Lower-crustal intrusion on the North Atlantic continental margin
Lower-crustal intrusion on the North Atlantic continental margin
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DOI：
10.1038/nature06687
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发表时间：
2008-03
期刊：
影响因子：
64.8
通讯作者：
Robert S. White;L. K. Smith;A. Roberts;P. Christie;N. Kusznir;A. Roberts;David Healy;R. Spitzer;A. Chappell;J. D. Eccles;R. Fletcher;N. Hurst;Z. Lunnon;C. J. Parkin;V. Tymms
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文献类型：
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作者：
Robert S. White;L. K. Smith;A. Roberts;P. Christie;N. Kusznir;A. Roberts;David Healy;R. Spitzer;A. Chappell;J. D. Eccles;R. Fletcher;N. Hurst;Z. Lunnon;C. J. Parkin;V. Tymms
当大陆分裂时，裂谷作用有时伴随着大量熔融岩石的产生。然而，总的熔体体积是不确定的，因为只有一部分在表面爆发。此外，岩浆活动的原因仍然存在争议，特别是，是否是由于地幔温度升高。我们在大西洋东北部的法罗群岛和哈顿银行火山边缘记录了深穿透法向入射和广角地震剖面。在法罗群岛附近，沿走向每沿着1 km，有360-400 km ~ 3的玄武岩被挤出，而540-600 km ~ 3的玄武岩侵入到大陆-海洋过渡带。我们发现，下地壳侵入体主要集中在一个狭窄的区域，50公里宽的过渡，虽然挤压玄武岩流超过100公里的裂谷。地震剖面显示，熔融物是以岩床的形式侵入下地壳的，岩床横切大陆组构，而不是像人们通常认为的那样，是100%熔融物的“底板”。从测得的地震速度和火成岩厚度的证据是一致的熔体生产的主要控制是地幔温度升高，没有必要在裂谷下或肥沃的地幔的存在下，在大陆分裂的时候，无论是显着的活跃的小规模地幔对流，如以前所建议的北大西洋，。
When continents break apart, the rifting is sometimes accompanied by the production of large volumes of molten rock,,. The total melt volume, however, is uncertain, because only part of it has erupted at the surface. Furthermore, the cause of the magmatism is still disputed—specifically, whether or not it is due to increased mantle temperatures. We recorded deep-penetration normal-incidence and wide-angle seismic profiles across the Faroe and Hatton Bank volcanic margins in the northeast Atlantic. Here we show that near the Faroe Islands, for every 1 km along strike, 360–400 km3of basalt is extruded, while 540–600 km3is intruded into the continent–ocean transition. We find that lower-crustal intrusions are focused mainly into a narrow zone ∼50 km wide on the transition, although extruded basalts flow more than 100 km from the rift. Seismic profiles show that the melt is intruded into the lower crust as sills, which cross-cut the continental fabric, rather than as an ‘underplate’ of 100 per cent melt, as has often been assumed. Evidence from the measured seismic velocities and from igneous thicknesses are consistent with the dominant control on melt production being increased mantle temperatures, with no requirement for either significant active small-scale mantle convection under the rift or the presence of fertile mantle at the time of continental break-up, as has previously been suggested for the North Atlantic Ocean,,.