西藏拉昂错剪切橄榄岩中橄榄石初步研究

Preliminary study on the olivine in the Laangcuo sheared peridotite,western Tibet.

本文报道作者在拉昂错湖的西部岸边发现的剪切橄榄岩及其所含橄榄石的镜下研究和矿物研究的初步结果。剪切橄榄岩由橄榄石、辉石和尖晶石组成,其主要类型是方辉橄榄岩、二辉橄榄岩和蛇纹石化橄榄岩。橄榄石是高镁的贵橄榄石,其牌号fo为89.54到90.34,说明是地幔橄榄岩,而不是堆晶橄榄岩。在偏光显微镜下,橄榄石呈现波状消光、鲍姆纹、膝折带和碎斑结构,反映了韧性变形的特点。运用氧化缀饰法、化学侵蚀法和透射电镜研究了橄榄石的微结构,表明有位错线、位错环和位错网络存在,进一步反映了剪切橄榄岩经受了塑性流动和韧性变形作用。

This paper reports our preliminary study on the petrography and olivine of sheared peridotite outcrops along the western bank of Laangcuo Lake in western Tibet. The sheared peridotites are harzburgite, lherzolite and serpentinized peridotite. The olivines are chrysolites with fo varying from 89.54 to 90.32. The olivines in thin sections indicate undulatory extinction, Bohm texture, kink band and mortar texture. The dislocations in olivine crystals are studied with oxidation-decoration, chemical-etching and electronmicrocopy methods. The dislocation lines, loops and networks are found, suggesting that the peridotites were undergone plastic flow and ductile deformation.