The origin of Neoarchean granitoid diversity in the Yinshan Block and its implications for the crustal evolution of the North China Craton

Neoarchean TTG and K-rich granitoids in the Yinshan Block provide a key to understanding the crustal evolution of the North China Craton (NCC), such as the change of continental crust composition, the micro-continent collision and the cratonization. Zircon U-Pb dating suggests that these Neoarchean TTG and K-rich granite rocks were emplaced at 2.7-2.5 Ga and similar to 2.5 Ga, respectively. The TTG rocks have low Cr, Co, and Ni contents and Mg-# values, indicative of a crustal source. The similar to 2.7 Ga Kuluedianlisu granodiorites have positive epsilon(Hf)(t) values ranging from +6.6 to +9.3, with crustal model ages (TDMC) of 2.59-2.75 Ga, indicating that they were formed by partial melting of juvenile lower crust. The Hejiao and Dajitu TTG rocks show lower positive epsilon(Hf)(t) values (+3.4 to +5.6) and older crustal model ages (T-DM (c) = 2.53-2.83 Ga) than the Kuluedianlisu granodiorites, demonstrating an origin of partial melts from the pre-existing lower crust. The Rentaihe K-rich granites show higher Sr/Y and (La/Yb)(N) ratios which similar to the high pressure sodium TTG rocks. They have low epsilon(Hf)(t) values varying from -1.7 to +4.9, with crustal model ages (TDMC) from 2.7 to 3.1 Ga. Therefore, it is reasonable to suggest that the Rentaihe K-rich granites were produced by remelting of preexisting TTG rocks. According to the complied Hf isotopic compositions, the crustal model age peaks at 2.6 - 2.7 Ga and 2.7 - 2.8 Ga, indicating a crucial period for crustal growth in the Western Block. In the Neoarchean, the K2O/Na2O, the A/CNK ratios, and delta O-18 values increased from similar to 3.1 Ga to similar to 2.5 Ga, indicating a rise of crustal maturity. The crustal thickness simulations show that the crust of the NCC thickened continuously from similar to 3.1 Ga to 2.5 Ga. Thus, we conclude that the increasing of crust thickness is induced by the amalgamation of micro-continents through collision and the more buried supracrustal material into deep crust. Subsequent partial melting of the deep crust generated magmas with high delta O-18 values and thus resulted in the formation of more mature continental crust.