| 河南桐柏围山城地区主要金银矿床的成矿年代学研究 |
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| 引用本文：JIANG SiHong,NIE FengJun,FANG DongHui,LIU YiFei,ZHANG WanYi,XU DongQing,ZHANG ZhiJun.2009.Geochronology of major gold and silver deposits in Weishancheng area, Tongbai County, Henan Province[J].Mineral Deposits,28(1):63~72 |
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| 基金项目:全国危机矿山项目（200641037）、地质大调查项目（1212010733803）和国土资源部百人计划项目 |
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| 中文摘要:河南省桐柏县围山城地区是秦岭－大别造山带上一个重要的金银矿集区，主要有破山大型银矿床、银洞坡大型金矿床和银洞岭大型银矿床。文章对围山城地区主要金银矿床内的蚀变矿物开展了40Ar/39Ar年代学研究，其中在破山银矿床内蚀变云斜煌岩的黑云母里获得的40Ar/39Ar坪年龄为（1290±11）Ma，等时线年龄为（1284±35）Ma(2σ)，MSWD＝0.12，40Ar/36Ar初始比值为(304±84)(2σ)；银洞坡金矿床含金石英脉中绢云母的40Ar/39Ar坪年龄为（3738±32）Ma，等时线年龄为（373±13）Ma(2σ)，MSWD＝0.073，40Ar/36Ar初始比值为(301±320)(2σ)；银洞岭银矿床矿化蚀变岩中绢云母的40Ar/39Ar坪年龄为（3774±26）Ma，等时线年龄为（3778±57）Ma(2σ)，MSWD＝0.70，40Ar/36Ar初始比值为(312±55)(2σ)，这些年龄基本上代表了矿床的形成时代。研究结果表明，围山城地区主要金银矿床（包括银洞坡金矿床、银洞岭银矿床和破山银矿床）的形成与二郎坪弧后盆地闭合导致的碰撞与挤压变质作用有关，均属于造山型金银矿床。由于受后期梁湾岩体燕山期岩浆活动的影响，破山银矿床可能遭受了改造，故在矿区蚀变云斜煌岩的黑云母里记录下了这期较晚的成矿事件。 |
| 中文关键词:地质学 40Ar/39Ar年代学 成矿年龄 金银矿床 围山城 河南 |
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| Geochronology of major gold and silver deposits in Weishancheng area, Tongbai County, Henan Province |
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| Abstract:The Weishancheng area in Tongbai County of Henan Province is an important Au_Ag ore concentration area in the Qinling_Dabie orogenic belt between the North China Plate and the Yangtze Plate. Three large_size gold and silver deposits, i.e., the Poshan Ag deposit, the Yindongpo Au deposit and the Yindongling Ag deposit, are hosted by the Neoproterozoic Waitoushan Formation within the Heqianzhuang anticline in Weishancheng area. In order to obtain the ore_forming ages, the authors studied the altered minerals separated from the major gold and silver deposits by the 40Ar/39Ar incremental heating method. The 40Ar/39Ar age dating of biotite from the altered kersantite dyke in the Poshan Ag deposit gives a plateau age of （129.0±1.1）Ma, an isochron age of （128.4±3.5） Ma (2σ) with the MSWD being 0.12，and an initial 40Ar/36Ar value of (304 ± 84) (2σ), while the sericite from the auriferous quartz vein in the Yindongpo Au deposit gives a plateau age of （373.8±3.2）Ma, an isochron age of （373±13）Ma (2σ) with the MSWD being 0.073，and an initial 40Ar/36Ar value of (301±320) (2σ). In comparison, the 40Ar/39Ar age dating of sericite from the altered rocks in the Yindongling Ag deposit gives a plateau age of （377.4±2.6） Ma, an isochron age of (377.8±5.7) Ma (2σ) with the MSWD being 0.70，and an initial 40Ar/36Ar value of (312±55) (2σ). These 40Ar/39Ar ages can represent the ore_forming time of these gold and silver deposits in Weishancheng area. It is thus held that the formation of these major gold and silver deposits in Weishancheng area, namely the Poshan Ag deposit, the Yindongpo Au deposit and the Yindongling deposit, are related to the collision and compressional metamorphism resulting from the closure of the Erlangping back_arc basin. Therefore, these gold and silver deposits are orogenic deposits. The Poshan Ag deposit might have been transformed during the intrusion of the Liangwan stock in Yanshanian period, as evidenced by the fact that the biotite from the altered Caledonian kersantite dyke in the Poshan Ag deposit has a 40Ar/39Ar plateau age of (129.0±1.1) Ma, a bit younger than the emplacement age of the Liangwan stock. |
| keywords:geology,40Ar/39Ar chronology,ore_forming age,Au_Ag deposit,Weishancheng,Henan |
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