DOCSLIB.ORG

Genesis of Gold-Bearing Quartz Veins of the Alleghany District, California (Abs.), 25

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Genesis of Gold-Bearing Quartz Veins of the Alleghany District, California (Abs.), 25 PROCEEDINGS OF THE SYMPOSIUM ON MINERAL DEPOSITS OF THE PACIFIC NORTHWEST GEOLOGICAL SOCIETY OF AMERICA, CORDILLERAN SECTION MEETING AT CORVALLIS, OREGON, MARCH 20-21, 1980 Edited by Miles L. Silbennan, Cyrus W. Field, and Anne L. Berry U.S. Geological Survey Open-File Report 81-355 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards. INTRODUCTION The following collection of 29 papers and abstracts was presented at a symposium on Mineral Deposits of the Pacific Northwest. This symposium consisted of four one-half day sessions held in conjunction with the 1980 Cordilleran Section meeting of the Geological Society of America at Oregon State University in Corvallis, Oregon. These papers and abstracts cover a broad spectrum of detail and breadth over a geologically complex terrain that extends from California northward through British Columbia to northwestern Alaska. Although the central theme was invariably concerned with metallization, the scientific emphasis varied appreciably according to the professional interests of the individual contributors. This emphasis not only included traditional geologic studies ranging from detailed investigations of single ore deposits, or of mining districts, to large-scale regional syntheses, but also of topical considerations such as geochronology, geophysics, geothermometry, mineralogy and phase equilibria, petro­ chemistry, plate tectonics, and radiogenic and stable isotope geo­ chemistry that are relevant to processes of ore genesis as well as to potentially useful methods of exploration. Among the specific types of mineral occurrences considered were epithermal and mesothermal deposits of mercury and precious metals; contact metasomatic deposits of molybdenum, tungsten, and base metals; placer gold; porphyry-type deposits of copper and molybdenum; strata-bound deposits of uranium and base and precious metals; and volcanogenic massive sulfide deposits ii Isotopic geochemistry of stratiform zinc-lead-barium deposits, Red Dog Creek and Drenchwater Creek areas, northwestern Brooks Range, Alaska I. M. Lange, University of Montana W. J. Nokleberg, U.S. Geological Survey J. T. Plahuta, University of Montana H. R. Krouse, University of Calgary B. R. Doe, U.S. Geological Survey Uldis Jansons, U.S. Bureau of Mines Zantop, Half, Paleozoic stratabound lead-zinc-copper deposits in the western United States, 29 Lange, I. M., Nockleberg, W. J., Plahuta, J. T., Krouse, H. R., Doe, B. R., and Jansons, Uldis, Isotopic geochemistry of stratiform zinc-lead-barium deposits, Red Dog Creek and Drenchwater Creek areas, northwestern Brooks Range, Alaska, 1 MacKevett, E. J., Jr., Armstrong, A. K., Potter, R. W., II, and Silberman, M. L., Kennecott-type copper deposits, Wrangell Mountains, Alaska an update and summary (abs.)» 6 Marshall, Brian, and Taylor, B. E., Origin of hydrothermal fluids responsible for gold deposition, Alleghany district, Sierra County, California, 26 McMillan, W. J., and Johan, Z., Rock geochemistry, geology and genesis of the Guichon Creek batholith in British Columbia, Canada, as it relates to highland Valley ore deposits, 9 Meinert, L. D., Newberry, Rainer, and Einaudi, M. T., An overview of tungsten, copper and zinc-bearing skarns in western North America, 28 Mitchell, P. A., Silberman, M. L., and O f Neil, J. R., Genesis of gold vein mineralization in an Upper Cretaceous turbidite sequence, Hope-Sunrise district, southern Alaska, 5 Radtke, A. S., Wittkopp, R. W., and Heropoulos, Chris, Genesis of gold-bearing quartz veins of the Alleghany district, California (abs.), 25 Robyn, T. L., Henage, L. F., and Hollister, V. F., Possible nonsubduc- tion associated porphyry ore deposits, Pacific Northwest, 13 Shreiner, Alexander, Jr. , and