新疆西准噶尔地区不同类型金矿床Rb-Sr同位素年代研究

Study on Rb-Sr Isotopic Ages of Gold Deposits in West Junggar Area, Xinjiang

西准噶尔地区是新疆最重要的金成矿区之一。已发现大、中、小型金矿床10余个,金矿化点数百处。矿石类型有含金石英大脉型、石英网脉型和蚀变岩型。矿床成因类型有4种:一为火山热液型,其成因与区内早—中石炭世火山作用有关;二为潜火山热液型,与中酸性斑岩体侵位有关;三为岩浆热液型,与花岗质岩浆的侵位有关;四为动力变质热液型,沿断裂带分布于蚀变玄武岩中,系区域动力变质作用的产物。成矿作用及相关地质事件同位素年代学研究表明,这4类金矿床形成于后碰撞陆内构造环境,成矿时代分别为早石炭世(340Ma±),中石炭世(310Ma±)、晚石炭世(290Ma±)和早二叠世(270Ma±)。

As one of the most important gold mineralization provinces, in Xinjiang, the West Junggar region is rich in gold resources with more than 10 deposits of different scales and hundreds of mineralized occurrences. Veined,stockwork and alteration-sheathed gold ores have been found in the area, belonging to four genetic types: the volcanic hydrothermal ores related to early-middle Carboniferous volcanism; subvolcanic hydrothermal ores related to intermediate-acidic porphyry intrusions; hydrothermal ores to the granitic intrusion and dynamo- hydrothermal ores related to regional dynamic metamorphism along the faults . Study of isotopic geochronology of mineralization and correlative geological events shows that these gold deposits were formed in a post-collision tectonic environment and four mineralization stages can be distinguished: the early Carbonif-erous(340Ma±) ,middle Carboniferous ( 310Ma± ), late Carboniferous (290Ma±) and early Per-mian(270Ma±).