Relationship between copper tonnage of Chilean base-metal porphyry deposits and Os isotope ratios

Abstract

Research Article| June 01, 2000 Relationship between copper tonnage of Chilean base-metal porphyry deposits and Os isotope ratios Ryan Mathur; Ryan Mathur 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar Joaquin Ruiz; Joaquin Ruiz 1Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar Francisco Munizaga Francisco Munizaga 2Departamento de Geologia, Universidad de Chile, Casilla 13518-C.21, Santiago, Chile Search for other works by this author on: GSW Google Scholar Geology (2000) 28 (6): 555–558. https://doi.org/10.1130/0091-7613(2000)28<555:RBCTOC>2.0.CO;2 Article history received: 15 Nov 1999 rev-recd: 07 Mar 2000 accepted: 29 Mar 2000 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Ryan Mathur, Joaquin Ruiz, Francisco Munizaga; Relationship between copper tonnage of Chilean base-metal porphyry deposits and Os isotope ratios. Geology 2000;; 28 (6): 555–558. doi: https://doi.org/10.1130/0091-7613(2000)28<555:RBCTOC>2.0.CO;2 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 Re-Os isotopes in pyrite and chalcopyrite from early high-temperature hypogene alteration assemblages in Chilean porphyry copper deposits identify the source of Os and, by inference, Cu in these ore systems. Typical concentrations for Os in both pyrite and chalcopyrite are between 7 and 30 ppt (10−12 g/g), and for Re between 0.200 and 10 ppb (10−9 g/g). Re-Os isochrons yield ages and initial 187Os/188Os ratios for the sulfides. The isotopic data reflect the relative contributions of copper from the mantle and crust in Chilean porphyry copper deposits. Seven ore deposits that reside in different tectonic terranes and represent distinct epochs of mineralization in Chile were studied. The initial osmium ratios of the first stage of mineralization at each of the deposits range from 0.15 to 5. These values are more radiogenic than the present chondritic mantle (∼0.13), and indicate significant crustal contributions of Os to the magmatic and/or hydrothermal systems. There is a strong correspondence between the total copper content and initial Os isotopic ratios in base-metal porphyry deposits. The larger deposits have lower initial Os ratios than the smaller, less significant deposits. This relationship implies that larger deposits acquire a greater proportion of Os from the mantle. The initial Os ratio of samples in the central segment of porphyry copper deposits of northern Chile also decreases with decreasing age of the deposit. A plausible interpretation of the Re-Os data is that the later and larger deposits use regional tectonic and structural features that allow sampling of deeper more primitive magmatic sources. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.