Magmatic activity plays an important role in mineralization, but little is understood of its role with respect to carbonate-hosted stratabound epigenetic Pb-Zn deposits. The Fule Pb-Zn deposit (~10 Mt of sulfide ore with mean grades of 15-20 wt. % Zn + Pb), is stratigraphically placed in middle Permian strata and spatially (~1 m) associated with late Permian continental flood basalts of the Emeishan Large Igneous Province (ELIP). It thus provides an ideal case to investigate its genetic relationship with the ELIP. In addition, the Fule deposit is characterized by high concentrations of Ag, Cd, Ge and Ga, and contains a variety of Cu and Ni sulfide minerals. Syn-ore calcite (δ 13 C = +2.57-+3.01‰) and associated fluids (δ 13 C = +2.96-+3.40‰) have δ 13 C values similar to those of fresh limestone (δ 13 C = +1.58-+2.63‰), but the δ 18 O values of calcite (+16.83-+19.92‰) and associated fluids (+7.80-+10.89‰) are distinctly lower than those of limestone (δ 18 O = +21.85-+23.61‰). This means that C is mainly derived from limestone, whereas the O isotope signature may be related to water/rock (W/R) interaction between mantle and/or metamorphic fluids and limestone. δ 34 S values of sulfide minerals obtained by in situ NanoSIMS and conventional bulk techniques record a range of +9.8-+23.1‰ and +10.04-+16.43‰, respectively, reflecting the enrichment of heavy S isotopes in the oreforming fluids and thermochemical sulfate reduction (TSR) is the principal mechanism for the formation of S 2-. Cores of sulfide crystals have much higher δ 34 S values than their rims, indicating a probable mixture of multiple S reservoirs and/or a dynamic fractionation of S isotopes occurred during sulfide precipitation. The uniform femtosecond (fs) LA-MC-ICPMS in situ Pb isotopic data for galena plot in the field that differs from any of the three potential 3 sources in the region. Such signatures demonstrate that metal Pb was most likely derived from a well-mixed source of basalts, sedimentary rocks and basement rocks. We propose that (a) the enrichment in Ag, Cu, Ni, Cd, Ge and Ga, and the isotope signatures of hydrothermal minerals in the Fule region are related to fluids derived from or flowed through multiple reservoirs; (b) Emeishan magmatism provided heat, elements and associated fluids, and its basalts acted as an impermeable and protective layer; and (c) fluid mixing caused TSR, and then resulted in W/R interaction and CO2 degassing, all of which played a key role in the precipitation of hydrothermal minerals.
In the western margin of the Yangtze Block, SW China, the Emeishan large igneous province (ELIP) is spatially associated with >400 carbonate-hosted epigenetic Pb-Zn deposits. These deposits form the giant Upper Yangtze Pb-Zn metallogenic province with >20 Mt base metals. In the southeastern part of this province, the important Pb-Zn deposits include those of the Yinchangpo, Yunluhe, Maozhachang, Tianqiao, Banbanqiao, Mangdong, Shaojiwan, Liangyan, Qingshan, Shanshulin, Nayongzhi and Guanziyao deposits. Sulfide ore bodies in these deposits are (i) hosted in late Ediacaran to middle Permian limestone, dolomitic limestone and dolostone; (ii) structurally controlled by reverse fault-anticline tectonic systems; and (iii) spatially associated with the ELIP flood basalts and mafic dikes, and early Permian, early Carboniferous and early Cambrian organic matter-rich black shales. CO isotopic compositions suggest that dolostone and limestone, mantle-derived rocks of the ELIP, and sedimentary organic matters supplied CO to the hydrothermal systems through water/rock (W/R) interaction. New and existing S isotopic compositions of sulfides imply multiple sources of S and the reduction of sulfate through both abiotic thermochemical (TSR) and bacterially mediated (BSR) processes. Zn isotopes indicate that the sources of Zn were most likely related to the ELIP with various contributions from sediments and basements locally. Pb isotope signatures are suggestive of derivation of Pb from basements and sedimentary rocks with variable influences from the ELIP. Sr isotopes support that mantle-derived rocks, sediments and basements were involved in Pb-Zn mineralization, and they have various contributions in different deposits. We consider that the Pb-Zn deposits in the Upper Yangtze province are the mixed products of multiple S species-bearing solutions and metal-rich fluids, both of which were derived from, flowed through or interacted with multiple lithostratigraphic units in the western Yangtze Block. The change of tectonic regimes from extension to compression after eruption of basalts of the ELIP, and then to extension during Early Mesozoic, facilitated extraction, migration, and excretion of ore-forming metals and associated fluids. Mixing of fluids and reduction geochemical barrier activated TSR, causing cyclical carbonate dissolution, CO 2 degassing and recrystallization (namely carbonate buffer). All these processes triggered continuous precipitation of huge amounts of hydrothermal minerals. Underplating and eruption of ELIP basalts provided heat flow, fluids and volatiles, whereas the basalts acted as an impermeable and protective layer, and even as ore-hosting rocks. These Pb-Zn deposits have spatial and genetic association with igneous activities of the ELIP, and are characterized by high ore grades (>10 wt. % Pb + Zn), high concentrations of associated metals (e.g. Cu, Ag, Ge, and Cd), and medium-low temperatures (usually <300 °C) and salinities (commonly <20 wt. % NaCl equiv.), all of which are significantly different fro...
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