High-Mg diorites derived from sanukitic HMA magmas, Kyushu Island, southwest Japan arc: evidence from clinopyroxene and whole rock compositions
High-Mg diorites derived from sanukitic HMA magmas, Kyushu Island, southwest Japan arc: evidence from clinopyroxene and whole rock compositions
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DOI：
10.1016/j.lithos.2004.03.006
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发表时间：
2004-08-01
期刊：
影响因子：
3.5
通讯作者：
Shiraki, K
中科院分区：
文献类型：
--
作者：
Kamei, A;Owada, M;Shiraki, K
与高镁安山岩整体岩石组成相似的高镁闪长岩不应简单地解释为由高镁安山岩岩浆固化而成的岩石，因为高镁闪长岩可能是源自与高镁安山岩不同岩浆的基性堆积。hma中含有独特的斜辉石，其Mg#和Si含量高于其他亚碱性系列火成岩。Mg#和Si主要受源岩浆组成的控制，而不是受源岩浆的结晶条件（如压力和温度）的控制。斜辉长岩的化学成分将为研究高镁闪长岩的来源提供重要信息。根据斜辉石和全岩组成，认为日本西南部九州岛早白垩世高镁闪长岩的来源为。斜辉石的化学特征与其他亚碱性岩石相似，而与hma岩石相似。整体岩石成分与闪质HMA相当，不具有基性堆积特征。这表明高镁闪长岩是由闪质HMA岩浆固化而成。一般认为，闪质HMA岩浆是由年轻的或热的大洋板块俯冲形成的。因此，高镁闪长岩的出现表明九州在早白垩世处于年轻和（或）热板块俯冲的构造环境。(C) 2004 Elsevier b.v.版权所有
High-Mg diorites that have similar whole rock composition to high-Mg andesites (HMAs) should not be simply interpreted as rocks solidified from the HMA magmas, because the high-Mg diorites may be mafic cumulates derived from a different magma from the HMAs.The HMAs contain unique clinopyroxenes with higher Mg# and Si than those of other sub-alkaline series igneous rocks. The Mg# and Si are controlled by the source magma composition rather than its crystallized conditions such as pressure and temperature. The chemical composition of clinopyroxenes would present important information for the investigation of the source of high-Mg diorites.We considered the source of Early Cretaceous high-Mg diorites on Kyushu Island, southwest Japan are, based on their clinopyroxene and whole rock compositions. The clinopyroxenes have similar chemical characteristics to those in HMAs rather than those in other sub-alkaline rocks. Moreover, the whole rock compositions are equivalent to the sanukitic HMA and do not show features of mafic cumulates. This indicates that the high-Mg diorites solidified from sanukitic HMA magmas. It is generally believed that the sanukitic HMA magmas involve the subduction of a young and/or hot oceanic slab was situated in their genesis. Therefore, the occurrence of the high-Mg diorites suggests that Kyushu was situated in the tectonic setting of young and/or hot slab subduction in the Early Cretaceous. (C) 2004 Elsevier B.V All rights reserved.