Neoarchean convergent margin Ni-Cu mineralization? Axis Lake and Nickel King Ni-Cu deposits in the south Rae craton of the Canadian Shield
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Research Article| December 01, 2002 The Chirwa dome: granite emplacement during late Archaean thrusting along the northeastern margin of the Zimbabwe craton Axel Hofmann; Axel Hofmann School of Geosciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa Department of Geology, University of Zimbabwe, P.O. Box MP 167, Harare, Zimbabwe, e-mail: hofmannaxel@hotmail.com Search for other works by this author on: GSW Google Scholar Oliver Jagoutz; Oliver Jagoutz Institut für Erdwissenschaften, ETH-Zürich, 8092 Zürich, Switzerland, e-mail: oliver.jagoutz@erdw.ethz.ch Search for other works by this author on: GSW Google Scholar Alfred Kröner; Alfred Kröner Institut für Geowissenschaften, Universität Mainz, 55099 Mainz, Germany, e-mail: kroener@mail.uni-mainz.de Search for other works by this author on: GSW Google Scholar Paul H.G.M. Dirks; Paul H.G.M. Dirks School of Geosciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa, e-mail: dirksp@geosciences.wits.ac.za Search for other works by this author on: GSW Google Scholar Hielke A. Jelsma Hielke A. Jelsma CIGCES-Centre of Interactive Graphical Computing of Earth Systems, Department of Geological Sciences, University of Cape Town, Rondebosch, 7701, South Africa, e-mail: jelsma@cigces.uct.ac.za Search for other works by this author on: GSW Google Scholar Author and Article Information Axel Hofmann School of Geosciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa Department of Geology, University of Zimbabwe, P.O. Box MP 167, Harare, Zimbabwe, e-mail: hofmannaxel@hotmail.com Oliver Jagoutz Institut für Erdwissenschaften, ETH-Zürich, 8092 Zürich, Switzerland, e-mail: oliver.jagoutz@erdw.ethz.ch Alfred Kröner Institut für Geowissenschaften, Universität Mainz, 55099 Mainz, Germany, e-mail: kroener@mail.uni-mainz.de Paul H.G.M. Dirks School of Geosciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa, e-mail: dirksp@geosciences.wits.ac.za Hielke A. Jelsma CIGCES-Centre of Interactive Graphical Computing of Earth Systems, Department of Geological Sciences, University of Cape Town, Rondebosch, 7701, South Africa, e-mail: jelsma@cigces.uct.ac.za Publisher: Geological Society of South Africa First Online: 07 Mar 2017 Online ISSN: 1996-8590 Print ISSN: 1012-0750 © 2003 Geological Society of South Africa South African Journal of Geology (2002) 105 (4): 285–300. https://doi.org/10.2113/1050285 Article history First Online: 07 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Axel Hofmann, Oliver Jagoutz, Alfred Kröner, Paul H.G.M. Dirks, Hielke A. Jelsma; The Chirwa dome: granite emplacement during late Archaean thrusting along the northeastern margin of the Zimbabwe craton. South African Journal of Geology 2002;; 105 (4): 285–300. doi: https://doi.org/10.2113/1050285 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract The Chirwa dome in northeast Zimbabwe is situated at the boundary between the Zimbabwe craton and Archaean gneisses of the Zambezi mobile belt. This circular granite intrusion has long been regarded as Archaean granite which was remobilized during Pan-African times and emplaced as a mantled gneiss dome into a Proterozoic metasedimentary sequence. Field mapping, structural work and new zircon dates indicate that the Chirwa dome and surrounding rocks underwent a very different history. The supracrustal sequence was deposited and moderately deformed between ~2613 and ~2601 Ma ago, as bracketed by a provenance date and an intrusive date, respectively. Shortly after deposition, the sequence was thrust westward and juxtaposed against a greenstone terrain of the Zimbabwe craton. This active thrust stack was intruded by successive syntectonic granitoids at ~2601 and ~2593 Ma. The Chirwa dome granite, ~2570 Ma old, represents the last intrusive event before cessation of deformation. Our data indicate that while the central Zimbabwe craton already behaved as a stable crustal block at ~2600 Ma, tectonism was active along its northeastern margin. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
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The Rae craton on Melville Peninsula, Nunavut, comprises several lithotectonic domains, including a structurally and lithologically distinct yet poorly known crustal terrane, the Repulse Bay block (RBb). This study presents new lithological and petrographic observations, combined with U–Pb zircon data, to better understand the Archean and Paleoproterozoic crustal evolution of the RBb. The new data demonstrate that the central-eastern RBb consists of the following: (i) upper amphibolite- to granulite-facies, ca. 2.73–2.71 Ga intermediate granitoid gneisses and gabbroic sheets; (ii) ca. 2.69 Ga two-pyroxene charnockite to enderbite intrusions; and (iii) thin slivers of both Archean and Paleoproterozoic supracrustal rocks. Inherited zircon also attests to the presence of a Mesoarchean to Paleoarchean substrate. A semi-pelitic gneiss from one of the Paleoproterozoic supracrustal panels was deposited sometime after ca. 1.89 Ga and shows a similar detrital zircon age profile to a <1.92 Ga semi-pelitic gneiss from the Lyon Inlet boundary zone at the northern extent of the RBb. Zircon in most rocks analyzed record metamorphism related to the Trans-Hudson orogeny between ca. 1.84 and 1.82 Ga. Results from this study are most consistent with the RBb, representing a piece of lower to middle crustal level of the Rae craton, rather than a distinct and separate crustal entity (i.e., an exotic block).
