Cheng, Yanbo, Mao, Jingwen, Xie, Guiqing, Chen, Maohong, Zhao, Caisheng, Yang, Zongxi, Zhao, Haijie, and Li, Xiangqian (2008) Petrogenesis of the Laochang-Kafang granite in the Gejiu area, Yunnan Province: constraints from geochemistry and zircon U-Pb dating. Acta Geologica Sinica, 82 (11). pp. 1478-1493.

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Abstract

A great deal of intrusive rocks closely related to metallogeny developed in the Gejiu area, Yunnan rovince. This paper aimed at the blind granites stocks in the Laochang-Kafang area, which intruded into Triassic limetone and carbonate sequence of the Gejiu Formation. The lithology of the granite is mainly medium to fine grained biotitic granitic rock, which is closely related to metallogency in the Gejiu area. The research shows that values of the ACNK are mostly over 1. 0 and the contents of U and Th are very high, suggesting that the Laoka granite belongs to shoshonitic and HHP granite. This kind of S-type granite had experienced high differentiation. The diagram of Rb/Sr vs. Rb/Ba and CaO/Na20 vs. A1203/ Ti02 all indicate the Laoka granite originated from the magma formed by argillite rocks. Zircon LA-ICP-MS dating result shows that the Laochang-Kafang rock complex empaced at 85 ± 0. 85Ma and spatial distribution are obviously different from the late granite formed in Yanshanian in the Cathaysia block. Regional geology and granite geochemistry disply hint that the Gejiu area was in an extensional structural setting during the late Yanshanian.

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