DOCSLIB.ORG

THE GABBROS and ASSOCIATED Rocksl at PRESTON, CONNECTICUT

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
THE GABBROS and ASSOCIATED Rocksl at PRESTON, CONNECTICUT DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY GEORGE OTIS SMITH, DIRECTOR BULLETIN A92 THE GABBROS AND ASSOCIATED ROCKSl AT PRESTON, CONNECTICUT BY G. F. LOUGHLIN WASHINGTON GOVERNMENT PRINTING OFFICE 1912 CONTENTS. Page. Preface................................................................... 9 Introduction:............................................................. 11 Location.............................................................. 11 Topography........................................................... 12 Hills...........,................................:................. 12 Valleys........................................................... 12 Drainage. .......................................--.-.-...- ------- 13 Lakes and ponds.................................................. 14 Historical review....................................................... 14 Areal geology.............................................................. 15* Roeks of sedimentary origin............................................ 16; Types............................................................ 16 Quartzite.......................................................... 16 Quartz-biotite schist. ............................................. 17 Hornblende schist. ............................................... 18 Black pseudoporphyritic schist (kinzigite).......................... 20 Dolomite.......................................................... 20 Igneous rocks......................................................... 21 Preston gabbro.................................................... 21 Sterling granite gneiss.............................................. 23 Lantern Hill quartz.................................................... 24 Structural geology........................................................ 24 Schistosity............................................................ 24 Folding.............................................................. 25 Undulations...................................................... 25 Minor folds:.....................................'................. 26 Major folds....................................................... 28 Arrangement of folds.............................................. 29 Origin of folds.................................................... 30 Effect of the gabbro intrusion.................................. 30 Effect of the granite intrusion................................... 32 Summary..................................................... 32 Igneous intrusions.................................................... 33 Preston gabbro.................................................... 33 Sterling granite gneiss.............................................. 35 Intrusive areas................................................ 35 Porphyritic granite gneiss areas............................ 35 Alaskite areas............................................. 36 Normal granite gneiss areas................................. 36 Minor sheets and dikes..................................... 37 Structural interrelations of the granite intrusions............. 37 Method of intrusion............................................ 3& 3 4 CONTENTS. Structural geology Continued. Page. Metamorphic deformation............................................. 38 Regional metamorphism of the Preston gabbro......I............ T.. 38 Contract metamorphism. due to the Preston gabbro................... 39 Regional metamorphism of the Sterling granite gneiss................ 43 Contact metamorphism due to the Sterling granite gneiss. ........... 43 Joints................................................................ 44 Distribution and directions......................................... 44 Origin of joints................................................... 47 Relation of joints to stream courses.................................. 48 Principal valleys............................................... 48 Major tributary valleys.......................................... 49 Minor tributary valleys......................................... 50 Conclusions................................................... 50 Faulting............................................................. 50 Character and distribution......................................... 50 Ashwillet intrusion fault........................................... 51 Broad Brook fault.................................................. 52 Minor faulting..................................................... 52 Veins................................................................ 53 Quartz veins....................................................... 53 Chlorite and asbestos veins in gabbro................................ 53 Special erosionalfeatures.............................................. 54 Pitted and warty surface of gabbro............:..................... 54 Dissolution holes................................................... 54 Historical geology......................................................... 57 Petrography............................................. r ................ 58 Metamorphic sedimentary rocks......................................... 58 Quartzite.......................................................... 58 Megascopic characters......................................... 58 Microscopic characters..............................;.......... 58 Variations and similar rock from other horizons.................. 59 Quartz-biotite schist. ............................................. 59 Megascopic characters......................................... 59 Microscopic characters......................................... 