• The Journal of the Petrological Society of Korea
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• v.13 no.4
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• pp.191-200
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• 2004

The Ubo fault Bone, which cross over the northwestern to southeastern direction at the Hwabuk damsite in Hakseongri, Gunwigun, Gyeongsangbukdo Province, has length about 20km. The Ubo fault zone in this area is segmented to several small faults and makes a gentle slope and hill along the right side of the drainage in the Hwabuk dam. In the storage area of Hwabuk dam, 2 pairs of faults occur and the width of fracture zones are about 2m. To define the fracture Bone using the geochemical data, the samples were collected at 0.5m, 1m, 2m, 4m, 8m, 16m and 32m apart from the center of the main fracture Bone toward north and south, respectively, and analyzed for major elements and mineral content Approaching the fracture Bone, Fe$_2$O$_3$, MgO, K$_2$O, quartz, muscovite and chlorite are increasing and Na$_2$O, CaO, plagioclase and biotite are decreasing, respectively. Based on the rock chemistry and mineral content, the range of the main fracture zone affected by the Ubo fault at Hakseongri is 2m width in total, the secondary deformed zone is 8m width in total. Finally the maximum affected range by the Ubo fault is inferred to 16m width in total.