1994 Fiscal Year Final Research Report Summary
Analysis of formation conditions for microcracking with fluid inclusions
| Project/Area Number |
04452077
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
地質学一般
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| Research Institution | HIROSHIMA UNIVERSITY (1993-1994)
Ehime University (1992) |
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Principal Investigator |
TAKESHITA Toru Hiroshima Univ.Faculty of Science, Associate Professor, 理学部, 助教授 (30216882)
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| Project Period (FY) |
1992 – 1994
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| Keywords | healed microcrack / fluid inclusion / Momonoki Subgroup / deformation microstructures in guartz / deformation lamella / kink band / paleostress field analysis / orientation distribution of microcracks |
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| Research Abstract |
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.
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