Combination study of magnetic method and 3-D inversion of gravity data to determine the Blawan-Ijen geothermal prospect zone

Integrated measurements of magnetic and gravity methods were carried out over Blawan-Ijen Geothermal Prospect area to discover the indication of prospect zone location more convincing. The acquisition was first conducted in 2017, followed by recent measurement in 2018 with a total of 151 stations for each method. In this research, Reduce to Pole for magnetic data was applied to identify the distribution of demagnetized rock which associated with reservoir zone. The prospect zone is usually indicated by low magnetic susceptibility value. Furthermore, to support the interpretation of prospect zone which usually located overlying the heat source, then 3D inversion of gravity data was conducted. Thus, by applying 3D inversion of gravity method, the distribution of density variation beneath the earth surface which represents the location of heat source can be obtained. The result of Reduce to Pole of magnetic data shows demagnetized zone with low magnetic susceptibility value located in the centre to the southeast at the study area. Moreover, 3D gravity data inversion delineates the existence of heat source indicated by high gravity anomaly which corresponds with demagnetized zone shown from magnetic data.