ABSTRACT

The Yugusayi mafic-ultramafic complex, located in the Qimantagh area, East Kunlun orogenic belt, consists of harzburgite, olivine orthopyroxenite, hornblende pyroxenite, and hornblende gabbro, which were once considered to be a part of the Early Palaeozoic ophiolite suite. However, the Yugusayi mafic-ultramafic rocks are characterized by thermal emplacement, accompanied by Cu-Ni sulphide mineralization, which is different from typical ophiolite suite. The LA-ICP-MS zircon U-Pb dating yields a 405 ± 2.8 Ma age for the hornblende gabbro, which belongs to the Early Devonian. All rocks are enriched in LREE but depleted in HREE, with a characteristic of ferrous mafic-ultramafic rocks. The εHf_(t) values of the zircons from hornblende gabbro are 5.6–14.8, the εNd_(t) values of whole rocks are from −4.27 to 0.08, and the δ³⁴S values of sulphide are 1.36–8.72‰, indicating that the magma originated from the depleted mantle and contaminated by continental crust material during the ascending process. Based on the regional geological background, it is reasonable that the rocks formed in the post-collision extension stage after the closure of the Proto-Tethys Ocean and the continental collision, which represents an important metallogenic period for Cu-Ni sulphide deposits in the East Kunlun oregenic belt. Early Devonian magmatic mafic-ultramafic intrusions are developed in the early Palaeozoic ophiolitic tectonic melange belt of Qimantagh area. Combined with good metallogenic conditions and remarkable mineralization characteristics, it is believed that the Qimantagh area is a potential area for the prospecting of magmatic Cu-Ni sulphide deposits.

摘要

玉古萨依基性-超基性杂岩位于东昆仑造山带奇曼塔格地区，由方方辉石、橄榄石斜辉石岩、角闪石辉石岩和角闪石辉长岩组成，曾被认为是早古生代蛇绿岩组的一部分。然而，尤古萨伊基性-超基性岩具有热侵位特征，并伴有Cu-Ni硫化物矿化，不同于典型的蛇绿岩套。LA-ICP-MS 锆石 U-Pb 测年得出属于早泥盆世的角闪石辉长岩的年龄为 405 ± 2.8 Ma。所有岩石均富含轻稀土，贫稀稀土，具有铁镁铁-超镁铁岩的特征。角闪石辉长岩锆石的 ε Hf (t) 值为5.6 ~ 14.8 _，ε Nd_(t)整块岩石的值从-4.27 到 0.08，δ ³⁴硫化物的S值为1.36~8.72‰，表明岩浆起源于亏损地幔，在上升过程中受到陆壳物质的污染。从区域地质背景来看，岩石形成于原特提斯洋闭合和大陆碰撞后的碰撞后伸展阶段是合理的，代表了东部铜镍硫化物矿床的重要成矿时期昆仑造山带。奇曼塔格地区早古生代蛇绿岩构造混杂岩带发育早泥盆世岩浆镁铁-超镁铁岩侵入体。结合良好的成矿条件和显着的成矿特征，认为奇曼塔格地区是岩浆型铜镍硫化物矿床找矿的潜力区。