Shepard, R. J., Geology and mineralization of the Washougal mining district, Skamania County, Washington, 15 Shreiner, Alexander, Jr., and Suemnicht, G. A., Subsurface intrusive rocks at The Geysers geothermal area, California, 27 Silberman, M. L., MacKevett, E. M., Jr., Connor, C. L., and Matthews, Alan, Metallogenic and tectonic significance of oxygen isotope data and whole-rock potassium-argon ages of the Nikolai Greenstone, McCarthy quadrangle, Alaska, 7 Smith, P. R., Geology update of the Quartz Hill molybdenum property near Ketchikan, Alaska (abs.), A Vulimiri, M. R., and Cheney, E. S., Stratiform mineralization and origin of some of the vein deposits, Bunker Hill mine, Couer d'Alene district, Idaho, 23 Yeend, Warren, Placer gold deposits, Mt. Hayes quadrangle, Alaska, 8 ix TABLE OF CONTENTS Ashley, R. P., and Evarts, R. C., Geology and ore deposits of the St. Helens mining district, Washington (abs.)» 14 Balla, J. C., and Smith, R. G., Geology of the Little Boulder Creek deposit, Custer County, Idaho (abs.)> 22 Briskey, J. A., Field, C. W., and Bellamy, J. R., Geology, petrology, and geochemistry of the Jersey, East Jersey, Heustis, and lona porphyry copper-molybdenum deposits, Highland Valley, British Columbia, 10 Case, J. E., Magnetic expression and mineralization of some Tertiary plutons of Prince William Sound and the Alaska Peninsula, southern Alaska (abs.)> 3 Casey, W. H., and Taylor, B. E., Stable isotopic investigation of hydrothermal ore fluids in massive sulfide deposits of the West Shasta Cu-Zn district, California, 24 Cheney, E. S., New concepts of regional geology and uranium exploration in northeastern Washington, 16 Derkey, R. E., Hydrothermal alteration and mineralization at the Blackbutte mercury mine, Lane County, Oregon, 17 Derkey, R. E., The Silver Peak volcanogenic massive sulfide, northern Klamath Mountains, Oregon, 19 Fahey, P. L., The Island copper porphyry copper-molybdenum deposit, Vancouver Island, British Columbia (abs.)» H Godwin, C. I., Sinclair, A. J., and Ryan, B. D., Lead isotope models for the genesis of carbonate-hosted Zn-Pb, shale-hosted Ba-Zn-Pb, and silver-rich deposits in the northern Canadian Cordillera, 12 Hitzman, M. W., Geology of the BT Claim Group, southwestern Brooks Range, Alaska, 2 Juhas, A. P., Freeman, P. S., and Fredericksen, R. S., Kuroko type copper-gold mineralization at the Iron Dyke mine, Oregon, 21 Juhas, A. P., and Gallagher, T. P., Kuroko type mineralization at the Red Ledge deposit, Idaho, 20 Koski, R. A., Volcanogenic massive sulfide deposits in ocean-crust and island-arc terranes, northwestern Klamath Mountains, Oregon and California, 18 viii 29. Paleozoic stratabound lead-zinc-copper deposits in the western United States Half Zantop 328 vii Several contributors attempt to relate the occurrences of specific types of mineral deposits to tectonic domains or to type and evolution of associated magma systems, and two others attempt to summarize genetic implication of the distributions of skarn and strata-bound types of mineral deposits throughout the western United States. Mineral deposits of hydrothermal origin clearly served as an unintentional theme to this symposium, as underscored by the paper concerning The Geysers geothermal area of west-central California. This apparent metallogenetic "excess" is attributable to the cordilleran locale of the Pacific Northwest, and not to editorial bias exercised by the co-conveners of this symposium. The participants of this symposium, both the contributors and the audience, represented a cross-section of the geologic profession that is concerned with mineral deposits, and with interests ranging from esoteric considerations of ore genesis to the more pragmatic considerations of exploration. They were comprised of members from the academic, governmental, and industrial sectors, and in many cases their contributions were co-authored by individuals from two or more of these communities. As co-convenors of this