Research on the Paragenesis(Coexist) Relationship of Lead—znic and Gold Mineralization in the Bafangshan—Baguamiao Deposit, Fengxian County, Southern Qinglin Mountains

Lower Paleozoic Fengxian—Taibai basin in the southern Qinling Mountains was the fault basin which developed from Late Paleozoic passive continental margin, belonging to the northern margin of the Yangtze platform. The basin is located at the Qinling micro tectonic plate. In this basin there exist the Baguamiao super large gold deposit and Bafangshan—Erlihe large-scale lead—zinc deposit. It is the typical area where lead—zinc and gold deposits paragenesis(coexist). There are some relationships between two kinds of deposits in geological background, position and mineralizing characteristics, etc. The lead—zinc ore-bodies lie in ankerite—albite—silicon hydrothermal sediment rock series between calcareous rocks of the Middle Devonian Gudaoling Formation and metapelite of the Upper Devonian Xinghongpu Formation. The gold ore bodies are located at the bottom of the Upper Devonian Xinghongpu Fm., which is composed of hydrothermal sediment rock series, including alteration albite, ankerite siltstone that suffer multiple phases of deformation, and quartz stringer vein.The silicon isotopic data reflect there are two types of different origin silicon in gold ore bodies. One is albitite and bedding-parallel quartz stringer veins (δ30Si=-0.40 ‰ ~-0.32 ‰), which is similar to the silicalite of lead—zinc ore-bearing beds. The silicon origin correlates with hydrothermal sediment. The other is transecting quartz vein in the gold ore bodies. The data reflect that silicon comes from magmatic fluid of the later period; The sulfur isotope data of sulfide in the lead—zinc deposit (δ34S=6.03~16.88 ‰) reflect that the sulfur mainly comes from the hydrothermal sediment and forms in the open system of early time basin; The sulfur isotope contents of sulfide in gold ore (δ34S=4.10~15.40‰) reflect that the sulfur are mainly from the strata and form at half seal—closed system of later period basin; The data of lead isotopic reflect the lead isotope evolution tendency of mantle material reducing and crust material increasing from the Xiba graniteDevonian strata lead—zinc ores gold ores; the hydrogen and oxygen isotope data indicate that the water of mineralization fluid in lead—zinc ore-bodies comes from meteoric water but the gold ore-bodies are charaterized by multiple sourced water, including magma water, meteoric water and metamorphic water. It is concluded that the Devonian sea-bottom hydrothermal sediment formed the main part of lead—zinc ore-beds and enriched obviously gold, silver and copper; then Mesozoic structure-fluid processes caused the gold ore-bodies allocation. The relationship of paragenesis between gold and lead—zinc is controlled by mineralization process, fluid chemistry and the physical—chemistry evolution. This temporal—spacial relationship of gold and lead—zinc can be regarded as the base for deep exploration and peripheral prospecting.