Abstract
Data are presented on Fe-Ti oxide compositions and assemblages in Malene supracrustal rocks from the Godthåb District and surrounding territory, West Greenland. Amphibolite facies samples contain ilmenite ± rutile, in which the ilmenite has a low Fe2O3-content (
Highlights
The Fe-Ti oxides are common accessory phases in metamorphic rocks, with the occurrence of each mineral or assemblage of minerals being controlled by several factors including rock composition, oxygen fugacity, temperature and pressure
This paper describes the occurrence and chemistry of Fe-Ti oxides in the Archaean Malene supracrustal rocks of southern West Greenland, and reports the discovery of Nb-rich rutile in certain 'cordierite-anthophyllite' rocks, which raises intriguing questions concerning the origin of the sedimentary protolith for this rock type
Prograde regional metamorphism of the Malene supracrustals at c. 2800 Ma ranged from middle amphibolite to granulite grade, and was followed by retrogressive metamorphism ranging from amphibolite to greenschist grade
Summary
The Fe-Ti oxides (hematite, magnetite, ilmenite and rutile) are common accessory phases in metamorphic rocks, with the occurrence of each mineral or assemblage of minerals being controlled by several factors including rock composition, oxygen fugacity, temperature and pressure. The Malene supracrustal rocks were defincd by McGregor (1973) to includc various types af amphibolitc and mctascdiment in the vicinity af Godthåb which are intfuded by - 3000 Ma Ni.lk orthogneiss and are largely in tectonic contact with -- 37.50 Ma Amitsoq orthognciss This name has subsequently beco applied through out the Archaean gneiss complex af West Greenland to all supracrustal rocks with lithological characteristics and stratigraphic position similar to the ones originally described by McGregor (cf Bridgwater et (~l., 1976). This convention is adopted here, and Fe-Ti oxides from two associations of Malene supracruslal rocks are described: granulite-grade occurrences from Langø, and amphibolite-grade occurrences from the Godthåbsfjord-Ameralik region. A prograde amphibolite facies metamorphism was followed locally by retrogression to greenschist fades
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