ZUO Chang-hu, MIAO Bo-hu, ZHAO Zeng-xia, XU Zhao-wen, LU Jian-jun, LU Rui, CHEN Jin-quan

(1. State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China; 2. Hunan Shuikoushan Nonferrous Metals Group Co., Ltd., Hengyang 421513, China)

Abstract: Based a detailed field geological investigation, this paper reports on the sulfur and lead isotopic compositions of the ores. It also presents a comprehensive study of the hydrogen and oxygen isotopic compositions of ore-bearing quartz, carbon and oxygen isotopic compositions of ore-bearing calcite, to explore the source of ore-forming material and the ore-forming mechanism of the Kangjiawan lead-zinc deposit. The δ³⁴S_VCDT values of the ores range from -2.71‰ to 0.70‰, with an average value of -1.42‰. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios of the ores range from 18.227 to 18.573, 15.661 to 15.695, and 38.673 to 38.964, respectively. The δD_SMOW and δ¹⁸O_H2O values of the ore-bearing quartz range from -68.00‰ to -60.00‰ (with an average of -64.00‰) and -7.25‰ to -5.17‰ (with an average of -6.23‰), respectively. The δC_VPDB and δ¹⁸O_SMOW values of ore-bearing calcites range from -1.80‰ to -3.70‰ and 12.20‰ to 16.00‰, respectively. The sulfur isotopic composition of ores show that the sulfur in the ore originates mainly from deep magma contaminated by crustal materials. Lead isotopic compositions of the ores indicate that the lead present in the ore are mainly derived from the crust with possibly some mantle material involved. Hydrogen and oxygen isotopic compositions of the ore-bearing quartz demonstrate that the ore-forming fluid is mainly of magmatic hydrothermal origin from the early mineralization stage and with meteoric water mixed in at a later stage of mineralization.  The C-O isotopic values of ore-bearing calcite and C-O isotopic values of the limestone occurring in the strata are largely similar, indicating that C-O isotopes present in the ore came from limestone formed in the Late Paleozoic era. Therefore, we conclude that the ore-forming fluid came mainly from a magmatic hydrothermal source and with meteoric water added in the late mineralization stage. The metallogenic material mainly came from the crust and may be contaminated with mantle material. The mixing effect is the main ore-forming mechanism of the Kangjianwan lead-zinc deposit.

Key word: isotopic geochemistry; material source; formation mechanism; lead-zinc deposit; Changning County, Hunan Province

ACTA MINERALOGICA SINICA Vol. 34, No. 3, 2014, Page 351-369