Archean Greenstone Granite Belts

Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within archaean and proterozoic cratons between granite and gneiss bodies.

Archean greenstone granite belts.

The name comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks. 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 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. These so called greenstone belts are the remnants of large volcano sedimentary complexes of archean and proterozoic age.

They are characterized by abundant volcanic rocks that include pillowed subaqueous basalt flows and subaerial and subaqueous volcaniclastic rocks. 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. Archean dome and keel structure granite greenstone belts metamorphism p t t paths vertical and horizontal tectonics 1. 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.

Other articles where greenstone granite belt is discussed. Discovered in 1909 the abitibi has generated over 160 million ounces of gold. 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. Full text access chapter 10 origin and evolution of archean granite greenstone terranes pages 313 381 download pdf.

Magnesian komatiites are for the most part absent however. Other rocks that occur in granulite gneiss belts zones of. 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 granite belts such as those of the archean continued to form in the proterozoic albeit in greatly reduced amounts.