Exceptionally Cr-rich basalts in the komatiitic volcanic association of the Archaean Kuhmo greenstone belt, eastern Finland

Autor:	Tapio Halkoaho, H. Papunen, J. Välimaa, J. Liimatainen
Rok vydání:	2000
Předmět:	Basalt geography Olivine geography.geographical_feature_category Fractional crystallization (geology) Archean Geochemistry Greenstone belt engineering.material Geophysics Volcano Geochemistry and Petrology engineering Fugacity Chromite Geology
Zdroj:	Mineralogy and Petrology. 70:105-120
ISSN:	1438-1168 0930-0708
DOI:	10.1007/s007100070016
Popis:	Exceptionally Cr-rich metabasalts related to a komatiite-dominant volcanic sequence occur in the Archaean Kuhmo greenstone belt, eastern Finland. These basalts contain more chromium (1300–4500 ppm) than any other terrestrial basalts analysed so far, and also have high nickel concentrations (200–1700 ppm). In stratigraphy, these Cr-rich basalts occur above the komatiite and komatiitic basalt units forming the uppermost units of the komatiite sequence. Extremely reducing conditions during magma generation or fractional crystallization are suggested as a reason for these exceptional compositions. Low oxygen fugacity has prevented crystallization of chromite and decreased the olivine/liquid partition coefficient for nickel in olivine fractionation, thus causing the enrichment of Cr and Ni in the residual melt.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::96852a32b6e81fbbb266b7ed74215480 https://doi.org/10.1007/s007100070016 Zobrazit plný text záznamu Full text from SpringerLink