【摘要】 雄村矿集区位于西藏冈底斯铜矿带南缘,是目前该带发现的唯一一个与新特提斯洋壳早期俯冲作用有关的斑岩型铜金矿集区。近年来,相继在该矿集区发现了1、2、3号矿体。为了全面厘定矿集区的岩浆作用与成矿的关系和深化对新特提斯洋壳早期俯冲作用相关的斑岩型矿床成矿作用的认识。本文在前期研究基础上,对雄村矿集区新发现的3号矿体含矿斑岩开展了锆石U-Pb定年、岩石地球化学和Sr-Nd-Pb-Hf同位素地球化学分析。锆石U-Pb定年结果表明,3号矿体含矿斑岩形成于早侏罗世(176. 9±1. 4Ma)。结合以往研究结果表明,雄村矿集区存在两期矿化作用,早期矿化事件发生在约172Ma,与早侏罗世(181～175Ma)石英闪长斑岩相关,形成了2、3号矿体;晚期成矿作用发生在161. 5Ma,与中侏罗世(167～161Ma)石英闪长斑岩相关,形成了1号矿体。雄村矿集区含矿岩体显示出高的εNd(t)(> 4. 5)值类似于马里亚纳大洋岛弧岩浆岩,结合雄村矿集区侏罗纪砂岩的年代学及地球化学特征,表明含矿岩体形成于新特提斯洋壳北向俯冲相关的大洋岛弧环境而非陆缘弧环境。Sr-Nd-Pb-Hf同位素组成表明含矿岩体起源于亏损地幔的部分熔融,且源区同时受到了俯冲洋壳释放的流体和俯冲沉积物熔体的交代。拉萨地体南缘具有强亏损Nd-Hf同位素组成(εHf(t)> 10、εNd(t)> 4. 5)的侏罗纪斑岩体有利于形成斑岩型铜金矿化,寻找与新特提斯洋壳俯冲相关的斑岩型矿床的重点区域应该是侏罗纪岩体被同期火山岩覆盖的区域。更多还原

【Abstract】 The Xiongcun district is located in the southern margin of the Gangdese porphyry copper belt( GPCB),Tibet,hosts the only known porphyry Cu deposit related to the early-stage subduction of the Neo-Tethys oceanic slab in the GPCB. In recent years,No. 1,No. 2,and No. 3 deposits were discovered successively in the district. In order to systematically investigate the magmatism and its relationship with mineralization in the district and improve the understanding of the porphyry metallogenesis related to the early-stage subduction of the Neo-Tethys oceanic slab,we reported zircon U-Pb ages along with Hf isotopic,whole-rock geochemical and Sr-Nd-Pb isotopic data for the ore-bearing porphyry of the newly discovered No. 3 deposit in the Xiongcun district. Zircon U-Pb dating for the orebearing porphyry of the No. 3 deposit indicates that they were emplaced in the Early Jurassic( 176. 9 ± 1. 4 Ma). Combined with previous research results, we consider that the presence of two episodes metallogenesis in the Xiongcun district. The early metallogenesis occurred ca. 172 Ma,which is associated with the Early Jurassic quartz diorite porphyry( 181 ～ 175 Ma),formed the No. 2 and No. 3 deposits. The late metallogenesis occurred ca. 161. 5 Ma,which is associated with the Middle Jurassic quartz diorite porphyry( 167 ～ 161 Ma),formed the No. 1 deposit. Ore-bearing porphyries in the Xiongcun district show relatively high values ofεNd( t)( > 4. 5) are similar to these magmatic rocks from the Mariana island arc,which is a typical intra-oceanic island-arc system within the western Pacific. In addition,combined with previous reported data of the geochronology and geochemistry of the Jurassic sandstones in the Xiongcun district,we conclude that the ore-bearing porphyries in the Xiongcun district formed in an intra-oceanic island-arc setting related to the northward subduction of the Neo-Tethys oceanic slab,rather than a continental island-arc setting. SrNd-Pb-Hf isotopic compositions suggest that the ore-bearing porphyries in the Xiongcun generated by partial melting of a depleted mantle source that was modified by fluids released from the Neo-Tethys oceanic slab and subducted sediments. Further research shows that these Jurassic porphyries have depleted Nd-Hf isotopic compositions( εHf( t) > 10,εNd( t) > 4. 5) are favorable for porphyry Cu( Au) mineralization,and the regions of Jurassic porphyries covered by contemporaneous volcanic rocks are favorable prospecting targets for porphyry Cu deposits related to the subduction of the Neo-Tethys oceanic slab.更多还原