64 5.2 Major Element Geochemistry - classification ....166 5.3 Major Element Geochemistry - Variations "'L69 5.4 Trace Element Geochemistry - Alteration " 'I73 5.5 Trace Element Geochemistry - Variations :l.75 5.6 Isotope GeochemistrY. 5.6.1 Potassium - Àrgon-. 'L77 5.6.2 Rubidium - Strõntium-.. "L78 5.6.3 Uranium Lead ..:.. ""'1-79 5.6.4 Carbon and Oxygen Isotope Geochemistry "180 6 5.7 Synopsis ....1'82 Chapter Six: Comparative Geochemistry of the Intrusives of the Peake and Denison Ranges wl-ttr lgmeous Rocks of the Adelaide Geoslmcline, I,achlan FoId BeIt and Gawler Craton- 6.L rntroduction .....185 6.2 Major Element Comparative Geochemistry ....L87 6.3 Comparative Trace Element Geochemistry ....1-92 6.4 Intrusives of the Willouran Ranges and Arkaroola Þegion..198 6.5 The Anabama and Bendigo Granites 200 6.6 Synopsis ----2o5 Ctrapter Seven: Petrogenesis of Intrusives of the Peake and Denison Ranges. 7.L Introduction .....2LL 7.2 Fiel-d and Petrographic Evidence 2LL 7.3 Mineralogical Evidence -----224 7.4 lJ.ajor Oxide Evidence - -226 7.5 Trace Element Evidence .... -228 7.6 Least-squares Fractionation Modell-ing. - - 229 7.7 Trace Element Fractionation Modetl-ing.. - ..233 7.8 Isotopes . -. -235 7.9 Àlteration . .236 7.1,O Geochemistry - Genetic Classification ....239 T.LJ_ Conclusions. ....242 Chapter Eight: Implications of lgmeous Activity in tlre Peake and neñison Ranges within the Adetaide Geosyncline. 8.l- Continental- Rifting and Initiation of the Adelaide GeosYncline. ..246 8.2 Rift-Associated Plutonism... ....249 8.3 Intrusives of the Peake and Denison Ranges .....252 7 ^â'BSTFLâ.CT The Adelaide Geosyncline is one of the best preserved Ies Late Proterozoic stratigraphy in the wor1d. Although a rel at minor component, the plutonic and volcanic rocks withín this exceptionalty ancient basin reflect successive tectonic stages of the basin's history. One of the largest and best preserved suite of plutonic rocks is found within the peáke and Denison Ranges,' a series of Adelaidean inliers located approximately lOOOkm north of Adelaide in the South Australia. This suite ot over fifÈy individual plutons is composed of a wide range of lithologies ranging from syenogabbros and monzogabbros to quartz iyenites and quartz monzonites and their altered equivalentsl which intrudea Early to Middle Adelaidean sediments and diapiric breecia. The largest pluton measures approximately three kilõmetres in diameter, but most plutons measure less than one kíIometre in diameter. The material comprising this so-called ildiapiric brecciatr is a very important featurã of tñe igneous intrusive rocks of the Peake and Oenison-Ranges as the plutons both intrude the breccia and have had their contaõts altered by further breccia mobilization. The breccia is best explained by syn-deþosítional diapírism and deformation.by Early Adelaidèan evapoi.itä bedè which have been subsequently remobilized during the Cambro-Ordovician Delamerian Oroqeny_..The location of Early adetaídean evaporite deposition corresponds to linear faults which controllea iniLial palaèo-basin development. Oiapirism and Delamerian remobilization were focused along these planes of crustal weakness. Many smaller igneous intrusive bodies in the Adelaide Geosyncline o"cür within tñese diapiric bodies, and may be exhumed remnants of Willouran volcanism. oue to Del-amerian remobilization, original contact relations have been displaced. Hohlever, undisturbed intrusive relations in the peake and Denièon Ranges suggest a pre-remobilization age for pluton emplacement. Contradicting structural evidence is present, supporting.both a pre-tectonic and þost-tectonic timing for emplacement. There is no ävidence to indicãte syn-tectonic plutonism. Geochronological investigations (both nË-Sr and U-Pb) of the intrusives of the Peake and Oenlson Ranges have failed to reveat the age of the plutons' Nonetheless, the timing of emplacement may correspond to a period of Ear1y to Middle Cambrian volcanic activity which_ was prevalent throughôut Australia, Tasmanía and Antarctica, which is expressed as a niief-period of exteñsional tectonism. In the Adelaide Geosyncline, Iate nãrly to Middle Cambrian volcanism is represented by the Truro Volcanicsl the tfarburton Vol-canics and those found within the BilIy Creek formation in the Arrowie Basin. The presence of dolerite dykes intruding fault lines and fold hinges (post-Delamerian magmatic ããtivityÍ, suggests pluton emplacement õccurred over a broad period of time. The geochemistry of the intrusives of the Peake and Denison 9 Ranges are best classifíed as a metaluminous to slightly peralkaline ãffáfi-calcic suite.