59 Allanite....................................................... 60 Variations...................................... J.............. 60 Epidote gneiss................................................. 61 Hornblende schist................................................. 62 Megascopic characters......................................... 62 Microscopic characters. ........................................ 63 Variations...............................'..................... 63 Basic slate........................................................ 63 Megascopic characters......................................... 63 Microscopic characters......................................... 64 Basic hornfels...................................................... 65 Hornblendic variety........................................... 65 Megascopic characters. .................................... 65 Microscopic characters..................................... 65 Pyroxenic variety................................'............. 65 Megascopic characters..................................... 65 Microscopic characters..................................... 65 Origin of the hornblende schist. ............................... 66 CONTENTS. 5 Petrography Continued. Metamorphic sedimentary rocks Continued. Page. Black pseudoporphyritic schist (kinzigite).......................... 68 Literature.................................................... 68 Megascopic characters......................................... 68 Microscopic characters......................................... 71 Chemical composition......................................... 72 Variations.................................................... 73 Origin........................................................ 74 Dolomite.......................................................... 76 Megascopic characters......................................... 76 Microscopic characters......................................... 77 Variation..................................................... 78 Preston gabbro........................................................ 78 Types............................:................................ 78 Porphyritic gabbro................................................ 79 Normal phase................................................ 79 Megascopic characters..................................... 79 Microscopic characters..................................... 80 Mineral structure.................................... 80 Diallage.............................................. 80 Secondary brown hornblende......................... 80 Biotite............................................... 84 Labradorite........................................... 84 Ilmenite...................... I..................... 87 Chlorite-magnetite aggregates......................... 88 Pyrite................................................ 88 Quartz-calcits veinlets................................... 93 Mechanical and chemical metamorphism ................... 98 Chemical composition..............................."...... 94 Classification............................................ 94 Norite phase (auvergnose-hessose).............................. 94 Megascopic characters..................................... 95 Microscopic characters..................................... 95 Mineral structure.................................... 95 Labradorite...............:........................... 95 Bronzite............................................. 95 Diallage.............................................. 96 Ilmenite and pyrite.................................. 96 Alteration products.................................. 96 Classification............................................ 96 Olivine gabbro phase......................................... 96 Megascopic characters..................................... 96 Microscopic characters....................................
Load more

Recommended publications
  • A Review of Feldspar Alteration and Its Geological Significance in Sedimentary Basins from Shallow Aquifers to Deep Hydrocarbon
    Originally published as: Yuan, G., Cao, Y., Schulz, H.-M., Hao, F., Gluyas, J., Liu, K., Yang, T., Wang, Y., Xi, K., Li, F. (2019): A review of feldspar alteration and its geological significance in sedimentary basins: From shallow aquifers to deep hydrocarbon reservoirs. - Earth-Science Reviews, 191, pp. 114—140. DOI: http://doi.org/10.1016/j.earscirev.2019.02.004 Earth-Science Reviews 191 (2019) 114–140 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev A review of feldspar alteration and its geological significance in sedimentary basins: From shallow aquifers to deep hydrocarbon reservoirs T ⁎ ⁎ Guanghui Yuana,b, , Yingchang Caoa,b, , Hans-Martin Schulzc, Fang Haoa, Jon Gluyasd, Keyu Liua, Tian Yanga, Yanzhong Wanga, Kelai Xia, Fulai Lia a Key laboratory of Deep Oil and Gas, School of Geosciences, China University of Petroleum, Qingdao, Shandong 266580, China b Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong 266071, China c GFZ German Research Centre for Geosciences, Section 4.3, Organic Geochemistry, Telegrafenberg, D-14473 Potsdam, Germany d Department of Earth Sciences, Durham University, Durham DH1 3LE, UK ARTICLE INFO ABSTRACT Keywords: The feldspar group is one of the most common types of minerals in the earth's crust. Feldspar alteration (in- Feldspar alteration cluding the whole processes of feldspar dissolution, transfer of released solutes, and secondary mineral pre- Dissolution mechanisms cipitation) is ubiquitous and important in fields including resources and environmental sciences. This paper Rate law provides a critical review of feldspar alteration and its geological significance in shallow aquifers to deep hy- Organic-inorganic interaction drocarbon reservoirs, as assessed from peer-reviewed paper in the literature.
