本文为青藏高原第二次科学考察专项(编号2019QZKK0801)、国家自然科学基金项目(编号92062215，42172069，41720104009)和中国地质调查局工作项目(编号DD20221817, DD20221630)、自然资源部深地动力学重点实验室自主研究课题(编号J1901- 28)联合资助成果。
Xiong Fahui
1) CARMA (Center for Advanced Research on Mantle), Key Laboratory of Deep- Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences，Beijing 100037, China; 2) Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou), Guangzhou, Guangdong 511458, ChinaXu Xiangzhen
1) CARMA (Center for Advanced Research on Mantle), Key Laboratory of Deep- Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences，Beijing 100037, China; 2) Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou), Guangzhou, Guangdong 511458, ChinaYang Jingsui
1) CARMA (Center for Advanced Research on Mantle), Key Laboratory of Deep- Earth Dynamics of Ministry of Natural Resources, Institute of Geology, Chinese Academy of Geological Sciences，Beijing 100037, China;7) School of Earth Sciences and Engineering，Nanjing University，Nanjing, Jiangsu 210023, China切里湖蛇绿岩出露于班公湖- 怒江缝合带中段，蕴含较为丰富的铬铁矿资源。蛇绿岩主要由蚀变地幔橄榄岩、辉长岩和辉绿岩组成，铬铁矿矿体呈透镜状分布在地幔橄榄岩内部。切里湖地幔橄榄岩橄榄石Fo(90. 06~90. 74)和铬尖晶石Cr#值(67. 45~85. 42)较高，全岩富集MgO、LREE和大离子亲石元素(LILEs，如Rb、Ba等)，亏损Al2O3、CaO、高场强元素(HFSE，如Th、Ta、Ce、Nb)和PPGE(Rh、Pt、Pd)，这些特征与缝合带其他地幔橄榄岩相似，指示它们具有深海地幔橄榄岩及弧前地幔橄榄岩特征，经历了早期高程度熔体抽取和晚期熔体交代过程。切里湖铬铁矿矿石具有致密块状和浸染状构造，包含磁铁矿、黄铜矿、方铅矿等多种包裹体。铬铁矿Cr#值为65. 5~75. 8，Mg#值为64. 89~76. 04,平衡熔体显示出玻安质熔体的亲缘性。与地幔橄榄岩相比，切里湖铬铁矿的IPGE与PPGE分馏更加明显，IPGE更加富集。地幔橄榄岩和铬铁矿Δlg〖KG-*4〗 fO2(FMQ)的相近，介于-1. 97~0. 69之间，表明两者起源于相同的构造背景。对比其他蛇绿岩，认为班公湖- 怒江缝合带的蛇绿岩起源于大洋中脊环境，后受到了俯冲带的影响，显示多阶段演化过程。
Qielihu ophiolite is located to the middle part of the Bangong- Nujiang suture which is rich in chromitite resources. Qielihu ophiolite is mainly composed of altered mantle peridotite, gabbro and diabase, and chromite orebodies are lenticular in the interior of mantle peridotite.The olivine Fo (90.06~90.74) and chromite Cr# (67.45~85.42) of the mantle peridotite from the Qielihu are relatively high, the whole rock is rich in MgO, LREE and large ion lithophile elements (such as Rb, Ba, etc.), and depleted in Al2O3,CaO, high field strength elements (such as Th, Ta, Ce, Nb) and PPGE (Rh, Pt, Pd). These characteristics are similar to other mantle peridotites in the Bangong- Nujiang suture zone, indicating that they have the characteristics of Abyssal mantle peridotite and Forearc mantle peridotite. Meantime, it has gone through the process of early high degree melt extraction and late melt metasomatism. The Qielihu chromitite ore has a dense massive and disseminated structure and contains many kinds of inclusions such as spinel, chalcopyrite, galena and so on. The Cr# value of chromitite is 65.5~75.8 and the Mg # value is 64.89~76.04. The equilibrium melt shows the affinity of vitreous melt. Compared with mantle peridotite, the IPGE and PPGE fractionation of Qielihu chromitite is more obvious. The ΔlgfO2 (FMQ) values of mantle peridotite and chromitite are similar, ranging from -1. 97 to 0.69, indicating that they are derived from the same tectonic setting. Compared with other ophiolites, it is considered that the ophiolite in the Bangong- Nujiang suture originated from the mid- ocean ridge environment and its formation experienced multi- stage evolution.
闫金禹,熊发挥,徐向珍,张承杰,卢雨潇,何兰芳,王天泽,杨经绥.2022.西藏班公湖- 怒江缝合带中段切里湖豆荚状铬铁矿地球化学特征及构造意义[J].地质学报,96(12):4294-4311.
Yan Jinyu, Xiong Fahui, Xu Xiangzhen, Zhang Chengjie, Lu Yuxiao, He Lanfang, Wang Tianze, Yang Jingsui.2022. Geochemical characteristics and tectonic significance of podiform chromitite in the Qielihu in the middle segment of the Bangong- Nujiang suture, Tibet[J]. Acta Geologica Sinica,96(12):4294-4311.
