Origin of the newly discovered ore bodies in the Upper Sinian Dengying Forma-tion of the Huize Pb-Zn deposit in Yunnan:Constraints from C-O-Sr isotopes
The Huize Pb-Zn deposit in Yunnan is a super large Pb-Zn deposit located within the Sichuan-Yunnan-Guizhou metallogenic belt of China.The ore bodies discovered previously were mainly concentrated in the Lower Carboniferous Baizuo Formation.In recent years,new ore bodies have been discovered in the Upper Sinian Dengying Formation,but the genesis of these ore bodies remains unclear.This article conducted C-O-Sr isotope analysis on near-ore dolomite and hydrothermal calcite in the the Upper Sinian Dengying Formation and Lower Carboniferous Baizuo Formation,and found that the Lower Carboniferous Baizuo Formation hydrothermal calcite(δ13CPDB=-10.6‰--2.01‰;δ18OSMOW=17.91‰-22.44‰)and near-ore dolomite(δ13CPDB=-2.22‰--0.03‰;δ18OSMOW=21.28‰-25.99‰),is similar to the hydrothermal calcite in Lower Carboniferous Baizuo Formation ore bodies(δ13CPDB=-3.99‰--3.34‰;δ18OSMOW=19.15‰-20.18‰)and near-ore dolomite(δ13CPDB=-2.67‰;δ18OSMOW=20.44‰),which indicate the near-ore dolomite has a similar C-O isotope composition to marine carbonates and the hydrothermal calcite may be the result of C-O isotopic exchange between deep-source mineralizing fluids and wall rocks.Previous studies have pointed out that the mineralization events of the Upper Sinian Dengying Forma-tion and the Lower Carboniferous Baizuo Formation lead-zinc deposits in the Huize deposit are both products of strong compression orogeny in the late Indosinian period.Combined with the initial Sr isotopes of sphalerite and pyrite((87Sr/86Sr)i=0.7148-0.7231,mean=0.7192)in the ore bodies from Upper Sinian Dengying Formation strata are consistent with those in the Lower Carboniferous Baizuo Formation ore bodies of the Carboniferous system((87Sr/86Sr)i=0.7119-0.7218,mean=0.7159),mainly characterized by crustal source characteristics.This indicates that the ore bodies in the Sinian and Carboniferous systems have similar crustal source characteristics.The ore-forming fluids mineralize at different layers,exhibiting a"multi-layer distribution and concentrated output"feature.This understanding indicates that the Sinian strata in Huize area also have prospecting potential similar to the Carboniferous strata.
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