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Evidence for As Contamination and the Partitioning of Pd into Pentlandite and Co + Platinum Group Elements into Pyrite in the Fazenda Mirabela Intrusion, Brazil

2017; Volume: 112; Issue: 8 Linguagem: Inglês

10.5382/econgeo.2017.4533

1554-0774

Robert D. Knight, Hazel M. Prichard, César Fonseca Ferreira Filho,

Geochemistry and Elemental Analysis

Research Article| December 01, 2017 Evidence for As Contamination and the Partitioning of Pd into Pentlandite and Co + Platinum Group Elements into Pyrite in the Fazenda Mirabela Intrusion, Brazil Robert D. Knight; Robert D. Knight 1School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, United Kingdom †Corresponding author: e-mail, R.D.Knight@soton.ac.uk Search for other works by this author on: GSW Google Scholar Hazel M. Prichard; Hazel M. Prichard 1School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, United Kingdom ☼☼Deceased Search for other works by this author on: GSW Google Scholar Cesar F. Ferreira Filho Cesar F. Ferreira Filho 2Instituto de Geociência, Universidade de Brasília, Campus Universitário, Brasília-DF 70910-900, Brazil Search for other works by this author on: GSW Google Scholar Author and Article Information Robert D. Knight 1School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, United Kingdom Hazel M. Prichard 1School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, United Kingdom Cesar F. Ferreira Filho 2Instituto de Geociência, Universidade de Brasília, Campus Universitário, Brasília-DF 70910-900, Brazil †Corresponding author: e-mail, R.D.Knight@soton.ac.uk ☼Present address: Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, United Kingdom. ☼☼Deceased Publisher: Society of Economic Geologists Accepted: 28 Aug 2017 First Online: 15 Nov 2017 Online Issn: 1554-0774 Print Issn: 0361-0128 © 2017 Economic GeologyEconomic Geology Economic Geology (2017) 112 (8): 1889–1912. https://doi.org/10.5382/econgeo.2017.4533 Article history Accepted: 28 Aug 2017 First Online: 15 Nov 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Robert D. Knight, Hazel M. Prichard, Cesar F. Ferreira Filho; Evidence for As Contamination and the Partitioning of Pd into Pentlandite and Co + Platinum Group Elements into Pyrite in the Fazenda Mirabela Intrusion, Brazil. Economic Geology 2017;; 112 (8): 1889–1912. doi: https://doi.org/10.5382/econgeo.2017.4533 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 Fazenda Mirabela intrusion in Brazil hosts two zones of mineralization, the Santa Rita Ni-Cu sulfide ore zone occurring predominantly in an orthopyroxenite layer, and an underlying basal platinum group element (PGE) anomaly hosted in S-poor dunite. We show that in the northern and southern (marginal) zones of the intrusion, (Pt,Pd,Ni,Cu)(Fe,Bi,Te)2 minerals are accompanied by As-bearing platinum group minerals (PGM) sperrylite (PtAs2), and irarsite ([RhIrPt]AsS). These As-bearing PGM are extremely rare in the central zone of the intrusion, suggesting that As has been introduced into the margins of the intrusion from the country rocks via crustal assimilation or synmagmatic hydrothermal processes. Other PGM and precious metal minerals (PMM) including hessite (Ag2Te), Pd-Ag tellurides, electrum, and native Au are observed in the Santa Rita ore zone and do not show any lateral variation. In the semimetal- and S-poor dunite hosting the basal PGE anomaly, PGE are predominantly retained in the base metal sulfides and only minor PGE alloys are present. In this S-poor dunite Pt, Au and semimetals partitioned into a fractionated Cu-rich liquid, which formed during the crystallization of monosulfide solid solution (MSS) and was largely removed by high-temperature magmatic fluids. Palladium was not affected by this process and significant concentrations of Pd are identified in pentlandite, suggesting that Pd preferentially partitioned into MSS as it crystallized and subsequently pentlandite as it exsolved. Pyrite in the Santa Rita ore zone is Co rich and contains higher concentrations of IPGE (Os, Ir, Ru) and Rh than pyrrhotite and pentlandite, suggesting that pyrite has not replaced and inherited the PGE concentrations of these sulfides. The Pd-poor nature of pyrite also indicates that it has not replaced Pd-rich pentlandite. It is proposed that the IPGE and Co preferentially partitioned into pyrite as it exsolved from MSS. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.