大兴安岭西坡二道河子铅锌矿床硫化物Rb-Sr、锆石U-Pb年龄及其对构造背景的制约

二道河子铅锌矿床位于额尔古纳地块得尔布干成矿带的中段，地处大兴安岭西坡。为有效限制该矿床的成矿时代，对硫化物Rb-Sr年龄和安山玢岩锆石U-Pb年龄开展研究得出：该矿床的内生成矿作用共经历了3个成矿阶段：石英-黄铁矿阶段(Ⅰ)、石英-多金属硫化物阶段(Ⅱ)和石英-方解石-黄铁矿阶段(Ⅲ)，其中石英-多金属硫化物阶段是主要的矿化阶段；Ⅲ号矿带主成矿阶段5件闪锌矿和3件黄铁矿的Rb、Sr含量分别为0.081×10-6~2.632×10-6和0.661×10-6~3.186×10-6，Rb-Sr同位素等时线年龄为140.8±2.3 Ma，(87Sr/86Sr)i值为0.71025~0.71205；与矿体平行、局部切穿矿体的安山玢岩脉的锆石U-Pb年龄为138.8±1.7 Ma。上述结果表明，二道河子矿床为热液脉状铅锌矿床，形成于早白垩世，与次火山岩(安山玢岩)热事件相近。结合前人研究成果，推测成矿与安山质岩浆作用有关，形成于蒙古-鄂霍茨克洋闭合后的伸展环境。

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.