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Origin and geological implication of the inherited zircon from felsic dykes, Youjiang basin, China TEXT SIZE: A A A
The relationship between the Carlin-type gold deposits with magmatism is still debatable. Numerous Carlin-type gold deposits occur in the Youjiang basin, Southwest China. Due to the limited exposures of magmatic rocks within this region, it is unknown if there is genetic connections between magmatism and gold mineralization. The inherited zircons found in igneous rocks could give insight into the older or hidden magmatic events which are poorly exposed at the surface. The Bama, Liaotun, and Xiabaha quartz porphyry dykes host plenty of inherited zircons, among which the Liaotun and Xiabaha dykes are spatially present within the Liaotun and Mingshan gold deposits, respectively. Five main age clusters at 130 similar to 140Ma, ca. 242Ma, 400 similar to 450Ma, 700 similar to 1000Ma, and 1700 similar to 1800Ma were recognized in the inherited zircons by both LA-ICP-MS and SIMS U-Pb dating. The two younger groups of inherited zircons from the Liaotun and Xiabaha dykes give concordant U-Pb ages of 136.3 +/- 3. 9Ma (2 sigma), 242.3 +/- 1. 7Ma (2 sigma) and 128.2 +/- 2. 3Ma (2 sigma), 243. 1 +/- 3. 6Ma (2 sigma), respectively. All the three dykes intruded the strata including the Middle Triassic Baifeng Formation ( Member 1 and 2; 247 similar to 244Ma) and older sequences. Therefore, those zircons with ages older than the Middle Triassic should be probably captured from the host sedimentary rocks. Conversely, those at 130 140Ma might be derived from the hidden magmatic intrusions. For the zircons at ca. 242Ma, though coeval to the first and second members of the Baifeng Formation, they usually occur as anhedral fractions, indicating they might be inherited from the detrital zircons hosted by the sandstone and siltstone of the Baifeng Formation. Combined with the regional magmatism and geological setting, we propose that the ages of Triassic zircon forming events could represent the magmatic pulse related to the closure of the Paleo-Tethys Ocean. The zircon ages of 130 140Ma and ca. 242Ma are generally consistent with the timing of gold mineralization in the Youjiang basin. Thus, we prefer that there might be genetic links between magmatism and the formation of Carlin-type gold deposits in the Youjiang basin.

Publication name

 ACTA PETROLOGICA SINICA, 32 (11):3269-3280; 2016

Author(s)

 Zhu JingJing; Zhong Hong; Xie GuiQing; Zhao ChengHai; Xu LeiLuo; Lu Gang

Corresponding author 

 ZHU Jingjing 
 zhujingjing@vip.gyig.ac.cn
 Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposits Geochem, Guiyang 550081, Peoples R China.

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