DOCSLIB.ORG

Stillwater Complex, Montana Structure, Mineralogy, and Petrology of the Basal Zone with Emphasis on the Occurrence of Sulfides

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Stillwater Complex, Montana Structure, Mineralogy, and Petrology of the Basal Zone with Emphasis on the Occurrence of Sulfides Stillwater Complex, Montana Structure, Mineralogy, and Petrology of the Basal Zone with emphasis on the Occurrence of Sulfides By NORMAN JPAGE GEOLOGICAL SURVEY PROFESSIONAL PAPER 1038 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1979 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Cataloging in Publication Data Page, Norman J Stillwater Complex, Montana Structure, Mineralogy, and Petrology of the Basal Zone with emphasis on the Occurrence of Sulfides (Geological Survey Professional Paper 1038) Bibliography: p. 61 Supt. of Docs. No.: I 19.16:1038 1. Rocks, Igneous. 2. Intrusions (Geology) Montana. 3. Sulphides. 4. Ore-deposits Montana. I. Title. II. Series: United States Geological Survey Professional Paper 1038 QE461.P289 552'.l'09786 77-608351 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 Stock Number 024-001-03179-5 CONTENTS Page Page Abstract ............................................................................................ 1 Petrology and mineralogy of the Basal zone Continued Introduction ...................................................................................... 1 Rocks derived by partial melting ...................................................... 34 Geologic history of the Stillwater Complex and adjacent rocks 2 Occurrence ................................................................................ 34 Previous work and acknowledgments ............................................... 3 Petrography and mineralogy ..................................................... 35 Definition of the Basal zone .................................................................... 4 Characteristics of hornfelses adjacent to quartz, norite .............. 36 Distribution and thickness of the Basal zone ................................... 4 Origin of the quartz norites ....................................................... 36 Shape of the Basal zone ................................................................... 5 Other silicate rocks ........................................................................... 38 Description of contacts ..................................................................... 6 Ultramafic xenoliths .................................................................. 38 Contact of the Basal zone with metasedimentary rocks ............ 6 Autohornfelsed Basal zone rocks .............................................. 39 Contact of the Basal zone with the Ultramafic zone ................. 7 Sulfide-bearing rocks ........................................................................ 39 Contact of the Basal zone with younger intrusive quartz mon- Occurrence, general terminology, and distribution .................... 39 zonitic rocks .......................................................................... 7 Development of terminology for sulfide-bearing rocks ............. 41 Contact of the Basal zone with mafic dikes .............................. 7 Textures of sulfide-bearing rocks .............................................. 41 Contact of the Basal norite with the Basal bronzite cumulate .. 7 Disseminated and matrix sulfide textures .......................... 42 Age restrictions on the Basal zone ................................................... 7 Textures of massive sulfide rocks ....................................... 44 Petrology and mineralogy of the Basal zone ........................................... 7 Textural relations between silicate and Rock types in the Basal zone ........................................................... 7 sulfide minerals ............................................................... 44 Cumulate rocks of the Basal zone .................................................... 9 Mineralogy of the sulfide-bearing rocks .................................... 44 Cumulate sequences .......................................................................... 16 Pyrrhotite ........................................................................... 46 Size variation of orthopyroxene cumulates ............................... 17 Pentlandite ......................................................................... 47 Evidence for current structures ................................................. 18 Chalcopyrite family ............................................................ 48 Modal mineral variation in cumulates ...................................... 19 Magnetite, ilmenite, and hematite ...................................... 48 Lateral and vertical variation of orthopyroxene composition ... 21 Other opaque minerals ....................................................... 49 Compositional variation of plagioclase ..................................... 21 Proportions of sulfide minerals ................................................. 49 Discussion of cumulate rocks in the Basal zone ........................ 23 Interrelation between sulfide mineralization and Igneous-textured (noncumulate) rocks of the Basal zone ................. 23 silicate rocks .......................................................................... 50 Modal variation of noncumulate rocks ..................................... 23 Interpretation and model of sulfide crystallization .................... 52 Chemical composition of the noncumulate igneous-textured rocks 24 Mechanisms for separation of immiscible Viscosity, density, and settling velocities ................................... 28 sulfide-oxide liquids from basaltic magma ..................... 53 Contaminated igneous rocks ............................................................ 31 Collection and concentration models ................................. 