Definitions and images to illustrate geological terms, links to images and website articles

greenstone belts

greenschist facies - chlorite hand-specimenGreenstone belts are zones named for the green hue imparted by chlorite (left) minerals within the rocks, which are variably metamorphosed (greenschist) mafic to ultramafic volcanic sequences associated with sedimentary rocks. Greenstone belts are found between granite and gneiss bodies in Archaean and Proterozoic cratons.
foliated greenschist
Greenstone belts are interpreted as having formed at ancient oceanic spreading centers and island arc terranes.

greenstone-hosted quartz-carbonate vein depositsGQCV

Shield greenstones are located in:
● Slave craton of Canada (Archaean and Proterozoic)
● Pilbara craton of Australia (Archaean)
● Barberton greenstone belt in Kapvaal craton of southeastern Africa (Archaean)
● western Africa (Archaean and Proterozoic)
● Madagascar (Archaean and Proterozoic)
● Isua greenstone belt of southwestern Greenland (Archaean)
● shield area in Brazil (Archaean)
Baltic craton of Scandinavia and the Kola Peninsula (Archaean and Proterozoic).

[links: images: hand-specimens: greenschists; 3.5 Ga komatiite from Lower Onverwacht Group of Barberton Greenstone Belt; formations: greenschists; Storø shear zone; geological maps: world distribution of world class greenstone-hosted quartz-carbonate vein deposits; Canadian greenstone-hosted quartz-carbonate vein districts; northeast-trending "greenstone" belts of ancient gneiss alternating with belts of metamorphosed volcanic and sedimentary rocks in Minnesota and Canada, Superior Province greenstone belts; x-c, and diagramatic model of northeast-trending belts most likely result from structural deformation of the crust following the formation of the volcanic and sedimentary rocks; diagrams: greenstone belts; model for deposition of volcanic and sedimentary rocks; setting of greenstone -hosted quartz-carbonate vein deposit]

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