西准噶尔萨尔托海蛇绿岩中尖晶石二辉橄榄岩中橄榄石的位错构造及其意义

DISLOCATION STRUCTURES IN OLIVINE FROM SPINEL LHERZOLITE OF SARTOKAY OPHIOLITE AND THEIR SIGNIFICANCE IN UPPER MANTLE RHEOLOGY

西准噶尔萨尔托海蛇绿岩中的尖晶石二辉橄榄岩的形成温度约为1100℃,压力1.6GPa。氧化缀饰和透射电镜观察,揭示了橄榄石的位错密度为2.5×10~8/cm^2,(100)位错壁间距为10μm 左右。计算得到的古应力为115—154MPa,应变速率为2×10^(11),古生代大洋上地幔粘滞度为2.37×10^(19)P,与新生代大洋上地幔比较,古生代大洋上地幔有低粘滞度和高应变速率的特点。

Sartokay ophiolite is a Late Paleozoic tectonic melange in the Western Junggar region, Xinjiang, China. Oxidation decoration and TEM study of olivine from spinel Iherzolite of the ophiolite suggest that dislocation density in the olivine is 2.5×108/cm2 and (100) tilt wall spacing is 0.01 mm. Single pyroxene thermobarom eter gives 1100℃ and 1.6GPa. Paleostress estimated is about 115-154 MPa, strain rate 2×10-11 and viscosity for the upper mantle 1019 Poisson. In comparison with the published data, the ma ntle in Late Paleozoic had a lower visscosity and higher strain rate than in Mesozoic and Cenozoic.