雙模火山活動

雙模火山活動（）
是指一種火山活動能從單一火山中心噴發出鎂鐵質和長英質熔岩，很少或沒有中間成分的熔岩。 這種類型的火山活動通常與伸展構造區域有關，特別是裂谷。

 產狀 
大多數雙模火山活動與地殼變薄有關，而在變質岩石中，若有此類岩石也被用來證明過去裂谷存在的證據Brewer, T.S., Ahall, K-L., Menuge, J.F., Storey, C.D. & Parrish, R.R. 2004. Mesoproterozoic bimodal volcanism in SW Norway, evidence for recurring pre-Sveconorwegian continental margin tectonism, Precambrian Research, 134, 249–273. 
。 在活躍的大陸裂谷地區有很多例子，如美國西部的盆地和山脈區。雙模式火山活動也被解釋為過渡區域產物Till, A.B., Roeske, S.M., Bradley, D.C., Friedman, R. & Layer, P.W. 2007. Early Tertiary transtension-related deformation and magmatism along the Tintina fault system, Alaska, The Geological Society of America Special Paper 434, 233–264，例如早期形成階段的弧後盆地Fujioka, K., Nishimura, A., Koyama, M., and Kotake, N., 1990. Bimodal arc volcanism and backarc rifting along Izu-Bonin Arc. Eos, 71, 956. 以及大陸和海洋殼的熱點，例如黃石公園、阿納欣（Anahim）和加那利（Canary）群島的產物Christiansen, R.L.; Foulger G.R.; Evans J.R. (2002). "Upper-mantle origin of the Yellowstone hotspot" (PDF). Bulletin of the Geological Society of America. 114 (10): 1245–1256. Bibcode:2002GSAB..114.1245C. doi:10.1130/0016-7606(2002)114<1245:umooty>2.0.co;2. Retrieved 3 December 2012. Kuehn, Christian; Guest, Bernard; K. Russell, James; A. Benowitz, Jeff (2015). "The Satah Mountain and Baldface Mountain volcanic fields: Pleistocene hot spot volcanism in the Anahim Volcanic Belt, west-central British Columbia, Canada". Bulletin of Volcanology. Springer: 25Freundt-Malecha, B.; Schminke H.-U.; Freundt A. (2001). "Plutonic rocks of intermediate composition on Gran Canaria: the missing link of the bimodal volcanic rock suite". Contributions to Mineralogy and Petrology. 141 (4): 430–445. Bibcode:2001CoMP..141..430F. doi:10.1007/s004100100250。 
 成因 
雙模火山活動通常被解釋是因爲地殼部分熔融。當大量熱的玄武質岩漿從地幔源中上升時，能造成地殼部分熔融而產生花崗質岩漿。這兩種岩漿分別在獨立的岩漿室，導致週期性噴發這兩種類型的熔岩Maria, A. & Hermes, O.D. 2001. Volcanic rocks in the Narragansett Basin, southeastern New England: Petrology and significance to early basin formation American Journal of Science, 301, 286–312. Tamura, Y. & Tatsumi, Y. 2002. Remelting of an Andesitic Crust as a Possible Origin for Rhyolitic Magma in Oceanic Arcs: an Example from the Izu–Bonin Arc. Journal of Petrology, 43, 1029–1047. 。
參考文獻

分類:火成岩學