Modeling for the development of the crust

利用高质量的岩石学、矿物学、地球化学和连续体动力学等方面的自然资料，构建了表征下地壳岩石形成机制和运动过程的定量数值模型。研究小组由“数据收集”组和“建模”组组成。1)破译了三八川带相邻区域俯冲路径的差异。结果表明，该带的隆升方向与俯冲方向平行。2)在Abukuma和Ryoke带，高品位部分发生部分熔化的范围比迄今所认识的要大。新的测年技术，如SHRIMP和CHIME，明确了这些带的原岩和变质时间。在这些带的较高品位部分发现了许多扇形带石榴石。这种石榴石的生长和高品位部分从片岩到片麻岩的突变，是由于高品位部分地壳物质的部分熔融作用造成的。否定了将良奥克带的热源归因于洋脊俯冲作用的假说。3)明确了苏鲁地区火成岩向超高压（UHP）岩石的转变，以及中压（MP）组合在超高压岩石上的叠加作用，表明苏鲁地区在100km深处曾存在一定的超高压正性，超高压岩石的分解过程相当迅速，没有明显的降温作用。4)二维x射线图显示，即使在品位较高的变质岩中，也存在通过单变线超越而实现过饱和体系不可逆结晶的现象，在品位较低的变质岩中，即使在石榴石的岩心中也发生了元素交换。这些事实表明，通过反演分析确定变质岩的P-T-t路径需要慎重处理。5)这些数据为建模提供了定量约束。提出了建立解释下地壳各种物理现象的定量数值模型的指导方针。少

This research was organized to construct a quantitative nemerical model for repressenting the rock forming mechanism and kinematic process in the lower crust using the high quality natural data on petrology, mineralogy, geochemistry and continuum dynamics. The study group is composed of a "data collection" group and "modeling" group.1) In Sanbagawa belt, the difference of subduction path between neighboring regions is deciphered. It became clear that the direction of the uplift of the belt is parallel to the trend of the subduction direction.2) In Abukuma and Ryoke belts, partial melting took place in a wider area of the higher grade parts than hitherto recognized. New dating techniques such as SHRIMP and CHIME make clear the protolith and metamophic timings of these belts. Many sector zoned garnets were found from the higher grade parts of these belts. The growth of such garnet and the abrupt texture change from schistose to gneissose in the higher grade parts were ascribed to the par … More tial melting of crustal material in the higher grade part. An hypothesis on the thermal source of the Ryoke belt ascribed to the subduction of the oceanic ridge was denied by this study.3) In the Su-Lu region, the transition of igneous rocks to ultrahigh pressure (UHP) rocks, and the overprinting of medium pressure (MP) assemblage on the UHP rocks are clarified, which demonstrated that some MP orthogneiss of the Su-Lu region were once located in the depth of 100km depth and that the decomposition process of UHP rocks are fairly rapid without significant cooling.4) 2-dimensional X-ray mappings reveal that the irreversible crystallization in over-saturated system, realized by overstepping of univarinat line, is common even in the higher grade metamorphic rocks, and that the element exchange took place even in the core of the garnet in the lower grade rock. These fact suggest that the careful treatment is need to determine the P-T-t path of metamorphic rock by inversion analyzes.5) These data give quantitative constraints on the modeling. The guide line for producing the quantitative numerical model for explaining various physical phenomenons in the lower crust is proposed. Less