symposium, we are particularly gratified at the response given to these technical sessions, both from the contributors and from the audience, which numbered more than 300. In order to make these papers and abstracts available without an intolerably long delay, we decided at an early date to publish them collectively as a U.S. Geological Survey Open-File Report. We selected this semiformal method of publication to expedite the printing and distribution of these papers because of the timely iii nature of many of these contributions that are in rapidly advancing fields of study. We wish to express our sincere thanks to the organizers of the Cordilleran Section meeting in Corvallis, Oregon; especially to co-chairmen George H. Keller and Robert S. Yeats of the local committee and E. Julius Dasch and Erwin Suess of the technical program, for providing the opportunity and assistance that enabled us to convene this synposium. We gratefully acknowledge the able assistance of John Derr, of the staff of technical reports unit of the U.S. Geological Survey in Menlo Park, California, for the assembly of this volume with a minimum of delay or difficulty. Lastly, we wish to extend our sincerest appreciation to the contributors of this volume, both for the high quality of their presentations at the symposium and for their cooperation in meeting the deadlines of manuscript submittal. The success of this volume is directly the result of our contributors and of those who have assisted us in this publication effort. Miles L. Silberman U.S. Geological Survey 345 Middlefield Road Menlo Park, California 94025 Cyrus W. Field Department of Geology Oregon State University Corvallis, Oregon 97331 Anne L. Berry U.S. Geological Survey 345 Middlefield Road Menlo Park, California 94025 iv TABLE OF CONTENTS 1. Isotopic
Load more

Recommended publications
  • Editorial for Special Issue “Ore Genesis and Metamorphism: Geochemistry, Mineralogy, and Isotopes”
    minerals Editorial Editorial for Special Issue “Ore Genesis and Metamorphism: Geochemistry, Mineralogy, and Isotopes” Pavel A. Serov Geological Institute of the Kola Science Centre, Russian Academy of Sciences, 184209 Apatity, Russia; [email protected] Magmatism, ore genesis and metamorphism are commonly associated processes that define fundamental features of the Earth’s crustal evolution from the earliest Precambrian to Phanerozoic. Basically, the need and importance of studying the role of metamorphic processes in formation and transformation of deposits is of great value when discussing the origin of deposits confined to varied geological settings. In synthesis, the signatures imprinted by metamorphic episodes during the evolution largely indicate complicated and multistage patterns of ore-forming processes, as well as the polygenic nature of the mineralization generated by magmatic, postmagmatic, and metamorphic processes. Rapid industrialization and expanding demand for various types of mineral raw ma- terials require increasing rates of mining operations. The current Special Issue is dedicated to the latest achievements in geochemistry, mineralogy, and geochronology of ore and metamorphic complexes, their interrelation, and the potential for further prospecting. The issue contains six practical and theoretical studies that provide for a better understanding of the age and nature of metamorphic and metasomatic transformations, as well as their contribution to mineralization in various geological complexes. The first article, by Jiang et al. [1], reports results of the first mineralogical–geochemical Citation: Serov, P.A. Editorial for studies of gem-quality nephrite from the major Yinggelike deposit (Xinjiang, NW China). Special Issue “Ore Genesis and The authors used a set of advanced analytical techniques, that is, electron probe microanaly- Metamorphism: Geochemistry, sis, X-ray fluorescence (XRF) spectrometry, inductively coupled plasma mass spectrometry Mineralogy, and Isotopes”.
