Simulated Organic Metamorphism in Diagenetic to Burial Metamorphic Stage.

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Original plan of this study attempted to apply a large scale triaxial rock mechanical testing machine for simulated organic metamorphic experiment if high temperature heating vessel was supplemented by sufficient financial support of the grant-in-aid. Owing to unexpected curtail of the financial support, the original plan had to reform and substitute characteristic natural geological phenomena as gigantic experimental result for the expected large scale simulated experiment.In order to replace the expected laboratory experiment to natural geological phenomena, two characteristic geotectonic provinces in Kyushu that have remarkable different tectonic history of the Shimanto accretionaly body in the outer zone and the central axial body near the Usuki-Yatsushiro Tectonic Line (M. T. L.) were adopted as the experimental target. The revised studies on the fields and an auxiliary small scale laboratory experiment have revealed rather satisfactory result by applying the vitrinite reflectance as one of the parameters of organic metamorphism.In the Shimanto accretionaly body, minimum vitrinite refrectance (Rmin) ranging from catagenetic to metamorphic stage shows rather regular pattern parallel to the direction of stress caused by the subducting movement of the Philippine Sea plate. On the other hand, minimum vitrinite reflectance (Rmin) ranging from catagenetic to metagenetic stage in the axial body shows different directions even at one location, which can be attributed not to simple deformation in a single heating process, but to multi-directional displacement and polymetamorphic thermal alteration. The results still remain quantitative solution on temperature and pressure levels during the deformation owing to insufficient laboratory experimental studies which is succeeded to future research.