西藏雅鲁藏布江蛇绿岩带罗布莎地幔橄榄岩的成因

广泛分布在雅鲁藏布江蛇绿岩带的地幔橄榄岩是没有蛇纹石化的新鲜岩石，因而通过显微镜下观察和全岩化学分布探索其成因和地幔活动，是十分有利和简便的。最近几年来，利用岩石化学资料揭示远洋橄榄岩，认为它不是原始地幔岩经分或分离熔化作用萃取出玄武岩熔体后的直接残余物。罗布落蛇绿岩橄的镜下观察和岩石化学资料也证明，它不是原始地幔岩经局部熔化后的残余物，而且由来自更深层的地幔过渡带的硅酸盐超高压矿物底辟上升经熔取

The Genesis of Luobusa Mantle Peridotites in the Yarlung Zangbo River Ophiolite Zone, Tibet

The mantle peridotites widely distributed along the Yarlung Zangbo River ophiolite zone are fresh rocks not subjected to serpentinization. Therefore, the observation under microscope and the whole rock chemical analysis are simple and convenient means for investigating their genesis and the mantle activity. Recent studies of abyssal peridotites show that they are not melt residues of batching or fractional melting of pyrolite directly after melt extraction of MORB. Petrological studies of peridotites from Luobusa ophiolite massif also indicate that the mantle peridotites are not simple residues of primary pyrolite either. Nevertheless, residue peridotites in Luobusa ophiolite were formed by two times of partial melting, i.e., the ultrahigh pressure silicates (octahedral spinel) from the transitional zone experienced melting and extracted MORB melt, and then the low pressure peridotites in the upper mantle were partially metlted again, thus forming residue peridotites.