    [Show full text]
  • Characterization of Sulfide Minerals from Gabbroic and Ultramafic Rocks by Electron Microscopy1 D.J
    Blackman, D.K., Ildefonse, B., John, B.E., Ohara, Y., Miller, D.J., MacLeod, C.J., and the Expedition 304/305 Scientists Proceedings of the Integrated Ocean Drilling Program, Volume 304/305 Data report: characterization of sulfide minerals from gabbroic and ultramafic rocks by electron microscopy1 D.J. Miller,2 T. Eisenbach,2 and Z.P. Luo3 Chapter contents Abstract Abstract . 1 This objective of this research was to investigate the potential of using transmission electron microscopy (TEM) to determine sul- Introduction . 1 fide mineral speciation in gabbroic rocks from Atlantis Massif, the Geologic background . 2 site of Integrated Ocean Drilling Program Expedition 304/305. Method development . 2 The method takes advantage of TEM analysis techniques and Results . 2 proved successful in sulfide mineral identification. TEM can pro- Discussion . 3 vide imaging of the sample morphology, crystal structure through Acknowledgments. 4 the electron diffraction, and chemical compositional information References . 4 through X-ray energy dispersive spectroscopy. Electron probe mi- Figures . 5 croanalysis was also used to determine the chemical composition. Table . 11 Introduction Integrated Ocean Drilling Program (IODP) Expedition 304/305 at Atlantis Massif, 30°N on the Mid-Atlantic Ridge (MAR) (Fig. F1) comprised a coordinated, dual-expedition drilling program aimed at investigating oceanic core complex (OCC) formation and the exposure of ultramafic rocks in young oceanic lithosphere. One of the scientific objectives of this drilling program is to investigate the role of magmatism in the development of OCCs. Whereas precruise submersible and geophysical surveys suggested the po- tential of recovering substantial amounts of serpentinized perido- tite and possibly fresh residual mantle, coring on the central dome of the massif returned a 1.4 km thick section of plutonic mafic rock with only a thin (<150 m) interval of ultramafic or near-ultramafic composition rocks of indeterminate origin.
    [Show full text]
  • LOW TEMPERATURE HYDROTHERMAL COPPER, NICKEL, and COBALT ARSENIDE and SULFIDE ORE FORMATION Nicholas Allin
    Montana Tech Library Digital Commons @ Montana Tech Graduate Theses & Non-Theses Student Scholarship Spring 2019 EXPERIMENTAL INVESTIGATION OF THE THERMOCHEMICAL REDUCTION OF ARSENITE AND SULFATE: LOW TEMPERATURE HYDROTHERMAL COPPER, NICKEL, AND COBALT ARSENIDE AND SULFIDE ORE FORMATION Nicholas Allin Follow this and additional works at: https://digitalcommons.mtech.edu/grad_rsch Part of the Geotechnical Engineering Commons EXPERIMENTAL INVESTIGATION OF THE THERMOCHEMICAL REDUCTION OF ARSENITE AND SULFATE: LOW TEMPERATURE HYDROTHERMAL COPPER, NICKEL, AND COBALT ARSENIDE AND SULFIDE ORE FORMATION by Nicholas C. Allin A thesis submitted in partial fulfillment of the requirements for the degree of Masters in Geoscience: Geology Option Montana Technological University 2019 ii Abstract Experiments were conducted to determine the relative rates of reduction of aqueous sulfate and aqueous arsenite (As(OH)3,aq) using foils of copper, nickel, or cobalt as the reductant, at temperatures of 150ºC to 300ºC. At the highest temperature of 300°C, very limited sulfate reduction was observed with cobalt foil, but sulfate was reduced to sulfide by copper foil (precipitation of Cu2S (chalcocite)) and partly reduced by nickel foil (precipitation of NiS2 (vaesite) + NiSO4·xH2O). In the 300ºC arsenite reduction experiments, Cu3As (domeykite), Ni5As2, or CoAs (langisite) formed. In experiments where both sulfate and arsenite were present, some produced minerals were sulfarsenides, which contained both sulfide and arsenide, i.e. cobaltite (CoAsS). These experiments also produced large (~10 µm along longest axis) euhedral crystals of metal-sulfide that were either imbedded or grown upon a matrix of fine-grained metal-arsenides, or, in the case of cobalt, metal-sulfarsenide. Some experimental results did not show clear mineral formation, but instead demonstrated metal-arsenic alloying at the foil edges.
