• journal_title：Economic Geology
• Contributor：Qihai Shu ; Yong Lai ; Yi Sun ; Chao Wang ; Shu Meng
• Publisher：Society of Economic Geologists
• Date：2013-06-01
• Format：text/html
• Language：en
• Identifier：10.2113/econgeo.108.4.835
• journal_abbrev：Economic Geology
• issn：0361-0128
• volume：108
• issue：4
• firstpage：835
• section：Papers

The Baiyinnuo’er zinc-lead deposit (32.74 Mt at 5.44% Zn, 2.02% Pb, and 31.36 g/t Ag), located in the south segment of the Great Xing’an Range, is the largest Zn-Pb deposit in northern China. Skarn and orebodies mainly occur between the different units of the Huanggangliang Formation, or within the contact zone between the intrusions and Permian marble.

Several phases of igneous rocks exposed within the mining areas, and among them the Yanshanian plutonic rocks, which intruded into limestone of the early Permian Huanggangliang Formation, are interpreted to be the source of ore, since their Pb isotope compositions (²⁰⁶Pb/²⁰⁴Pb = 18.25–18.35, ²⁰⁷Pb/²⁰⁴Pb = 15.50–15.56, and ²⁰⁸Pb/²⁰⁴Pb = 38.14–38.32) are highly consistent with the sulfides, including sphalerite, galena, and chalcopyrite (²⁰⁶Pb/²⁰⁴Pb = 18.23–18.37, ²⁰⁷Pb/²⁰⁴Pb = 15.47–15.62, and ²⁰⁸Pb/²⁰⁴Pb = 37.93–38.44). Sulfur isotope values of the sulfides give a narrow δ³⁴S interval of −6.1 to −4.6‰ (mean = −5.4‰, n = 15), suggesting the ore-forming fluid is of magmatic origin.

Three main paragenetic stages of skarn formation and ore deposition have been recognized based on petrographic observation, which are the preore stage (garnet-clinpyroxene-wollastonite-magnetite ± sulfides), the synore stage (sulfides-epidote-quartz-calcite ± garnet), and the postore stage (calcite-chlorite-quartz-fluorite). Several fluid evolution episodes can be inferred from microthermometric results at the Baiyinnuo’er Zn-Pb deposit:

Systematic fluid inclusion studies also indicate that the mineralization-related fluid is of magmatic origin. Prograde minerals formed during the preore-stage fluid immiscibility while sulfides deposition occurred during the synore-stage fluid boiling. Mixing with external fluids began as the hydrothermal system cooled to <300°C, when the main metal precipitation process had ended.