西藏当雄地区拉屋矿床磁黄铁矿Re-Os同位素测年和成矿物质来源示踪

Re-Os dating and ore-forming material tracing of the Lawu ore deposit in Damxung area, Tibet

摘要: 拉屋矿床位于西藏自治区当雄县境内,大地构造位置处于冈底斯成矿区申扎-旁多铜、银、铅、锌、金成矿带,为大型矽卡岩型铜铅多金属矿床。在系统研究拉屋矿床地质地球化学特征的基础上,以矿石的磁黄铁矿为对象,测定Re-Os同位素年龄,获得等时线年龄数据为(309±31)Ma,187Os/188Os的初始值为0.51±0.12,γOs值为306.90~880.29,Re/Os为20.46~80.46。上述结果,结合矿区野外地质特征和稳定同位素特征,证明拉屋矿床主要形成于晚石炭世来故期,其成矿物质来源于地幔,并在喷流过程中与地壳海底卤水汇合,遭受了壳源物质的混染,形成喷流成因矽卡岩型矿床。

Abstract: The Lawu ore deposit is located in Damxung County of Tibet and within the Shenzha-Pangduo Cu-Ag-Pb-Zn-Au ore-forming belt in the Gangdise metallogenic district. A 187Re-187Os isochron of 309±31 Ma was obtained for samples of pyrrhotite from the Lawu district,with the initial value being 187Os/188Os, γOs values and Re/Os ratios being 0.51±0.12, 306.90~880.29 and 20.46~80.46, respectively. In combination with the field geological and stable isotopic features, the Lawu ore deposit is considered to have been formed in Late Carboniferous Laigu period, and the ore-forming materials were probably derived from the mantle and severely contaminated by the crust, thus forming a sedex skarn ore deposit.