    [Show full text]
  • The Genetic Model of the Hohentauern/Sunk Sparry Magnesite Deposit (Eastern Alps/Austria)
    Dissertation Amir Morteza Azim Zadeh The genetic model of the Hohentauern/Sunk sparry magnesite deposit (Eastern Alps/Austria) Dissertation PhD Thesis submitted to obtain the degree of: Doktor der montanistischen Wissenschaften Amir Morteza Azim Zadeh BSc. & MSc. Supervisor: O. Univ.-Prof. Dr. phil. Fritz Ebner Department of Applied Geosciences and Geophysics Geology and Economic Geology University of Leoben, Austria 2009 Referees: O. Univ.-Prof. Dr. phil. Fritz Ebner Ao. Univ.-Prof. Dr. Ronald J. Bakker I declare in lieu of oath, that I wrote this thesis and performed the associated research myself, using only literature cited in this volume. Amir M. Azimzadeh Leoben, May 2009 „…und dicht neben meinem Wissen lagerte mein schwarzes Unwissen.“ Also sprach Zarathustra Friedrich Wilhelm Nietzsche Contents . Contents: Abstract I Zusammenfassung II Publications and conference presentations of A. M. Azim Zadeh related to this thesis IV Acknowledgment VI List of figures VIII List of tables XVI 1. Introduction 1 1.1 Aim 2 1.2 Applied methods 2 1.2.1 Field methods and sampling 3 1.2.2 Analytical techniques 3 1.2.2.1 Petrography 3 1.2.2.2 Cathodoluminescence microscopy 3 1.2.2.3 Electron microprobe analysis (EPMA) 3 1.2.2.4 X-ray fluorescence spectrometry (XRF) 4 1.2.2.5 Inductively coupled plasma mass spectrometry (ICP-MS) 4 1.2.2.6 Atomic absorption spectroscopy (AAS) 5 1.2.2.7 Fluid inclusion analysis 6 1.2.2.7.1 Ion chromatography (IC) 6 1.2.2.7.2 Microthermometry 7 1.2.2.8 Raman spectroscopy 8 1.2.2.9 Laser-ablation MC-ICP-MS isotope analysis 9 1.3 Magnesite as mineral and ore 9 1.4 Types and origin of magnesite 11 Contents .
    [Show full text]
  • The Mineralogical Fate of Arsenic During Weathering Of
    THE MINERALOGICAL FATE OF ARSENIC DURING WEATHERING OF SULFIDES IN GOLD-QUARTZ VEINS: A MICROBEAM ANALYTICAL STUDY A Thesis Presented to the faculty of the Department of Geology California State University, Sacramento Submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in Geology by Tamsen Leigh Burlak SPRING 2012 © 2012 Tamsen Leigh Burlak ALL RIGHTS RESERVED ii THE MINERALOGICAL FATE OF ARSENIC DURING WEATHERING OF SULFIDES IN GOLD-QUARTZ VEINS: A MICROBEAM ANALYTICAL STUDY A Thesis by Tamsen Leigh Burlak Approved by: __________________________________, Committee Chair Dr. Charles Alpers __________________________________, Second Reader Dr. Lisa Hammersley __________________________________, Third Reader Dr. Dave Evans ____________________________ Date iii Student: Tamsen Leigh Burlak I certify that this student has met the requirements for format contained in the University format manual, and that this thesis is suitable for shelving in the Library and credit is to be awarded for the project. _______________________, Graduate Coordinator ___________________ Dr. Dave Evans Date Department of Geology iv Abstract of THE MINERALOGICAL FATE OF ARSENIC DURING WEATHERING OF SULFIDES IN GOLD-QUARTZ VEINS: A MICROBEAM ANALYTICAL STUDY by Tamsen Leigh Burlak Mine waste piles within the historic gold mining site, Empire Mine State Historic Park (EMSHP) in Grass Valley, California, contain various amounts of arsenic and are the current subject of remedial investigations to characterize the arsenic present. In this study, electron microprobe, QEMSCAN (Quantitative Evaluation of Minerals by SCANning electron microscopy), and X-ray absorption spectroscopy (XAS) were used collectively to locate and identify the mineralogical composition of primary and secondary arsenic-bearing minerals at EMSHP.