    [Show full text]
  • Bedrock Geology Glossary from the Roadside Geology of Minnesota, Richard W
    Minnesota Bedrock Geology Glossary From the Roadside Geology of Minnesota, Richard W. Ojakangas Sedimentary Rock Types in Minnesota Rocks that formed from the consolidation of loose sediment Conglomerate: A coarse-grained sedimentary rock composed of pebbles, cobbles, or boul- ders set in a fine-grained matrix of silt and sand. Dolostone: A sedimentary rock composed of the mineral dolomite, a calcium magnesium car- bonate. Graywacke: A sedimentary rock made primarily of mud and sand, often deposited by turbidi- ty currents. Iron-formation: A thinly bedded sedimentary rock containing more than 15 percent iron. Limestone: A sedimentary rock composed of calcium carbonate. Mudstone: A sedimentary rock composed of mud. Sandstone: A sedimentary rock made primarily of sand. Shale: A deposit of clay, silt, or mud solidified into more or less a solid rock. Siltstone: A sedimentary rock made primarily of sand. Igneous and Volcanic Rock Types in Minnesota Rocks that solidified from cooling of molten magma Basalt: A black or dark grey volcanic rock that consists mainly of microscopic crystals of pla- gioclase feldspar, pyroxene, and perhaps olivine. Diorite: A plutonic igneous rock intermediate in composition between granite and gabbro. Gabbro: A dark igneous rock consisting mainly of plagioclase and pyroxene in crystals large enough to see with a simple magnifier. Gabbro has the same composition as basalt but contains much larger mineral grains because it cooled at depth over a longer period of time. Granite: An igneous rock composed mostly of orthoclase feldspar and quartz in grains large enough to see without using a magnifier. Most granites also contain mica and amphibole Rhyolite: A felsic (light-colored) volcanic rock, the extrusive equivalent of granite.
    [Show full text]
  • The Geology, Petrography and Geochemistry of Gabbroic Rocks Of
    The Geology, Petrography and Geochemistry of Gabbroic Rocks of the Pants Lake Intrusive Suite on the Donner/Teck South Voisey's Bay Property, North-Central Labrador, Canada Heather E. MacDonald A thesis submitted in conformity with the requirements for the degree of Mastet's of Science Graduate Department of the Department of Geology University of Toronto O Copyright by Heather E. MacDonald, 1999 National Library Bibliothèque nationale 1*1 of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellingtori Street 395. rue Wellington OttawaON K1A ON4 OnawaON KlAONQ 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 Bibliothèque nationale du Canada de reproduce, loan, distribute or seii reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de rnicrofiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur consewe la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantiai extracts fiom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. The Geology, Petrography and Ceochernistry of Gabbroic Rocks of the Pants Lake Intrusive Suite on the Donner/Teck South Voisey's Bay Property, North-Central Labrador, Canada Heather E. MacDonald Master's of Science, 1999 Department of Geology University of Toronto Abstract The South Voisey's Bay property held by Donner Minerals Limited in North-Central Labrador hosts Ni-Cu-Co mineralization within gabbroic rocks of the Pants Lake Intrusive Suite (PLIS).
    [Show full text]
  • Structural Geology of the Upper Rock Creek Area, Inyo County, California, and Its Relation to the Regional Structure of the Sierra Nevada
    Structural geology of the upper Rock Creek area, Inyo County, California, and its relation to the regional structure of the Sierra Nevada Item Type text; Dissertation-Reproduction (electronic); maps Authors Trent, D. D. Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 27/09/2021 06:38:23 Link to Item http://hdl.handle.net/10150/565293 STRUCTURAL GEOLOGY OF THE UPPER ROCK CREEK AREA, INYO COUNTY, CALIFORNIA, AND ITS RELATION TO THE REGIONAL STRUCTURE OF THE SIERRA NEVADA by Dee Dexter Trent A Dissertation Submitted to the Faculty of the DEPARTMENT OF GEOSCIENCES In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 1 9 7 3 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE I hereby recommend that this dissertation prepared under my direction by __________ Dee Dexter Trent______________________ entitled Structural Geology of the Upper Rock Creek Area . Tnvo County, California, and Its Relation to the Regional Structure of the Sierra Nevada ________________ be accepted as fulfilling the dissertation requirement of the degree of ____________Doctor of Philosophy_________ ___________ P). /in /'-/7. 3 Dissertation Director fJ Date After inspection of the final copy of the dissertation, the following members of the Final Examination Committee concur in its approval and recommend its acceptance:* f t M m /q 2 g ££2 3 This approval and acceptance is contingent on the candidate's adequate performance and defense of this dissertation at the final oral examination.
