Sulfides Rb-Sr and zircon U-Pb ages of the Erdaohezi Pb-Zn deposit in the western slope of the Great Xing'an Range and their constraints on tectonic setting

The Erdaohezi Zn-Pb deposit is located in the middle segment of the Derbugan metallogenic belt in the Erguna block that is on the western slope of the Great Xing'an Range.Rb-Sr dating for sulfides and U-Pb dating for zircons from the andesitic porphyrite were carried out in order to constrain the mineralization age.Three endogenic mineralization stages have been identified, namely a quartz-pyrite stage(I), a quartz-polymetallic sulfide stage(Ⅱ), and a quartz-calcite-pyrite stage(Ⅲ), of which, the second stage is the main ore-forming stage.The Rb and Sr contents of 5 sphalerites and 3 pyrites formed at the main mineralization stage in the ore belt Ⅲ vary from 0.081×10^-6 to 2.632×10^-6 and 0.661×10^-6 to 3.186×10^-6, respectively.Accordingly, Rb-Sr isotopic dating of sulfides yields a well-defined isochron age of 140.8±2.3 Ma, close to the zircon U-Pb age(138.8±1.7 Ma)of the andesitic porphyrite crosscutting or parallel to the ore body.The calculated initial ⁸⁷Sr/⁸⁶Sr ratios range from 0.71025 to 0.71205, which is lower than that of the earth's crust, but higher than that of mantle.Combined with the previous studies, we suggest that the Erdaohezi deposit is a hydrothermal-vein deposit and is associated with the andesitic magmatism event(andesitic porphyrite).Additionally, mineralization occurred in an Early Cretaceous extensional setting after the closure of the Mongolia-Okhotsk Ocean.