Origin of primary PGM assemblage in chromitite from a mantle tectonite at Harold's Grave (Shetland Ophiolite Complex, Scotland)

Inna Yu Badanina, Kreshimir N. Malitch, Richard A. Lord, Thomas C. Meisel

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

In this paper we present textural and mineral chemistry data for a PGM inclusion assemblage and whole-rock platinum-group element (PGE) concentrations of chromitite from Harold's Grave, which occurrs in a dunite pod in a mantle tectonite at Unst in the Shetland Ophiolite Complex (SOC), Scotland. The study utilized a number of analytical techniques, including acid digestion and isotope dilution (ID) ICP-MS, hydroseparation and electron microprobe analysis. The chromitite contains a pronounced enrichment of refractory PGE (IPGE: Os, Ir and Ru) over less refractory PGE (PPGE: Rh, Pt and Pd), typical of mantle hosted 'ophiolitic' chromitites. A 'primary' magmatic PGM assemblage is represented by euhedrally shaped (up to 60 μm in size) single and composite inclusions in chromite. Polyphase PGM grains are dominated by laurite and osmian iridium, with subordinate laurite + osmian iridium + iridian osmium and rare laurite + Ir-Rh alloy + Rh-rich sulphide (possibly prassoite). The compositional variability of associated laurite and Os-rich alloys at Harold's Grave fit the predicted compositions of experiment W-1200-0.37 of Andrews and Brenan (Can Mineral 40: 1705-1716, 2002) providing unequivocal information on conditions of their genesis, with the upper thermal stability of laurite in equilibrium with Os-rich alloys estimated at 1200-1250 °C and f(S2) of 10-0.39-10-0.07.

Original languageEnglish
Pages (from-to)963-970
Number of pages8
JournalMineralogy and Petrology
Volume107
Issue number6
DOIs
Publication statusPublished - Dec 2013
Externally publishedYes

Fingerprint Dive into the research topics of 'Origin of primary PGM assemblage in chromitite from a mantle tectonite at Harold's Grave (Shetland Ophiolite Complex, Scotland)'. Together they form a unique fingerprint.

Cite this