    [Show full text]
  • The Role of Interaction Between Paenibacillus Polymyxa Bacteria and Pyrolusite-Hematite System Through Bioflotation Nagui A
    International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395 -0056 Volume: 04 Issue: 04 | Apr-2017 www.irjet.net p-ISSN: 2395-0072 The Role of Interaction between Paenibacillus polymyxa Bacteria and Pyrolusite-Hematite System through Bioflotation Nagui A. Abdel-Khalek1, Khaled A. Selim1, Mohamed M.A. Hassan2, Moharram M.R.3 Saleh A. M.3, A. M. Ramadan3 1Central Metallurgical Research and Development Institute, (CMRDI), Helwan, Egypt 2Mining and Petroleum Engineering Department, Faculty of Engineering, Al-Azhar University, Qena, Egypt 3Mining and Petroleum Department, Faculty of Engineering, Al-Azhar University, Cairo, Egypt -----------------------------------------------------------------------------------***--------------------------------------------------------------------------------- Abstract –Applying Paenibacillus polymyxa bacterial furnace with parts entering the slag. This is why the strain as a surface modifier in flotation process and at the reduction behavior of Mn in the blast furnace was studied optimum conditions, succeeded in the removal of 64.89 % of extensively before, trying to avoid the harmful effect of Mn MnO2.Applying the same conditions for flotation of a natural in the ironmaking and steel industries [4, 5, 6]. At the iron ore yielded a concentrate containing 3.7% MnO2, 0.5% same time, due to the similarity of their chemical and SiO2 and 71.30% Fe2O3 with a hematite recovery of 72.46% physical properties, Fe and Mn are always associated in from a feed containing 8.79% MnO2, 0.49% SiO2 and
    [Show full text]
  • Recent Advances in BIF-Related Iron Ore Models and Exploration Strategies
    Ore Deposits and Exploration Technology _________________________________________________________________________________________ Paper 54 Recent Advances in BIF-related Iron Ore Models and Exploration Strategies Hagemann, S. [1], Dalstra, H. I. [2], Hodkiewicz, P. [3], Flis, M. [4], Thorne, W. [1] McCuaig, C. [1] _________________________ 1. University of Western Australia, CET-Centre for Exploration Targeting, Crawley, Australia 2. Rio Tinto Exploration Pty, Ltd, Belmont WA, Australia 3. SRK Consulting, West Perth, Australia 4. Rio Tinto Iron Ore, Perth, Australia ABSTRACT Recent research on BIF-related high-grade iron ore mineralization has resulted in new genetic models that emphasize the structurally controlled hypogene alteration and upgrade of BIF to high-grade (>65% Fe) iron ore. Conventional structural and stratigraphic mapping and reconstructions of the tectonic history of iron districts, in combination with high-tech geochemical analyses such as laser ICP-MS analyses of in situ oxides and fluid inclusions, stable (C-O-H) and radiogenic (Sr) isotopes, provide the iron explorationists with an invaluable set of tools to discover concealed iron ore bodies, deposits and districts. Two case studies from Western Australia illustrate: (1) the power of a tectonic reconstruction of the Paraburdoo Ranges and its significance for the location of high-grade hematite mineralization, and (2) the interpretation of structural controls on iron mineralization in the C deposit and its implications for resource estimation. INTRODUCTION RECENT ADVANCES IN GENETIC MODELS The past 15 years has seen significant new research conducted on BIF-related iron ore mineralization leading to new genetic In the mid-1990’s Hamersley Iron established a task force to models that emphasize the role of hypogene alteration and investigate the potential of exploring for concealed iron ore structurally controlled hydrothermal fluid flow in the upgrade of bodies in the Hamersley Province of Western Australia.
    [Show full text]
  • Oxidation of Sulfide Minerals. V. Galena, Sphalerite and Chalcogite
    Canadian Mineralogist Vol. 18,pp. 365-372(1980) OXIDATIONOF SULFIDEMINERALS. V. GALENA,SPHALERITE AND CHALCOGITE H.F. STEGBR eup L.E. DESJARDINS Mineral SciencesLaboratories, Canada Centre lor Mineral and Energy Technology, Department ol Energy, Mines and Resources,Ottawa, Ontaio KIA OGI AssrRecr long-term stability of sulfide-bearing ores and concentrates.Part of this study was concerned Samples of galena, sphalerite and cbalcocite were with the nature of the products and kinetics of oxidized at 52oC and, 68Vo of relative humidity the oxidation of the commonly encountered periods to five weeks, and the prqd- in air for up sulfide minerals. The oxidation of pyrite, chal- for metal and sulfur-bearing ucts were analyzed pyrrhotite at 52oC and, 687o of. species. Galena is. oxidized to PbSOa, sphalerite copyrite and (RH) has already been in- to ZnSO. * FezO, if iron-bearing, and chalcocite relative humidity to CuO and CuS. The oxidation of galena and vestigated (Steger & Desjardins 1978). This re- sphalerite proceeds according to a linear rate potr summarizes the results of the study 9f tle law: that of chalcocite leads to the formation of a bxidation of galena, sphalerite and chalcocite coherent product layer impenetrable to Oz and HrO under the same conditions. vapor. The air oxidation of galena at relatively low without Keywords: air oxidation, oxidation products, sul- temperatures has been investigated fide minerals, galena, sphalerite, chalcocite. reaching a consensuson the nature of the oxida- tion product. Hagihara (1952), using a re- Sourvrlrnp flection electron-diffraction technique, and Kirkwood & Nutting (1965), using a trans- Nous avons 6tudi6 I'oxydation dans I'air d'6chan- mission electron-diffraction technique, found tillons de galdne, de sphal6rite et de chalcocite i this product to be PbSOo,whereas Leia et al.
