FORMATIVE PROCESSES AND EXHUMATION TECTONICS OF HIGH-TEMPERATURE METAMORPHIC BELTS IN ISLAND ARCS

1) Hidaka变质带研究：通过分析Hidaka变质带麻粒岩相变质岩的部分熔融和调质岩浆的生成条件和过程，揭示了岛弧深部地壳的热结构和岩浆对变质作用的影响。结合研究结果，提出地壳深熔的起裂深度制约了地壳内部形成的地壳尺度脱脱深度。2)里奥克变质带研究：通过对里奥克变质带主要变质场的原始岩性、构造和构造变质史的研究，明确了以下几个方面；1)原始岩性包括燧石-碎屑层序、页岩-砂岩的相干地层、破碎地层和混杂岩。2)将变形阶段定义为D1（变平伴S1片理作用）、D2（局部剪切伴枝内褶皱和剪切面S2伴进变质作用）、D3（局部剪切伴逆行变质作用）和D4（缩短伴直立褶皱和砾岩裂解作用）。通过对其热结构和加热过程的分析和数值模拟，证实了同变质花岗岩侵入岩为热源。进一步进行了CHIME独居石年龄测定，表明变质期为100Ma，花岗岩侵入期为95Ma ~ 80Ma。黎奥克带侵入年龄没有自西向东的年轻化趋势，而迄今所主张的K-Ar年龄年轻化趋势暗示了一个自西向东的连续发掘过程。3) Higo片麻岩区研究：发现滑石-刚玉质过铝质岩石以块体形式赋存于蛇纹岩中。Nd-Sm和SHRIMP锆石锆石表明，变质岩形成于250Ma，在Ryoke期受到多变质热效应的影响。4)开展了该区高温变质岩烃源岩研究，明确了沉积岩的性质和烃源区；早至晚元古界碎屑被包括在黎奥克带的副长岩中，就像在构成侏罗纪增生杂岩的沉积岩中一样。少

1) Study of the Hidaka metamorphic belt : Thermal structure and effects of magma to metamorphism in the deep island arc crust was revealed based on the analyzes of conditions and processes of partial melting and generation of tonalitic magma of granulite facies metamophic rocks in the Hidaka belt. Related to the results, it is proposed that the depth of initiation of crustal anatexis constraints the depth of crustal scale decollement formed in the crust.2) Study of the Ryoke metamorphic belt : The following aspects were made clear according to the studies of original lithology, structures and tectono-metamorphic histories in major metamorphic fields of the Ryoke belt ; 1) the original lithology involves chert-clastic sequence, coherent strata of shale and sandstone, broken formation, and melange. 2) deformational stages are defined as D1 (flattening with S1 foliation), D2 (local shearing with intrafolial folds and shear planes S2 accompnied with prograde metamorphism), D3 (local sheari … More ng with retrograde metamorphism) and D4 (shortening with upright folds and crenulation cleavages).The thermal structure and heating process were analyzed and numerically sumilated to confirm that syn-metamorphic granitic intrusives playd as a heat source. CHIME monazite age determinations have been advanced and showed that the metamorphic age is 100Ma, and granitic intrusions were continued from 95Ma to 80Ma. There is no younging trend of intrusive age from west to east of the Ryoke belt, while the younging trend of K-Ar ages so far advocated implies a continuous exhumation taking place from west to east.3) Study of the Higo gneiss region : Saphilline-corundum bering peraluminous rocks were found to occur as blocks included in serpentinite. The Nd-Sm and SHRIMP zircon ages indicate that the metamorphic rocks were formed at 250Ma, and suffered polymetamorphic thermal effect during the Ryoke period.4) Studies on source rocks of high temperature metamorphic rocks in these belts have been advanced to make clear the nature of sedimentary rocks and their source regions ; Early to late Proterozoic clastics are included in paragneisses in the Ryoke belt as in the sedimentary rocks consisting Jurassic accretionary complex. Less