滇中地区的岩石圈结构及其动力学意义  

Lithospheric structure beneath the central Yunnan and its geodynamic implications

作　　者：瞿梦茹 梁坤 杨海燕 QU MengRu;LIANG Kun;YANG HaiYan(Yunnan Yuzhen Earthquake Engineering Co.,Ltd.,Kunming 650224,China;Department of Geophysics,Yunnan University,Kunming 650091,China)

机构地区：[1]云南宇震地震工程有限公司,昆明650224 [2]云南大学地球物理系,昆明650091

出　　处：《地球物理学进展》2022年第4期1464-1474,共11页Progress in Geophysics

基　　金：国家自然科学基金(42174064,41964002)资助。

摘　　要：虽然地球化学和地质学的研究确信峨眉山大火成岩省的形成与二叠纪地幔柱活动有关,但从二叠纪至今,峨眉山大火成岩省所在的华南板块至少向北漂移了3000 km,以致大火成岩省与地幔柱的空间位置不再对应.本研究使用川滇地区75个宽频固定台记录的远震事件计算P、S波接收函数,并利用参考地球模型把单个接收函数从时间域变换到深度域,最后从叠加道上读取地壳厚度和岩石圈厚度.结果表明,Moho面深度从云南南部的33 km向北逐渐增厚,在青藏高原东部可达约66 km,滇中地区地壳厚度变化剧烈,在攀枝花附近明显增厚.在金沙江—红河断裂西侧的印支块体下方,岩石圈厚度仅为70~80 km,但在滇中地区从约70 km变化约到120 km,最薄处发生于攀枝花附近,仅约为70 km.另外,滇中地区部分台站的S波接收函数显示Moho面的Sp转换相一致性较差,而P波接收函数则表明在Moho面附近存在一个正极性的转换界面.综合已有的研究结果,我们推测Moho面附近这一正极性界面是地幔柱岩浆底侵的结果.The studies from chemistry and geology are believed that the Emeishan Large Igneous Province(ELIP)is associated with Permian mantle plume,while the South China Plate,where the ELIP is located,has being floated northward at least 3000 km since Permian,so that the modern ELIP’s position is not corresponding to mantle plume. In the study,the teleseimic events recorded at 75broadband stations located at Sichuan and Yunnan provinces are used to compute P and S receiver functions. We use a reference earth model to shift the individual receiver functions from time domain to depth domain,and pick up crustal and lithospheric depths from stacked trace,respectively. Our results demonstrated that the Moho depth increase from 33 km at the southern of Yunnan province to about 66 km at the eastern of Tibet,it rapidly changes at the central Yunnan,and is obviously thicken around Panzhihua city. The lithospheric thickness is 70~80 km on the Indo-China block to the west of Jinshajiang-Red River Fault,while it increases from 70 km about to 120 km at the central Yunnan,the thinnest lithosperic thickness is occured around Panzhihua city,where the LAB depth is only about 70 km. In additon,the S receiver functions recorded at some of stations located at the central Yunan showed that the Sp converted phases at Moho lost their coherencies.Moreover,the P receiver functions recorded at the stations also demonstrated that there exist a positive polarity conversion interface near the Moho. According to previous studies,we attribute that the positive polarity conversion interface near the Moho was resulted from magma underplating associated with mantle plume.

关 键 词：P、S波接收函数 时间-深度转换 地壳厚度 岩石圈厚度 地幔柱物理模型 岩浆底侵 

分 类 号：P315[天文地球—地震学]