Hydrothermal deposits in the Gyeongsang Basin show the genetic relationship with igneous activity from Late Cretaceous to Early Tertiary in the spatial and temporal viewpoints. Many hydrothermal Au-Ag-Cu-Pb-Zn and clay deposits are dominantly distributed within the Gyeongsang Basin. The Gyeongsang Basin is divided into seven metallogenic provinces by spatial distribution. The age ranges of igneous activity and mineralization are 140~40 Ma and 100~40 Ma, respectively, and the most dominant age ranges of the both activities are from 90 Ma (Coniacian) to 50 Ma (Eocene). The age consistency between igneous activity and mineralization suggests that this age range is the climactic period of the hydrothermal activity of the Gyeongsang Basin. The metallogenic epochs in the Gyeongsang Basin are divided into three epochs of 100~80 Ma (western part of the Gyeongsang Basin), 80~60 Ma (central part of the Gyeongsang Basin), and 60~40 Ma (eastern part of the Gyeongsang Basin). The mineralization and igneous activity tend to become young eastward in the Gyeongsang Basin.NNW-SSE mineralized veins from 100 to 80 Ma in the western part of the Gyeongsang Basin are interpreted as the control of the parallel tensional fissures caused by NNW-SSE compressional stress. NW-SE mineralized veins from 80 to 60 Ma in the central part of the Gyeongsang Basin seem to have been formed under the same stress as that of the Gaeum and Yangsan Fault Systems. Namely, NW-SE tensional stress is associated with a conjugate set of fracturing of the WNW-ESE Gaeum Fault System and NNE-SSW Yangsan Fault System. Also NE-SW mineralized veins from 60 to 40 Ma in the eastern part of the Gyeongsang Basin seem to be controlled by the NE-SW fractures. The fractures are related with NE-SW compressional stress and are developed as secondary fractures within the dextral strike slip Yangsan Fault System.
Kinematical and fractal analyses were conducted on a fracture network in a well-exposed granite outcrop in SE Korea. The objective of this study is to examine the temporal and spatial evolution of the fracture network. From the orientation and abutting relationships of fracture sets, six fracturing events and their relative ages were established, several of which included strike-slip reactivations of earlier formed fractures. These events may be correlated with the Cenozoic to Recent evolution of the Yangsan Fault and surrounding areas. 2-D box counting analyses were performed on maps of the fracture network at the six stages of its evolution. For the earliest event D = 1.11, and represents a clustered development of fractures. Event 2 leads to a large increase of D = 1.51, with subsequent events producing a gradual increase up to 1.55 after the final event. This stabilization of the fractal dimension involved a change from the widespread development of new fractures (event 2) to the greater importance of reactivation of existing fractures, with only localized development of new fractures, usually as tip and linkage damage around pre-existing fractures. Fracture density was greatest for the event 2 fractures and increased only gradually after that. This pattern is similar to that of the fractal dimension and a good linear correlation was found between these two parameters. Although fractal dimensions and density show little change during the late stages of deformation, the fracture connectivity continued to increase due to the formation of local secondary fractures developed during reactivation of earlier formed fractures.
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