54 Types, textures, and mineralogy of the contaminated igneous Crystallization of the collected sulfide-oxide liquid ........... 59 rocks ...................................................................................... 31 Limitations and speculations on origin of Basal zone ............................. 61 Relation of mixed rocks to inclusions of metasedimentary rocks 32 References cited ....................................................................................... 61 Processes for forming mixed or contaminated rocks ................ 33 Index ....................................................................................................... 67 ILLUSTRATIONS Page PLATE I. Interpretative map, cross sections, and long sections of the Basal zone ...................................................... In pocket 2. Vertical variation in orthopyroxene compositions and grain size from 15 cross sections of the Basal zone In pocket FIGURH 1. Index map of the Stillwater Complex ................................................................................................................................ 2 2. Geologic map of the Stillwater block ................................................................................................................................. 3 3. Frequency diagram of estimated stratigraphic thickness of Basal zone at 48 localities ...................................................... 5 4. Interpretative sketches of basin structures in Basal zone and Peridotite member .............................................................. 6 5. Sections showing rock types and mineralogy in Basal zone ............................................................................................... 9 6. Histograms of orthopyroxene and plagioclase compositions ............................................................................................. 16 7. Graph of mean length, width, and average grain size of orthopyroxene versus stratigraphic position for part of Basal bron/ite cumulate, upper Nye Basin ......................................................................................................................................... '8 IV CONTENTS Page FIGURE 8. Length-frequency distributions of orthopyroxene crystals for a segment of Basal bronzite cumulate, upper Nye Creek Basin .. 18 9. Photographs of scour and local unconformities in Basal norite ......................................................................................... 19 10. Plot of modes of cumulates from Basal zone ..................................................................................................................... 20 1 1. Orthopyroxene in Basal zone plotted against stratigraphic position. West Benhow, Golf Course section ......................... 20 12. Diagram of plugioclase composition plotted against stratigraphic position, upper Nye Basin section ............................... 22 13. Plot of coexisting plagioclase and orthopyroxene compositions in Basal /one .................................................................. 22 14. Diagram showing proportions, by volume, of clinopyroxene. plagioclase, and orthopyroxene in noncumulate rocks ...... 24 15. ARM diagram of noncumulate rock compositions compared with cumulate rock compositions ...................................... 27 16. Projections of analyses of noncumulate igneous-textured rocks in the system olivine-clinopyroxene - plagioclase - silica 27 17. Calculated dry density-temperature curves of possible Stillwater magmas ......................................................................... 28 18. Diagram of calculated viscosities of possible parent magmas for the Stillwater complex plotted against reciprocal temperature ................................................................................................................................................................
Load more

Recommended publications
  • Beneficiation of Stillwater Complex Rock for the Production of Lunar Simulants
    National Aeronautics and NASA/TM—2014–217502 Space Administration IS20 George C. Marshall Space Flight Center Huntsville, Alabama 35812 Beneficiation of Stillwater Complex Rock for the Production of Lunar Simulants D.L. Rickman Marshall Space Flight Center, Huntsville, Alabama C. Young Metallurgical and Materials Engineering, Montana Tech, Butte, Montana D. Stoeser USGS, Denver, Colorado J. Edmunson Jacobs ESSSA Group, Huntsville, Alabama March 2014 The NASA STI Program…in Profile Since its founding, NASA has been dedicated to the • CONFERENCE PUBLICATION. Collected advancement of aeronautics and space science. The papers from scientific and technical conferences, NASA Scientific and Technical Information (STI) symposia, seminars, or other meetings sponsored Program Office plays a key part in helping NASA or cosponsored by NASA. maintain this important role. • SPECIAL PUBLICATION. Scientific, technical, The NASA STI Program Office is operated by or historical information from NASA programs, Langley Research Center, the lead center for projects, and mission, often concerned with NASA’s scientific and technical information. The subjects having substantial public interest. NASA STI Program Office provides access to the NASA STI Database, the largest collection of • TECHNICAL TRANSLATION. aeronautical and space science STI in the world. English-language translations of foreign The Program Office is also NASA’s institutional scientific and technical material pertinent to mechanism for disseminating the results of its NASA’s mission. research and development activities. These results are published by NASA in the NASA STI Report Specialized services that complement the STI Series, which includes the following report types: Program Office’s diverse offerings include creating custom thesauri, building customized databases, • TECHNICAL PUBLICATION.
