雅鲁藏布江蛇绿岩中橄榄石的位错构造及上地幔流变状态

本文通过对雅鲁藏布江蛇绿岩中橄榄石的透射电子显微分析(TEM)和变形参数测算,划分出3个应变带,即强应变带、过渡型应变带和弱应变带,并详细地研究了它们的岩石结构、位错构造、变形机制和流变状态。镁铁质糜棱岩组成的强应变带中橄榄石发育亚颗粒和位错网络,具有低自由位错密度(10~7～10~8cm~(-2)),是在温度为850～950℃、压力10～13kbar、差异应力2～3MPa、应变速率为10~(-16)～10~(-17)s~(-1)、粘度10~(22)～10~(23)Pa.s,大致相当于35～40km的岩石圈深部由位错机制控制的深层剪切流变作用形成的。

DISLOCATION OF OLIVINE IN THE OPHIOLITE ALONG THE YARLUNGZANGBOJIANG AND RHEOMORPHIC STATE OF THE UPPER MANTLE

Three deformation zones that include strong strain zone, middle strain and weak strain zone are divided by TEM analysing of olivine and determining physical conditions in the ophiolite along the Yarlungzangbojiang and studied in detail about their structure, mi- crostructure, deformation mechanism and rheomorphic state. Mafic mylonites show sub- grains, dislocation networks and kink band and have low dislocation density (107～108 cm-2 ), and are formed by the horizontal shearing rheomorphism at a temperature of 850～ 950°C, a pressure of 10～13 kbar, a differential stress of 2～3 MPa, a strain rate of 10-16 ～10-17s-1, a viscosity of 1022～1023 Pa.s, a depth of 35～40 km.