Analysis of formation conditions for microcracking with fluid inclusions
Grant-in-Aid for General Scientific Research (B)
|Allocation Type||Single-year Grants|
|Research Institution||HIROSHIMA UNIVERSITY(1993-1994)|
TAKESHITA Toru Hiroshima Univ.Faculty of Science, Associate Professor, 理学部, 助教授 (30216882)
|Project Period (FY)
1992 – 1994
Completed(Fiscal Year 1994)
|Budget Amount *help
¥5,600,000 (Direct Cost : ¥5,600,000)
Fiscal Year 1994 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1993 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1992 : ¥4,400,000 (Direct Cost : ¥4,400,000)
|Keywords||healed microcrack / fluid inclusion / Momonoki Subgroup / deformation microstructures in guartz / deformation lamella / kink band / paleostress field analysis / orientation distribution of microcracks / ヒールドマイクロフラック / 中新統桃の木亜層群 / 変形石英粒子 / 定方位薄片 / 糸魚川ー静岡構造線 / 焼地蔵花崗岩 / 桃の木層 / 接触変成帯 / 石英c軸ファブリック / マイロナイト / ヒールドクラック|
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.
Research Output (18results)