Tectonic Evolution of the Southern Negros Geothermal Field and Implications for the Development of Fractured Geothermal Systems

Figure 8

Cross-cutting observations. (a) NE–SW sinistral group 2 fault (in yellow broken line) offsets a WNW-ESE sinistral group 1 fault zone (in red). (b) Group 2 tensile fractures (yellow broken lines) also cut group 1 tensile fractures (red broken lines). (c) Group 1 pyrite-filled (in red) tensile fracture is reactivated and filled with quartz with sulphur precipitates (in yellow). (d) Cross-cutting pyrite (group 1) and quartz vein (group 2) in thin section. (e) An E-W moderately dipping group 2 fault (red line) has preserved two sets of overlapping slickenlines—(f) near vertical and (g) subhorizontal, suggesting two directions of movement along one fault.