    [Show full text]
  • Washington State Minerals Checklist
    Division of Geology and Earth Resources MS 47007; Olympia, WA 98504-7007 Washington State 360-902-1450; 360-902-1785 fax E-mail: [email protected] Website: http://www.dnr.wa.gov/geology Minerals Checklist Note: Mineral names in parentheses are the preferred species names. Compiled by Raymond Lasmanis o Acanthite o Arsenopalladinite o Bustamite o Clinohumite o Enstatite o Harmotome o Actinolite o Arsenopyrite o Bytownite o Clinoptilolite o Epidesmine (Stilbite) o Hastingsite o Adularia o Arsenosulvanite (Plagioclase) o Clinozoisite o Epidote o Hausmannite (Orthoclase) o Arsenpolybasite o Cairngorm (Quartz) o Cobaltite o Epistilbite o Hedenbergite o Aegirine o Astrophyllite o Calamine o Cochromite o Epsomite o Hedleyite o Aenigmatite o Atacamite (Hemimorphite) o Coffinite o Erionite o Hematite o Aeschynite o Atokite o Calaverite o Columbite o Erythrite o Hemimorphite o Agardite-Y o Augite o Calciohilairite (Ferrocolumbite) o Euchroite o Hercynite o Agate (Quartz) o Aurostibite o Calcite, see also o Conichalcite o Euxenite o Hessite o Aguilarite o Austinite Manganocalcite o Connellite o Euxenite-Y o Heulandite o Aktashite o Onyx o Copiapite o o Autunite o Fairchildite Hexahydrite o Alabandite o Caledonite o Copper o o Awaruite o Famatinite Hibschite o Albite o Cancrinite o Copper-zinc o o Axinite group o Fayalite Hillebrandite o Algodonite o Carnelian (Quartz) o Coquandite o o Azurite o Feldspar group Hisingerite o Allanite o Cassiterite o Cordierite o o Barite o Ferberite Hongshiite o Allanite-Ce o Catapleiite o Corrensite o o Bastnäsite
    [Show full text]
  • Pamphlet to Accompany Scientific Investigations Map 3131
    Bedrock Geologic Map of the Seward Peninsula, Alaska, and Accompanying Conodont Data By Alison B. Till, Julie A. Dumoulin, Melanie B. Werdon, and Heather A. Bleick Pamphlet to accompany Scientific Investigations Map 3131 View of Salmon Lake and the eastern Kigluaik Mountains, central Seward Peninsula 2011 U.S. Department of the Interior U.S. Geological Survey Contents Introduction ....................................................................................................................................................1 Sources of data ....................................................................................................................................1 Components of the map and accompanying materials .................................................................1 Geologic Summary ........................................................................................................................................1 Major geologic components ..............................................................................................................1 York terrane ..................................................................................................................................2 Grantley Harbor Fault Zone and contact between the York terrane and the Nome Complex ..........................................................................................................................3 Nome Complex ............................................................................................................................3
    [Show full text]
  • Introduction to Igneous Petrology
    Cambridge University Press 978-1-107-02754-1 - Essentials of Igneous and Metamorphic Petrology B. Ronald Frost and Carol D. Frost Excerpt More information Chapter 1 Introduction to Igneous Petrology 1.1 Introduction Igneous petrology is the study of magma and the rocks that solidify from magma. Th us igneous petrologists are concerned with the entire spectrum of processes that describe how magmas are produced and how they ascend through the mantle and crust, their mineralogical and geochemical evolution, and their eruption or emplacement to form igneous rocks. Igneous petrology requires a working knowledge of mineralogy. Readers who wish to review the characteristics of the major rock-forming igneous minerals will fi nd a concise sum- mary in Appendix 1. Th e appendix emphasizes the identifi cation of rock-forming minerals in hand sample and in thin section. In addition, the appendix includes descriptions of minerals found in minor abundance but commonly occurring in igneous rocks, including accessory minerals that contain trace amounts of uranium and are important geochronometers. Before geologists can understand the origin of igneous rocks, they must classify and describe them. Th is chapter introduces the classifi cation of igneous rocks using the mineralogical classifi cation system recom- mended by the International Union of Geological Sciences (IUGS) Subcommission on the Systematics of Igneous Rocks, which has the advantage that it is relatively simple and can be applied in the fi eld. For rocks that are too fi ne-grained to name using this classifi cation, a geochemical classifi cation can be employed instead. Th e simplest of these, the total alkali versus silica classifi cation, is introduced in this text.
