辽西100Ma火山事件的动力学过程及其构造背景

Dynamic process and tectonic background of the 100Ma volcanic events in west Liaoning province

通过辽西及邻区106Ma 来源于软流圈亏损地幔玄武岩的年代学及玄武岩底部不整合面的研究,认识到:(1)这一时期伴随岩石圈地幔物质的更新,存在着"岩浆间隙"和强烈构造运动的现象,从而推断软流圈底辟体上涌、岩石圈减薄、岩浆活动间隙、强烈构造运动这四者之间的因果关系,其中被软流圈熔体带上来的物质和热能是主导因素,岩石圈减薄是关键;(2)106Na 与116Ma、93Ma、80Ma、45Ma 火山岩之间的对比研究,表明106Ma 开始的岩石圈地幔的更新是一个漫长的不可逆转的过程。(3)通过本区火山岩的演变与相邻大洋板块同期热扩张历史的对比研究,推测晚中生代(120～80Ma)大洋与大陆岩石圈板块同步的演化特征可能反映了它们共同受到岩石圈板块之下同一深部热扰动的控制。

Through chronological research of the 106Ma asthenosphere-originated depleted mantle basalts and study on the plane of unconformity on bottom of the basalts, it is recognized that： （ 1 ） there have been ＂magmatic hiatus＂ and strong tectogenesis occurring with replacement of the lithospheric mantle materials, revealing correlation between 4 elements-upwelling of diapers of asthenosphere, lithosphere thinning, magmatic hiatus, and strong tectogenesis, among which upwelling of materials and heat energy with asthenospbere melts is the initiative factor and the lithosphere thinning is critical; （2） comparison of the ll6Ma, 106Ma, 93Ma, 80Ma, and 45Ma volcanic rocks reveals an irreversible and very long process of lithospheric-mantle replace starting from 106Ma; and （3） comparing evolution of the volcanic rocks in this area and the contemporaneous thermal spreading of its adjacent oceanic plate suggests that it is perhaps the same deep thermal disturbance beneath the lithospheric plate that controls the synchronic evolutional features of the oceanic and the continental plates in the Late Mesozoic （ 120 - 80Ma）.