A Rock Magnetism Approach Using Magnetic Anomaly and Susceptibility Analysis to Identify Hydrothermal Alteration Zones at Mount Lawu
Choirul Singgih Munandar, Budi Legowo, Budi Purnama, dan Jamhir Safani

Sebelas Maret University & Halu Oleo University

Abstract

This study aims to characterize hydrothermal alteration and the distribution of geothermal manifestations based on Earth Magnetic Model (EMM) 2019 satellite data, which was then processed using the Reduce To Pole (RTP) transformation to identify the distribution of magnetic anomalies. The RTP results show anomaly values ranging from -6.21 nT to 2.33 nT, with high-anomaly zones primarily located in the northern and eastern parts of the study area, which are composed of young volcanic rocks, while low-anomaly zones can be found in the western to southwestern parts, associated with hydrothermal alteration and geological structures. Magnetic susceptibility analysis was conducted using the parameters &#967-LF, &#967-HF, and &#967-FD (%). Measurement results indicate that most samples have &#967-FD (%) values < 2%, suggesting a predominance of superparamagnetic grains due to intense hydrothermal alteration. Integration of magnetic and susceptibility data indicates that the distribution of geothermal manifestations is controlled by geological structures such as faults, fractures, and lineaments, which act as pathways for hydrothermal migration toward the surface.

Keywords: Hydrothermal Alteration, Magnetic Anomaly, Magnetic Susceptibility, Mount Lawu

Topic: Earth Physics and Space Science