    [Show full text]
  • Module 7 Igneous Rocks IGNEOUS ROCKS
    Module 7 Igneous Rocks IGNEOUS ROCKS ▪ Igneous Rocks form by crystallization of molten rock material IGNEOUS ROCKS ▪ Igneous Rocks form by crystallization of molten rock material ▪ Molten rock material below Earth’s surface is called magma ▪ Molten rock material erupted above Earth’s surface is called lava ▪ The name changes because the composition of the molten material changes as it is erupted due to escape of volatile gases Rocks Cycle Consolidation Crystallization Rock Forming Minerals 1200ºC Olivine High Ca-rich Pyroxene Ca-Na-rich Amphibole Intermediate Na-Ca-rich Continuous branch Continuous Discontinuous branch Discontinuous Biotite Na-rich Plagioclase feldspar of liquid increases liquid of 2 Temperature decreases Temperature SiO Low K-feldspar Muscovite Quartz 700ºC BOWEN’S REACTION SERIES Rock Forming Minerals Olivine Ca-rich Pyroxene Ca-Na-rich Amphibole Na-Ca-rich Continuous branch Continuous Discontinuous branch Discontinuous Biotite Na-rich Plagioclase feldspar K-feldspar Muscovite Quartz BOWEN’S REACTION SERIES Rock Forming Minerals High Temperature Mineral Suite Olivine • Isolated Tetrahedra Structure • Iron, magnesium, silicon, oxygen • Bowen’s Discontinuous Series Augite • Single Chain Structure (Pyroxene) • Iron, magnesium, calcium, silicon, aluminium, oxygen • Bowen’s Discontinuos Series Calcium Feldspar • Framework Silicate Structure (Plagioclase) • Calcium, silicon, aluminium, oxygen • Bowen’s Continuous Series Rock Forming Minerals Intermediate Temperature Mineral Suite Hornblende • Double Chain Structure (Amphibole)
    [Show full text]
  • A Geochemical Study of the Riddle Peaks Gabbro, North Cascades: Evidence for Amphibole Accumulation in the Mid-Crust of an Arc
    Western Washington University Western CEDAR WWU Graduate School Collection WWU Graduate and Undergraduate Scholarship 2014 A geochemical study of the Riddle Peaks gabbro, North Cascades: evidence for amphibole accumulation in the mid-crust of an arc Angela C. Cota Western Washington University Follow this and additional works at: https://cedar.wwu.edu/wwuet Part of the Geology Commons Recommended Citation Cota, Angela C., "A geochemical study of the Riddle Peaks gabbro, North Cascades: evidence for amphibole accumulation in the mid-crust of an arc" (2014). WWU Graduate School Collection. 362. https://cedar.wwu.edu/wwuet/362 This Masters Thesis is brought to you for free and open access by the WWU Graduate and Undergraduate Scholarship at Western CEDAR. It has been accepted for inclusion in WWU Graduate School Collection by an authorized administrator of Western CEDAR. For more information, please contact [email protected]. A GEOCHEMICAL STUDY OF THE RIDDLE PEAKS GABBRO, NORTH CASCADES: EVIDENCE FOR AMPHIBOLE ACCUMULATION IN THE MID CRUST OF AN ARC By Angela C. Cota Submitted for Partial Completion Of the Requirements for the Degree Master of Science Kathleen L. Kitto, Dean of the Graduate School ADVISORY COMMITTEE Chair, Dr. Susan DeBari Dr. Elizabeth Schermer Dr. Robert Miller MASTER’S THESIS In presenting this thesis in partial fulfillment of the requirements for a master’s degree at Western Washington University, I grant to Western Washington University the nonexclusive royalty‐free right to archive, reproduce, distribute, and display the thesis in any and all forms, including electronic format, via any digital library mechanisms maintained by WWU. I represent and warrant this is my original work, and does not infringe or violate any rights of others.
