赣南淘锡坑钨多金属矿床花岗岩和云英岩岩石特征及云英岩中白云母^40Ar／^39Ar定年

Petrologic Characteristics of the Granites and Greisens and Muscovite ^(40)Ar/^(39)Ar Dating in the Taoxikeng Tungsten Polymetallic Deposit,Southern Jiangxi Province

赣南崇义县淘锡坑钨矿位于南岭东西向构造带东段,属于以黑钨矿石英脉型为主的钨多金属矿床。矿床形成与燕山期中酸性岩浆作用有密切关系,石英矿脉受一组北西向断裂控制,穿切新元古界。本文在淘锡坑钨矿区3个揭露到花岗岩体顶部的中段(206、106、56中段)采集到岩体顶部云英岩样品,利用40Ar/39Ar同位素定年测得云英岩中的白云母的坪年龄分别为152.7±1.5Ma(206中段),153.4±1.3Ma(106中段),155.0±1.4Ma(56中段)。与前人用其他方法测定的花岗岩成岩和成矿年龄几乎一致。花岗岩和云英岩全岩稀土元素均具有M型四分组效应和强烈的Eu亏损特征,反映出花岗质岩浆经历了高度分异演化及其岩体结晶晚期流体/熔体相互作用。综合前人在南岭地区同类矿床的研究资料,可知南岭地区160~150Ma成岩成矿作用主要分布于南岭中-东段,可能为大陆边缘弧后岩石圈伸展的构造动力学背景的产物。

The Taoxikeng tungsten-polymetallic deposit, Congyi County, Southern Jiangxi Province, in the central Nanling region, South China, consists of vein-type ore bodies hosted in Cambrian to Jurassic strata, and is closely related to Mesozoic granitic intrusions. Wolframite is the dominant ore minerals intergrown with gangue minerals of quartz, feldspar, phlogopite, and muscovite. We have carried out muscovite ^40Ar/^39Ar dating to better understand the time and genesis of mineralization. Muscovite ^40Ar/^39Ar dating of five greisen samples from different intermediate sections yielded well-defined ^40Ar/^39Ar plateau ages of 152. 7±1.5Ma, 153.4±1.3Ma and 155.0±1.4 Ma. Compared with known other datings, we found that the formation of granite and mineralization are at the same time. Based on the analytical data and experimentally geochemical data available, it is pointed out that the tetrad effects of REE in the granites and greisens are produced in the meh-fluid system. Intense fractional crystallization of granitic melt （containing REE accessories） and its interaction with volatile-rich （F, CI） fluid are the major factors leading to the tetrad effects of REE. Our new data, when combined with published geochronological results from other major deposits in Nanling region, suggest that large-scale W, Sn, Mo, Bi, Nb, Ta, Pb, Zn mineralization occurred throughout the central and eastern Nanling region at 160-150Ma, which indicates a geodynamic setting of crustal extension during the transformation of tectonic regimes during the Mid-Late Jurassic.