| 从地壳上地幔构造看大陆岩石圈伸展与裂解 |
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| 引用本文： | 杨文采.从地壳上地幔构造看大陆岩石圈伸展与裂解[J].地质论评,2014,60(5):945-961. |
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| 作者姓名： | 杨文采 |
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| 作者单位： | “大地构造与动力学”国家重点实验室、中国地质科学院地质研究所,北京,100037 |
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| 基金项目： | 本文由国家自然科学基金委员会和中国科学院“板块构造与大陆动力学”学科发展战略项目的成果。 |
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| 摘 要： | 本篇讨论大陆岩石圈拆沉、伸展与裂解作用过程。由于大陆岩石圈厚度大而且很不均匀,产生裂谷的机制比较复杂。大陆碰撞远程效应的触发,岩石圈拆沉,以及板块运动的不规则性和地球应力场方向转折,都可能产生岩石圈断裂和大陆裂谷。岩石圈拆沉为在重力作用下"去陆根"的作用过程,演化过程可分为大陆根拆离、地壳伸展和岩石圈地幔整体破裂三个阶段。大陆碰撞带、俯冲的大陆和大洋板块、克拉通区域岩石圈,都可能产生岩石圈拆沉。大陆岩石圈调查表明,拉张区可见地壳伸展、岩石圈拆离、软流圈上拱和热沉降;它们是大陆岩石圈伸展与裂解早期的主要表现。从初始拉张的盆岭省到成熟的张裂省,拆离后地壳伸展成复式地堑,下地壳幔源玄武岩浆侵位,断裂带贯通并切穿整个岩石圈,表明地壳伸展进入成熟阶段。中国东北松辽盆地和西欧北海盆地曾处于成熟的张裂省。岩石圈破裂为岩浆侵位提供了阻力很小的通道网。岩浆侵位作用伴随岩石圈破裂和热流体上涌,成熟的张裂省可发展成大陆裂谷。多数的大陆裂谷带并没有发展成威尔逊裂谷带和洋中脊,普通的大陆裂谷要演化为威尔逊裂谷带,必须有来自软流圈的长期和持续的热流和玄武质岩浆的供应。威尔逊裂谷带岩石圈地幔和软流圈为地震低速带,其根源可能与来自地幔底部的地幔热羽流有关。
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| 关 键 词： | 大陆板块 地壳伸展 岩石圈裂解 拆沉 张裂省 幔源浆侵位 |
| 收稿时间： | 2013/9/21 0:00:00 |
| 修稿时间： | 2014/8/18 0:00:00 |
Continental Extension and Rifting Reveled by Worldwide
Comparison of Crust and Upper Mantle Structures |
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| YANG Wencai.Continental Extension and Rifting Reveled by Worldwide
Comparison of Crust and Upper Mantle Structures[J].Geological Review,2014,60(5):945-961. |
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| Authors: | YANG Wencai |
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| Institution: | State Lab of Continental Tectonics and Dynamics, Institute of Geology,
Chinese Academy of Geological Sciences, Beijing, 100037 |
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| Abstract: | This paper reviews continental extension, delamination and rifting processes. As continental lithosphere is usually much thicker and of heterogeneity than the oceanic, its corresponding faulting and rifting processes are much more complex. The mechanics that can generate lithospheric rifts includes long distance effects of continental collision, lithospheric detachment and delamination, as well as irregular plate movements. Delamination of part of lithosphere under gravitational forces causes subsidence of the continental roots, it usually contains three stages as break off the lithospheric root, crustal extension and geothermal subsidence with faulting of the lithospheric mantle. Delamination can occur under continental collision zones, cratons and subduction zones of continental or oceanic plates. Expansion of the grabens or sedimentary basins together with mantle origin magma intrusion indicates maturity of the extension provinces. In this mature stage the extension provinces are characterized by faults cutting whole lithosphere and fast magma intrusion in the lower crust. In the early stage of the rifting, crustal extension, lithospheric detachment, asthenosphere uplifting and heat subsidence are usually occur in the extensional provinces. Further development of a rift shows wide graben complex in the upper crust, uplifting of mantle origin basaltic magmas and creating magma chambers in the lower crust. Take the Suongliao basin in northeast China for an example, in a mature extension province the lithospheric faults should link up together and across through whole basins. Lithospheric faulting provides good pass ways for magma intrusions, letting fast basaltic intrusion and rift expansion. However, most of continental rifts would not become the Wilson rifts that should further develop into an oceanic ridge. The process of creating a Wilson rift requires long period supply of basaltic melts and heat upsweeping from the asthenosphere. Low velocity layers located beneath a Wilson rift indicate partial melting of rocks in the lower crust and uppermost mantle, it is possible caused by mantle plumes that originates from interaction between the mantle and outer core of the solid earth. |
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| Keywords: | continental plate crustal extension rifting of continental lithosphere delamination extension province mantle origin magma intrusion |
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