江苏六合地区上地幔流体P-T条件的限定:流体包裹体证据

Constrains on P-T conditions of fluids from upper mantle underneath Liuhe,Jiangsu province:Evidence from fluid inclusions.

赋存于碱性玄武岩中被岩浆带到地表的地幔橄榄岩捕掳体中发育有大量的包裹体,这些包裹体为地幔流体研究提供了直接信息。本文对江苏六合地区地幔捕掳体中的 CO_2包裹体开展了详细的岩相学、显微测温学及激光拉曼光谱学工作,并对获得的数据进行计算分析。结果显示地幔橄榄岩矿物中发育有两类流体包裹体:早期原生 CO_2包襄体,晚期次生CO_2包裹体。本次研究通过对这两类包裹体的分析,初步探讨了CO_2包裹体的成因,并对六合地区及中国东部上地幔岩石圈演化提供了进一步的 P-T 限制:早期包裹体捕获于≥0.83GPa(对应28km 深处)压力,晚期包裹体形成于6～18km 深处的再平衡过程。

Abundant fluid inclusions in minerals from lherzolite xenoliths hosted in basalt are good samples for understanding mantle fluids. Petrographic observation, microthermometric and Raman spectroscopy analysis were conducted on the fluid inclusions in lherzolite xenoliths from Liuhe,Jiangsu province. Two kinds of CO2 inclusions in minerals from mantle peridotite were identified： early primary CO2 inclusion and late secondary CO2 inclusion. On the basis of the results, the origin of CO2 inclusions was discussed and yielded the new constrain on P-T condition on the evolution of upper mantle lithosphere underneath Liuhe and eastern China- The early CO2 inclusions were trapped at 0. 83GPa （ at depth of 28km ） ; later CO2 inclusions were formed during re-equilibrium with host minerals at depth of 6 - 18km.