Spatial Evolutions Of S-Pb-Fe-Zn Isotopes In The Dongshengmiao Polymetallic Deposit And Their Implications For Ore Genesis

The Dongshengmiao deposit represents the largest known Zn-Pb-Cu deposit in the Langshan-Zhaertai area and is the most representive Proterozoic Sedex-type Zn-Pb ore deposit in China.Different ore types at Dongshengmiao formed by various ore-forming progresses,and filling-replacement is one of the most important ways.Our Pb isotope data indicate that a long-term duration of focused circulation of hydrothermal fluids were involved in the formation of the Dongshengmiao deposit and that younger or genetically unrelated fluids did not significantly disturb the Pb isotopic composition of the original sulfide mineralization.Key evidence in support of this view is that the Cu-Zn-Pb ores are analogous,in both Pb and S isotope composition,to the pyrite ores from the same stratigraphic position.The lead of the discordant sulfide veins was primarily supplied by a reservoir similar to that of the overlying strata-bound mineralization,with variable addition of evolved rock lead during subsequent magmatic or metamorphic processes.The high?³⁴S values(37.5?39.8‰)of barite samples at Dongshengmiao are first reported,which represets sulfur isotope compositions of evolved seawater sulfate.Various ore sulfides have very heavy sulfur isotope composition(14.6?41.1‰).Ore sulfide have similar sulfur isotope composition with diagenetic pyrite from same stratigraphic position,indicating syn-sedimentary or syn-diagenetic mineralization.A lateral trend of increasing?⁶⁶Zn and?⁵⁶Fe values of sphalerite and pyrrhotite minerals from southwest to northeast within the Dongshengmiao main orebody can been observed.Precipitations of sphalerite and pyrrhotite have played vital roles in controlling Zn and Fe isotopic variations,respectively,of ore sulfide minerals within the Dongshengmiao main orebody.Isotopically light Zn and Fe isotopes at Dongshengmiao have vectored toward the center of a large hydrothermal system in the southwest section of the main orebody,which is consistent with the occurrence of the Cu-rich cystic-shaped breccia zone.The patterns revealed by Zn and Fe isotopes within a single orebody have potential for exploration.