Contrasting platinum-group mineral assemblages from chromitites of the Nizhny Tagil and Guli massifs (Russia): implications for composition, sources and age

K. N. Malitch*, A. A. Efimov, I. Yu Badanina

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

The Nizhny Tagil and Guli clinopyroxenite-dunite massifs, located in the Middle Urals and Maimecha-Kotui Province, respectively, are associated with world-class platinum-group elements (PGE) placer deposits. Both massifs contain small bodies of schlieren to massive chromitite associated with dunite. The predominance of Pt-Fe alloys at Nizhny Tagil is consistnt with the whole-rock "M"-shaped mantle-normalized PGE pattern of the chromitite. In contrast, the preponderance of laurite and Os-Ir alloys at Guli is consistent with a negatively sloped PGE pattern, the latter being characteristic of ophiolite-type podiform chromitites. The 'unradiogenic' 187Os/ 188Os values obtained for both platinum-group minerals (PGM) and chromitite are indicative of a common near-to-chondritic source for the PGE and implies that the osmium isotope budget of chromitite is largely controlled by laurite and Os-rich alloy. Average model 187Os/ 188Os ages calculated for the Nizhny Tagil and Guli massifs correspond to the late Riphean (e.g., 862 ± 48 Ma and 616 ± 8 Ma, respectively). The compositional and isotope-geochemical results provide new constraints on the temporal evolution of ultramafic rocks of the Uralian Platinum Belt and northern segment of the Siberian Platform.

Original languageEnglish
Pages (from-to)1514-1518
Number of pages5
JournalDoklady Earth Sciences
Volume441
Issue number1
DOIs
Publication statusPublished - Nov 2011
Externally publishedYes

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