The Early Precambrian Geology of Wutaishan

The Wutaishan (Wutai Mountain) area is situated in the central part of the North China Platform, where Precambrian strata are rather completely exposed and are distributed the China's standard stratigraphic units-the Wutai Group and the Hutuo Group. Characterized by its continuous outcrop and distinct limits, the area remains one of typical places for studying the Early Precambrian in China and has been undergoing geological researches over a century. The 1980's study shows that the parent rocks of the Wutai Group are polycyclic volcanic-sedimentary greenstone formation. It suffered multistage deformation, which was characterized by recumbent fold and over thrust structure, and polyphasic metamorphism of amphibolite to sub-greenschist facies. Large-scale emplacement of granitic rocks occurred also. Geological events of various formations and reworking took place alternately. In the beginning of the Hutuo Group deposition, the compositions in the atmosphere, biosphere and crust became rich in oxygen, a large amount of prokaryote multiplied, magnesium-rich carbonate rocks appeared in a great number, the mafic upper crust became sialic, and maturity got higher. The tectonic kinematic model is horizontal compression-shearing to lateral compression. All of these indicate a global crustal evolution and great change in the tectonic regimes.