Magmatic salt melt and vapor: Extreme fluids forming porphyry gold deposits in shallow subvolcanic settings

Abstract

Research Article| June 01, 2014 Magmatic salt melt and vapor: Extreme fluids forming porphyry gold deposits in shallow subvolcanic settings Peter Koděra; Peter Koděra 1Department of Geology of Mineral Deposits, Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovakia Search for other works by this author on: GSW Google Scholar Christoph A. Heinrich; Christoph A. Heinrich 2Department of Earth Sciences, ETH Zürich, 8092 Zürich, Switzerland Search for other works by this author on: GSW Google Scholar Markus Wälle; Markus Wälle 2Department of Earth Sciences, ETH Zürich, 8092 Zürich, Switzerland Search for other works by this author on: GSW Google Scholar Jaroslav Lexa Jaroslav Lexa 3Geological Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05 Bratislava, Slovakia Search for other works by this author on: GSW Google Scholar Author and Article Information Peter Koděra 1Department of Geology of Mineral Deposits, Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovakia Christoph A. Heinrich 2Department of Earth Sciences, ETH Zürich, 8092 Zürich, Switzerland Markus Wälle 2Department of Earth Sciences, ETH Zürich, 8092 Zürich, Switzerland Jaroslav Lexa 3Geological Institute, Slovak Academy of Sciences, Dúbravská cesta 9, 840 05 Bratislava, Slovakia Publisher: Geological Society of America Received: 06 Nov 2013 Revision Received: 05 Mar 2014 Accepted: 12 Mar 2014 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2014 Geological Society of America Geology (2014) 42 (6): 495–498. https://doi.org/10.1130/G35270.1 Article history Received: 06 Nov 2013 Revision Received: 05 Mar 2014 Accepted: 12 Mar 2014 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Peter Koděra, Christoph A. Heinrich, Markus Wälle, Jaroslav Lexa; Magmatic salt melt and vapor: Extreme fluids forming porphyry gold deposits in shallow subvolcanic settings. Geology 2014;; 42 (6): 495–498. doi: https://doi.org/10.1130/G35270.1 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 SocietyGeology Search Advanced Search Abstract The recently discovered Biely Vrch deposit in the Western Carpathian magmatic arc is the most extreme example of a porphyry gold deposit, being practically free of copper, molybdenum or any other sulfide minerals. Microanalytical data on fluid inclusions in quartz veinlets, including a characteristic type of banded veinlets, show that this deposit formed from nearly anhydrous Fe-K-Na-Cl salt melts containing ∼10 ppm Au, coexisting with hydrous vapor of very low density. This exceptional fluid evolution required an Fe-rich dioritic source magma that was emplaced at shallow subvolcanic depth (<3.5 km), directly exsolving a hypersaline liquid and magmatic vapor at high temperature (∼850 °C). During ascent to the level of the porphyry intrusion (0.5–1 km), fluid expansion at high temperature but low pressure led to halite precipitation and further water loss to the vapor, generating an increasingly Fe-K-rich salt melt that transported high concentrations of Au but negligible Cu into the fractured porphyry stock. The low sulfur fugacity resulting from fluid expansion suppressed precipitation of sulfide, explaining the gold-only enrichment in this globally recurring but rare type of gold ore. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.