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The Porphyry Cu-(Mo-Au) Deposit at Altar (Argentina): Tracing Gold Distribution by Vein Mapping and LA-ICP-MS Mineral Analysis

2014; Volume: 109; Issue: 5 Linguagem: Inglês

10.2113/econgeo.109.5.1341

1554-0774

Carmen Zwahlen, Stefania Cioldi, Thomas Wagner, Roger Rey, Christoph A. Heinrich,

Heavy metals in environment

Research Article| August 01, 2014 The Porphyry Cu-(Mo-Au) Deposit at Altar (Argentina): Tracing Gold Distribution by Vein Mapping and LA-ICP-MS Mineral Analysis Carmen Zwahlen; Carmen Zwahlen † 1ETH Zurich, Institute of Geochemistry and Petrology, Clausiusstr. 25, CH-8092 Zurich, Switzerland †Corresponding author: e-mail, zwahleca@gmail.com Search for other works by this author on: GSW Google Scholar Stefania Cioldi; Stefania Cioldi 1ETH Zurich, Institute of Geochemistry and Petrology, Clausiusstr. 25, CH-8092 Zurich, Switzerland Search for other works by this author on: GSW Google Scholar Thomas Wagner; Thomas Wagner 1ETH Zurich, Institute of Geochemistry and Petrology, Clausiusstr. 25, CH-8092 Zurich, Switzerland *Present address: Department of Geosciences and Geography, Division of Geology, University of Helsinki, P.O. Box 64 (Gustaf Hällströmin katu 2a), FI-00014 Helsinki, Finland. Search for other works by this author on: GSW Google Scholar Roger Rey; Roger Rey 2Peregrine Metals LTD., Avda. El Bosque Norte 0123, Oficina 604, Las Condes, Santiago, Chile Search for other works by this author on: GSW Google Scholar Christoph Heinrich Christoph Heinrich 1ETH Zurich, Institute of Geochemistry and Petrology, Clausiusstr. 25, CH-8092 Zurich, Switzerland Search for other works by this author on: GSW Google Scholar Author and Article Information Carmen Zwahlen † 1ETH Zurich, Institute of Geochemistry and Petrology, Clausiusstr. 25, CH-8092 Zurich, Switzerland Stefania Cioldi 1ETH Zurich, Institute of Geochemistry and Petrology, Clausiusstr. 25, CH-8092 Zurich, Switzerland Thomas Wagner *Present address: Department of Geosciences and Geography, Division of Geology, University of Helsinki, P.O. Box 64 (Gustaf Hällströmin katu 2a), FI-00014 Helsinki, Finland. 1ETH Zurich, Institute of Geochemistry and Petrology, Clausiusstr. 25, CH-8092 Zurich, Switzerland Roger Rey 2Peregrine Metals LTD., Avda. El Bosque Norte 0123, Oficina 604, Las Condes, Santiago, Chile Christoph Heinrich 1ETH Zurich, Institute of Geochemistry and Petrology, Clausiusstr. 25, CH-8092 Zurich, Switzerland †Corresponding author: e-mail, zwahleca@gmail.com Publisher: Society of Economic Geologists Received: 19 Aug 2012 Accepted: 14 Aug 2013 First Online: 09 Mar 2017 Online ISSN: 1554-0774 Print ISSN: 0361-0128 © 2014 Society of Economic Geologists. Economic Geology (2014) 109 (5): 1341–1358. https://doi.org/10.2113/econgeo.109.5.1341 Article history Received: 19 Aug 2012 Accepted: 14 Aug 2013 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Carmen Zwahlen, Stefania Cioldi, Thomas Wagner, Roger Rey, Christoph Heinrich; The Porphyry Cu-(Mo-Au) Deposit at Altar (Argentina): Tracing Gold Distribution by Vein Mapping and LA-ICP-MS Mineral Analysis. Economic Geology 2014;; 109 (5): 1341–1358. doi: https://doi.org/10.2113/econgeo.109.5.1341 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 SocietyEconomic Geology Search Advanced Search Abstract The Altar porphyry Cu-(Mo-Au) deposit occurs in the Miocene to early Pliocene copper belt of the high Andes of western Argentina, close to the Chilean border. A cluster of late Miocene porphyries intruded a more extensive complex of early Miocene rhyolitic to andesitic volcanic and subvolcanic rocks. Potassic alteration in the Central Porphyry was partially overprinted by feldspar-destructive alteration and finally by argillic to advanced argillic alteration. Early stockwork veins have been cut successively by quartz-pyrite veins, tourmaline veins, and enargite veins. Based on correlation analysis of assay results and mapped abundances of these four vein types, we estimate that approximately 11 to 26% of the copper in the Altar orebody is associated with enargite veins, whereas the remainder is associated with the early stockwork veining and potassic alteration. Gold concentration is low compared with typical Cu-Au porphyries of the Andean back-arc region, but higher than in the giant Miocene deposits of Chile, at an average Au/Cu ratio of 0.14 × 10−4 by weight across the Central Porphyry orebody at Altar. Gold is dominantly associated with chalcopyrite in the domain of stockwork veining and potassic alteration. Small-scale assays in combination with petrographic observations and laser ablation-inductively coupled plasma-mass spectrometry microanalyses show that a significant fraction of the gold in the stockwork veins is enclosed in pyrite as submicroscopic particles attached to inclusions of a Bi-Te-Pb-Ag–enriched Cu-Fe sulfide phase. Microscopic grains of native gold also occur along grain boundaries between pyrite and chalcopyrite, and rarely as larger particles in enargite veins. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.