辽西中生代软流圈底辟体的脉动式上涌  

Mesozoic Pulsative Upwelling Diapirs of Asthenosphere in West Liaoning Province

作　　者：邵济安[1] 陈福坤[2] 路凤香[3] 周新华[2] 

机构地区：[1]北京大学地球与空间科学学院 [2]中国科学院地质与地球物理研究所,北京100029 [3]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学（中国地质大学学报）》2006年第6期807-816,共10页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金项目(No.40372103);中国科学院矿产资源研究重点实验室资助项目.

摘　　要：岩石学-地球化学数据揭示了辽西中生代火山岩组分存在的3个特征：（1）Mg^#值和Cr、Ni含量比较高；（2）多数火山岩源自受到地壳物质混染的富集的岩石圈地幔；（3）相当部分火山岩的εNd（t）值偏高．对辽西及其邻区中生代（230～65Ma）火山岩年代学的研究发现：火山活动具有平均间隔20～30Ma的周期性，火山岩活动的峰期为230Ma、190Ma、160Ma、1304120Ma、1104100Ma、80Ma．同时火山岩εNd（t）值在时间上显示了类似的周期性波动．在空间上，中、新生代火山岩有呈环状分布的趋势，从中心向外逐渐变新．根据上述特点，提出辽西晚中生代的火山岩活动可能与软流圈底辟体脉动式上涌有关，研究区被岩石圈断裂围限的特定构造背景为软流圈底辟体的上涌提供了天然通道．Petrologicos-geochemical data reveals the compositional features of Mesozoic volcanic rocks in West Liaoning： （1） Relatively high values of Mg^# and higher contents of Cr and Ni; （2） Most of volcanic magmas are derived from enriched lithospheric mantle hybridized by crust materials; （3） Considerable volcanic rocks have relatively high εNd （t） values. Chronologic researches on the Mesozoic （230--65 Ma） volcanic rocks in West Liaoning and adjacent areas indicate that the volcanic activities were periodic with an average period of 20--30 Ma, and that the peak ages of the volcanic activities were determined at 230 Ma, 190 Ma, 160 Ma, 130--120 Ma, 110--100 Ma, and 80 Ma, respectively. Temporally, the εNd （t） values of the volcanic rocks also show similar periodic variation responsible for the ages. Specifically, the Mesozoic-Cenozoic volcanic rocks are distributed in a ring-like shape with their ages ranging from old to young in an outward order from the center. These evidences lead to the conclusion that the Late Mesozoic volcanic activities in the study area are related to pulsative upwelling diapirs of asthenosphere, for which a natural passage is provided by the specific tectonic background confined by large-scale lithospheric faults in the study area.

关 键 词：辽西 中生代火山岩 同位素年龄 εNd(t) 软流圈底辟体. 

分 类 号：P588.14[天文地球—岩石学]