Delineating geothermal system through 3D geomagnetic and gravity data inversion on Blawan Ijen geothermal area, East Java

Blawan-Ijen is a caldera hosted geothermal system that located in Bondowoso, East Java. To delineate the existence of the geothermal system of Blawan-Ijen, gravity and geomagnetic studies were conducted. Since no impressive manifestation in this area, to delineate the prospect area is very challenging. Both methods are used to detect the presence of basements and potential heat sources. Gravity data processing was processed to obtain CBA and residual gravity anomalies, while geomagnetic data was processed until reduce to pole. The results of data processing are used for 3D inversion of gravity and geomagnetic data to find out anomaly distribution horizontally and vertically. To understanding potential heat source, 3D inversion results are displayed at an elevation of 500 m to 1,000 m. The existence of resources using the geomagnetic method is represented by a low magnetic anomaly value as an indication of demagnetized rocks, but high gravity anomalies are seen in the demagnetization area. The potential heat source from gravity and geomagnetic interpretation located in the center of the Blawan-Ijen geothermal prospect, that is the northern part of the south mountainous area, those areas are located around Mt. Gendingwuluh and the northern part of Mt. Genteng and Mt. Glaman.