摘要
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。
In recent years, ultrahigh pressure minerals, such as diamond and coesite, and other unusual minerals were discovered in chromitites of the Luobusa ophiolite in Tibet, and 4 new minerals have been approved by the CNMMN. These results have raised many questions： What are the occurrences of the diamonds, what is the source of their carbon and how were they formed？ What is the origin of the chromites hosting the diamonds, and at what depth did they form？ What is the genetic relationship between the diamonds and the host chromitites？ in what geological, geophysical and geochemical environments can the diamonds be formed and how are they preserved？ To approach these problems, we have also collected two one-ton samples of harzburgite hosting chromitite orebodies in the Luobusa ophiolite. These samples were taken at elevations of 4040 m and 4070 m above sea level, close to chromitite orebody 31, from which the diamonds, coesite and other unusual minerals were recovered. We processed these two samples in the same manner as the chromitites and discovered diamonds and more than 50 other mineral species. These preliminary results show that the minerals in the harzburgites are similar to those in the chromitites, suggesting a genetic relationship between them.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2008年第7期1445-1452,共8页
Acta Petrologica Sinica
基金
中国地质调查(1212010610107,1212010610105)
国家自然科学基金重大国际合作项目(40610098)资助
