張裂

張裂（英語：Rift）是岩石圈被拉開的線性區域^[1] ^[2] ，是伸展構造的一種^[3]。

典型的張裂特徵在中央有線狀的斷陷窪地，稱為地塹，但更常見的是半地塹。半地塹的正斷層和張裂側隆起都在一側，另一側缺失^[4] 。張裂若保持在海平面以上，它們形成一個板塊裂谷，若被水填滿，就形成一個裂谷湖。張裂區的軸心可能含有火山岩，但不是張裂都有火山活動。

大多數大洋中脊的中心軸都有張裂，是兩塊板塊之間的分離板塊邊緣，也是新生洋殼和岩石圈的地區。

衰退張裂（英語：Failed Rift）是大陸在分裂時未能達到分開擴張。通常從張裂活動到擴張的過渡期常發生在三叉匯接區，此區有三條張裂集聚在一個熱點 (地質學)。其中兩條張裂持續發展到海底擴張的地步，而第三條中途停止發展，形成拗拉槽。

張裂發展

張裂起始

張裂成熟度可由對局部應變反應而形成的張裂盆地變化來分期。在裂陷開始形成時，岩石圈上部發展一系列不連通的正斷層，形成孤立的盆地^[5]。若在陸上形成張裂，此期的排水通常是內部的。

成熟張裂階段

隨着張裂的發展，一些單獨的斷層會增長，最終連接在一起形成邊界斷層。隨後的擴張運動都集中在這些邊界斷層。斷層的延長和斷層間距的加寬，導致沿張裂軸的沉降區域更加連續。此階段張裂肩的發育有明顯隆升，對張裂盆地的排水和沈積有強烈的影響^[5]。

在張裂活動的高潮期，地殼會變薄，地表下沉，莫霍面相應升高。與此同時，因地幔岩石圈（英語：mantle lithosphere）變薄，導致軟流圈頂部上升。這將使高熱流從上升的軟流圈帶入到變薄的岩石圈，導致岩石圈進行脫水熔融，通常在這種大於 30 °C 的高熱梯度下，引起極端變質作用。在碰撞造山帶中，變質產物為的高溫至超高溫的麻粒岩及其伴生的混合岩和花崗岩。在大陸張裂帶可能有變質核雜岩，而在擴張脊中可能有洋核雜岩。這就形成一種在伸展構造中的造山運動，稱為裂谷造山運動（英語：Rift orogeny）^[6]。

張裂後期沉降

一旦張裂停止活動，張裂下面的地幔就會冷卻，並伴隨着大面積的張裂後期沉降。沉降量與張裂期地殼減薄量直接有關，以β因子來計算（初始地殼厚度除以最終地殼厚度）。沉降量也受張裂盆地在每個階段的填充程度及物質的影響，因為沉積物的密度比水更大。「McKenzie 模型」是一種簡單的張裂形成模型，它假設張裂形成階段是瞬時的。根據張裂後期沉降量的觀察，來估計地殼變薄量^[7] ^[8]。另一種模型為「彎曲懸臂模型」 'flexural cantilever model'，該模型考慮了張裂斷層的幾何形狀和地殼上部的彎曲均衡flexural isostasy ^[9]。

張裂多期活動

一些張裂顯示出複雜而漫長的張裂歷史，具幾個不同的成長階段。北海張裂就是一個實列，從二疊紀到最早白堊紀，超過 1 億年的時期，經歷了的幾個獨立的張裂發展階段^[10]。

分裂到分開

張裂可能導致大陸分開和海洋盆地的形成。張裂演變到大陸分開時，海底會沿着大洋中脊而擴張，造成洋盆，並分隔兩側共軛大陸邊緣。^[11]。張裂活動可能是主動的，受地幔對流控制。它也可能是被動的，被遠場拉伸岩石圈的構造力驅動。受拉伸變形階段之間的空間和時間影響，造成不同邊緣區結構的發展。邊緣區的分割最終導致形成莫霍面不同變化的張裂域，包括近端張裂域，具有由斷層旋轉的地殼塊、頸縮張裂帶，其地殼基底變薄、遠端張裂域，具有深凹陷盆地、洋-陸過渡張裂帶和大洋張裂帶域^[12]。

在張裂演化過程中，常見變形和岩漿相互作用^[12]。具岩漿活動的邊緣有主要的火山活動特徵。此種火山邊緣均在被動大陸邊緣^[13]。缺乏岩漿活動的張裂邊緣，一般會受到大規模斷層和地殼超伸展的影響^[14]，在海底伸展滑脫帶，常具有被蛇紋石化的上地幔的橄欖岩和輝長岩。

