A new concept for the genesis of felsic magma: the separation of slab-derived supercritical liquid
A new concept for the genesis of felsic magma: the separation of slab-derived supercritical liquid
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DOI：
10.1038/s41598-020-65641-6
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发表时间：
2020-05
影响因子：
4.6
通讯作者：
H. Taniuchi;T. Kuritani;T. Yokoyama;E. Nakamura;M. Nakagawa
中科院分区：
文献类型：
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作者：
H. Taniuchi;T. Kuritani;T. Yokoyama;E. Nakamura;M. Nakagawa
俯冲带产生的长英质岩浆对陆壳的形成和演化起着重要作用。对于长英质岩浆的成因，曾有人提出诸如镁铁质岩浆的分离结晶、地壳物质的部分熔融、俯冲板片的部分熔融和辉石岩地幔楔成分的部分熔融等过程。最近的实验研究预测，长英质熔体也可以产生在地幔楔中的板状超临界流体的分离超过深度对应的临界点。然而，到目前为止，这种起源的长英质岩浆的存在还没有报道。在这项研究中，我们调查了英安质熔岩和之前的钙碱性安山岩熔岩从利尻火山，位于后方的千岛弧。结果表明，在地幔楔中，含水长英质熔体和含水流体与板状超临界流体分离。前者喷发为英安质岩浆，而含水流体诱导生成的原始玄武质岩浆参与创造钙碱性安山岩岩浆。我们推断，板片衍生的超临界液体是将富含硅酸盐的成分从俯冲板片移动到地球表面的有效传输介质，并且这一过程可能有助于大陆地壳的生长。
Felsic magmas produced at subduction zones have played an important role in the generation and evolution of the continental crust. For the origin of felsic magmas, processes such as fractional crystallization of mafic magmas, partial melting of crustal materials, partial melting of subducting slabs, and partial melting of pyroxenitic mantle wedge components have been proposed. Recent experimental studies have predicted that felsic melt can also be produced in the mantle wedge by the separation of slab-derived supercritical liquid beyond depths corresponding to the critical point. To date, however, the presence of felsic magma of this origin has not yet been reported. In this study, we investigated dacitic lavas and preceding calc-alkaline andesite lavas from the Rishiri Volcano, located at the rear of the Kuril arc. We show that hydrous felsic melt and aqueous fluid were separated from slab-derived supercritical liquid in the mantle wedge. The former erupted as dacitic magma whilst the aqueous fluid induced the generation of primary basaltic magma involved in creating calc-alkaline andesite magma. We infer that slab-derived supercritical liquid is an efficient transport medium for moving silicate-rich components from subducting slabs to the Earth’s surface, and that this process may have contributed to the growth of the continental crust.