Geology and Geochemistry of the Craig A-2 Quadrangle and Vicinity, Prince of Wales Island, Southeastern Alaska

Total Page:16

File Type:pdf, Size:1020Kb

Geology and Geochemistry of the Craig A-2 Quadrangle and Vicinity, Prince of Wales Island, Southeastern Alaska GEOLOGY AND GEOCHEMISTRY OF THE CRAIG A-2 QUADRANGLE AND VICINITY, PRINCE OF WALES ISLAND, SOUTHEASTERN ALASKA BY Gordon Herreid, Thomas K. Bundtzen, and Donald L. Turner GEOLOGIC REPORT 48 STATE OF ALASKA Jay S. Hammond, Governor Robert E. LeResche, Commissioner, Dept. of Natural Resources Ross G. Schaff, State Geologist STAFF C.M. Adams. Cartographer L.F. Larson, Publications specialist M.R. Ashwell, Laboratory assistant W.E. Long, Hydrologist N.J. Bragg, Secretary W.M. Lyle, Petroleum geologist G.A. Broker, Clerk-typist R.A. Mann, Clerk M.E. Brown, Geologic information technician U.O. McBride. Clerk T.K. Bundtzen, Mining geologist D.L. McGee, Petroleum geologist C.N. Conwell, Mining engineer J. Newgaard, Accountant P. Coonrod, Clerk-typist G.H. Pessel, Petroleum geologist N.D. Coursey, Geochemical analyst R.D. Reger, Geologist C.L. Daniels, Geological assistant J.R. Riehle, Geological engineer J.T. Dillon, Mining geologist R.G. Schaff, State Geologist G.R. Eakins. Chief mining geologist L.C. Schell. Cartographer K.S. Emmel, Geological assistant R.H. Schultz, Laboratory technician W.G. Gilbert, Mining geologist D.R. Stein, Assayer S.W. Hackett. Exploration geophysicist C.H. Stevenson, Geologic information technician M.W. Henning, Mining geologist N.C. Veach, Assayer chemist J.T. Kline. Geological assistant G.M. Zartman, Clerk C.C. Landis. Clerk For sale by Alaska Division of Geological and Geophysical Surveys, P.O. Box 80007, College, 99708; 3327 Fairbanks St., Anchorage, 99503: P.O. Box 7438, Ketchikan, 99901: and Pouch M, Juneau, 99811. CONTENTS Page Summary ................................................................................................................................................................... Scope of present investigations .................................................................................................................................. Previous investigations ............................................................................................................................................... Geography ................................................................................................................................................................. Geologic units ............................................................................................................................................................ Wales Group.......................................................................................................................................................... Introduction ..................................................................................................................................................... Marble (Wm).................................................................................................................................................... Dolomite-rich marble ( Wdm) ............................................................................................................................ Dark-gray phyllite (Wp).................................................................................................................................... Phyllite, marble, and green schist (Wpmg)...................................................................................................... Green tuffaceous schist (Wg)............................................................................................................................ Metakeratophyre tuff(?) and related rocks (K, Kxt, Kd).................................................................................. Quartz sericite schist (Ws)................................................................................................................................ Silicified schist (Wss)........................................................................................................................................ Phyllite and limestone (Wpl)............................................................................................................................ Migmatitic gneiss (Wgm)................................................................................................................................... Age of the Wales Group.................................................................................................................................... Descon Formation ................................................................................................................................................ Introduction ..................................................................................................................................................... Spilite(?) and mixed volcanic rocks (Odv)........................................................................................................ Sheared conglomeratic graywacke (Odsg)......................................................................................................... Banded mudstone (Odm)................................................................................................................................. Graywacke (Odg)............................................................................................................................................. Argillite (Oda)................................................................................................................................................ Basalt (Odb)..................................................................................................................................................... Age