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Abundant gold deposits are distributed in the Jiao-Liao-Ji Belt of the North China Craton. Gold deposits, characterized by quartz lode or disseminated styles of mineralization with extensive alteration of wall rock, of the Jiaodong Peninsula and Liaodong Peninsula are underlain by rocks of similar geological settings characterized by uplifted blocks of metamorphosed Archean and Proterozoic rocks surrounded by relatively unmetamorphosed Mesoproterozoic rocks and Mesozoic granitoid plutons. The huge order-of-magnitude difference in reserves between the Liaodong gold province (500 t) and the Jiaodong gold province (5000 t) attract the attention of geologists. Different C–H-O-S-Pb isotopes and isotopic dating have sparked controversy over the source of the gold deposits. In this study, we conducted integrated analyses of zircon U-Pb dating, bulk-rock compositions, mineralogical compositions and high-precision gold analyses on a series of meta-clastic sedimentary rocks from the Paleoproterozoic Liaohe Group in the Jiao-Liao-Ji Belt, North China Craton, of which the Au analyses reveal Au mobilization during prograde metamorphism. In the Gaizhou Barrovian-type metamorphic zone, the bulk-rock Au contents of samples within various metamorphic zones show a monotonic decrease up-temperature, from 2.09 ppb in the chlorite zone to 0.07 ppb in the sillimanite zone. The evolution in Au content during prograde metamorphism of other formations are identical to that of the Gaixian Formation. The Au concentrations of biotite in different metamorphic zones show little variation ranging from 0.66 to 0.35 ppb, whereas the Au concentrations of muscovite in different metamorphic zones mainly decrease from 2.60 ppb in the chlorite zone to 0.57 ppb in the sillimanite zone with increasing metamorphic grade in samples without metallic sulfides. Coincidently, there is a dechlorination process in biotites during regional metamorphism. Chlorine, released by metamorphism, may have played a vital role in the migration of Au, which could absorb onto muscovite and other minerals, during prograde metamorphism. Given an Au content of 4.67 t/km3 in the chlorite zone rock approximately equivalent to the protolith, metamorphism up to upper amphibolite grade would force the rocks to release 52% of the Au in the Gaizhou Barrovian-type metamorphic zone. Taking into account previous studies in the interpretation of our results, we propose that Precambrian rocks, such as the meta-clastic sedimentary rocks of the Gaixian Formation, may have contributed considerable amounts of Au to the Liaodong gold province. The Liaohe Group releasing large amounts of Au during Paleoproterozoic metamorphism, may thus provide the primary Au enrichment for the Mesozoic gold deposits.
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Abstract Globally, significant examples of hydrothermal Cu-Co mineralization are rare within Archean greenstone belts, especially relative to the endowment of these terranes with other world-class hydrothermal ore deposits, particularly Au deposits. Using U-Pb geochronology of hydrothermal apatite, this study provides the first absolute age constraints on the timing of mineralization for the Carlow Castle Cu-Co-Au deposit. Carlow Castle is a complex, shear zone-hosted, veined Cu-Co-Au mineral system situated within the Paleo-Mesoarchean Roebourne greenstone belt of the Pilbara craton of northwestern Western Australia. Although U-Pb geochronology of this deposit is challenging due to low levels of radiogenic Pb in synmineralization apatite, mineralization is best estimated at 2957 ± 67 Ma (n = 61). Additionally, analysis of alteration phases associated with Carlow Castle mineralization suggests that it is dominated by a propylitic assemblage that is characteristic of alkaline fluid chemistry and peak temperatures >300°C. Within proximal portions of the northwest Pilbara craton, the period of Carlow Castle’s formation constrained here is associated with significant base-metal volcanogenic massive sulfide mineralization and magmatic activity related to back-arc rifting. This rifting and associated magmatic activity are the most likely source of Carlow Castle’s unique Cu-Co-Au mineralization. Carlow Castle’s Mesoarchean mineralization age makes it among the oldest discovered Cu-Co-Au deposits globally, and unique in the broader context of hydrothermal Cu-Co-Au deposits. Globally, hydrothermal Cu-Co mineralization occurs almost exclusively as Proterozoic and Phanerozoic stratiform sediment-hosted Cu-Co deposits due to the necessity of meteorically derived oxidized ore fluids in their formation. This research therefore has implications for exploration for atypical Cu-Co deposits and Cu-Co metallogenesis through recognition of comparably uncommon magmatic-hydrothermal Cu-Co-Au ore-forming processes and, consequently, the potential for analogous Cu-Co-Au mineralization in other Archean greenstone belts.
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