苏鲁造山带地壳上地幔结构层析成像研究  

Tomography Images of Crustal and Upper Mantle Structure beneath Sulu Orogenic Belt

作　　者：郑洪伟[1] 李廷栋[2] 苏刚 Zheng Hongwei;Li Tingdong;Su Gang(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Chinese Academy of Geological Sciences,Beijing 100037,China;China Earthquake Disaster Prevention Center,Beijing 100029,China)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质科学院,北京100037 [3]中国地震灾害防御中心,北京100029

出　　处：《地球科学》2020年第7期2485-2494,共10页Earth Science

基　　金：国家自然基金“桐柏造山带及其邻区地壳上地幔三维结构与地球动力学研究”(No.41374101);国家重点研发计划(No.2016YFC0600301);中国地质调查项目(Nos.DD20190448,DD20190370)。

摘　　要：扬子与华北板块在三叠纪的俯冲碰撞形成了著名的苏鲁超高压造山带,其板块碰撞接触关系一直是热点问题.利用国家台网中心64个省台记录的1079个近震事件的10922个P波到时和251个远震事件的11931个P波到时数据,采用远近震联合反演的层析成像方法对苏鲁地区进行了地壳上地幔速度结构反演.结果显示,研究区内两个低速异常区分别对应山东半岛西部的华北板块地幔上隆区和壳幔相互作用强烈的长江中下游成矿带地区.在地幔300 km深度之下出现的高速异常体可能代表了早中生代扬子与华北板块碰撞之前俯冲拆沉的古特提斯洋板块.传统观点的扬子板块岩石圈向北俯冲不明显,华北板块表现为向东南俯冲的高速特征.华北板块俯冲以苏鲁造山带中部的北纬35°为界,分为南北两种俯冲样式.北部俯冲不明显,华北板块停滞在郯庐断裂带以西;南部则表现华北板块向东南陡倾俯冲到苏鲁造山带之下.The Sulu Triassic collision zone between the North China block and the Yangtze block contains the largest ultrahighpressure(UHP)metamorphic belt in the world.It has become a hot spot in the research of plate convergence,subduction,and collision.We determined a detailed three-dimensional P-wave velocity structure of the crust and upper mantle beneath the Sulu orogenic belt by applying 10922 arrival times from 1079 local and regional earthquakes,and 11931 data from 251 teleseismic events,which were recorded by 64 seismic stations in our study region.Our tomographic imaging shows that prominent low velocity anomalies are imaged beneath Shandong Peninsula and the middle and lower Yangtze River metallogenic belt,which may represent the asthenosphere upwelling.A high velocity anomaly which may represent the subducted Paleo-Tethyan oceanic slab is imaged clearly in the east of Tanlu fault beneath the depth of over 300 km.The crustal and mantle velocity structure of the Sulu orogenic belt formed by the collision of the North China block and the Yangtze block is mainly characterized by high velocity anomalies.The north subduction of the Yangtze block is not obviously,and the North China block is characterized by the southeastward subdction of the high velocity anomalies.The subduction of the north China block can be divided into two subduction styles bounded by 35°N.In the north of the 35°N,the southeastward subduction of North China block is not obvious and is stopped in the west of Tanlu fault.In the south of the 35°N,North China block southeastward subducted under the Sulu orogenic belt.

关 键 词：苏鲁造山带 壳幔速度结构 P波层析成像 华北板块东南俯冲 地球物理 

分 类 号：P313[天文地球—固体地球物理学]