Analysis of formation conditions for microcracking with fluid inclusions

该基金资助的研究主要以分布在山梨县北库马区木川村的中中新世Momonoki亚群为样板。(1)对研究区Momonoki亚群的地层和褶皱结构有了许多新的发现.(2)Momonoki亚群起源的糜棱岩化接触光环沿Yakegizo花岗岩存在，可能代表与花岗岩侵入有关的围岩的塑性变形.(3)Momonoki亚群砂岩中的古应力场与石英碎屑颗粒中的变形微构造有关，即变形片层、扭结带和愈合的微裂缝.(4)愈合微裂隙中流体包裹体的均一温度在200~260ﾟC之间。当对均一温度进行适当的压力校正时，认为石英在300ﾟC左右发生变形。此外，我研究了三巴川变质带梯状石英脉中流体包裹体的变形显微结构和均一温度，截断了其褶皱结构。(2)石英脉的均化温度范围为150~350ﾟC，最高温度群为300~330ﾟC，表明流体被困在400ﾟC左右。高温流体可能指示桑巴川变质带抬升后出现新的热源。

The research supported by the grant has mainly been conducted on the Middle Miocene Momonoki Subgroup distributed in the Mukawa village, Kitakoma district, Yamanashi prefecture as a model field. The obtained results are following.(1) I have obtained many new findings concerning the stratigraphy and fold structure in the Momonoki Subgroup in the studied area.(2) A mylonitized contact aureole originated from the Momonoki Subgroup exisits along the Yakegizo granite, which presumably represents plastic dcformation of the wall rock associated with the intrusion of the granite.(3) Paleostress field in the sandsones from the Momonoki Subgroup has been inferred with deformation microstructures in the quartz detrital grains, namely defrormation lamellae, kink bands and healed microcracks. The paleostress field perhaps indicates that the one during the folding of the Momonoki Subgroup (Takeshita, 1995, in press).(4) Homogenization temperatures of the fluid inclusions along the healed microcracks range between 200-260ﾟC.When an appropriate pressure correction is applied to the homogenization temperatures, it is suggested that the quartz deformed at ca.300ﾟC.Furthermore, I investigated the deformation microstructures and homogenization temperatures of fluid inclusions in echelon quartz veins from the Sambagawa metamorphic bets, which truncated its fold structures. The following results have been obtained.(1) The preferred orientations of healed microcracks are characterized by orthogonal pattern, where each preferred orientation is normal to one of the principal stress axs.(2) The hmogenization temperatures in the quartz veins range from 150 to 350ﾟC,and the highest temperature group, 300-330ﾟC suggests that the fluid was trapped at ca.400ﾟC.The high temperature fluid could indicate the emergence of a new heat source after the elevation of the Sambagawa metamorphic belts.