    [Show full text]
  • Ocean Drilling Program Scientific Results Volume
    Von Herzen, R. P., Robinson, P. T., et al., 1991 Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 118 22. PLASTIC DEFORMATION AT AN OCEANIC SPREADING RIDGE: A MICROSTRUCTURAL STUDY OF THE SITE 735 GABBROS (SOUTHWEST INDIAN OCEAN)1 Mathilde Cannat2 ABSTRACT Microstructural analysis suggests that some Site 735 gabbros were deformed in the crystal mush stage, before they had completely crystallized. Later, solid-state deformation began in granulite-facies metamorphic conditions. At this stage, temperature-dependent diffusion processes may have controlled the plastic deformation of these gabbros, and mylonites formed only in intervals containing more than 10% Fe-Ti oxides. Most oxides in these mylonites are interpreted as magmatic in origin. A sharp change of deformation processes occurred as temperature decreased to the stability conditions of amphibolite-facies metamorphic assemblages: dislocation slip in plagioclase may have become the leading plastic flow mechanism. This change of deformation processes coincides with increased availability of hydrothermal water and with a marked decrease of the plagioclase recrystallized grain size. This reduction in recrystallized grain size is thought to result from an increase of the deviatoric stress, and thus from an increase of the yield strength of the gabbros. In amphibolite-facies metamorphic conditions, dynamic recrystallization of plagioclase locally caused strain-softening, leading to the formation of mylonites. Relict porphyroclasts (plagioclase, olivine, and pyroxenes) in these mylonites are fractured and boudinaged. The cracks produced by this brittle failure are filled with green to brown hydrothermal hornblende. INTRODUCTION the Site 735 deformed gabbros. These results are used to interpret the tectonic evolution of these gabbros (Cannat et A total of 500 m of gabbro was drilled at Site 735 during al., this volume).
    [Show full text]
  • Petrology, Geochemistry of Hornblende Gabbro and Associated
    Petrology, geochemistry of hornblende gabbro and associated dolerite dyke of Paharpur, Puruliya, West Bengal: Implication for petrogenetic process and tectonic setting Aditi Mandal, Arijit Ray∗, Mayukhee Debnath and Sankar Prasad Paul Presidency University, Kolkata 700 073, India. ∗Corresponding author. e-mail: [email protected] Paharpur gabbroic intrusive is an arcuate body running east–west paralleling the foliation of Chhota- nagpur Granite Gneiss which acts as country rock. The main gabbroic body is intruded by a number of dolerite dykes running north–south. It is composed of clinopyroxene (Wo48En40Fs12–Wo51En40Fs09,mg no. 72–82), plagioclase (An52–An90), hornblende (magnesian hornblende to ferro-tschermackite), orthopy- roxene (En76–En79) and ilmenite. Hornblende occurs as large poikilitic grain and constitutes around 60% of the rock. Both gabbro and associated dolerite dykes, show relatively primitive character (mg no. 65– 73). Primitive mantle-normalized and MORB-normalized spider diagrams indicate enrichment in Rb, Ba, Th, La, Sr and depletion in Nb, Zr, Y, Ti and Nd. The LILE enrichment and Nb, Ti, Zr, Y depletion suggest arc like geochemical signature for the gabbroic and doleritic rocks of Paharpur. Flat to slightly LREE fractionated pattern and variable degree of REE enrichment is observed. An early stage fraction- ation of clinopyroxene, plagioclase, orthopyroxene, ilmenite and late stage reaction of cumulate pile and evolved melt/hydrous fluid is suggested for magmatic evolution of gabbro. Associated dolerite dykes, which are geochemically similar to the gabbro, have tholeiitic with boninitic character. The mineralogi- cal and chemical compositions of intrusive rocks also have some similarity with mafic rocks of ophiolite complex of subduction zone.
