ARCHEAN GREENSTONE BELTS IN CHINA

Archean greenstone belts of China are mainly distributed in the North China platform Their exposed areas are small,generally only a few dozens to a few hundreds of square kilometers. The stratigraphic thickness of the greenstone belts is 2-7km The sequence of the belts is as follows: mafic volcanic rocks at the base,andesitic-felsic volcanic rocks and Pyroclastic rocks in the middle and clastic-pelitic rocks and banded iron-formations （BIF） in the upper. The rocks of the belts are of relatively high metamorphic grade,generally of upper greenstone-lower amphiibolite facies. They underwent polyphase structural deformation, giving rise to well developed recumbent folds, ductile shear zones and nappe structures. The associated granitic rocks in the belts are mainly represented by the trondjemite-tonalite granodiorite series of the TTG series According to available isotopic age data,China’s granite-greenstone terranes originated in the late Archeau ranging approximately between 2900 and 2500 Ma. The useful minerals occurring in the greenstone belts are mainly gold and iron. From their protolith formations and geochemical features, it may be inferred that they were formed in continental rift belts or continental-margin mobile belts.