The magmatic plumbing of the submarine Hachijo NW volcanic chain, Hachijojima, Japan: Long‐distance magma transport?
The magmatic plumbing of the submarine Hachijo NW volcanic chain, Hachijojima, Japan: Long‐distance magma transport?
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日本八丈岛海底八丈西北火山链的岩浆管道：长距离岩浆输送？
DOI：
10.1029/2007jb005325
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发表时间：
2008
影响因子：
--
通讯作者：
Taqumi Tuzino
中科院分区：
文献类型：
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作者：
O. Ishizuka;N. Geshi;J. Itoh;Y. Kawanabe;Taqumi Tuzino
[1] 近期对伊豆 - 小笠原弧的玄武质复合火山进行的地球物理观测揭示了弧地壳内岩浆长距离横向迁移的过程。为了从地质学和岩石学方面阐明玄武质弧火山的长距离岩浆迁移系统，我们对伊豆弧北部前沿20千米长的海底火山链（八丈西北链和八丈小岛链）以及东北坡上的火山锥（东北山体）以及八丈西山火山上的空中卫星火山锥进行了研究。八丈西北链的玄武岩比其他山体的玄武岩成分更原始。八丈西北链玄武岩的成分受分离结晶作用控制，而斜长石堆积作用发生在东北山体和空中卫星火山锥中。微量元素和同位素特征表明，同一玄武质原生岩浆参与了火山的各个部分。这使我们认为岩浆在西山火山和八丈西北链之间进行了长距离迁移。原始岩浆从西山火山在中 - 下地壳（10 - 20千米深）沿北北西方向横向迁移了至少20千米，且地壳层面的改变极小，并形成了八丈西北链。另一方面，在西山火山下方浅部岩浆房经历了晶体分离和堆积的岩浆似乎进行了短距离（<5千米）迁移，并形成了东北走向的山体和空中卫星火山锥。长距离岩浆迁移似乎受区域伸展应力体制控制，而短距离迁移可能受主火山山体负荷影响的局部应力体制控制。
[1] Recent geophysical observations on basaltic composite volcanoes in Izu-Bonin arc reveal the process of long-distance lateral magma transport within arc crust. To clarify a long-distance magma transport system of the basaltic arc volcano from geological and petrological aspects, we investigated 20-km-long submarine volcanic chains (Hachijo NW chain and Hachijo-kojima chain) and cones on the northeastern slope (NE edifices) as well as subaerial satellite cones nested Hachijo Nishiyama volcano in the northern Izu arc front. Basalts from Hachijo NW chain have more primitive composition than those from other edifices. The composition of the Hachijo NW chain basalts is controlled by fractional crystallization, while plagioclase accumulation occurred in NE edifices and subaerial satellite cones. Trace element and isotopic characteristics indicate that the same basaltic primary magma is involved in all sections of the volcano. This leads us to consider that magma was transported long distances between the Nishiyama volcano and the Hachijo NW chain. Primitive magma was laterally transported NNW for at least 20 km in the middle to lower crust (10–20 km deep) from Nishiyama volcano with only minimal crustal level modifications and formed Hachijo NW chain. On the other hand, magmas experienced crystal fractionation and accumulation at shallow magma chamber beneath Nishiyama volcano seems to have been transported in a short distance (<5 km) and formed NE trending edifices and subaerial satellite cones. The long-distance magma transport seems to be controlled by a regional extensional stress regime, while short-distance transport may be controlled by local stress regime affected by load of main volcanic edifice.