A RING-FAULT DELINEATION OF AN ANCIENT VOLCANIC CALDERA BASED ON 3-D GRAVITY INVERSE MODELING IN MAJENANG REGION, INDONESIA

Calderas are important geological features in all volcanic environments due to give directives clues of resources such as geothermal system, mineralization, or even oil and gas potential reserved. The ability recognizing these specific play an role the exploration activities. A good understanding settings will bring right direction make activities becomes optimized cost effective. Gravity method is commonly used for preliminary study almost any cases lightweight, low-cost, figure out a wide region quickly. has excellent lateral resolution but it limitation with vertical resolution. Applying depth-weighting mechanism makes, inverse-modeling result interpretable. According research, there northwest-southeast dextral strike-slip fault area, which belongs Pamanukan-Cilacap Fault Zone (PCFZ). Circular anomaly pattern also delineated interpreted ring-fault ancient caldera area. Several high gravity located within caldera-rims lava domes intrusion rocks. eruption center point estimated at around Majenang city. PCFZ behaves weak zones area where magmatism rise through create volcano, now remain Caldera.
 Keywords: Gravity, Caldera, Ring-Fault, Geological-Resources, Indonesia.