| 粤西-桂东成矿带园珠顶铜钼矿床成矿年代学及其地质意义 |
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| 引用本文：林秀广,徐力峰,林良庄.2010.Metallogenic geochronology of Yuanzhuding Cu-Mo deposit in western Guangdong-eastern Guangxi metallogenic belt and its geological significance[J].Mineral Deposits,29(3):395~404 |
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| 基金项目:国家自然科学重点基金“班公湖_怒江蛇绿岩形成、侵位时限及其新特提斯构造演化”项目（40534019） |
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| 中文摘要:最近在粤西-桂东成矿带园珠顶地区发现了大型斑岩Cu-Mo矿床。为研究其成矿时代，笔者选取了该矿床钼矿体中的2个钻孔岩芯样品中的辉钼矿进行了Re-Os法同位素定年，2个岩芯共11个辉钼矿样品获得的Re-Os模式年龄为149.8～155.9 Ma；对ZK12-112岩芯8个辉钼矿分析数据进行Re-Os等时线拟合，获得等时线年龄为（157.3±4.3）Ma，初始187Os为（-0.15±0.18）ng/g，MSWD=0.92；对2个钻孔样品测得的11个数据进行Re-Os等时线拟合，获得等时线年龄为（155.6±3.4）Ma，初始187Os为（-0.08±0.15）ng/g，MSWD=0.85。这些年龄数据表明该矿床形成于中侏罗世晚期。选自钻孔ZK16_104岩芯的辉钼矿样品的Re含量非常高，可能指示园珠顶Cu-Mo矿床成矿物质来源于地幔，这也被区域内出露的许多同时代的基性侵入体所佐证。园珠顶斑岩Cu-Mo矿床辉钼矿Re、Os同位素数据可能指示早侏罗世具高浮力块体的Izanagi板块俯冲到粤西_桂东地区而改变了俯冲角度，导致俯冲板片撕裂而开天窗或岩石圈加厚而发生拆沉，在该地区出现一系列NE向壳幔相互作用强烈的伸展带，引发了软流圈物质在中晚侏罗世沿着NE向深断裂与EW向古断裂的交汇部位上涌，形成了粤西-桂东地区许多同时代的花岗岩类岩体、基性侵入体（或包体）和与此相关的Cu、Pb、Zn、Au、Ag矿床、W-Sn多金属矿床以及园珠顶斑岩型Cu-Mo矿床。 |
| 中文关键词:地质学 Re-Os同位素定年 辉钼矿 园珠顶矿床 粤西-桂东成矿带 华南 |
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| Metallogenic geochronology of Yuanzhuding Cu-Mo deposit in western Guangdong-eastern Guangxi metallogenic belt and its geological significance |
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| Abstract:A large-size porphyry Cu-Mo deposit was recently discovered in Yuanzhuding area of the western Guangdong-eastern Guangxi metallogenic belt. For the purpose of understanding geochronology of Cu-Mo mineralization in this area, the authors separated molybdenite samples from two borehole cores in the ore deposit. Re-Os dating of these molybdenite minerals from the two borehole cores has yielded eleven model ages ranging from 149.8 to 155.9 Ma. Eight analytical results of borehole ZK12-112 samples have yielded a Re-Os isochron age of (157.3±4.3) Ma (2σ, MSWD=0.92). Eleven analytical results from borehole ZK12-112 and ZK16-104 samples have yielded another Re-Os isochron age of (155.6±3.4) Ma (2σ, MSWD=0.85). The two isochron ages are in accordance with the Re-Os model ages withi n the range of error, which demonstrates that the age results are reliable and t he Yuanzhuding porphyry Cu-Mo deposit was formed in late Middle Jurassic.The rhenium content of ZK16-104 samples is very high, suggesting that the me tallogenic material of the Yuanzhuding ore deposit originated from the mantle. A nd this is further confirmed by the existence of many regional contemporaneous m afic intrusive rocks. Re-Os isotopic data of molybdenite from the Yuanzhuding or edeposit may imply that Izanagi plate with relatively buoyant topographic anoma lies was subducted beneath the Yuanzhuding area in Early Jurassic. The variation of the subduction angle resulted in the tearing up of the subducting slab and t he thickening of the lithosphere. As a result, a big slab window occurred or th e partially over-thickened lithospheric keel was delaminated, and a series of NE -striking extension belts with strong crust-mantle interaction were formed, whic h triggered the upwelling of the asthenosphere along the intersection of the NE-striking deep fault and the former EW-striking fault in Mid-Late Jurassic. Consequently, many contemporaneous granitoids and mafic intrusives or enclaves as wel l as Cu, Pb, Zn, Au, Ag deposits, W-Sn polymetallic deposits and the Yuanzhuding porphyry Cu-Mo deposit related to these intrusives were formed in the western G uangxi-eastern Guangdong region. |
| keywords:geology, Re-Os isotopic dating, molybdenite, Yuanzhuding ore deposit, western Guangdong-eastern Guangxi metallogenic belt, South China |
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