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Ruthenium variation in chromite from komatiites and komatiitic basalts; a potential mineralogical indicator for nickel sulfide mineralization

Marek Locmelis, Marco L. Fiorentini, Stephen J. Barnes and Norman J. Pearson
Ruthenium variation in chromite from komatiites and komatiitic basalts; a potential mineralogical indicator for nickel sulfide mineralization
Economic Geology and the Bulletin of the Society of Economic Geologists (March 2013) 108 (2): 355-364

Abstract

More than 390 chromite grains from komatiites and komatiitic basalts from the Yilgarn craton of Western Australia and the Finnish part of the Fennoscandian Shield were analyzed using in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to identify ruthenium (Ru) signatures in chromite associated with nickel sulfide-bearing rocks. Results indicate a potential method to discriminate mineralized and barren komatiite and komatiitic basalt units based on Ru concentrations in chromite and indicate potential for chromite to be used as a resistate indicator mineral in exploration for komatiite-associated nickel sulfide deposits. Chromites from barren komatiites and komatiitic basalts display Ru concentrations mostly between approximately 150 and 600 ppb. Chromites from mineralized units have distinctly lower Ru contents (<150 ppb). These results can be interpreted in terms of the much higher partition coefficient for Ru into sulfide liquid compared to that of Ru into chromite, resulting in much lower Ru concentrations in chromite where both chromite and sulfide liquid are present and competing for Ru. As a result, the Ru content of chromite can be used to determine if a komatiite melt equilibrated with a sulfide liquid during crystallization, and therefore, if a system and/or sequence is prospective for nickel sulfide mineralization. The strength of this method compared to previous whole-rock exploration techniques derives from combining (1) the geochemical properties of a chalcophile element that records an ore-forming process while being strongly immobile during postmagmatic processes, with (2) the in situ analysis of a mineral that is generally preserved even in highly altered and mildly weathered komatiites and that is a common constituent of detrital heavy mineral samples. Chromite Ru content has potential as a prospectivity indicator, applicable to a wide range of media including bedrock, laterites, and detrital resistates heavy mineral samples.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 108
Serial Issue: 2
Title: Ruthenium variation in chromite from komatiites and komatiitic basalts; a potential mineralogical indicator for nickel sulfide mineralization
Affiliation: University of Western Australia, School of Earth and Geographical Sciences, Crawley, West. Aust., Australia
Pages: 355-364
Published: 201303
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 64
Accession Number: 2013-030579
Categories: Economic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch map
S32°00'00" - S26°00'00", E120°00'00" - E122°00'00"
Secondary Affiliation: Macquarie University, AUS, AustraliaCSIRO, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Society of Economic Geologists. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201319
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