    [Show full text]
  • Noritic Anorthosite Bodies in the Sierra Nevada Batholith
    MINERALOGICAL SOCIETY OF AMERICA, SPECIAL PAPER 1, 1963 INTERNATIONALMINERALOGICAL ASSOCIATION,PAPERS, THIRD GENERAL MEETING NORITIC ANORTHOSITE BODIES IN THE SIERRA NEVADA BATHOLITH ALDEN A. LOOMISl Department of Geology, Stanford University, Stanford, California ABSTRACT A group of small noritic plutons were intruded prior to the immediately surrounding granitic rocks in a part of the composite Sierra Nevada batholith near Lake Tahoe. Iron was more strongly concentrated in the late fluids of individual bodies than during the intrusive sequence as a whole. Pyroxenes are more ferrous in rocks late in the sequence, although most of the iron is in late magnetite which replaces pyroxenes. Both Willow Lake type and normal cumulative layering are present. Cumulative layering is rare; Willi ow Lake layering is common and was formed early in individual bodies. Willow Lake layers require a compositional uniqueness providing high ionic mobility to explain observed relations. The Sierran norites differ from those in large stratiform plutons in that (1) the average bulk composition is neritic anorthosite in which typical rocks contain over 20% AbO" and (2) differentiation of both orthopyroxene and plagioclase produced a smooth progressive sequence of mineral compositions. A plot of modal An vs. En for all the rocks in the sequence from early Willow Lake-type layers to late no rite dikes defines a smooth non-linear trend from Anss-En76 to An,,-En54. TLe ratio An/ Ab decreased faster than En/Of until the assemblage Anso-En65 was reached and En/Of began to decrease more rapidly. Similar plots for large stratiform bodies show too much scatter to define single curves.
    [Show full text]
  • List of New Mineral Names: with an Index of Authors
    415 A (fifth) list of new mineral names: with an index of authors. 1 By L. J. S~v.scs~, M.A., F.G.S. Assistant in the ~Iineral Department of the,Brltish Museum. [Communicated June 7, 1910.] Aglaurito. R. Handmann, 1907. Zeita. Min. Geol. Stuttgart, col. i, p. 78. Orthoc]ase-felspar with a fine blue reflection forming a constituent of quartz-porphyry (Aglauritporphyr) from Teplitz, Bohemia. Named from ~,Xavpo~ ---- ~Xa&, bright. Alaito. K. A. ~Yenadkevi~, 1909. BuU. Acad. Sci. Saint-P6tersbourg, ser. 6, col. iii, p. 185 (A~am~s). Hydrate~l vanadic oxide, V205. H~O, forming blood=red, mossy growths with silky lustre. Founi] with turanite (q. v.) in thct neighbourhood of the Alai Mountains, Russian Central Asia. Alamosite. C. Palaehe and H. E. Merwin, 1909. Amer. Journ. Sci., ser. 4, col. xxvii, p. 899; Zeits. Kryst. Min., col. xlvi, p. 518. Lead recta-silicate, PbSiOs, occurring as snow-white, radially fibrous masses. Crystals are monoclinic, though apparently not isom0rphous with wol]astonite. From Alamos, Sonora, Mexico. Prepared artificially by S. Hilpert and P. Weiller, Ber. Deutsch. Chem. Ges., 1909, col. xlii, p. 2969. Aloisiite. L. Colomba, 1908. Rend. B. Accad. Lincei, Roma, set. 5, col. xvii, sere. 2, p. 233. A hydrated sub-silicate of calcium, ferrous iron, magnesium, sodium, and hydrogen, (R pp, R',), SiO,, occurring in an amorphous condition, intimately mixed with oalcinm carbonate, in a palagonite-tuff at Fort Portal, Uganda. Named in honour of H.R.H. Prince Luigi Amedeo of Savoy, Duke of Abruzzi. Aloisius or Aloysius is a Latin form of Luigi or I~ewis.
