Archean Greenstone Granite Belts

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Archean greenstone granite belts.

Introduction it is thought that mantle potential temperatures were higher in the archean although how much higher than the present day and whether the mantle was warming during the eoarchean mesoarchean to a high. Discovered in 1909 the abitibi has generated over 160 million ounces of gold. The abitibi belt canada. Greenstone belts occur sandwiched between regions dominated by granitoids and gneiss greenstones are generally of low to moderate metamorphic grade.

Greenstone belts are generally elongate archean to proterozoic terrains comprising intrusive and extrusive mafic to ultramafic igneous rocks felsic volcanics and inter flow or cover sedimentary rocks. 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. They are characterized by abundant volcanic rocks that include pillowed subaqueous basalt flows and subaerial and subaqueous volcaniclastic rocks. The typical green minerals are chlorite actinolite and other green.

Precambrian precambrian greenstones and granites. Archean granite greenstone belts are important components of ancient cratons and are composed of elongate slivers of volcano sedimentary sequences and tonalite trondhjemite granodiorite ttg suites ranging in age from eoarchean 3 6 ga to end of neoarchean 2 5 ga anhaeusser 2014 furnes et al 2014 manikyamba et al 2015. Magnesian komatiites are for the most part absent however. Other rocks that occur in granulite gneiss belts zones of.

Archean dome and keel structure granite greenstone belts metamorphism p t t paths vertical and horizontal tectonics 1. Greenstone granite belts such as those of the archean continued to form in the proterozoic albeit in greatly reduced amounts. Archean rocks that occur in greenstone granite belts zones rich in volcanic rocks that are primitive types of oceanic crust and island arcs formed on or near the surface of earth and thus preserve evidence of the early atmosphere oceans and life forms. The name comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks.

The archean superior province of canada contains the abitibi greenstone belt which contains some of the world s largest gold and copper zinc deposits with significant amounts of nickel copper platinum group element pge mineralization too.