Ye CAO^1,2, Shengrong LI¹, Meijuan YAO^1,2, Huafeng ZHANG¹, Shaoqing JIANG³ & Huapeng NIU^4
1State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing
100083, China
²Department of Earth Sciences, Laurentian University, Sudbury P3E2C6, Canada.
³Chinese Academy of Geological Sciences, Beijing 100037, China
⁴China University of Petroleum, Beijing 102249, China
Corresponding author: cykaiyang@yahoo.com.cn

ISOTOPE GEOCHEMISTRY OF THE SHIHU GOLD DEPOSIT, HEBEI PROVINCE, NORTH CHINA: IMPLICATION FOR THE SOURCE OF ORE FLUID AND MATERIALS

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The Shihu deposit, which is a well known quartz vein type gold deposit in the northern part of the Taihang orogen of the North China craton (NCC), is hosted by ductile-brittle faults within Archean metamorphic core complex of the Fuping Group. Lead, sulfur, carbon, oxygen, hydrogen and strontium isotope geochemistry is used to help understand the sources of the ore fluid and materials. Pb isotopic compositions from sulfides range from 16.002-16.958 for ²⁰⁶Pb/²⁰⁴Pb, 15.134-15.345 for ²⁰⁷Pb/²⁰⁴Pb, and 36.825-37.8194 for ²⁰⁸Pb/²⁰⁴Pb. The data straddle the lower crust and upper mantle growth curve. These values are similar to those of country rocks, and indicate that there are mixed sources for the Pb, with end members equating to mantle and crustal reservoirs. Most δ³⁴S values of the sulfides range from +1.5 to +2.5 ‰ and display a pronounced tower effect, and suggest that magmatic sulfur dominates in sulfides, mixed with minor, isotopically light sulfur. Sulfur isotope temperatures calculated by mineral pairs are between 160℃ and 315℃. Gangue calcite in three samples from the veins have similar isotope compositions, with δ¹³C values in the range of -5.93 to -6.92 ‰ with respect to PDB and δ¹⁸O values in the range of 8.81 to 12.36 ‰ with respect to SMOW. δD values of fluid inclusions in the seven samples of auriferous quartz have a narrow range of -101 to -91 ‰ and the δ¹⁸O_H2O values calculated from δ¹⁸O values of quartz range from 2.21 to 7.05 ‰. These data suggest that the ore fluid is likely a mixture of meteoric water and magmatic water. The initial ⁸⁷Sr/⁸⁶Sr values range from 0.714057 to 0.825903 for quartz, from 0.71345 to 0.723227 for pyrite, which are lower than that of the host rock ranging from 0.77569 to 1.06413. Those results suggest that the ore-forming elements were leached from the Precambrian basement that reacted with deep-source fluids.