Scanning electron microscopy and Raman spectroscopy as combined methods for studying zoning in minerals: The case of spinels from Archean komatiites
| Autor: | S. Yu. Chazhengina, Zoya Rybnikova, Sergey Svetov |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
010504 meteorology & atmospheric sciences
Metamorphic rock Archean Spinel Geochemistry Mineralogy Geology engineering.material 010502 geochemistry & geophysics 01 natural sciences Mantle (geology) law.invention symbols.namesake Geochemistry and Petrology law engineering symbols Economic Geology Fugacity Chromite Crystallization Raman spectroscopy 0105 earth and related environmental sciences |
| Zdroj: | Geology of Ore Deposits. 58:628-635 |
| ISSN: | 1555-6476 1075-7015 |
| DOI: | 10.1134/s1075701516080067 |
| Popis: | Several types of both magmatic and metamorphic spinels have been found in Archean komatiites of the Sovdozero and Kostomuksha greenstone belts in the eastern part of the Fennoscandian Shield. Scanning electron microscopy and Raman spectroscopy revealed relics of cores of primary magmatic chrome-spinels with high Cr and Al contents. In the Sovdozero structure, the relics are better retained than those in the Kostomuksha structure, which is caused by a different degree of metamorphic transformation. The comparable 100 · Cr/(Al + Cr) values of spinel cores from Sovdozero and Kostomuksha reflect similar conditions of partitional melting in the mantle. These data agree with the fact that both komatiite complexes belong to the Al-undepleted petrogenic type. Wide variations in the Cr and Al contents in primary chrome-spinel cores together with a constant Mg/(Fe2+ + Mg) ratio correspond to low oxygen fugacity during magma crystallization. In general, the composition of these primary chrome-spinels is similar to that of accessory phases in peridotites from suprasubduction zones and agrees with hypothesis of komatiite complex formation in back-arc basins. |
| Databáze: | OpenAIRE |
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