of the Descon Formation .......................................................................................................................... Silurian(?) igneous rocks....................................................................................................................................... Altered granodiorite (Sgd)................................................................................................................................ Alaskite (Sa)..................................................................................................................................................... Keratophyre(?) (Sk)......................................................................................................................................... Devonian bedded rock units .................................................................................................................................. Introduction .................................................................................................................................................... Basal conglomerate and red beds (Dbc, Dar) .................................................................................................... Argillite-siltstone (Da), siltstone-graywacke (Dsg), pebble-conglomerate (Dpc), limestone (Dl), and felsite pebble conglomerate (Dkpc)............................................................................................................. Age ................................................................................................................................................................... Andesite(?) (Dand)............................................................................................................................................... Paleozoic(?) dikes (Pdk)........................................................................................................................................ Introduction..................................................................................................................................................... Felsite dikes ..................................................................................................................................................... Amygdaloidal porphyritic basaltic andesite dikes ............................................................................................. Porphyritic diabasesdikes .................................................................................................................................. Amygdaloidal porphyritic andesite dikes.......................................................................................................... Thermally metamorphosed dikes...................................................................................................................... Structure .......................................................................................................................................................... Age ................................................................................................................................................................... Cretaceous intrusive rocks ..................................................................................................................................... Altered porphyritic diorite (Kdip).................................................................................................................... Granodiorite (Kgdi)........................................................................................................................................ Epidotized gabbro and diorite (Keg).............................................................................................................. Breccia dikes (Kbd).........................................................................................................................................
Recommended publications
  • Mineralogy and Geochemistry of Ocelli in the Damtjernite Dykes and Sills, Chadobets Uplift, Siberian Craton: Evidence of the Fluid–Lamprophyric Magma Interaction
    minerals Article Mineralogy and Geochemistry of Ocelli in the Damtjernite Dykes and Sills, Chadobets Uplift, Siberian Craton: Evidence of the Fluid–Lamprophyric Magma Interaction Anna A. Nosova 1,*, Ludmila V. Sazonova 1,2, Alexey V. Kargin 1 , Elena O. Dubinina 1 and Elena A. Minervina 1 1 Institute of Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry, Russian Academy of Sciences (IGEM RAS), 119017 Moscow, Russia; [email protected] (L.V.S.); [email protected] (A.V.K.); [email protected] (E.O.D.); [email protected] (E.A.M.) 2 Geology Department, Lomonosov Moscow State University, 119991 Moscow, Russia * Correspondence: [email protected]; Tel.:+7-499-230-8414 Abstract: The study reports petrography, mineralogy and carbonate geochemistry and stable iso- topy of various types of ocelli (silicate-carbonate globules) observed in the lamprophyres from the Chadobets Uplift, southwestern Siberian craton. The Chadobets lamprophyres are related to the REE-bearing Chuktukon carbonatites. On the basis of their morphology, mineralogy and relation with the surrounding groundmass, we distinguish three types of ocelli: carbonate-silicate, containing carbonate, scapolite, sodalite, potassium feldspar, albite, apatite and minor quartz ocelli (K-Na-CSO); carbonate–silicate ocelli, containing natrolite and sodalite (Na-CSO); and silicate-carbonate, con- taining potassium feldspar and phlogopite (K-SCO). The K-Na-CSO present in the most evolved Citation: Nosova, A.A.; Sazonova, damtjernite with irregular and polygonal patches was distributed within the groundmass; the patches L.V.; Kargin, A.V.; Dubinina, E.O.; consist of minerals identical to minerals in ocelli. Carbonate in the K-Na-CSO are calcite, Fe-dolomite Minervina, E.A.
