藏南错那洞铍稀有多金属成矿时代:来自热液白云母Ar-Ar年龄的约束

特提斯喜马拉雅是继华南和新疆阿尔泰之后又一条新发现的大型稀有金属成矿带,其成矿时代受到广泛的关注。本文以代表性矿床错那洞铍稀有多金属矿床为研究对象,挑选出矽卡岩型矿化体中的热液白云母,利用Ar-Ar同位素定年的方式测定热液活动时间,以此限制成矿时代。结果显示错那洞穹窿矽卡岩型矿体中白云母Ar-Ar同位素坪年龄为14.21±0.22Ma,对应的~(40)Ar/~(36)Ar-~(39)Ar/~(36)Ar的等时线年龄为14.21±0.27Ma,与错那洞穹窿中具有高分异特征的白云母花岗岩浆侵位时间(～14Ma)一致,表明错那洞矽卡岩型铍稀有多金属矿床的成矿年龄为～14Ma,而与穹窿内高分异白云母花岗岩一致的年龄暗示了该高分异花岗岩为该期矽卡岩型稀有金属矿化的成矿母岩浆。

Cuonadong Be-rare polymetallic metal deposit: constraints from Ar-Ar Age of hydrothermal Muscovite

The Tethys Himalaya is a newly-recognized rare metal metallogenic belt(RMMB). It mainly produces rare metal such as beryllium, tungsten, tin, niobium and tantalum. Cuonadong Be-rare polymetallic metal deposit is located in the Cuonadong Gneiss Dome(CGD) with three types of mineralized bodies, consisting of pegmatitic type, skarn type and hydrothermal vein type. Among them, the skarn type is mainly occurred in the deformed zone around the mantle area of the CGD. Field and microscopic features show that Ar-Ar age of muscovite can represent the hydrothermal activity time of skarn. The Ar-Ar isotope of muscovite from the skarnized marble in the Cuonadong dome was dated, yielded a Ar-Ar plateau age of 14.21±0.22Ma, corresponding to a ⁴⁰Ar/³⁶Ar-³⁹Ar/³⁶Ar isochron age of 14.21±0.27Ma. This age consistented with emplacement activity time (~14Ma) of the highly fractional muscovite granite within the CGD, and it was confirmed that the skarn-type rare metal mineralization in this period indeed result from the muscovite granite from chronological perspect.