湖南芙蓉锡矿床^(40)Ar/^(39)Ar同位素年龄及地质意义

^(40)Ar/^(39)Ar isotopic dating of tin mineralization in Furong deposit of Hunan Province and its geological significance

文章以金云母、角闪石和白云母为测试对象,利用40Ar/39Ar同位素定年的方法,精确厘定了芙蓉超大型锡矿床的形成时间。研究结果表明,白腊水矿区3个金云母样品的40Ar/39Ar坪年龄分别为(150.6±1.0)Ma、(157.3±1.0)Ma和(154.7±1.1)Ma;热液成因角闪石的坪年龄为(156.9±1.1)Ma。淘锡窝矿区云英岩中2个白云母样品的40Ar/39Ar坪年龄为(159.9±0.5)Ma和(154.8±0.6)Ma;因此芙蓉矿床的形成时间为151～160Ma,这与骑田岭主体花岗岩的侵入时间(151～162Ma)相吻合。湘南地区的柿竹园超大型W-Sn-Mo-Bi-F矿床、新田岭大型W矿床、瑶岗仙W矿床和黄沙坪Pb-Zn多金属矿床的形成时间亦集中在150～160Ma之间,因此,湘南有色金属矿化集中区可能主要集中在150～160Ma发生成矿,这种大规模成矿作用可能与中生代华南岩石圈的拉张、伸展作用密切相关。

The newly-discovered Furong ore deposit, located in the southern part of the Qitianling pluton emplaced at 151-162 Ma in southern Hunan, is a superlarge tin deposit. It consists of Bailashui-Anyuan, Taoxiwo-Sanmenkou and Maziping-Heishanli ore districts, and its ore veins occur in Qitianling pluton and the inner or outer contact zone between the granite pluton and the Late Palaeozoic sedimentary rocks. In this study, Ar-Ar isotope dating of muscovite, hornblende and phlogopite was carried out in order to constrain the tin mineralization timing of the Furong deposit. The plateau ages of three phlogopite samples from the Bailashui ore district are （150.6± 1.0） Ma, （157.3 ±1.0） Ma and （154.7 ±1.1） Ma, respectively; and the plateau age of hydrothermal hornblende from the same mining district is （ 156.9 ± 1.1 ） Ma. The plateau ages of two muscovite samples from the Taoxiwo ore district are （159.9 ±0.5） Ma and （154.8 ± 0.6） Ma, respectively. These age data are coincident with the intrusion time of the Qitianling granite （151-162 Ma）, and also in accordance with the ages of other nonferrous metal deposits such as the Shizhuyuan W-Sn-Mo-Bi-F deposit, the Xintianling W deposit, the Yaogangxian W deposit and the Huangshaping Pb,Zn polymetallic deposit in this area. The large-scale mineralization in southern Hunan is probably ascribed to the Mesozoic lithospheric extension in South China.