    [Show full text]
  • EVIDENCE for MAGMATIC-HYDROTHERMAL ACTIVITY on MARS from Cl-RICH SCAPOLITE in NAKHLA
    45th Lunar and Planetary Science Conference (2014) 1620.pdf EVIDENCE FOR MAGMATIC-HYDROTHERMAL ACTIVITY ON MARS FROM Cl-RICH SCAPOLITE IN NAKHLA. J. Filiberto1, C.A. Goodrich2, A.H. Treiman3, J. Gross4, and P.A. Giesting1, 1Southern Illinois University, Geology Dept, Carbondale, IL 62901 USA, [email protected], 2Planetary Science Institute, Tucson AZ 85719 USA. 3Lunar and Planetary Institute, Houston, TX 77058 USA, 4American Museum of Natural History, New York, NY USA. Introduction: Scapolite is a common terrestrial The melt inclusion containing the Cl-scapolite (Fig. hydrothermal, metamorphic, and metasomatic mineral 1) is dominated by high-Ca pyroxene, K-feldspar and which forms by the reaction of plagioclase and a Cl- or K-rich glass, with minor chromite, Fe-sulfides, Fe-Ti CO2-rich fluid [1-3]. It is less common as a primary oxides, and alteration material [9]. The occurrence of igneous phase, but has been reported as megacrysts, the scapolite appears to be texturally equivalent to the phenocrysts, and oikocrysts in alkali-rich basaltic K-feldspar or the glass (i.e., interstitial to the pyrox- magmas [4-6]. Based on reflectance spectra, scapolite enes), and may therefore be replacing, or contempora- has also been suggested to exist on the surface of Mars neous with, one of these phases. It contains ~3.9 wt.% as a possible alteration mineral [7]. Cl, and has the formula (Na2.8Ca0.7K0.3)3.9(Si8.3Al3.7)12ClO24. Scapolite has three main end member composi- It is almost pure end-member marialite with little tions: marialite (Na4Al3Si9O24Cl), meionite meionite component (Fig. 2).
    [Show full text]
  • Sulfate-Rich Scapolite on Mars?
    Lunar and Planetary Science XXXVIII (2007) 1152.pdf Sulfate-rich Scapolite on Mars? J.J. Papike, J.M. Karner, and C.K. Shearer Astromaterials Institute, Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131 INTRODUCTION also shows selected bonds to neighboring Ca atoms. The surface of Mars shows abundant evidence for This configuration is remarkably stable in P-T space sulfur activity over a prolonged period in martian discussed below. history. Evidence goes back to the Viking landers in STABILITY 1976 but more recent orbital and landed in situ Figure 3 illustrates the stability field of SM [3]. The missions, including the two MER rovers, which are diagram shows that SM can be stable over the still active, confirm this. The identification of the pressure interval ~ 10 to 27 Kb at 1200 degrees C. sulfate jarosite with ferric iron confirms highly This corresponds to a depth interval of ~90 – 243 km oxidizing conditions near the martian surface. We depth in Mars (Fig. 4). In this depth range SM may speculate that conditions oxidizing enough to crystallize if the fO2 is high enough for S to exist as + crystallize a SO4 containing scapolite exist in the 6 . lower martian crust or upper mantle. This scapolite TERRESTRIAL OCCURENCES could be a important reservoir for sulfate in Mars and Terrestrial occurrences of igneous scapolite are might form either directly from sulfur-rich, oxidizing discussed in [2,4, and 5]. Boivin and Camus [4] magmas or by metasomatism of previously discuss a scapolite assemblage found as megacrysts crystallized plagioclase in basalt.
