【摘要】 对中国东部新生代玄武岩及其包体的矿物学、岩石学和地球化学研究的总结发现 ,中国东部在燕山期主要表现为岩石圈的减薄 ,并在其东部出现软流圈地幔与地壳直接接触的独特地质现象。早先应该存在的古老岩石圈地幔大多由于拆沉作用而不复存在 ,现今岩石圈地幔主体是在燕山晚期及其以后形成的。因此 ,中国东部燕山运动的本质就是岩石圈的减薄乃至岩石圈地幔的消失。研究认为 ,这种岩石圈减薄的触发因素可能与当时东侧大洋板块的俯冲有关。软流圈地幔与地壳直接接触的动力学效应是产生强烈的岩浆板底垫托作用及相伴随的深部地壳的高温变质作用和部分熔融作用 ,形成巨量岩浆的侵位与喷发 ,并造成新生地壳的显著增生和原有地壳的重新调整。同时 ,这种地球动力学过程将携带大量地幔物质 (包括成矿物质 )进入地壳 ,并形成地壳尺度的大规模流体循环 ,从而产生大面积、突发性的巨量成矿作用。更多还原

【Abstract】 The eastern China was characterized by intensive magmatic activities, structrual deformation, basin formation and mineralization in the Mesozoic, which was described as the Yanshain Movement Wong (1927). Although a lot of studies have been conducted in the past 70 years on the Yanshain Movement, a warmly debate still exists about its geodynamic background, such as the subduction and back?arc extension of Pacific plate, continental?continental collision, sheared strike?slip continental margin, impacting and lithospheric thinning, etc. A comprehensive study about the mineralogical, petrological and Sr Nd isotopic features of Cenozoic basalts and their mantle xenoliths has indicated that the eastern China in Yanshain Period was characterized by lithospheric delamination, especially the direct contact of asthenospheric mantle with the crust. Most of the pre?existed ancient lithospheric mantle had been delaminated, the present lithospheric mantle was formed since the Late Mesozoic. According to the present study, this lithospheric removal is probably related to the subduction of Pacific Oceanic Plate. The early stage (170 Ma or so) of subduction of eastern oceanic plate thickened the lithosphere in the eastern China, which resulted in the mantle delamination in 160 and 145～120 Ma duo to the gravity instability of thickened lithosphere. Therefore, the nature of Yanshain movement is the thinning, even disappearing of lithospheric mantle beneath eastern China. This phenomenon is rare in the world and was reported only in the Basin and Range of western United States. During the period of lithospheric removal, the asthenosphere upwelling and heating, and the underplating of mantle? derived magma in the lower crust resulted in the intensive Late Mesozoic magmatism?tectonism?mineralization of Yanshain Movement in China. This research also suggests that the present lithospheric mantle beneath eastern China is juvenile, and does not correspond to the old ages found in the overlying crustal rocks. This implies a mantle?crust decoupling, which is inconsistent with the results of present researches on the major Archean Cratons in the world. Therefore, further investigation should be conducted to study the mechanism of this process.更多还原