内蒙古哈达门沟石英正长岩锆石SHRIMP年龄及其地质意义

SHRIMP U-Pb Zircon Age and Its Implications of Quartz Syenite in Hadamengou, Inner Mongolia

采用同位素稀释法(TIMS)和二次离子探针法(SHRIMP)对内蒙古哈达门沟大型金矿床主矿体控矿岩石进行了锆石测年研究,最终确定了石英正长岩形成于古元古代早期,其锆石SHRIMP U-Pb谐和年龄为(2483 ±10) Ma(1σ),上交点年龄为(2508 ±41) Ma(1σ)。哈达门沟石英正长岩是国内迄今报道的元古代最古老的富碱侵入岩,其时空分布具有重要大地构造意义,指示了华北古陆在经历太古代末的碰撞拼合事件已经结束,地壳具有一定厚度,并已经开始向拉张性构造环境转变。

Based on dating zircon TIMS and SHRIMP U-Pb ages for the ore-controlling quartz syenite of Hadamengou large gold deposit, Inner Mongolia, the authors confirmed that the quartz syenite intruded upon during the early of Pa-leoproterozoic. Its zircon SHRIMP U-Pb concordant point age was (2483 ±10) Ma(1σ) and the upper intersection age gived (2508 ±41) Ma(1σ) on the disaccording line respectively. The quartz syenite in Hadamengou was proved the oldest Paleoproterozoic alkali-rich intrusive rock inChinatill now. Its old age and its distribution of the alkali-rich intrusive rock had important tectonic significance. It revealed that after the amalgamation at the end period of Archean, the crust of North China Craton had reached some thickness and had transformed into a kind of extensional tectonic settings since the intrusion of the alkali-rich intrusive rock in Hadamengou.