Role and chemical characteristics of magmatic fluid on material recycling process between earth's crust and upper mantle at subduction zone.

在日本岛弧东北部的岩手、南造、田田良火山和秋田驹岳火山前缘内侧采集了具有代表性的低碱拉斑玄武岩样品。本研究的基本思想是，板源流体的特征必须从单一火山岩浆源区地幔的不均匀性来推断。这种地幔不均一性需要通过岩石化学研究来揭示，岩石化学研究的目的是弄清拉斑玄武岩岩浆批次系统的母岩浆和演化过程的多样性，岩手火山已识别出5个拉斑玄武岩岩浆批次系统，每个批次都有不同的母岩浆和演化过程。同样，在南藏王火山拉斑系列中也可区分出3个同生岩浆岩套。秋田-驹岳火山在后破火山口阶段至少存在4套拉斑质岩浆，基于同一火山内部拉斑质母岩浆的独特化学特征，火山前缘下方的岩浆源区可能通过板片流体的交代作用富集Rb和K，而不富集Ba。此外，拉斑玄武岩和钙碱性岩浆岩套在火山前缘共存的LIL/HFS的差异可能反映了岩浆源区的这种不均匀性。此外，还揭示了拉斑系列中的演化过程并不总是以分离结晶作用为主，岩浆混合或同化作用可能是主要的

Representative low-alkali tholeiitic rock samples are collected from Iwate, Minami-Zao and Adatara volcanoes at volcanic front and also from Akita-Komagatake at inner side from the volcanic front in northeastern Japan arc. Basic concept of this research is that the characteristics of slab-derived fluid must be inferred from the heterogeneity postulated in magma source mantle beneath a single volcano. Such mantle heterogeneity should be revealed through petrochemical investigations trying to make clear the diversity of parental magmas and evorutionary processes for the tholeiitic magma batch systems that is believed to originate in mantle.Five tholeiitic magma batch systems are recognized at Iwate volcano, and each batch has distind parental magma and evolutionary process. Similarly, 3 co-genetic magma suites are distinguished among the tholeiitic series at Minami-Zao volcano. As for the Akita-Komagatake volcano, at least 4 suites of tholeiitic magmas exist in its post-caldera stage.Based on distinctive chemical characteristics among the tholeiitic parental magmas within a single volcano, the magma source region beneath the volcanic front may be enriched in Rb and K but not Ba through matasomatism by slab-derived fluid. Further, difference in LIL/HFS between tholeiitic and calc-alkaline magma suites coexisting at the volcanic front may reflect such heterogeneity in magma source region. In addition, it is revealed that the fractional crystallization is not always the main evorutionary process in the tholeiitic series ; magmatic mixing or assimialation may be the main