大兴安岭南段主要金属矿床的矿石铅同位素特征及其意义

Ore-lead isotope composition and its significance of some major ore deposits in the southern segment of the Daxinganling Mountains

大兴安岭南段金属矿床的成矿时代(海西期/燕山期)及某些金属矿床(如白音诺尔、大井及花敖包特等)的成因(喷流沉积或岩浆热液,或二者的叠加)和成矿物质来源一直存在争议。文章系统分析了大兴安岭南段主要金属矿床的矿石铅同位素组成特征,结果表明:大部分矿石铅同位素组成具幔源铅特征;矿石铅同位素组成与古生代侵入岩存在明显差异,但与中生代侵入岩具有很好的吻合性。这些特征表明:研究区内金属矿床的形成大都与中生代岩浆活动有关;矿石铅主要来自于中生代侵入体,二叠系地层、古生代火成岩和锡林浩特杂岩对矿石铅的供给有限;该区可能存在海西期和燕山期两期成矿事件,花敖包特矿床的形成时代与蒙恩陶勒盖矿床相近,都形成于燕山早期;大井和白音诺尔矿床是燕山期岩浆活动的产物。

There has been controversy on the mineralization age and genesis of some ore deposits in the southern segment of the Great Xing’an Range.Ore lead isotope compositions of major ore deposits in the southern segment of the Great Xing’an Range have been systematically studied.Most of the ore lead isotope compositions show a mantle lead affinity.Ore lead isotope compositions are confined in the region that were constructed by the Mesozoic intrusive rocks.The lead of the ore deposits are mainly derived from the Mesozoic plutons,however,it can’t exclude the possibility that a few of the lead originated from the Permian strata,the Paleozoic igneous rocks and the Xilinhaote complex.The mineralization age of the Huaaobaote deposit could be similar to that of Meng’entaolegai deposit.As for the Dajing and Baiyingnuoer deposits,they are most likely the products of the Yanshannian magmatism.