Archean Greenstone Belts and Granitic Gneisses of North America
The Precambrian shields of all continents contain belts of folded metavolcanic and metasedimentary rocks surrounded by granitic gneisses. These so-called greenstone belts are the remnants of large volcano-sedimentary complexes of Archean and Proterozoic age. The volcanic rocks range in composition from komatiites and low-K tholeiites to dacites and rhyolites and consist of lava flows, sills, and stratified tuffs. The sedimentary rocks are typically composed of greywacke, quartzite, argillites, and cherty iron formations with uncommon carbonate units (de Wit and Ashwal 1997; Goodwin 1996).
KeywordsCrystallization Convection Recrystallization Olivine Rutile
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