| 论燕山运动的深部地球动力学本质 |
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| 引用本文： | 吴福元,孙德有,张广良,任向文.论燕山运动的深部地球动力学本质[J].高校地质学报,2000,6(3):379-388. |
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| 作者姓名： | 吴福元 孙德有 张广良 任向文 |
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| 作者单位： | 长春科技大学 地球科学学院,吉林 长春130061 |
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| 基金项目： | 中国科学院资助项目，教育部高校骨干教师资助计划，49872031，，， |
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| 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。
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| 关 键 词： | 地球动力学 岩石圈拆沉 燕山活动 中国东部 |
| 收稿时间： | 2000-09-20 |
| 修稿时间： | 2000-01-20 |
Deep Geodynamics of Yanshain Movement |
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| WU Fu-yuan,SUN De-you,ZHANG Guang-liang,REN Xiang-wen.Deep Geodynamics of Yanshain Movement[J].Geological Journal of China Universities,2000,6(3):379-388. |
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| Authors: | WU Fu-yuan SUN De-you ZHANG Guang-liang REN Xiang-wen |
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| Institution: | College of Earth Sciences, Changchun University of Science and Technology, Changchun 130061, China |
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| Abstract: | The eastern China was characterized by intensive magmatic ac tivities, structrual deformation, basin formation and mineralization in the Mesozoic, whic h wa s described as the Yanshain Movement Wong (1927). Although a lot of studies have been conducted in the past 70 years on the Yanshain Movem ent, a warmly debate still exists about its geodynamic background, such as the sub duction and back-arc extension of Pacific plate, continental -continental collisi on, sheared strike-slip continental margin, impacting and lithosph eric thinning , etc. A comprehensive study about the mineralogical, petrological and Sr-Nd isotopic features of Cenozoic basalts and their mantle xenoliths has indicated t hat the eastern China in Yanshain Period was characterized by lithospheric delaminat ion, especially the direct contact of asthenospheric mantle with the crust. Most of the pre-existed ancient lithospheric mantle had been delaminat ed, the present lithospheric mantle was formed since the Late Mesozoic. According to the presen t st udy, 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 p lat e thickened the lithosphere in the eastern China, which resulted in the mantle d elamination in 160 and 145～120 Ma duo to the gravity instability of thicken ed lithosphere. Therefore, the nature of Yanshain movement is the thinning, even disappearing of lithospheric mantle beneath eastern China. This phenomenon is r are in the world and was reported only in the Basin and Range of western United States. Du ring the period of lithospheric removal, the asthenosphere upwelling and heating , and the underplating of mantle-derived magma in the lower cr ust resulted in th e intensive Late Mesozoic magmatism-tectonism-minera lization of Yanshain Movement in China.
This research also suggests that the present lithospheric mantle beneath e astern China is juvenile, and does not correspond to the old ages found in the o verlyi ng 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. Th erefore, further investigation should be conducted to study the mechanism of th is process. |
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| Keywords: | geodynamics lithospheric delamination Yanshain Movement eastern China |
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