Trace element signature of pyrite from the los colorados iron oxide-apatite (IOA) Deposit, Chile: A missing link between andean ioa and iron oxide copper-gold systems?

M. Reich, A.C. Simon, A. Deditius, F. Barra, S. Chryssoulis, G. Lagas, D. Tardani, J. Knipping, L. Bilenker, P. Sánchez-Alfaro, M.P. Roberts, R. Munizaga

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

© 2016 Society of Economic Geologists, Inc. Although studies have proposed that iron oxide-apatite (IOA) deposits may represent the deeper roots of some Andean iron oxide copper-gold (IOCG) systems, their genetic links remain obscure and controversial. A key question when considering an integrated genetic model is whether a magmatic-hydrothermal fluid that precipitates massive magnetite will continue transporting significant amounts of dissolved Fe, Cu, and Au after IOA precipitation. Here we provide new geochemical data for accessory pyrite from the Los Colorados IOA deposit in the Chilean iron belt that confirm the role of this sulfide as a relevant repository for economic metals in IOA deposits. Pyrite occurs at Los Colorados as disseminated grains and as veinlets associated with magnetite and actinolite that postdate the main igneous magnetite stage. Electron probe microanalysis (EPMA) data for pyrite show anomalously high Co and Ni concentrations (up ~3.9 and ~1.5 wt %, respectively) and relatively high As contents (100s of ppm to a maximum of ~2,000 ppm). When combined with results from secondary ion mass spectrometry (SIMS) spot analyses, pyrite data show significant amounts of Cu that range from sub-ppm values (~100 ppb) up to 1,000s of ppm, plus nonnegligible concentrations of Zn, Pb, Cd, Sb, Se, and Te (up to ~100 ppm). The highest contents of Cu measured (wt % level) most likely record the presence of Cu-bearing submicron-sized mineral inclusions. Contents of Au and Ag are up to ~1 and 10 ppm, respectively, with maximum concentrations that can rise up to ~800 ppm Au and ~300 ppm Ag due to the presence of submicron-sized inclusions. The high Co/Ni ratios of pyrite from Los Colorados are consistent with a magmatic-hydrothermal origin associated with a greater mafic affinity, compared to pyrite from porphyry Cu deposits. Furthermore, the geochemical signature of Los Colorados pyrite shares important similarities of composition and microtexture with the few published data for pyrite from IOCG deposits (e.g
Original languageEnglish
Pages (from-to)743-761
Number of pages19
JournalEconomic Geology
Volume111
Issue number3
DOIs
Publication statusPublished - 2016

Fingerprint Dive into the research topics of 'Trace element signature of pyrite from the los colorados iron oxide-apatite (IOA) Deposit, Chile: A missing link between andean ioa and iron oxide copper-gold systems?'. Together they form a unique fingerprint.

  • Cite this