Formation of a giant Zn–Pb deposit from hot brines injecting into a shallow oil–gas reservoir in sandstones,Jinding, southwestern China |
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| Authors: | Guoxiang Chi Chunji Xue Xianda Sun Jianqing Lai Peng Luo Hao Song Sheng Li Rong Zeng |
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| Institution: | 1. Department of Geology, University of Regina, Regina, Saskatchewan, Canada;2. China University of Geosciences (Beijing), Beijing, China;3. Daqing Oilfield Exploration and Development Research Institute, Daqing, Heilongjiang, China;4. Central‐South University, Changsha, Hunan, China;5. Energy Division, Saskatchewan Research Council, Regina, Saskatchewan, Canada;6. Chengdu University of Technology, Chengdu, Sichuan, China;7. Chang'An University, Xi'An, Shaanxi, China |
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| Abstract: | The association between mineralisation and hydrocarbons in sedimentary basins is widely recognised, but the nature and significance of their relationships are not fully understood. This paper provides an example of metalliferous brines injecting into a palaeo‐oil–gas reservoir to form a world‐class Zn–Pb deposit (Jinding, China). Petrographic and microthermometric studies of oil inclusions and PVT simulations suggest that oil and gas were charged in a shallow (<1300 m) environment before mineralisation. This environment favoured bacterial sulphate reduction (BSR), which produced large amounts of H2S that accumulated in the gas cap. Forceful injection of hot brines penetrated the oil zone to reach the H2S‐rich gas cap and precipitated sulphide ores. Individual fluid injection events were short‐lived, and the reservoir was only partly and briefly heated to beyond the bacterial survival temperature. Episodic injection of metalliferous brines and sustained supply of H2S through BSR resulted in the formation of a large Zn–Pb deposit. |
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