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

1)东高变质带研究：通过对东高变质带麻粒岩相变质岩部分熔融和形成的条件和过程的分析，揭示了深岛弧地壳的热结构和岩浆对变质作用的影响。结合研究结果，提出地壳深熔作用的启动深度制约着地壳形成的地壳规模滑脱深度。2)Ryoke变质带的研究：通过对Ryoke带主要变质区的原始岩性、构造和构造变质史的研究，明确了以下几个方面：1)原始岩性包括硅质岩-碎屑层序、页岩和砂岩的相干地层、破碎地层和混杂岩。2)将变形阶段定义为：D_1(S1面理压扁)、D_2(局部剪切、叶内褶皱和剪切面S_2伴随进变质作用)、D_3(局部剪切…D4(带直立褶皱和褶皱解理的缩短作用)。对热结构和加热过程进行了分析和数值总结，证实了同变质花岗岩侵入岩是热源。嵌合体独居石年龄测定取得进展，变质年龄为100 Ma，花岗岩侵入作用延续时间为95~80 Ma。Ryoke带自西向东没有侵入年龄的年轻化趋势，而迄今所主张的K-Ar年龄的年轻化趋势意味着从西向东发生了持续的折返作用。3)HIGO片麻岩地区的研究：萨菲林-刚玉白令辉铝质岩石以块状产出于蛇纹岩中。Nd-Sm和SHRIMP锆石年龄表明变质岩形成于250 Ma，并在Ryok期遭受了多次变质热效应。4)对这些带高温变质岩源岩的研究已经深入，以弄清沉积岩及其源区的性质；Ryoke带的副片麻岩中含有早至晚元古代碎屑岩，与侏罗纪增生杂岩的沉积岩一样。较少

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