Origin of ultra rear-arc magmatism at Rishiri Volcano, Kuril Arc, Ge
Origin of ultra rear-arc magmatism at Rishiri Volcano, Kuril Arc, Ge
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千岛弧利尻火山超弧后岩浆作用的起源
DOI：
10.1002/2016gc006594
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
M.
中科院分区：
文献类型：
--
作者：
Kuritani;T. and Nakagawa;M.
日尻火山位于千岛岛弧的最后方，与日本东北岛弧的交界处，其300公里的深度是世界上最深的活火山之一。本文通过对火山玄武岩熔岩的分析，探讨了超弧后岩浆活动的成因。熔岩由低钾和高钾两类组成，低钾熔岩早于高钾熔岩。由于高钾岩浆不太可能是低钾岩浆的衍生物，因此这两种岩浆被认为来自不同的源幔物质。多组分热力学分析表明，这些岩浆都是在1280-1340°C和~ 2.3 GPa条件下，由含0.04-0.11 wt.% H2O的源地幔熔融~ 2%产生的。据估计，太平洋俯冲板块的表面温度为860-960°C（低钾岩浆）和930-1040°C（高钾岩浆）。这些板坯表面的温度明显高于热模型预测的温度。板块表面的高温估计和最新的详细地震层析成像结果表明，低钾和高钾岩浆活动是板块表面流体的递进产生的结果，这是由于热地幔物质注入到俯冲太平洋板块扭曲部分的一个相对大规模的裂缝中而产生的加热。
The Rishiri Volcano is located at the very rear of the Kuril Arc at its junction with the NE Japan Arc, and its 300 km depth to the slab surface is one of the deepest among the active arc volcanoes in the world. In this study, the origin of this ultra rear‐arc magmatism was investigated by analyzing the basaltic lavas from the volcano. The lavas consist of low‐K and high‐K groups, with the low‐K lavas predating the high‐K lavas. Since it is unlikely that the high‐K magmas are derivatives of the low‐K magmas, the two magmas are thought to be derived from different source mantle materials. Analyses using multicomponent thermodynamics suggest that these magmas were both generated through the ∼2% melting of a source mantle with 0.04–0.11 wt.% H2O at 1280–1340°C and ∼2.3 GPa. The temperatures at the surface of the subducting Pacific slab, from which the slab fluids were released, were estimated to be 860–960°C for the low‐K magmas and 930–1040°C for the high‐K magmas. These temperatures of the slab surface are remarkably higher than those predicted by thermal models. The estimated high temperatures of the slab surface and the latest detailed seismic tomography results suggest that the low‐K and high‐K magmatism resulted from the progressive production of fluids at the slab surface due to heating by the injection of hot mantle materials into a relatively large‐scale fracture in the distorted portion of the subducting Pacific plate.