    [Show full text]
  • Facies and Mafic
    Metamorphic Facies and Metamorphosed Mafic Rocks l V.M. Goldschmidt (1911, 1912a), contact Metamorphic Facies and metamorphosed pelitic, calcareous, and Metamorphosed Mafic Rocks psammitic hornfelses in the Oslo region l Relatively simple mineral assemblages Reading: Winter Chapter 25. (< 6 major minerals) in the inner zones of the aureoles around granitoid intrusives l Equilibrium mineral assemblage related to Xbulk Metamorphic Facies Metamorphic Facies l Pentii Eskola (1914, 1915) Orijärvi, S. l Certain mineral pairs (e.g. anorthite + hypersthene) Finland were consistently present in rocks of appropriate l Rocks with K-feldspar + cordierite at Oslo composition, whereas the compositionally contained the compositionally equivalent pair equivalent pair (diopside + andalusite) was not biotite + muscovite at Orijärvi l If two alternative assemblages are X-equivalent, l Eskola: difference must reflect differing we must be able to relate them by a reaction physical conditions l In this case the reaction is simple: l Finnish rocks (more hydrous and lower MgSiO3 + CaAl2Si2O8 = CaMgSi2O6 + Al2SiO5 volume assemblage) equilibrated at lower En An Di Als temperatures and higher pressures than the Norwegian ones Metamorphic Facies Metamorphic Facies Oslo: Ksp + Cord l Eskola (1915) developed the concept of Orijärvi: Bi + Mu metamorphic facies: Reaction: “In any rock or metamorphic formation which has 2 KMg3AlSi 3O10(OH)2 + 6 KAl2AlSi 3O10(OH)2 + 15 SiO2 arrived at a chemical equilibrium through Bt Ms Qtz metamorphism at constant temperature and =
    [Show full text]
  • Virgin Islands National Park Geologic Resources Inventory Report
    National Park Service U.S. Department of the Interior Natural Resource Program Center Virgin Islands National Park Geologic Resources Inventory Report Natural Resource Report NPS/NRPC/GRD/NRR—2010/226 THIS PAGE: Underwater ecosystems including coral reefs are a primary natural resource at Virgin Islands National Park. National Park Service photograph. ON THE COVER: This view of Trunk Bay shows the steep slopes characteristic of Virgin Islands Na- tional Park. National Park Service photo- graph courtesy Rafe Boulon (Virgin Islands National Park). Virgin Islands National Park Geologic Resources Inventory Report Natural Resource Report NPS/NRPC/GRD/NRR—2010/226 Geologic Resources Division Natural Resource Program Center P.O. Box 25287 Denver, Colorado 80225 July 2010 U.S. Department of the Interior National Park Service Natural Resource Program Center Fort Collins, Colorado The National Park Service, Natural Resource Program Center publishes a range of reports that address natural resource topics of interest and applicability to a broad audience in the National Park Service and others in natural resource management, including scientists, conservation and environmental constituencies, and the public. The Natural Resource Report Series is used to disseminate high-priority, current natural resource management information with managerial application. The series targets a general, diverse audience, and may contain NPS policy considerations or address sensitive issues of management applicability. All manuscripts in the series receive the appropriate level of peer review to ensure that the information is scientifically credible, technically accurate, appropriately written for the intended audience, and designed and published in a professional manner. This report received informal peer review by subject-matter experts who were not directly involved in the collection, analysis, or reporting of the data.
    [Show full text]
  • Metasomatic Alteration Associated with Regional Metamorphism: an Example from the Willyama Supergroup, South Australia
    Lithos 54Ž. 2000 33±62 www.elsevier.nlrlocaterlithos Metasomatic alteration associated with regional metamorphism: an example from the Willyama Supergroup, South Australia A.J.R. Kent a,),1, P.M. Ashley a,2, C.M. Fanning b,3 a DiÕision of Earth Sciences, UniÕersity of New England, Armidale, NSW, 2351, Australia b Research School of Earth Sciences, The Australian National UniÕersity, Canberra, ACT, 0200, Australia Received 20 October 1998; accepted 12 May 2000 Abstract The Olary Domain, part of the Curnamona Province, a major Proterozoic terrane located within eastern South Australia and western New South Wales, Australia, is an excellent example of geological region that has been significantly altered by metasomatic mass-transfer processes associated with regional metamorphism. Examples of metasomatically altered rocks in the Olary Domain are ubiquitous and include garnet±epidote-rich alteration zones, clinopyroxene- and actinolite-matrix breccias, replacement ironstones and albite-rich alteration zones in quartzofeldspathic metasediments and intrusive rocks. Metasomatism is typically associated with formation of calcic, sodic andror iron-rich alteration zones and development of oxidised mineral assemblages containing one or more of the following: quartz, albite, actinolite±hornblende, andradite-rich garnet, epidote, magnetite, hematite and aegerine-bearing clinopyroxene. Detailed study of one widespread style of metasomatic alteration, garnet±epidote-rich alteration zones in calc-silicate host rocks, provides detailed information on the timing of metasomatism, the conditions under which alteration occurred, and the nature and origin of the metasomatic fluids. Garnet±epidote-bearing zones exhibit features such as breccias, veins, fracture-controlled alteration, open space fillings and massive replacement of pre-existing calc-silicate rock consistent with formation at locally high fluid pressures and fluidrrock ratios.