    [Show full text]
  • Micro-Gabbro 0.34 Grams
    61224,6 Micro-Gabbro 0.34 grams Introduction 61224 contained several white and off-white particles as well as 3 peppered black and white rock fragments that appeared to fit together as one (figure 1). Thin section studies showed this to be a shocked lunar gabbro (albiet very fine-grained for a gabbro). Petrography Marvin and Warren (1980) describe 61224,6 and liken it to a eucritic meteorite – accept that the Fe/Mn ratio Figure 1: Group photo for 61224,6. Scale in mm. proves it is lunar in origin. Marvin (1972) originally called it “gabbroic microporphry”. The gabbroic texture and mineral mode is illustrated in figure 2. Grain size is about 1- 2 mm. Marvin and Mosie (1980) wrote 61224,6: “is a coarse- grained, pristine, plutonic gabbro with a cumulate texture in which chains of anhedral hyperthene and augite grains coexist with plagioclase (An83). The plagioclase has been shocked in situ to a leafy, optically-randomized state, and the grain boundaries are occupied by a selvage of pyroxene-plagioclase glass containing minute cyrstallites”. Mineralogical Mode 40 % plagioclase 60% pyroxene Mineralogy Olivine: none Pyroxene: Marvin and Warren (1980) and Takeda et al. (1981) studied the composition and structure of pyroxene (figures 3 and 4). The Fe/Mn ratio of pyroxene seems to indicate that this is a lunar gabbro, not a meteorite (figure 5). Bersch et al. (1983) give precise analyses of high- and low-Ca pyroxene in 61224,6. Plagioclase: Marvin and Warren (1980) reported plagioclase as An79-87. Selvage glass: Marvin and Warren (1980) reported the composition of shock-melted glass in 61224,6.
    [Show full text]
  • Mineralogy of a Layered Gabbro Deformed During Magmatic
    American Mineralogist, Volume 74, pages 101-112, 1989 Mineralogy of a layered gabbro deformedduring magmatic crystallizationo western Sierra Nevada foothills" California Rorrnr K. SpmNcrn Departmentof Geology,Brandon University, Brandon, Manitoba R7A 6A9, Canada ABSTRACT In the 162 Ma Pine Hill intrusive complex of northern California, a synformal, layered pyroxenite-gabbro-dioritebody, the crystallization sequenceand compositional variation of cumulus and intercumulus minerals indicate that magmatic crystallization was char- acteized by a high initial oxygenfugacity, log,ofo,in the rangeof -4 to -9, which allowed the early precipitation of abundant titanomagnetite; the oxygen fugacity decreasedless than two log units with crystallizalion. The magmatic crystallization sequenceis ol + aug, ol + aug * mt, ol + aug + mt + pl, ol + aug + mt + pl + opx(invertedfrom pig) and aug + mt + pl + opx (inverted from pig) * qz. Pigeonite crystallization is evidenced by 001 exsolution lamellae in orthopyroxene of Enrr. Superimposedupon this sequenceare intercumulus minerals, which crystallized from magma trapped within cumulates, and biotite and calcic amphibole, which largely formed from a subsolidusreaction of a residual hydrous fluid phasewith primary minerals. Mineral compositional rangesare plagioclase, Ann, to Anrr; olivine, Fo, to Fooo;augite, CanrMgrFento CaorMg.rFerr;Ca-poor pyroxene, Ca,Mgr"Fe' to Ca,MgorFeon;Mgl(Mg * Fe * Mn) of calcic amphibole, 0.74 to 0.48; and Me/(Me * Fe * Mn) of biotite, 0.78 to 0.45. Prior to complete solidification (>900/o crystallized), deformation of the complex coincided with an abrupt decreasein Mg/(Mg * Fe) values for the mafic silicates. This compositional discontinuity is attributed to a decreasein oxygen fugacity of the crystallizing magma causedby an exchangebetween the fluid phaseof adjacentcountry rock and the fluid phaseof the magma during deformation.
