Granitoid evolution in the Late Archean Wutai Complex, North China Craton

Two temporally discrete episodes of granite magmatism have been identified in the Wutai Complex of the North China Craton, based on SHRIMP U-Pb zircon dating of all major granitoid bodies in the area. The older period is latest Archean and ranges in age from 2560 to 2515 Ma, whereas the younger episode is Paleoproterozoic, with magmatism at 2170 and 2120 Ma. Archean magmatism can be further separated into two pulses based on geochemistry and the association of the younger plutons with extensive coeval volcanic activity in the Wutai Complex. The early phase of Archean activity is represented by the Lanzhishan, Ekou and portions of the Chechang-Betai granites, with ages ranging from 2560 to 2540 Ma. The Lanzhishan Granite is the only one at Wutaishan that contains inherited zircon, with a number of cores and individual grains giving ages in excess of 2700 Ma. These are relatively evolved granitoids, interpreted to be derived from older basement of the Eastern Block of the North China Craton. The Shifo, Guangmingshi, the main grey phase of the Wangjiahui granite and the major components of the Chechang-Betai granite have ages of ∼2540-2515 Ma and are coeval with felsic volcanism in the Wutai Complex which is a consequence of subduction and related arc magmatism. The Dawaliang granite and pink phase of the Wangjiahui granite are considerably younger with Paleoproterozoic ages of ∼2170 and ∼2120 Ma, respectively. These are also evolved granitoids, most likely derived by partial melting of the older basement, although we have found no evidence of inheritance. The petrogenesis of the granitoids reflects the Precambrian amalgamation history of the North China Craton, indicating derivation along the western edge of the Eastern block during development and amalgamation of the Wutai arc, and prior to collision with the Western block of the craton 1.8 Ga ago.