大火成岩省是地幔柱作用引起的吗?

自Morgan在1971年提出地幔柱假说来解释大洋岛链的火山迁移规律以来,对于地幔柱是否存在一直存在着争论。大火成岩省以短时间内的巨量喷发为特征,这种特殊现象一般被认为是地幔柱作用的结果,原因是它可以解释大火成岩省中的许多现象:(1)短时间内的巨量幔源岩浆;(2)喷发前>500 m的隆起;(3)高温苦橄岩和科马提岩的存在;(4)热点轨迹;(5)在没有挥发分和压力降低的条件下地幔发生熔融;(6)高的3He/4He比值。但是并不是所有大火成岩省都具有上述特征,而且上述现象有的也可以用其他机制来解释,如边缘对流、大规模岩石圈拆沉、裂谷减压和陨石撞击等。但是目前还没有一个模式可以解释所有大火成岩省的所有现象,而总体上大火成岩省的许多地质现象与地幔柱模式较为吻合。

Were Large Igneous Provinces Caused by Mantle Plumes?

It has long been debated around the mantle plume since Morgan(1971)proposed mantle plume that was used to explain the trail of volcanoes.Large igneous provinces(LIPs)are characterized by large volume of magmas during short interval,which is generally considered to be related to mantle plume.The main reason is that the hypothesis of mantle plume is supported by many geologic evidences:(1)large volume mantle-derived magmas;(2)>500 m uplift before magmatism;(3)high-temperature picrites or komatiites;(4)hotspot trail leading LIPs;(5)melting of mantle without volatiles or decompressing;(6)high 3He/4He ratio.However,not all LIPs are consistent with the all above predictions.Alternately,some of the above predictions can also be reached by other models,such as edge-drive convection,large scale of delamination of lithosphere,rift-related decompression melt and meteorite impact.It is noted that,until now,no models are consistent with the geologic evidences from LIPs.Comparably,many evidences from LIPs account for the prediction of plume model.