North Atlantic magmatism controlled by temperature, mantle composition and buoyancy
North Atlantic magmatism controlled by temperature, mantle composition and buoyancy
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DOI：
10.1038/ngeo2264
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发表时间：
2014-11-01
影响因子：
18.3
通讯作者：
Lesher, Charles E.
中科院分区：
文献类型：
--
作者：
Brown, Eric L.;Lesher, Charles E.
大的火成岩省的特点是岩浆产生的速度非常高（1）。这种大量的岩浆活动通常归因于热的、强烈上涌的地幔柱物质的部分熔融（2，3）。然而，由洋壳俯冲引起的地幔成分不均匀性也可以增加岩浆的产生，减少与上涌羽流相关的高温需求（4，5）。北大西洋大火成岩省的地幔柱起源受到质疑，因为熔岩成分与地壳厚度相关，这意味着岩浆生产力和地幔源成分之间存在联系（4，6）。在这里，我们使用一个数值模型，模拟成分不均匀的地幔物质的上涌和熔融，以限制在北大西洋引起岩浆活动的条件。利用北大西洋的熔岩成分和体积的观察，我们表明，俯冲地壳物质代表不到10%的地幔源。我们进一步表明，地幔温度一直保持在85-210摄氏度的升高，并增加地幔上涌高达14倍的速度板块分离已经发生在过去的5600万年。温度升高和上升流速率沿沿着1,000多公里的古第三纪裂谷延伸，但沿沿着现代大西洋中脊则受到更大的限制。这些发现反映了地幔柱的长期表现。
Large igneous provinces are characterized by anomalously high rates of magma production(1). Such voluminous magmatism is commonly attributed to partial melting of hot, buoyantly upwelling mantle plume material(2,3). However, compositional heterogeneity in the mantle, caused by the subduction of oceanic crust, can also enhance magma production, diminishing the need for elevated temperatures associated with upwelling plumes(4,5). A plume origin for the North Atlantic large igneous province has been questioned because lava compositions correlate with crustal thickness, implying a link between magma productivity and mantle source composition(4,6). Here we use a numerical model that simulates upwelling and melting of compositionally heterogeneous mantle material to constrain the conditions that gave rise to magmatism in the North Atlantic. Using observations of lava compositions and volumes from the North Atlantic, we show that subducted crustal material represented less than 10% of the mantle source. We further show that mantle temperatures have remained elevated by 85-210 degrees C and increased mantle upwelling up to 14 times the rate of plate separation has occurred over the past 56 Myr. The enhanced temperatures and upwelling rates extended along more than 1,000 km of the Palaeogene rift, but are substantially more restricted along the modern Mid-Atlantic Ridge. These findings reflect the long-term manifestation of a mantle plume.