    [Show full text]
  • Oregon Geologic Digital Compilation Rules for Lithology Merge Information Entry
    State of Oregon Department of Geology and Mineral Industries Vicki S. McConnell, State Geologist OREGON GEOLOGIC DIGITAL COMPILATION RULES FOR LITHOLOGY MERGE INFORMATION ENTRY G E O L O G Y F A N O D T N M I E N M E T R R A A L P I E N D D U N S O T G R E I R E S O 1937 2006 Revisions: Feburary 2, 2005 January 1, 2006 NOTICE The Oregon Department of Geology and Mineral Industries is publishing this paper because the infor- mation furthers the mission of the Department. To facilitate timely distribution of the information, this report is published as received from the authors and has not been edited to our usual standards. Oregon Department of Geology and Mineral Industries Oregon Geologic Digital Compilation Published in conformance with ORS 516.030 For copies of this publication or other information about Oregon’s geology and natural resources, contact: Nature of the Northwest Information Center 800 NE Oregon Street #5 Portland, Oregon 97232 (971) 673-1555 http://www.naturenw.org Oregon Department of Geology and Mineral Industries - Oregon Geologic Digital Compilation i RULES FOR LITHOLOGY MERGE INFORMATION ENTRY The lithology merge unit contains 5 parts, separated by periods: Major characteristic.Lithology.Layering.Crystals/Grains.Engineering Lithology Merge Unit label (Lith_Mrg_U field in GIS polygon file): major_characteristic.LITHOLOGY.Layering.Crystals/Grains.Engineering major characteristic - lower case, places the unit into a general category .LITHOLOGY - in upper case, generally the compositional/common chemical lithologic name(s)
    [Show full text]
  • Geology and Mineral Resources
    UNITED STATES DEPARTMENT OF THE INTERIOR Harold L. Ickes, Secretary GEOLOGICAL SURVEY W. C. Mendenhall, Director Bulletin 879 GEOLOGY AND MINERAL RESOURCES OF THE BAKER QUADRANGLE, OREGON BY JAMES GILLULY Prepared in cooperation with the OREGON STATE MINING BOARD UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1937 For sale by the Superintendent of Documents, Washington, D. C. ------ Price -65 cents CONTENTS Page Abstract. ______________.________--_-_---_-_--.--_-.---------.---_ 1 Introduction._ _ _ ________________________________________________ 2 Field work and acknowledgments.______________________________ 2 Bibliography_.____._____..._.._.-_..---.._--_-...--......-._. 3 Geography.________ ...........^..-..-....... __-_____--__--.__--_. 4 Location and general features of the region.._____-_-.-___---._.._ 4 Topography.____..__.______._._._.___..-___ __-_.__.___.__. 5 Climate_._______-___--__.---__--__---_---_----__.-----.---_ 6 Drainage_ _ -__-_----_----.---------------------------------- 6 Geology .__.____-___.-____-.-__._.---.--_-_.._-.-.--....-_-. 7 General features.______-____----_--------_-____---_-_---__--__ 7 Pre-Tertiary rocks.___.-_-----------------------.--------.--.. 9 Supracrustal rocks_______________--_--__-___-_-_-------__ 9 Burnt River schist.__-____-__---__--__-_---_---__---__ 9 Distribution and topographic expression.._.._....._. 9 Thickness.__-__---_----------_-----------------_- 9 Lithology __-_-_______-_---_-..------.-__--_-_--_- 10 Conditions of sedimentation._..______--___-_.__-.._ 12 Stratigraphic relations and age_________._____.-.__ 12 Elkhorn Ridge argillite.-..__._-.----_-__-..-_-____-_-. 14 General features-___---___-------_----------_--___ 14 Thickness-__--__--_--_---_----------_-_-----_--__ 14 Lithology _____._---_-__-__--__--_-_--__-_-.-_-___ 14 Nonfissility of the argillite____-.______._-__-_---_ 18 Conditions of deposition.______.-___.-__._-___.____ 20 Age and relations to other formations.-.--._------_-.
