Neoarchean magmatism, metamorphism in the Yinshan Block: Implication for the genesis of BIF and crustal evolution

The Yinshan Block is a coherent Neoarchean basement of the Western Block in the North China Craton. The representative is at Guyang area, which composed of granite-greenstone rocks at western and high-grade metamorphic complexes at eastern. The result of statistics of zircon U-Pb age statistics show either the granite-greenstone or the protoliths of the high-grade metamorphic complexes formed at the late Neoarchean (2562 similar to 2510Ma), and experienced two stage metamorphic event at similar to 2500Ma, similar to 2480Ma respectively. The P-T path of the similar to 2.50Ga metamorphism is an anti-clockwise type, which is related with the mid-oceanic ridge subduction. There are a variety of special rocks which indicating the certain tectonic background in this area, such as: komatiite, komatiitic basalt, Nb-rich basalt, high-Mg andesite, TTGs and Sanukitoid. In conclusion, the Yinshan block is controlled by the plate tectonics, and experienced the mid-oceanic ridge subducted and collision orogeny successively. The BIFs in this are related with the mid-oceanic ridge subduction. The Si and Fe of BIFs are derived from the basalt at the bottom of greenstone belt and the komatiite, respectively.