Compounds of Ru–Se–S, alloys of Os–Ir, framboidal Ru nanophases, and laurite–clinochlore intergrowths in the Pados-Tundra complex, Kola Peninsula, Russia
| Autor: | Nadezhda D. Tolstykh, Vladimir N. Korolyuk, Andrey A. Nikiforov, Gennadiy I. Shvedov, Andrei Y. Barkov |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
010504 meteorology & atmospheric sciences
Laurite Geochemistry chemistry.chemical_element 010502 geochemistry & geophysics 01 natural sciences Ruthenium chemistry.chemical_compound chemistry Geochemistry and Petrology Ultramafic rock Telluride Selenide Chromitite Osmium Iridium 0105 earth and related environmental sciences |
| Zdroj: | European Journal of Mineralogy. 29:613-621 |
| ISSN: | 0935-1221 |
| DOI: | 10.1127/ejm/2017/0029-2666 |
| Popis: | This is the first report of occurrences of platinum-group minerals (PGM) and unnamed phases of platinum-group elements (PGE) from the Pados-Tundra ultramafic complex of Paleoproterozoic age, Kola Peninsula. The PGM occur as individual inclusions or intergrowths (≤1–10 μm) hosted by cores of zoned grains of chromite–magnesiochromite (Chr) in chromitite of the Dunite block in the eastern portion of the complex. Osmium-poor laurite is abundant, commonly as intimate intergrowths with clinochlore (>80% laurite grains), followed by Os- and Ir-dominant alloys (i.e., the minerals osmium and iridium, respectively); unnamed phases of ruthenium selenide [RuSe 2 ] and rhodium telluride [RhTe] are rare. Selenium-rich laurite, not reported previously, likely belongs to an inferred RuS 2 –RuSe 2 series. Native Ru forms micro-(nano)-spherules in framboid-type aggregates, in association with relict laurite, which are surrounded by a skeletal grain of clinochlore; the host is Chr. The framboidal texture of nanophases of ruthenium, hitherto unreported in PGE alloys, likely formed as a result of deposition from a H 2 -bearing fluid, involving a reaction of desulfurisation and reduction of laurite. A highly S-deficient environment is indicated; a low sulfur fugacity, presumably below the Os–OsS 2 buffer, caused the observed coexistence of a low-Os variety of laurite with Os-dominant alloy. An ultimate loss of total S is implied to have decreased the S/Se ratio, which resulted in the precipitation of Ru-dominant sulfoselenide–selenide phases, likely from an oxidizing fluid at a late stage of mineralization. We also infer that the laurite–clinochlore intergrowths crystallized relatively late, from microvolumes of an H 2 O-bearing fluid of contrasting composition, enriched in Ru, S, and lithophile elements. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|