    [Show full text]
  • A Systematic Nomenclature for Metamorphic Rocks
    A systematic nomenclature for metamorphic rocks: 1. HOW TO NAME A METAMORPHIC ROCK Recommendations by the IUGS Subcommission on the Systematics of Metamorphic Rocks: Web version 1/4/04. Rolf Schmid1, Douglas Fettes2, Ben Harte3, Eleutheria Davis4, Jacqueline Desmons5, Hans- Joachim Meyer-Marsilius† and Jaakko Siivola6 1 Institut für Mineralogie und Petrographie, ETH-Centre, CH-8092, Zürich, Switzerland, [email protected] 2 British Geological Survey, Murchison House, West Mains Road, Edinburgh, United Kingdom, [email protected] 3 Grant Institute of Geology, Edinburgh, United Kingdom, [email protected] 4 Patission 339A, 11144 Athens, Greece 5 3, rue de Houdemont 54500, Vandoeuvre-lès-Nancy, France, [email protected] 6 Tasakalliontie 12c, 02760 Espoo, Finland ABSTRACT The usage of some common terms in metamorphic petrology has developed differently in different countries and a range of specialised rock names have been applied locally. The Subcommission on the Systematics of Metamorphic Rocks (SCMR) aims to provide systematic schemes for terminology and rock definitions that are widely acceptable and suitable for international use. This first paper explains the basic classification scheme for common metamorphic rocks proposed by the SCMR, and lays out the general principles which were used by the SCMR when defining terms for metamorphic rocks, their features, conditions of formation and processes. Subsequent papers discuss and present more detailed terminology for particular metamorphic rock groups and processes. The SCMR recognises the very wide usage of some rock names (for example, amphibolite, marble, hornfels) and the existence of many name sets related to specific types of metamorphism (for example, high P/T rocks, migmatites, impactites).
    [Show full text]
  • Geologica Macedonica
    UDC 55 In print: ISSN 0352–1206 CODEN – GEOME 2 On line: ISSN 1857–8586 GEOLOGICA MACEDONICA Geologica Macedonica Vol. No pp. Štip 31 1 1–102 2017 Geologica Macedonica . . Geologica Macedonica Vol. No pp. Štip Geologica Macedonica . 31 1 . 1–102 2017 GEOLOGICA MACEDONICA Published by: – : "Goce Delev" University in Štip, Faculty of Natural and Technical Sciences, Štip, Republic of Macedonia „ “ , , , EDITORIAL BOARD Todor Serafimovski (R. Macedonia, Editor in Chief), Blažo Boev (R. Macedonia, Editor), David Alderton (UK), Tadej Dolenec (R. Slovenia), Ivan Zagorchev (R. Bulgaria), Wolfgang Todt (Germany), acad. Nikolay S. Bortnikov (Russia), Clark Burchfiel (USA), Thierry Augé (France), Todor Delipetrov (R. Macedonia), Vlado Bermanec (Croatia), Milorad Jovanovski (R. Macedonia), Spomenko Mihajlovi (Serbia), Dragan Milovanovi (Serbia), Dejan Prelevi (Germany), Albrecht von Quadt (Switzerland) ! " #" $ %&' ( (. , ), #) # (. , ), (. ), (. ), (. ), ! (" ), . # . ( ), $ ! (%), & (' ), (. ), " ((), ) (. ), " * + (, ), + (, ), - + (" ), %,* ! $ ( ) Language editor . Marijana Kroteva (English) ( ) Georgi Georgievski * *( (Macedonian) (" ) Technical editor * Blagoja Bogatinoski #* # * ( Proof-reader $ Alena Georgievska *( Address % GEOLOGICA MACEDONICA GEOLOGICA MACEDONICA EDITORIAL BOARD +!, Faculty of Natural and Technical Sciences ' * P. O. Box 96 /. !* 96 MK-2000 Štip, Republic of Macedonia $-2000 , , Tel. ++ 389 032 550 575 . 032 550 575 E-mail: [email protected]
    [Show full text]
  • INVESTIGATION of a CAT's-EYE SCAPOLITE from SRI LANKA by K