    [Show full text]
  • The Sierra Nevada Batholith a Synthesis. of Recent Work Across the Central Part
    I _; The Sierra Nevada Batholith A Synthesis. of Recent Work Across the Central Part By PAUL C. BATEMAN, LORIN ~- CLARK, N. KING HUBER, JAMES G. MOORE, and C. DEAN RINEHART SHORTER CONTRIBU.TIONS TO GENERAL GEOLOGY· G E 0 L 0 G I CAL SURVEY P R 0 FE S S I 0 N A L PAPER 414-D Prepared in cooperation with the State of Caltfornia, Division of Mines and Geology · ti II R fA u 0 F u' N f I ._rBRARV SPUI\ANf:.. !NASH. JUN 31971 . ·~-~ - ~ ... -- --s PtfASf RfT,fJR~ fO liBRARY UNITED S.TATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1963 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 CONTENTS Page Abstract------------------------------------------- D1 Constitution' of the batho1ith-Continued Introduction ______________________________________ _ 2 Contact relations _______________ ~ ______ - -- _----- D22 Genernl geologic relations _______________________ _ 2 Contacts between different granitic rocks _____ - 22 Previous geologic work _________________________ _ 4 Contacts between granitic rocks and meta- Acknowledgments _____________________________ _ 5 morphic rocks or diorite ___________ -- __ ---- 22 Wu.llrocks u.nd roof rocks ___________________________ _ 5 Felsic dike swarms __________________ - ___ -------- 24 Pu.leozoic rocks ________________________________ _ 5 Mafic dike swarms _________________________ ----- 25 Mesozoic rocks ________________________________ _ 6 Structure
    [Show full text]
  • Primary Igneous Analcime: the Colima Minettes
    American Mineralogist, Volume 74, pages216-223, 1989 Primary igneous analcime: The Colima minettes Jlnrns F. Lurrn Department of Earth and Planetary Sciences,Washington University, St. Louis, Missouri 63 130, U.S.A. T. Kunrrs Kvsnn Department of Geological Sciences,University of Saskatchewan,Saskatoon, Saskatchewan S7N 0W0, Canada Ansrnrcr Major-element compositions, cell constants, and oxygen- and hydrogen-isotopecom- positions are presentedfor six analcimes from differing geologicenvironments, including proposed primary @-type) analcime microphenocrysts from a late Quaternary minette lava near Colima, Mexico. The Colima analcimehas X.,.,",: 0.684, ao: 13.712A, and one of the lowest D'sOvalues yet recorded for analcime (+9.28m).The major difficulty in identifuing primary @-type) igrreousanalcime is distinguishing it from analcime formed by ion-exchangeconversion of leucite (L-type analcime) or other precursor minerals. Pet- rographic criteria are shown to be unreliable in discriminating P and L analcimes,although the higher KrO and Rb contents and D'8Ovalues of L-type crystals may be diagnostic. P- and L-type analcimescan be distinguishedfrom classichydrothermal varieties (H-type) by the lower Fe contents of the latter. H-type analcimes,however, can have 6t8Ovalues as low as 8.9Vmand cannot be distinguished from P-type analcimes by this criterion. Analcimes formed from volcanic glass or zeolite precursorsin saline, alkaline lakes (S- type) or metamorphic sequences(M-type) can be distinguished from other varieties by their higher silica contents, smaller cell constants,and higher d'8O values of > + 17.7Vm. For all types of analcime, d'8O of the channel water does not correlate with 6180of the framework oxygen.
    [Show full text]