參考文獻

[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]
Plate Tectonics: Lecture 2, Geology Department at University of Leicester
[4]
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. Vol. 28. pp. 139–152. ISBN 9780632016051.
[5]
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. Vol. 73. Society for Sedimentary Geology. Retrieved 28 October 2012
[6]
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
[7]
McKenzie, D. (1978). "Some remarks on the development of sedimentary basins" (PDF). Earth and Planetary Science Letters. 40 (1): 25–32. Bibcode:1978E&PSL..40...25M. CiteSeerX 10.1.1.459.4779. doi:10.1016/0012-821x(78)90071-7. Archived from the original (PDF) on 1 March 2014. Retrieved 25 October 2012
[8]
Kusznir, N.J.; Roberts A.M.; Morley C.K. (1995). "Forward and reverse modelling of rift basin formation". In Lambiase J.J. (ed.). Hydrocarbon habitat in rift basins. Special Publications. Vol. 80. London: Geological Society. pp. 33–56. ISBN 9781897799154. Retrieved 25 October 2012
[9]
Nøttvedt, A.; Gabrielsen R.H.; Steel R.J. (1995). "Tectonostratigraphy and sedimentary architecture of rift basins, with reference to the northern North Sea". Marine and Petroleum Geology. 12 (8): 881–901. doi:10.1016/0264-8172(95)98853-W.
[10]
Ravnås, R.; Nøttvedt A.; Steel R.J.; Windelstad J. (2000). "Syn-rift sedimentary architectures in the Northern North Sea". Dynamics of the Norwegian Margin. Special Publications. Vol. 167. London: Geological Society. pp. 133–177. ISBN 9781862390560. Retrieved 28 October 2012
[11]
Ziegler P.A.; Cloetingh S. (2003). "Dynamic processes controlling evolution of rifted basins". 64. Earth-Science Reviews
[12]
Péron-Pinvidic G.; Manatschal G.; Osmundsen P.T. (2013). "Structural comparison of archetypal Atlantic rifted margins: a review of observations and concepts". 43. Marine and Petroleum Geology
[13]
Reston T.J.; Manatschal G. (2011). "Arc-Continent Collision". In Brown D. & Ryan P.D. (ed.). Building blocks of later collision. Frontiers in Earth Sciences
[14]
Péron-Pinvidic G.; Manatschal G. (2009). "The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view". 98. International Journal of Earth Sciences

[”Rift”-1] [1]
Rift valley: definition and geologic significance, Giacomo Corti, The Ethiopian Rift Valley

[Decom”-2] [2]
Decompressional Melting During Extension of Continental Lithosphere, Jolante van Wijk, MantlePlumes.org

[”Plate”-3] [3]
Plate Tectonics: Lecture 2, Geology Department at University of Leicester

[”Leeder”-4] [4]
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. Vol. 28. pp. 139–152. ISBN 9780632016051.

[”Withjack”-5] [5]
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. Vol. 73. Society for Sedimentary Geology. Retrieved 28 October 2012

[”Zheng”-6] [6]
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

[”McKenzie”-7] [7]
McKenzie, D. (1978). "Some remarks on the development of sedimentary basins" (PDF). Earth and Planetary Science Letters. 40 (1): 25–32. Bibcode:1978E&PSL..40...25M. CiteSeerX 10.1.1.459.4779. doi:10.1016/0012-821x(78)90071-7. Archived from the original (PDF) on 1 March 2014. Retrieved 25 October 2012

[”Kusznir”-8] [8]
Kusznir, N.J.; Roberts A.M.; Morley C.K. (1995). "Forward and reverse modelling of rift basin formation". In Lambiase J.J. (ed.). Hydrocarbon habitat in rift basins. Special Publications. Vol. 80. London: Geological Society. pp. 33–56. ISBN 9781897799154. Retrieved 25 October 2012

[”Nøttvedt”-9] [9]
Nøttvedt, A.; Gabrielsen R.H.; Steel R.J. (1995). "Tectonostratigraphy and sedimentary architecture of rift basins, with reference to the northern North Sea". Marine and Petroleum Geology. 12 (8): 881–901. doi:10.1016/0264-8172(95)98853-W.

[”Ravnås”-10] [10]
Ravnås, R.; Nøttvedt A.; Steel R.J.; Windelstad J. (2000). "Syn-rift sedimentary architectures in the Northern North Sea". Dynamics of the Norwegian Margin. Special Publications. Vol. 167. London: Geological Society. pp. 133–177. ISBN 9781862390560. Retrieved 28 October 2012

[”Ziegler”-11] [11]
Ziegler P.A.; Cloetingh S. (2003). "Dynamic processes controlling evolution of rifted basins". 64. Earth-Science Reviews

[”Péron”-12] [12]
Péron-Pinvidic G.; Manatschal G.; Osmundsen P.T. (2013). "Structural comparison of archetypal Atlantic rifted margins: a review of observations and concepts". 43. Marine and Petroleum Geology

[”Reston”-13] [13]
Reston T.J.; Manatschal G. (2011). "Arc-Continent Collision". In Brown D. & Ryan P.D. (ed.). Building blocks of later collision. Frontiers in Earth Sciences

[”Pinvidic”-14] [14]
Péron-Pinvidic G.; Manatschal G. (2009). "The final rifting evolution at deep magma-poor passive margins from Iberia-Newfoundland: a new point of view". 98. International Journal of Earth Sciences

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