10월 27일(수)
․구조지질학 | 지체구조학
52 2010 추계지질과학연합학술발표회 초록집
Tectonic Conditions and Fluid Flow: An Example from the Fracture and Dyke System Developed in West Goseong
Paul Edwards
*․Jin-Hyuck Choi․Young-Seog Kim Pukyong National University, [email protected]
The West Goseong area is composed of coastal outcrops in the South of South Korea, which have been studied extensively on a sedimentary level. In this study, we outline the post-deposition tectonic history and fluid flow characteristics of this area. Multiple stages of passive intrusive igneous activity and fluid movement, that results in vein filled joints over time, record the progressive changes in the tectonic regime in the area, resulting from the changing tectonic stresses over time. The development of joint sets, fault movement, dyke emplacement and their cross-cutting relationships allow us to build a relative tectonic history of the area.
Five clear tectonic events can be found in West Goseong, The earliest E-W compression, is characterized by mode I E-W trending joints, dykes and left-lateral NW strike-slip faulting.
The next stage of deformation is caused by N-S compression, resulting in E-W extension with mode I N-S joints, dykes, normal faulting, and reactivated right-lateral NW strike-slip faults.
This stage is followed by NE trending extension and pre-existing NW trending faults are reactivated as normal faults with dyke emplacement. Some NW dykes are associated with transgressive (stair-case) sills. N70°W compression resulted in N70°W trending mode I joints and dyke emplacement. Finally a second E-W compression produced further E-W mode I joints, left-lateral strike-slip on N70°W fractures and a second swarm of E-W dykes. We found that fluid flow in rocks is strongly controlled by in-situ stress conditions. Thus, geological fluids such as hydrothermal solutions and magma predominantly flow into and precipitate in extensional fractures rather than faults. Therefore, thick veins and dykes generally form in linkage zones between segment faults, where large extensional fractures are developed.
The way that fluids are transported through and/or in faults and fractures is becoming more important in petroleum geology, structural geology and various other fields. This study can help us to understand how changes in tectonic conditions can influence fluid migration pathways in brittle rocks.
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