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Origin of placer laurite from Borneo; Se and As contents, and S isotopic compositions

K. H. Hattori, L. J. Cabri, B. Johanson and M. L. Zientek
Origin of placer laurite from Borneo; Se and As contents, and S isotopic compositions (in Special issue in honour of Dr. A. J. Criddle, S. A. T. Redfern (editor), Adrian J. Brearley (editor), A. G. Christy (editor), M. T. Dove (editor), D. J. Prior (editor), P. W. Scott (editor) and J. Touret (editor))
Mineralogical Magazine (April 2004) 68 (2): 353-368

Abstract

We examined grains of the platinum-group mineral, laurite (RuS (sub 2) ), from the type locality, Pontyn River, Tanah Laut, Borneo, and from the Tambanio River, southeast Borneo. The grains show a variety of morphologies, including euhedral grains with conchoidal fractures and pits, and spherical grains with no crystal faces, probably because of abrasion. Inclusions are rare, but one grain contains Ca-Al amphibole inclusions, and another contains an inclusion of chalcopyrite + bornite + pentlandite + heazlewoodite (Ni (sub 3) S (sub 2) ) that is considered to have formed by a two-stage process of exsolution and crystallization from a once homogeneous Fe-Cu-Ni sulphide melt. All grains examined are solid solutions of Ru and Os with Ir (2.71-11.76 wt.%) and Pd (0.31-0.66 wt.%). Their compositions are similar to laurite from ophiolitic rocks. The compositions show broad negative correlations between Os and Ir, between As and Ir, and between As (0.4-0.74 wt.%) and Se (140 to 240 ppm). Laurite with higher Os contains more Se and less Ir and As. The negative correlations between Se and As may be attributed to their occupancy of the S site, but the compositional variations of Os, Ir and As probably reflect the compositional variation of rocks where the crystals grew. Ratios of S/Se in laurite show a narrow spread from 1380 to 2300, which are similar to ratios for sulphides from the refractory sub-arc mantle. Sulphur isotopic compositions of laurite are independent of chemical compositions and morphologies and are similar to the chondritic value of 0 per mil. The data suggest that S in laurite has not undergone redox changes and originated from the refractory mantle. The data support the formation of laurite in the residual mantle or in a magma generated from such a refractory mantle, followed by erosion after the obduction of the host ultramafic rocks.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 68
Serial Issue: 2
Title: Origin of placer laurite from Borneo; Se and As contents, and S isotopic compositions
Title: Special issue in honour of Dr. A. J. Criddle
Author(s): Hattori, K. H.Cabri, L. J.Johanson, B.Zientek, M. L.
Author(s): Redfern, S. A. T.editor
Author(s): Brearley, Adrian J.editor
Author(s): Christy, A. G.editor
Author(s): Dove, M. T.editor
Author(s): Prior, D. J.editor
Author(s): Scott, P. W.editor
Author(s): Touret, J.editor
Affiliation: University of Ottawa, Ottawa, Canada
Affiliation: University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom
Pages: 353-368
Published: 200404
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 58
Accession Number: 2004-067433
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables, sketch maps
S00°34'50" - S00°34'50", E115°00'00" - E115°00'00"
Secondary Affiliation: University of New Mexico, USA, United StatesAustralian National University, AUS, AustraliaUniversity of Liverpool, GBR, United KingdomCamborne School of Mines, GBR, United KingdomFree University, NLD, NetherlandsGeological Survey of Finland, FIN, FinlandU. S. Geological Survey, USA, United States
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200420
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