Geothermal Fluid Determination and Geothermal Stones Mineral Identification at Geothermal Area Tinggi Raja Simalungun, North Sumatera, Indonesia using 2d Resistivity Imaging

This reserach is done to determine the geothermal fluid flows beneath the ground by using 2D resistivity imaging and to identify the stones that compile the mineral by using XRD at geothermal Area Tinggi Raja Dolok Morawa Simalungun, North Sumatera Province. The area is located at 02º36’- 03º18’ N and 98º32’- 99º35’ E. The results from XRD by using difractometer Jeol-350 Shimadzu 6100 Show that the intensity from x ray difraction has the geothermal fluid spreads laterally to the geothermal manifestation. Three lines were surveyed by using 2d resistivity imaging for geothermal delineation purpose. At Tinggi Raja, the 2d resistivity imaging survey site shows the existence of geothermal fluid flows. The maximum depth of investigations for the surveys is 25 - 30 meters and 155 m of length of each line. The array used in this study are Schlumberger. In general the results show that the subsurface is made up of limestone (resistivity value of less 100 ohm-m) and clay with resistivity also less than 100 ohm-m in all the sections. XRD survey shows the mean mineral that compile the getothermal stones at Tinggi Raja are calsit (CaCO3) with trigonal crystal system (hexagonal). This mineral is the mean mineral that compile the clay. Keywords: resistivity method, XRD, clay and limeston