High Cu grades in porphyry Cu deposits and their relationship to emplacement depth of magmatic sources

Abstract

Research Article| August 01, 2009 High Cu grades in porphyry Cu deposits and their relationship to emplacement depth of magmatic sources John M. Proffett John M. Proffett 1P.O. Box 772066, Eagle River, Alaska 99577, USA Search for other works by this author on: GSW Google Scholar Author and Article Information John M. Proffett 1P.O. Box 772066, Eagle River, Alaska 99577, USA Publisher: Geological Society of America Received: 26 Jan 2009 Revision Received: 13 Mar 2009 Accepted: 15 Mar 2009 First Online: 03 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2009 Geological Society of America Geology (2009) 37 (8): 675–678. https://doi.org/10.1130/G30072A.1 Article history Received: 26 Jan 2009 Revision Received: 13 Mar 2009 Accepted: 15 Mar 2009 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation John M. Proffett; High Cu grades in porphyry Cu deposits and their relationship to emplacement depth of magmatic sources. Geology 2009;; 37 (8): 675–678. doi: https://doi.org/10.1130/G30072A.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 Observations at several porphyry Cu deposits indicate that in those formed above source magma chambers emplaced to relatively shallow levels (roofs ~3–4 km deep), zones of higher Cu grade are associated with the oldest intrusions of a central porphyry cluster, abundant early (A-type) quartz veins, secondary feldspar alteration, and usually high Fe/Fe + Cu, low S/Fe + Cu sulfide-oxide mineral assemblages. In deposits for which source magma chambers were deeper (roofs >5 km), porphyries closest in age to ore are spatially less directly related to mineralization. In these, higher Cu grades in early mineralization comprise swarms of veinlets with alteration halos that include sericite as well as secondary feldspar and biotite. Sulfide ± oxide assemblages are usually of lower Fe/Fe + Cu and higher S/Fe + Cu. These differences in deposit characteristics appear to correspond with a change from two-phase, chloride-bearing, aqueous fluids that would exsolve from magma at shallow depths, to one-phase fluids deeper. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.