板塊裂谷

板塊裂谷(英語:rift valley)是岩石圈被拉开而形成的线性伸展构造,通常位於分離板塊邊緣[1][2]。 典型的裂谷特征是兩測有断陷的洼地,類似地堑[3]。地堑與板塊裂谷不同之處在於規模大小和深度。前者小而淺,只限於地殼上部,而板塊裂谷大而深可達到岩石圈,其轴线区可能包含火山岩,板塊裂谷是板塊分離前的構造運動。板塊裂谷可處於陸上例如東非裂谷及紅海裂谷,或海底例如洋脊裂谷。

在裂谷开始形成时,岩石圈上部开始形成一序列不相连的正断层,造成孤立盆地[4]。當裂谷繼續成長時,一些短断层會伸延互相連接形成邊界断层。這些邊界断层變成岩石圈的伸展運動的主要活動地區[4]。随着地壳变薄,地球表面下沉,莫霍面相应升高。与此同时,地幔岩石圈变薄,导致软流圈顶部上升。这将高热流带入岩石圈,引起高温至超高温变质作用。产生麻粒岩及其伴生的混合岩和花岗岩,再入侵到裂谷带,而导致裂谷造山運動(英語:rifting orogeny[5]

參考文獻编辑

  1. ^ Rift valley: definition and geologic significance, Giacomo Corti, The Ethiopian Rift Valley
  2. ^ Decompressional Melting During Extension of Continental Lithosphere, Jolante van Wijk, MantlePlumes.org
  3. ^ Leeder, M.R.; Gawthorpe, R.L. (1987). "Sedimentary models for extensional tilt-block/half-graben basins" (PDF). In Coward, M.P.; Dewey, J.F.; Hancock, P.L. (eds.). Continental Extensional Tectonics. Geological Society, Special Publications. 28. pp. 139–152. ISBN 9780632016051
  4. ^ 4.0 4.1 Withjack, M.O.; Schlische R.W.; Olsen P.E. (2002). "Rift-basin structure and its influence on sedimentary systems" (PDF). In Renaut R.W. & Ashley G.M. (ed.). Sedimentation in Continental Rifts. Special Publications. 73. Society for Sedimentary Geology. Retrieved 28 October 2012
  5. ^ Zheng, Y.-F.; Chen, R.-X. (2017). "Regional metamorphism at extreme conditions: Implications for orogeny at convergent plate margins". Journal of Asian Earth Sciences. 145: 46–73. Bibcode:2017JAESc.145...46Z. doi:10.1016/j.jseaes.2017.03.009