    INVESTIGATION OF A CAT'S-EYE SCAPOLITE FROM SRI LANKA By K. Schmetzer and H. Bank A cut gemstone with intense chatoyancy that Furthermore, hexagonal plates up to 0.4 x 0.4 originated from Sri Lanka was determined to be a mm in size with metallic luster were determined member of the scapolite solid-solution series, Indices to be pyrrhotite in these samples (Graziani and of refraction and unit-cell dimensions were found as Gubelin, 1981). w = 1.583, e = 1.553 and2 = 12.169, = 7.569 A, This article describes a scapolite crystal from respectively; a meionite content of 69% was Sri Lanlza that was cut into a 1.68-ct cabochon established by microprobe analysis. The chatoyancy (approximately 9 mm x 5 mm) with particularly is caused by needle-like inclusions with an orientation parallel to the c-axis of the scapolite host intense chatoyancy (figure 1). The ray of light crystal. Microprobe analysis of these needles showed crossing the surface of the cabochon is relatively them to be pyrrl~otite. broad compared to the sharpness of rays in other gemstones with chatoyancy or asterism, such as the more familiar cat's-eye chrysoberyls or aste- riated corundum. The physical and chemical properties of this cat's-eye scapolite are pre- Natural scapolites are members of the solid- sented, and the cause of the distinctive chatoy- solution series marialite, Nag[(C12,S04,C03)1 (A1 ancy in this stone is explained. Si308)e],and meionite, CadClaSO+C03) (A12 1 PHYSICAL AND CHEMICAL PROPERTIES Si20g)g].Scapolite crystals of gem quality occur colorless and in white, gray, yellow, pink, and A small facet was cut and polished on the bottom violet.
    [Show full text]
  • Stratigraphy of Ontario Ridge Metasediments
    Pseudo-stratigraphic Column of Ontario Ridge Metasediments Member 10: Upper portion leucocratic migmatite with minor melanocratic gneiss and locally containing small pods of hornblende rock derived from marble; melanocratic gneiss in lower portion; large swath of marble in lower portion with basal calc-silicate and calc-silicate east of Bighorn Peak, sparse quartzite outcrops. Also includes quartzite layer near Shortcut Ridge with several feet of biotite-hornblende-quartz gneiss near center. *Migmatite: light gray, medium to ne-grained; vague irregular compositional layering, layers locally intrude one another; ptygmatically folded; thin irregular aplite bodies common; average composition about 55% feldspar, 35% quartz and 10% hornblende; biotite locally present; scattered euhedra of sphene usually visible in hand specimen. *Melanocratic gneiss: conspicuously banded with dark gray layers a fraction of an inch to several inches thick alternating with whitish gray layers mostly less 10 than two inches thick; layers irregularly to semiregularly folded with wavelengths of a few inches; fold axes subparallel; dark layers ne-grained, foliated, compositionally variable but typically about 60% hornblende and/or biotite, 30% plagioclase and 10% quartz; light layers ne- to medium-grained; aplitic in appearance, lenticular with irregular shapes, composed of quartz and feldspar. *Quartzite: light gray, granoblastic, ne- to medium-grained; very thin poorly-dened bedding; tightly folded in most outcrops with fold amplitudes of a few inches to a few feet, sheared folds locally simulate crossbedding; average quartz content about 80%, biotite most common accessory. 210 meter thickness Member 9: Gneisses and migmatites dominant; migmatite extensively developed along south side of Icehouse Canyon; roughly 50 feet of dolomite marble and minor calc-silicate rocks 250 feet below top of member; minor marble and calc-silicate rocks interbedded near base; graphite-rich schists locally present.
    [Show full text]