The Huangjiawan Ni-Mo polymetallic ore deposit occurred in the basal black shale sequence of the Cambrian strata in the Zunyi area, Guizhou Province, China. In order to investigate the sources of ore-forming fluids and the mechanism of mineralization, fluid inclusion, REE, carbon and oxygen isotopes studies have been performed on calcite of the main mineralization stage from the studied area. Three types of fluids inclusions, i. e., liquid-rich two-phase fluid inclusions, gas-rich two-phase inclusions, and pure liquid aqueous inclusions, have been recognized in this study. In addition, different types of inclusions with remarkably varied vapor-liquid ratios exist together, implying that boiling might have occurred during mineralization. Meanwhile, microthermometric measurement of the fluid inclusions show that the ice melting temperatures range from -11. 6 degrees C to -5. 5 degrees C and the corresponding salinities vary from 8. 55% to 15. 57% NaCleqv. The homogenization temperatures range from 109. 0 degrees C to 181. 1 degrees C, with densities from 0. 97g . cm(-3) to 1. 44g . cm(-3). Rare earth element (REE) analyses show that the calcites are characterized by high Sigma REE content (39.9 x 10(-6) similar to 275 x 10(-6)), enrichment in LREE, ((La/Yb)(N) = 29.6 similar to 63. 3), right-inclining chondrite-normalized patterns, and positive Eu anomalies (Eu/Eu* = 2. 14 similar to 14. 8), which are coincident with those of sea-floor exhalative-hydrothermal deposits. Carbon and oxygen isotopic results of the calcites are characterized by delta(18)C(V)-(PDR) = -6. 3 parts per thousand similar to -5. 7 parts per thousand, delta(18)O(V-SMOW) = 15. 6 parts per thousand similar to 16. 0 parts per thousand, and the calculated oxygen isotopic compositions (delta(18) O(V-SMOW-H2O)) of the hydrothermal fluids are from -0. 97 parts per thousand to + 5. 16 parts per thousand, which suggested that the carbon in ore-forming fluids was mainly derived from seawater-derived hydrothermal fluids. Based on the above discussion, we conclude that the ore-forming fluids of Huangjiawan Mo-Ni-polymetallic deposits are mainly composed of sea water and formation water (basin hot brine), and the seafloor hydrothermal fluid evolved from sea water participated ore-forming fluid process.

Publication name	ACTA PETROLOGICA SINICA　Volume: 27 　Issue: 12 　Pages: 3763-3776 　Published: DEC 2011
Author(s)	Feng CaiXia; Chi GuoXiang; Hu RuiZhong; Liu Shen; Liu JiaJun; Luo TaiYi; Qi YouQiang
Corresponding author	FENG Caixia  fengcaixia@vip.gyig.ac.cn  Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550002, Peoples R China

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