    [Show full text]
  • Copper in South Africa-Part 11
    J. S. Afr. Inst. Min. Metall., vol. 85, no. 4. Apr. 1985. pp. 109-124 Copper in South Africa-Part 11 by C.O. BEALE* SYNOPSIS This, the second and final part of a review on the subject(the first part was published in the March issue of this Jouma/), deals in detail with the 9 copper-producing companies in the Republic of South Africa. These are The Phosphate Development Corporation, Prieska Copper Mines (Pty) Ltd, Black Mountain Mineral Development Co. (Pty) Ltd, Rustenburg Platinum Holdings Ltd, Impala Platinum Holdings Ltd, Western Platinum Ltd, The O'okiep Copper Co. Ltd, Messina Ltd, and Palabora Mining Co. Ltd. The following are described for each company: background, development, geology, mining, concentration, and current situation. The last-mentioned company, being South Africa's largest producer, is dealt with in greatest detail. SAMEVATTING . Hierdie tweede en slotdeel van 'n oorsig oor die onderwerp (die eerste deal het in die Maart-uitgawe van hierdie Tydskrif verskyn) handel in besonderhede oor die 9 koperproduserende maatskappye in the Republiek van Suid- Afrika. Hulle is die Fosfaat-ontginningskorporasie, Prieska Copper Mines (Pty) Ltd, Black Mountain Mineral Develop- ment Co. (Pty) Ltd, Rustenburg Platinum Holdings Ltd, Impala Platinum Holdings Ltd, Western Platinum Ltd, The O'okiep Copper Co. Ltd, Messina Ltd, en Palabora Mining Co. Ltd. Die volgende wQfd met betrekking tot elkeen van die maatskappye bespreek: agtergrond, ontwikkeling, geologie, mynbou, konsentrsie en huidige posisie. Die laasgenoemde maatskappy, wat Suid-Afrika se grootste produsent is, word in die meeste besonderhede bespreek. THE PHOSPHATE DEVELOPMENT CORP. CFOSKOR)' This Company was formed in 1951, on Government Foskor concentrate contributes significantly to the load initiative, to exploit the apatite (phosphate) resources of on Palabora's smelter and refinery, and also the annual the Phalaborwa Igneous Complex (Fig.
    [Show full text]
  • Igneous Textures and Structures
    GLG 333 -- IGNEOUS TEXTURES AND STRUCTURES The following is a reorganization and amplification of Blatt, Tracy, and Owens, 2006, pages 29-35. (You may also want to refer to Barker, 1983, pages 106-120; Hyndman, 1985, pages 49-61; or Jackson, 1970, pages 255-273 and 317-323. You will also definitely want to look at MacKenzie et al., 1982, pages 4-73, to see what these igneous textures look like when viewed in thin-section under a petrographic microscope.) I. SHAPE OF INDIVIDUAL CRYSTALS (indicates sequence of crystallization) A. Euhedral. Crystal completely bounded by its own crystal faces. Indicates early crystallization from the magma, i.e. before enough other crystals were present to cause interference for space. B. Anhedral. Crystal not bounded by any of its own crystal faces; rather, its form is imposed on it by the adjacent crystals. Indicates late crystallization from the magma, i.e. after most of the available space was already occupied by earlier-formed crystals. C. Subhedral. Intermediate between euhedral and anhedral. II. GENERAL ROCK TEXTURES A. Based on Degree of Crystallinity 1. Holohyaline. Rock composed entirely of glass; no crystals visible even with magnification. Indicates cooling so rapid that no crystal growth could occur, i.e. quenching. a. Obsidian Massive volcanic glass. b. Pumice Frothy (micro-vesicular) volcanic glass. 2. Hypocrystalline (or Hyalocrystalline). Rock composed of both crystals and glass. a. Pitchstone Volcanic glass with a resinous luster or streaky appearance caused by microscopic crystallites. b. Vitrophyre Volcanic glass with macroscopic phenocrysts. c. Perlite Volcanic glass with a cloudy or milky appearance caused by devitrification.
    [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]
  • The Rustenburg Layered Suite Formed As a Stack of Mush with Transient Magma Chambers ✉ Zhuosen Yao1, James E
    ARTICLE https://doi.org/10.1038/s41467-020-20778-w OPEN The Rustenburg Layered Suite formed as a stack of mush with transient magma chambers ✉ Zhuosen Yao1, James E. Mungall 1 & M. Christopher Jenkins 1 The Rustenburg Layered Suite of the Bushveld Complex of South Africa is a vast layered accumulation of mafic and ultramafic rocks. It has long been regarded as a textbook result of fractional crystallization from a melt-dominated magma chamber. Here, we show that most 1234567890():,; units of the Rustenburg Layered Suite can be derived with thermodynamic models of crustal assimilation by komatiitic magma to form magmatic mushes without requiring the existence of a magma chamber. Ultramafic and mafic cumulate layers below the Upper and Upper Main Zone represent multiple crystal slurries produced by assimilation-batch crystallization in the upper and middle crust, whereas the chilled marginal rocks represent complementary supernatant liquids. Only the uppermost third formed via lower-crustal assimilation–fractional crystallization and evolved by fractional crystallization within a melt-rich pocket. Layered intrusions need not form in open magma chambers. Mineral deposits hitherto attributed to magma chamber processes might form in smaller intrusions of any geometric form, from mushy systems entirely lacking melt-dominated magma chambers. 1 Department of Earth Sciences, Carleton University, 2115 Herzberg Laboratories, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada. ✉ email: [email protected] NATURE COMMUNICATIONS | (2021) 12:505 | https://doi.org/10.1038/s41467-020-20778-w | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-020-20778-w ayered mafic intrusions represent portions of the plumbing derived by incremental crystallization must be removed.
