新疆阿尔泰印支期伟晶岩的成矿年代学研究

^(40)Ar/^(39)Ar Isotope Dating on Muscovites from Indosinian Raremetal Depositsin Central Altay, Northwestern China

阿尔泰的伟晶岩长期以来被认为是海西期造山过程的产物。为了查明伟晶岩矿床的成矿时代,本文通过对伟晶岩型稀有金属矿床中白云母的40Ar 39Ar法同位素定年研究,首次在阿尔泰中部的大喀拉苏大型稀有金属矿床和小喀拉苏稀有金属矿床获得了新的同位素年龄数据,其坪年龄分别为248.42±2.11Ma和233.79±0.41Ma,从而证实了印支期稀有金属成矿作用的存在,提出了伟晶岩型矿床形成于多个时代,且稀有金属成矿作用主要发生在海西期造山运动之后的看法。

The pegmatitetype raremetal deposits in Altai, which is the most important raremetal metallogenic province in China, have long been taken as products of Hercynian orogenesis. In order to investigate the oreforming ages of the raremetalbearing pegamatites, this paper applies40Ar/39Ar method on muscovite from middle to large size raremetalbearing pegmatites and presents some new isotopic geochronology data. The results showed that the Dakalasu raremetal deposit formed at 248.42±2.11Ma, while the Xiaokalasu raremetal deposit formed at 233.79±0.41Ma. These results suggest that Indosinian is an important mineralization epoch in the Altay area and that most of the important pegmatitetype raremetal deposits formed after the Hecynian orogenic process. 