摘要
中国东部含幔源包体的早第三纪玄武岩已发现的有吉林双辽、河北阳原和山西繁峙。本文详细研究了这三个地点幔源包体的变形特征，结果表明，这些地点的幔源包体以尖晶石二辉橄榄岩为主，其结构主要为残斑结构。包体中橄榄石显示明显的优选方位，发育有反映高温位错蠕变机制的位错亚构造。包体的平衡温度在８００一１１００℃之间，压力为０．７一１．７ＣＰａ。来源深度为２８一５２ｋｍ。采用显微构造应力计计算的差异应力在１７一２４ＭＰａ之间，由橄榄岩高温流变律计算的应变速率为１０￣（－１５）－１０￣（－１８）ｓ￣（－１）等效粘滞度为１０￣（２１）一１０￣（２５）ｓｐａ．Ｓ之间。中国东部早第三纪与晚第三纪以后的幔源包体具有基本相同的特征，表明晚第三纪以后的上地幔继承和发展了早第三纪时的特征。中国东部早第三纪以来的上地幔符合大陆拉张带和裂谷上地幔的流变特征。
The presently known xenolith一bearing Paleogene basalts in the eastern China are located in Shuangliao of Jilin Province, Yangyuan of Hebei province,and Fanshi of Shanxi Province. The mantle xenoliths collected from these three localities have been described in this paner.The xenoliths are dominated by spinel lherzolite,having mainly porphyroclastic texture, The olivine from the xenoliths exhibits obvious preferred orientation and dislocation substructures indicative of high temperature creep mechanism. The equiiibrium temperature and pressure of the xenoliths have been calculated as 800一1100℃ and 0.7-1. 6 GPa respectively. The xenoliths are deduced to have been derived from a depth of 28一52 km. The differential stress estimated by inicrostructural pie- zometry is 12一25 MPa, while the strain rate and equivalent viscosity derived from the high temperature flow law of peridotites are 10￣(-15)-10￣(-18)s￣(-1) and 10￣(21)一10￣(25)pa· S respectively. The man the xenoliths from the,aleogene basalts have principally the same characteristics as the xenoliths from the Neogne and Quaternary basalts, indicating that the upper mantle of Neogene and Quatern-ary inherited and developed the rheological characteristics of Paleogene. The characteristics of the upper mantle in the eastern China have been coincident with those of the upper mantle in the continental extensional zone or rift sin-ce Tertiary.
出处
《岩石矿物学杂志》
CSCD
1995年第4期299-312,T001,共14页
Acta Petrologica et Mineralogica
基金
国家自然科学基金
关键词
幔源包体
上地幔
流变学
显微构造
玄武岩
mantle xenolith
upper mantle
rheology
eastern China
microstructures
