Study on zircon LA-ICP-MS U-Pb age of skarn Cu mineralization related intrusion in the southern margin of the Gangdese ore belt,Tibet and its geological implication
Study on zircon LA-ICP-MS U-Pb age of skarn Cu mineralization related intrusion in the southern margin of the Gangdese ore belt,Tibet and its geological implication
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作者：
L. Hua
在冈底斯南部发现大量斑岩型铜钼矿床和铜铅锌多金属矿床，在冈底斯南部分别形成斑岩型铜矿带和多金属矿带。以往的研究表明，冈底斯南部发现的矿床形成于碰撞后环境，同位素年龄小于30Ma。本文报道了与冈底斯南缘矽卡岩型铜（金）成矿有关的桑布家拉侵入岩锆石LA-ICP-MS U-Pb年龄。桑布拉家岩体锆石LA-ICP-MS U-Pb年龄为92.1±0.6Ma， MSWD=1.0。锆石颗粒Ce4+/Ce3+比值在90 ~ 562之间，平均值为287，与玉龙矿带铜钼矿化斑岩相似，表明该侵入熔体具有较高的氧逸度特征。印度与亚洲的碰撞发生在65~45Ma。桑布家拉岩体的锆石年龄与铜（金）矿化有关，表明冈底斯南部的成矿事件不仅与碰撞后的环境有关，而且与新特提斯洋壳的俯冲有关。桑布家拉岩体的新锆石年龄表明，冈底斯南部可能是下一个与洋壳俯冲有关的矿化勘探目标。
A lot of porphyry Cu-Mo deposits and Cu-Pb-Zn polymetal ore deposits have been found in the southern Gangdese,which form a porphyry copper ore belt and polymetal ore belt in the southern Gangdese,respectively. Former work suggests that the deposits found in the southern Gangdese were formed in post collision environment with isotope age less than 30Ma. Here we report a relatively older zircon LA-ICP-MS U-Pb age for the Sangbujiala intrusion genetically associated with skarn Cu (Au) mineralization in the southern margin of the Gangdese terrain. The Sangbulajia intrusion has zircon LA-ICP-MS U-Pb age of 92.1±0.6Ma with MSWD=1.0. The Ce4+/Ce3+ ratios of the zircon grains vary from 90 to 562,with an average value of 287,which is similar to those of porphyries associated with Cu-Mo mineralization in the Yulong ore belt,suggesting that the intrusive melt is characterized by relatively high oxygen fugacity. The collision of India with Asia occurred during 65~45Ma. Our new zircon age of the Sangbujiala intrusion genetically associated with Cu (Au) mineralization suggests that the southern Gangdese has undergone mineralization events not only associated with postcollision environment but also with subduction of the Neotethyan ocean crust. The new zircon age for the Sangbujiala intrusion reveals that the southern Gangdese could be next exploring target for mineralization related to oceanic crust subduction.