A wide variety of unusual mantle has been reported from podiform chromitite orebodies Cr-31 and Cr-74 in the Luobusa （罗布莎） ophiolite, Tibet. A detailed investigation of chromitite ore- body Cr-ll, located in the ...A wide variety of unusual mantle has been reported from podiform chromitite orebodies Cr-31 and Cr-74 in the Luobusa （罗布莎） ophiolite, Tibet. A detailed investigation of chromitite ore- body Cr-ll, located in the Kangjinla （康金拉） district at the eastern end of the ophiolite, has revealed many of the same minerals, including diamond, moissanite, and some native elements, alloys, oxides, sulphides, silicates, carbonates, and tungstates. This orebody is particularly rich in diamonds, with over 1 000 grains recovered from about 1 100 kg sample of chromitite. More detailed studies and experiments are needed to understand the origin and significance of these unusual minerals because they have not been found in situ. It is a great breakthrough in mineralogical research that we have picked up more than 40 kinds of minerals from the Kangjinla chromite deposit in Luobusa. It is notable that a large amount of diamonds were firstly discovered from the Kangjinla chromite deposit as well as many other unusual minerals, such as moissanites, rutiles, native irons, and metal alloys. Especially, that diamond was found again in different chromitites in the same ophiolite belt provided new key evidence for discussing the origin of the diamond and the hosted chromitite and ophiolite. The mantle mineral group in Tibet has great significance in mineralogy and geodynamics.展开更多
文摘近些年,我们在西藏罗布莎蛇绿岩型铬铁矿中发现金刚石和柯石英等超高压矿物和异常地幔矿物,成果多次在美国 AGU 会议上做特邀报告,发表在2007年《Geology》和国内期刊上,并有4个新矿物获得国际新矿物委员会批准。这些成果在国内外引起广泛关注,也引发出一系列新的科学问题,例如,金刚石的赋存状态,物质来源和成因?与其伴随的铬铁矿的成因,与金刚石的关系?两者形成的地质背景、物理化学环境、保存和运移的规律、机制,等等。为了探讨这些问题,我们认为除了研究罗布莎铬铁矿之外,还应该开展铬铁矿的围岩地幔橄榄岩的研究,看看它们中都有什么矿物,与铬铁矿中的矿物究竟存在什么异同以及两者之间的成因联系?为此,我们从西藏罗布莎铬铁矿31号矿体不同高度取回两个各自为1吨重的方辉橄榄岩围岩样品,开展人工重砂矿物的分选。通过矿物成分、激光拉曼和 X 射线衍射光谱的研究,从中识别出金刚石等50余种矿物。经初步对比,认为铬铁矿围岩方辉橄榄岩中发现的矿物组合与铬铁矿中相似,表明两者存在成因上的联系,并可能共同经历了从深部到浅部的地质过程。
基金supported by China Geological Survey (Nos. 1212010610107 and 1212010610105)the National Natural Science Foundation of China (No. 40610098)
文摘A wide variety of unusual mantle has been reported from podiform chromitite orebodies Cr-31 and Cr-74 in the Luobusa （罗布莎） ophiolite, Tibet. A detailed investigation of chromitite ore- body Cr-ll, located in the Kangjinla （康金拉） district at the eastern end of the ophiolite, has revealed many of the same minerals, including diamond, moissanite, and some native elements, alloys, oxides, sulphides, silicates, carbonates, and tungstates. This orebody is particularly rich in diamonds, with over 1 000 grains recovered from about 1 100 kg sample of chromitite. More detailed studies and experiments are needed to understand the origin and significance of these unusual minerals because they have not been found in situ. It is a great breakthrough in mineralogical research that we have picked up more than 40 kinds of minerals from the Kangjinla chromite deposit in Luobusa. It is notable that a large amount of diamonds were firstly discovered from the Kangjinla chromite deposit as well as many other unusual minerals, such as moissanites, rutiles, native irons, and metal alloys. Especially, that diamond was found again in different chromitites in the same ophiolite belt provided new key evidence for discussing the origin of the diamond and the hosted chromitite and ophiolite. The mantle mineral group in Tibet has great significance in mineralogy and geodynamics.
