吉林龙冈火山群金龙顶子火山喷发物中幔源包体的基本特征及其地质意义  

Principal Features of Mantle Xenoliths in Jinlongdingzi Volcanics,Longgang Volcano Cluster,Jilin Province and Their Geological Implications

作　　者：史兰斌[1] 林传勇[1] 韩秀伶[2] 陈孝德[1] 

机构地区：[1]中国地震局地质研究所,北京100029 [2]中国科学院地质研究所,北京100029

出　　处：《地质论评》1999年第S1期308-318,共11页Geological Review

摘　　要：龙冈火山群金龙顶子火山喷发发生在距今1500年前,其火山喷发物中所含的幔源橄榄岩包体是我国在最新火山喷发物中所发现的幔源包体。这些包体以普遍含有韭闪石为特征。包体的结构和位错构造反映这些包体在上地幔条件下经历过一定程度的变形作用。包体的平衡温度大多数集中在800～950℃之间,只有个别样品温度达到1050℃;平衡压力大多数集中在1.0～1.5GPa之间。由包体平衡温度、压力得到的上地幔地温线稍低于中国东部由新第三纪包体得到的上地幔地温线,但接近第四纪包体得到的地温线。包体在上地幔条件下变形时的差异应力在30～44MPa,应变速率为10^(-18)s^(-1)～10^(-15)s^(-1)。角闪石的出现反映上地幔流体的渗透及交代作用。金龙顶子火山喷发的玄武岩浆直接来自35～50km的上地幔顶部。The Jinlongdingzi volcanic eruption occurred 1500 years before present. The mantle lherzolite xenoliths contained in the volcanic products are the ones found only in the latest volcanic products in China. These mantle xenoliths are characterized by the pervasive occurrence of pargasite. The textures and dislocation of sub-structures of olivine of these xenoliths reveal that they have been subjected to a certain degree of deformation under the upper mantle condition. The equilibrium temperatures of these xenoliths are concentrated within the range of 800～950℃,and the equilibrium pressures within the range of 1. 0～1. 5GPa. The upper mantle geotherm constructed on the basis of the equilibrium temperature and pressure of these xenoliths is slightly lower than that from mantle xenoliths in the Neogene basalts, but is closer to that from Quaternary basalts. The differential stress of these mantle xenoliths is estimated to be in the range of 30 ～45 MPa, while the strain rate is from 10^(-19)s^(-1)～10^(-15)s^(-1). The occurrence of pargasite reflects the participation of the upper mantle fluids and the metasomatism. It seems that the basaltic magma from the Jinlongdingzi eruption directly came from the top of upper mantle at depths of 35～50km.

关 键 词：金龙顶子 火山喷发 幔源包体 上地幔 流变参数 龙冈火山群 

分 类 号：P317.3[天文地球—固体地球物理学]