| 西藏罗布莎豆荚状铬铁矿床深部找矿突破与成因模式讨论 |
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| 引用本文： | 章奇志,巴登珠,熊发挥,杨经绥.西藏罗布莎豆荚状铬铁矿床深部找矿突破与成因模式讨论[J].中国地质,2017,44(2):224-241. |
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| 作者姓名： | 章奇志 巴登珠 熊发挥 杨经绥 |
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| 作者单位： | 西藏自治区地质矿产勘查开发局第六地质大队, 西藏 堆龙德庆 851400,CARMA, 大陆构造与动力学重点实验室, 中国地质科学院地质研究所, 北京 100037;西藏矿业发展股份有限公司, 西藏 拉萨 850000,CARMA, 大陆构造与动力学重点实验室, 中国地质科学院地质研究所, 北京 100037,CARMA, 大陆构造与动力学重点实验室, 中国地质科学院地质研究所, 北京 100037 |
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| 基金项目： | 中国地质调查局项目（DD20160023）、国家自然科学基金（41502062、41672046、41541017、41641015）和IGCP-649项目联合资助。 |
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| 摘 要： | 中国铬铁矿资源的瓶颈状态已持续多年。最近,在西藏罗布莎蛇绿岩地幔橄榄岩的深部勘探发现200万t致密块状铬铁矿床,这是中国近50年来铬铁矿找矿的重大突破,对今后继续寻找同类型的铬铁矿床具有重要指导意义。蛇绿岩地幔橄榄岩中产出的豆荚状铬铁矿床是工业需求铬的重要来源。研究豆荚状铬铁矿的成矿作用和矿体围岩地幔橄榄岩地质特征,建立铬铁矿的成矿模型和找矿标志,是开展寻找同类型矿床的重要保证。随着近些年在豆荚状铬铁矿及围岩地幔橄榄岩中金刚石等深部矿物的不断发现和深入研究,人们对蛇绿岩型铬铁矿的物质来源和形成过程,有了新的认识,提出了铬铁矿的深部成因模式。研究认为深部成因铬铁矿床主要经历了4个阶段:(1)早期俯冲到地幔过渡带(410~660 km)的陆壳和洋壳物质被脱水和肢解,过渡带产生的热和流体促成了地幔的熔融和Cr的释放和汇聚;(2)铬铁矿浆在地幔柱驱动下,运移到过渡带顶部冷凝固结,并有强还原的流体进入,后者携带了深部形成的金刚石、斯石英等高压矿物,进入"塑性—半塑性地幔橄榄岩"中;(3)随着物质向上移动,深度降低,早期超高压相矿物发生相变,如斯石英转变成柯石英,高压相的铬铁矿中出溶成柯石英和单斜辉石;(4)在侵位过程和俯冲带环境下,含水熔体与方辉橄榄岩反应形成了不含超高压矿物的规模相对较小的浸染状铬铁矿及纯橄岩岩壳。进一步研究表明,同处雅鲁藏布江缝合带西段的几个大型地幔橄榄岩岩体与罗布莎岩体可以对比,经历了相同的构造背景和豆荚状铬铁矿的成矿作用,存在较大的找矿空间。
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| 关 键 词： | 豆荚状铬铁矿 蛇绿岩 多阶段 深部成因 雅鲁藏布江缝合带 |
| 收稿时间： | 2017/3/31 0:00:00 |
| 修稿时间： | 2017/4/12 0:00:00 |
Discussion on genesis process and deep prospecting breakthrough of Luobusa chromitite, Tibet |
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| ZHANG Qizhi,BA Dengzhu,XIONG Fahui and YANG Jingsui.Discussion on genesis process and deep prospecting breakthrough of Luobusa chromitite, Tibet[J].Chinese Geology,2017,44(2):224-241. |
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| Authors: | ZHANG Qizhi BA Dengzhu XIONG Fahui and YANG Jingsui |
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| Institution: | No.6 Geological Party, Tibet Bureau of Geological Exploration and Exploitation of Mineral Resources, Doilungdeqen 8751400, Tibet, China,CARMA, Key Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Tibet Ore Industry Co., Ltd., Lhasa 8750000, Tibet, China,CARMA, Key Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China and CARMA, Key Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| Abstract: | The chromitite bottleneck has been going on for many years in China. In October 2015, Bureau of Land and Resources of Tibet announced the discovery of a 200 million tons of massive chromite deposit in deep exploration at Luobusa in Tibet, which achieved a major breakthrough in China''s chromite prospecting, and the direction of finding more chromite deposits in the future was also pointed out. The podform chromite produced in the ophiolitic mantle peridotite is the main source of chromium. The study of podiform chromite mineralization and mantle peridotite is necessary for further finding the chromite deposit and relieve the bottleneck of the chromitite resources in China. Podiform chromite produced in the ophiolite is the main source of chromium and an important strategic resource for China. Research on the genesis of the podiform chromitite and mantle peridotite is necessary for further finding the chromite deposit and relieve the bottleneck of the chromitite resources in China. With the discovery of deep minerals such as diamonds in podiform chromite and mantle peridotites in recent years, researchers have also begun to question the theory of formation of podiform chromite. With the first discovery of 200 million tons of massive chromite orebody, the new understanding that podiform chromite is formed in the depth was raised, and its formation process mainly has gone through four stages. The crust and oceanic crust material of the early subduction to the mantle transition zone (410-660 km) is dehydrated and dismembered, and the heat and fluid produced by the transition zone contribute to the melting of the mantle and the release and aggregation of chromium. The chromitite ore slurry is driven by the mantle plume and is transported to the top of the transition zone for condensation and consolidation. The authors have reached the conclusion that the formation of ophiolites is a mutli -stage process involving subduction of lithospheric slabs into the transition zone, crystallization of chromian spinel and some massive chromitites at depth, incorporation of UHP and highly reduced phases into the chromitites, and entrapment of oceanic lithospheric slabs above subduction zones where they undergo varying degrees of interaction or reaction with MORB melts and SSZ melts. Several large massifs in the western part of the Yarlung Zangbo suture are similar to Luobusa in many aspects. They have experienced the same tectonic setting and the mineralization of podiform chromite, and there is a large prospecting space. |
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| Keywords: | podiform chromitite ophiolite multi-stage deep process Yarlung Zangbo suture zone |
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