中文摘要：

从西藏雅鲁藏布江蛇绿岩带的罗布莎蛇绿岩的铬铁矿中，发现一个由70-80种奇异矿物组成的地幔矿物群，其中包括一种成分特殊的尖晶石类矿物。该种尖晶石呈包裹体分布在毒砂中，28粒该矿物的平均化学成分：Na2O 1.58％，MgO7．52％，Al2O3 36．59％，SiO2 44．45％，FeO 8．72％，并含少量CaO和TiO2。经激光拉曼谱仪测试，一部分颗粒具有Franclinite（锌铁尖晶石ZnFe2O4）拉曼谱。根据尖晶石结构和化学成分，可以得出两种分子式：（Mg0．52Na0．14Fe0.32Al0.74）1.72（Si2.00Al1.20）3.20O8和（Mg0.52Na0.14Fe0.32Si0.50）1.48相（Si1.50Al1.94）3．44O8。两种分子式都表明阳离子Si呈六配位占据尖晶石八面体晶格位置。Si离子呈六配位的硅酸盐。实验证明具有超高压性质，来自相当于过渡带400-670km的深部。表明西藏雅鲁藏布江蛇绿岩（古大洋岩石圈）的岩浆活动达到过渡带。可能是地幔柱活动将硅尖晶石类等超高压矿物搬运到上地幔浅部的。

英文摘要：

A mantle mineral assemblage consisting of 70-80 unusual varieties of minerals has been found in chromitite of the Luobusa ophiolite in the Yarlung Zangbo ophiolite zone, Tibet. This mineral assemblage includes a spinel-group mineral with a special composition. The mineral occurs as inclusions in arsenopyrite. The average chemical composition for 28 grains of the spinels is as follows：Na2O 1.58%, MgO 7.52%, Al2O3 36.59%, SiO2 44.45% and FeO 8.74 （%）, with minor CaO and TiO2. Laser Raman spectrometry shows that several grains have the Raman spectrum of franclinite （zinc-iron spinel Zn Fe2O4）. According to the crystal structure and chemical composition, the spinel （franclinite） has two formulas, i.e. ： （Mg0.52Na0.14Fe0.32Al0.74）1.72 （Si2.00Al1.20）3.20O8 and （ Mg0.52Na0.14Fe0.32Si0.50）1.48（Si1.50Al1.94）3.44O8. The two formulas both show that the six-coordinated Si cations occupy octahedral sites of the crystal structure of the spinel. Experiments demonstrate that silicate with six-coor- dinated Si has the UHP nature and should be derived from the 400-670 km depth equivalent to the transition zone of the Earth. This indicates that the magmatism of the Yarlung Zangbo ophiolite （paleo-oceanic lithosphere） may have reached the transition zone. It is possible that the mantle plume might transport UHP minerals such as silicon spinels from the transition zone to the shallow level of the upper mantle.