湘南中生代花岗质岩石成岩成矿的时限

The Time Ranges of Granitoid Emplacement and Related Nonferrous Metallic Mineralization in Southern Hunan

位于南岭中段的湘南地区,中生代花岗质岩石广泛分布;该区W、Sn、Pb、Zn、Mo、Bi等金属矿床密集产出,很多钨、锡矿床达到大型、超大型规模,且找矿潜力巨大,构成一个世界级的有色金属矿集区。最近大量的同位素年代学研究表明,南岭中段钨、锡、铅锌等金属的成矿是一个爆发性、区域性的地质事件,成矿时间高度集中,成矿时限主要在150～160 Ma之间,与该区主要花岗岩的成岩时间相当吻合;对单个钨、锡矿床而言,其矿区的成岩、成矿存在着一种准同期性,即成矿与矿区花岗岩的成岩基本上是同时的、或稍晚于花岗岩的成岩作用。因此,该区中生代的花岗岩与钨锡成矿作用具有明显的时、空联系。南岭中段花岗岩大规模的侵入和钨、锡等金属的爆发性成矿均形成于一种岩石圈伸展减薄、地壳拉张的构造环境,可能与华南中生代第二幕岩石圈伸展事件密切相关。

Mesozoic granitoids are widespread in southern Hunan, central Nanling district, and there are a lot of tungsten, tin, molybdenum, lead-zinc deposits in this area, which constitute a world-class nonferrous metallic deposit cluster, among them, many tungsten and tin deposits are large- and giantscaled. The known geochronological data reveal that, the metal mineralization including tungsten, tin, lead-zinc deposits was an explosive regional event, and predominately took place during 150 to 160 Ma, largely coincides with the timing of granitoid intrusion in this area. For an individual mining district, granitoid emplacement and related hydrothermal mineralization are basically penecontemporaneous, i. e. , tungsten-tin mineralization occurred contemporaneously or immediately after granite intrusion. Therefore, the tungsten-tin mineralization are temporally, spatially and genetically associated with granitoids in central Nanling district. The large-scale granitoid intrusion and explosive tungsten tin mineralization formed under the geodynamic setting of lithospheric thinning and crustal extension, probably are closely connected with the second episode lithospheric extension event during the Mesozoic.