松辽盆地南部岩石圈地幔变形特征及各向异性分析——来自橄榄岩包体的约束  

Deformation and seismic anisotropy of the lithospheric mantle in southern Songliao Basin: Constraints from peridotite xenoliths

作　　者：商咏梅 周永胜[1] 马玺 SHANG YongMei;ZHOU YongSheng;MA Xi(State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;College of Geographical Science and Tourism,Jilin Normal University,Siping 136000,China;Jilin Changbaishan Volcano National Observation and Research Station,Changchun 130000,China)

机构地区：[1]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [2]吉林师范大学地理科学与旅游学院,四平136000 [3]吉林长白山火山国家野外科学观测研究站,长春130000

出　　处：《岩石学报》2024年第4期1285-1298,共14页Acta Petrologica Sinica

基　　金：地震动力学国家重点实验室开放基金课题(LE-20-25)资助。

摘　　要：SKS测量结果显示松辽盆地快波方向分布较为复杂,由于缺乏深部岩石变形资料约束,制约了地震波各向异性成因解释。本文通过对松辽盆地南部双辽地区橄榄岩包体进行详细的岩石学、地球化学、显微结构、各向异性研究,结果显示双辽地区橄榄岩包体的平衡温度为893~1152℃,来源于岩石圈地幔。橄榄岩中橄榄石的晶格优选方位(CPO)类型主要为A型、D型和AG型,其中,AG型和D型CPO可能形成于西太平洋板块向欧亚大陆俯冲回撤导致的岩石圈变形,AG型橄榄石CPO也可能形成于熔体存在下的橄榄石变形。基于CPO计算获得的橄榄岩包体全岩VP各向异性(AVP)为4.79%~11.80%,最大剪切波各向异性(AVSmax)为3.13%~7.93%。结合地球物理测量结果,推断松辽盆地南部复杂的SKS各向异性的主要贡献可能来源于面理陡倾或直立的岩石圈地幔。SKS wave splitting measurements revealed that the distribution of fast wave direction in the Songliao Basin is complex. The formation of seismic anisotropy is restricted by the lack of study in lithospheric mantle deformation. To better understand lithospheric deformation and upper mantle anisotropy observed in this region, we performed studies on petrology, geochemistry, microstructures and seismic anisotropy of peridotite xenoliths collected from Shuangliao, southern Songliao Basin. The results show that equilibrium temperature of peridotite xenoliths in Shuangliao is 893~1152℃, which suggest that peridotite xenoliths were derived from the lithospheric mantle. The mantle peridotite xenoliths show three types crystallographic preferred orientation (CPO) of olivine, which are A-type, D-type and AG-type CPO. The AG-type and D-type olivine CPO were probably formed by lithospheric deformation caused by the subduction and retreat of western Pacific Plate. Moreover, the AG-type olivine CPO may be formed by deformation in the presence of melt. The VP anisotropy (AVP) and maximum shear wave anisotropy (AVSmax) of peridotite xenoliths calculated from the fabric of xenoliths are 4.79%~11.80% and 3.13%~7.93%, respectively. Based on the seismic properties of peridotite xenoliths and geophysical measurements, it is inferred that the complex SKS wave splitting is attributed to the lithospheric mantle in the southern Songliao Basin with a vertical structural frame.

关 键 词：地震波各向异性 橄榄岩包体 晶格优选方位 岩石圈变形 松辽盆地 

分 类 号：P545[天文地球—构造地质学]