    [Show full text]
  • Monchegorsk Layered Intrusion, Fennoscandian Shield)
    minerals Article Chromite Mineralization in the Sopcheozero Deposit (Monchegorsk Layered Intrusion, Fennoscandian Shield) Artem V. Mokrushin 1,* and Valery F. Smol’kin 2 1 Geological Institute—Subdivision of the Federal Research Centre “Kola Science Centre of the Russian Academy of Sciences”, 14 Fersman Street, 184209 Apatity, Russia 2 Vernadsky State Geological Museum of the Russian Academy of Sciences, 11/11 Mokhovaya Street, 125009 Moscow, Russia; [email protected] * Correspondence: [email protected]; Tel.: +7-(902)133-39-95 Abstract: In 1990, the Sopcheozero Cr deposit was discovered in the Monchegorsk Paleoprotero- zoic layered mafic-ultramafic layered intrusion (Monchepluton). This stratiform early-magmatic deposit occurs in the middle part of the Dunite Block, which is a member of the Monchepluton layered series. The Cr2O3 average-weighted content in ordinary and rich ores of the deposit is 16.65 and 38.76 wt.%, respectively, at gradually changing concentrations within the rich, ordinary and poor ore types and ore body in general. The ores of the Sopcheozero deposit, having a ratio of Cr2O3/FeOtotal = 0.9–1.7, can serve as raw materials for the refractory and chemical industries. The ore Cr-spinel (magnochromite and magnoalumochromite) is associated with highly magnesian olivine (96–98 Fo) rich in Ni (0.4–1.1 wt.%). It confirms a low S content in the melt and complies with the low oxygen fugacity. The coexisting Cr-spinel-olivine pairs crystallized at temperatures ◦ from 1258 to 1163 C, with accessory Cr-spinel crystallizing at relatively low, while ore Cr-spinel at higher temperatures. The host rock and ore distinguish with widespread plastic deformations of ◦ Citation: Mokrushin, A.V.; Smol’kin, olivine at the postcrystallization phase under conditions of high temperature (above 400 C) and V.F.
    [Show full text]
  • Porphyry Copper Deposits of the American Cordillera
    Porphyry Copper Deposits of the American Cordillera Frances Wahl Pierce and John G. Bolm, Editors Arizona Geological Society Digest 20 1995 The Helvetia Area Porphyry Systems, Pima County, Arizona S. A. ANZALONE ASARCO Incorporated, Tu cson, Arizona ABSTRACT INTRODUCTION The Helvetia area porphyry copper deposits occur within The Helvetia area copper deposits occur within a large an extensive Laramide porphyry system located in the Santa Laramide porphyry system located in the Santa Rita Mountains, Rita Mountains, Pima County, Arizona. The entire system Pima County, Arizona. This porphyry copper system consists of consists of four separate centers of copper mineralization: four separate areas of copper mineralization - Rosemont, Peach­ Rosemont, Peach-Elgin, Broadtop Butte, and Copper Wo rld. Elgin, Broadtop Butte, and Copper World - lying within a Mineralization and alteration are primarily of the contact broad alteration zone in the northern segment of the Santa Rita pyrometasomatic type and hydrothermal alteration and zon­ Mountains. Mineralization and alteration are primarily contact ing of sulfide mineral assemblages resemble those observed at pyrometasomatic, and zoning of hydrothermal alteration and sul­ the Twin Buttes Copper Mine located approximately 30 kilo­ fide mineral assemblages is similar to those observed at the meters west of Helvetia. The stratigraphic sequence, ranging Twin Buttes and Mission Copper Mines located approximately from Cambrian Bolsa Formation to Permian Rain Va lley For­ 30 kilometers west of Helvetia. ASARCO acquired the copper mation, correlates well with sections developed in the Tw in deposits within the Helvetia area porphyry systems in 1988 and Buttes and Mission Mine areas. The Paleozoic section in the has continued the exploration and development effort since then.
