The Changshagou gold deposit, Eastern Tianshan, NW China: orogenic gold mineralization overprinting a porphyry gold occurrence

Posted on 27.09.2021 - 12:54
The temporal–spatial relationships of porphyry and orogenic gold mineralization in the Eastern Tianshan Orogenic Belt are ambiguous. The newly discovered Changshagou deposit in this belt contains both porphyry and orogenic gold mineralization, which are characterized by polymetallic–sulfide veinlets and quartz–pyrite veins, respectively. Fluid inclusions in the porphyry mineralization episode were trapped at 290–340°C with salinities of 3.0–8.0 wt% NaClequiv. The homogenization temperatures and salinities in the orogenic mineralization episode range from 240 to 300°C and 1.0–5.0 wt% NaClequiv. Coexisting V-type and L-type fluid inclusions with similar homogenization temperatures are indicative of fluid immiscibility. The δ18Ow and δDw values range from 7.6 to 9.1‰ and –70.9 to –84.0‰ in the porphyry mineralization episode, and from 6.4 to 7.1‰ and –65.7 to –72.1‰ in the orogenic mineralization episode, overlapping magmatic and metamorphic ranges, respectively. The pyrite δ34S values range from 3.5 to 4.9‰, falling into the magmatic range. Pyrite in porphyry and orogenic mineralization episodes yield Re–Os isotopes ages of 269.1 ±2.9 Ma and 257.4 ±2.4 Ma. The porphyry and orogenic gold mineralizations are genetically associated with the quartz syenite porphyry and Kanggur strike-slip shear activity, respectively.

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Liu, Yihao; Zhao, Yun; Xue, Chunji; Yu, Liang; Chu, Haixia; Zhao, Xiaobo (2021): The Changshagou gold deposit, Eastern Tianshan, NW China: orogenic gold mineralization overprinting a porphyry gold occurrence. Geological Society of London. Collection. https://doi.org/10.6084/m9.figshare.c.5635584.v1
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