    [Show full text]
  • Mineral Collecting Sites in North Carolina by W
    .'.' .., Mineral Collecting Sites in North Carolina By W. F. Wilson and B. J. McKenzie RUTILE GUMMITE IN GARNET RUBY CORUNDUM GOLD TORBERNITE GARNET IN MICA ANATASE RUTILE AJTUNITE AND TORBERNITE THULITE AND PYRITE MONAZITE EMERALD CUPRITE SMOKY QUARTZ ZIRCON TORBERNITE ~/ UBRAR'l USE ONLV ,~O NOT REMOVE. fROM LIBRARY N. C. GEOLOGICAL SUHVEY Information Circular 24 Mineral Collecting Sites in North Carolina By W. F. Wilson and B. J. McKenzie Raleigh 1978 Second Printing 1980. Additional copies of this publication may be obtained from: North CarOlina Department of Natural Resources and Community Development Geological Survey Section P. O. Box 27687 ~ Raleigh. N. C. 27611 1823 --~- GEOLOGICAL SURVEY SECTION The Geological Survey Section shall, by law"...make such exami­ nation, survey, and mapping of the geology, mineralogy, and topo­ graphy of the state, including their industrial and economic utilization as it may consider necessary." In carrying out its duties under this law, the section promotes the wise conservation and use of mineral resources by industry, commerce, agriculture, and other governmental agencies for the general welfare of the citizens of North Carolina. The Section conducts a number of basic and applied research projects in environmental resource planning, mineral resource explora­ tion, mineral statistics, and systematic geologic mapping. Services constitute a major portion ofthe Sections's activities and include identi­ fying rock and mineral samples submitted by the citizens of the state and providing consulting services and specially prepared reports to other agencies that require geological information. The Geological Survey Section publishes results of research in a series of Bulletins, Economic Papers, Information Circulars, Educa­ tional Series, Geologic Maps, and Special Publications.
    [Show full text]
  • The Original Lithologies and Their Metamorphism
    BASIC PLUTONIC INTRUSIONS OF THE RISÖR­ SÖNDELED AREA, SOUTH NORWAY: THE ORIGINAL LITHOLOGIES AND THEIR METAMORPHISM IAN C. STARMER Department of Geology, University of Nottingham, England Present address: Dept. of Geo/ogy, Queen Mary College, London, E. l STARMER, I. C.: Basic plutonic intrusions of the Risör-Sändeled area South Norway: The original Jithologies and their metamorphism Norsk Geologisk Tidsskri/1, Vol. 49, pp. 403-431. Oslo 1969. The emplacement of Pre-Cambrian basic intrusions is shown to have been a polyphase process and to have occurred Jargely between two major periods of metamorphism. The original igneous lithologies are discussed and a regional differentiation series is demonstrated, with changes in rock-type accompanied by some cryptic variation in the component minerals. Metamorphism after consolidation converted the intrusives to coronites and eaused partial amphibolitisation. Corona growths are described and attributed to essentially isochemical recrystal­ lisations in the solid-state, promoted by the diffusion of ions in inter­ granular fluids. The amphibolitisation of the bodies is briefly outlined, and it is concluded that the formation of amphibolite involved the intro­ duction of considerable amounts of extraneous water. The criterion for demoostrating the onset of amphibolitisation is thought to be the intemal replacement of pyroxene by homblende, contrasting with the replacement of plagioclase by various amphiboles during corona growth. Both amphibolites and coronites have been scapolitised, and this may have been an extended process which certainly continued after amphi­ bolitisation. Regional implications are considered and it is suggested that a !arge mass of differentiating magma may have underlain the whole region in Pre-Cambrian times.
    [Show full text]