    [Show full text]
  • Why Magnesite, Talc, and MVT Ore Deposits Are Associated with Burial Dolostones: Serpentinization Provides the Magnesium
    Why magnesite, talc, and MVT ore deposits are associated with burial dolostones: Serpentinization provides the magnesium Enrique Merino Dept of Earth and Atmospheric Sciences, Indiana University, Bloomington IN 47405, USA. [email protected] Àngels Canals Dept of Mineralogy, Petrology and Applied Geology, Universitat de Barcelona, Spain. [email protected] Abstract. Magnesite, talc, and MVT ore deposits are dolomite and may also replace quartz in quartzites hosted in burial dolomites in several districts because (Tornos and Spiro 2000). they all form from the same deep hot Mg-rich brines that However, saying that Mg is needed to make first drive replacement of limestone by dolomite. Then magnesite and talc does not make it clear which are the talc and magnesite replace the dolomite. These mineral reactions involved, or what are their driving replacements are Mg-driven and happen by forces, or how to account for the fact that all the ores precipitation/pressure-dissolution, which is why mineral and the dolomite that hosts them occur as volume is preserved, which warrants adjusting replacements, or where the necessary magnesium replacement mass balances on volume. The dolomite- comes from. Our approach below is to adjust for-calcite replacement is self-accelerating via the Ca2+ replacement mass balances on volume (as required by released and affects huge volumes of limestone. the conservation of volume shown in Figures 1-3), and Continued infiltration of the dolostone by the Mg-rich to take account of the new replacement physics (Merino brine causes its replacement by magnesite and talc. The and Dewers 1998; Merino and Canals 2011), by which talc, magnesite, and MVT ores, and dedolomitization replacement forms not by dissolution-precipitation as too, are part and parcel of the dolomitization process.
    [Show full text]
  • Garnet U-Pb and O Isotopic Determinations Reveal a Shear-Zone
    www.nature.com/scientificreports OPEN Garnet U-Pb and O isotopic determinations reveal a shear-zone induced hydrothermal system Received: 22 March 2019 Zhongjiang Zang3, Leilei Dong1,2,4, Wei Liu1,2, Han Zhao1,2, Xinshui Wang5, Keda Cai6 & Accepted: 5 July 2019 Bo Wan 1,2 Published: xx xx xxxx The absolute crystallization ages of minerals from hydrothermal fuids measured in situ can unravel the timing of key events leading to the formation of, for instance, ore deposits and hydrothermally derived geological terrains. In this study, a skarn iron deposit from northwest (NW) China is shown to have U-Pb garnet and U-Pb zircon ages of 254.2 ± 1.7 Ma and 255.5 ± 1.0 Ma, respectively, which are both signifcantly younger than magmatism and metamorphism of the region. This skarn age instead correlates with the occurrence of strike-slip and thrust faulting in the region. The water/rock mass ratio of 0.065~0.115 suggests the δ18O garnet composition is ~1‰ at temperatures ranging from 250–450 °C. The low oxygen isotopic composition indicates the role of meteoric water in the garnet formation. These measurements can be interpreted as the shear along faults circulating meteoric water ~10 km below the hanging wall of meta-volcanic sedimentary rock. Meteoric water in this hydrothermal system would leach cations from the meta-volcano-sedimentary rocks necessary for mineralization. Silica-rich hydrothermal fuid reacts with calcic-rich materials in the meta-volcano-sedimentary rocks, depositing the garnet and magnetite. Our work suggests that the shear zone is rich in ores, rendering this deposit for NW China a prospective source for future mineral resource exploration.
    [Show full text]