江苏六合方山幔源包体橄榄石的位错构造研究  

DISLOCATIONS IN MANTLE-DERIVED OLIVINE XENOLITHS FROM FANGSHAN,JIANGSU PROVINCE

作　　者：董火根[1] 闵茂中[1] 张富生[2] 洪建明[2] 

机构地区：[1]南京大学地球科学系 [2]南京大学现代分析中心

出　　处：《地质论评》1993年第5期459-464,T001,共7页Geological Review

基　　金：国家自然科学基金(编号地85079)

摘　　要：本研究采用光学显微镜(氧化缀饰)法和透射电子显微镜法,首次查明江苏六合方山玄武岩的包体橄榄石中存在自由位错、位错壁、位错弓弯、位错环、亚晶粒和位错扭折条带等显微、超显微构造,它们是包体橄榄石在上地幔高温、高压条件下发生塑性蠕变的产物,不同位错形态反映主矿物塑性变形的不同状态。根据橄榄石中自由位错密度和包体中辉石的化学成分,估算江苏六合方山地区上地幔某些流变学参数为:温度(t)为1052℃,压力(P)为2060MPa;深度(Z)为66.6km;流动应力(σ_1—σ_3)为51.3MPa;流动速率(ε)为3.6×10^(-14)/s;粘稠应(η)为5.7×10^(21),这些参数值与中国东部其它地区上地幔的同类参数值相接近。In the paper the following dislocation struotures in olivine xenoliths of basaltfrom Fangshan, Jiangsu Province, are firstly revealed by means of the transmissionelectron microscope (TEM) and optical microscope: free dislocations, dislocationwalls, disocation bows, dislocation loops, subgrains and kind bands. Those disloca-tion structures result from plastic creep of olivine xenoliths under the conditionsof high temperatures and high pressures in the upper mantle. According to the aver-age free dislocation density of olivine xenoliths and chemical composition of pyrox-ene which is associated with olivine in mantle xenoliths, some rheological parame-ters of the upper mantle for the Fangshan region have been calculated as follows:temperature(t), 1052℃; confining pressure (P), 2060MPa;depth (Z), 66.6km;flowstress (σ_1--σ_3),51. 3MPa;strain rate(ε), 3.6 ×10^(-14)/S;viscosity(η), 5.7×10^(21).

关 键 词：幔源包体 玄武岩 橄榄石 位错 

分 类 号：P578.942[天文地球—矿物学]