Magnetotellurics (MT) is an important geophysical method for exploring geothermal systems, with the Earth resistivity obtained from the MT method proving to be useful for the hydrothermal imaging changes of the system. In this research, we applied the MT method to map the geothermal system of the Seulawah Agam volcano in northern Sumatra, a site intended for the construction of a geothermal power plant with an estimated energy of 230 Mwe. Herein, 3D MT measurements were carried out, covering the entire area of the volcano and the various intersecting local faults from the Seulimeum segment in the NW–SE direction. Based on Occam 2D inversion, a conductive anomaly (<10 ohm·m) near the surface was identified in response to specific manifestation areas, including the Heutsz crater on the northern side and the Cempaga crater on the southern side. A further conductive anomaly was also found at a depth of 1 km, which was presumably due to a clay cap layer covering the fluid in the reservoir layer below the surface, where the manifestation areas are formed at various locations (where faults and fractures are found) owing to the fluid in the reservoir rising to the surface. The MT modeling also revealed that the reservoir layer in Seulawah Agam lies at a depth of 2 km with a higher resistivity of 40–150 ohm·m, which is the main target of geothermal energy exploration. At the same time, the heat source zone where magma is located was estimated to lie in two locations, namely, on the northern side centering on the Heutsz crater area and the southern side in the Cempaga crater area. A clear 3D structure obtained via Occam inversion was also used to visualize the hydrothermal flow in the Seulawah Agam volcano that originates from two heat source zones, where one structure that was consistent across all models is the conductive zone that reaches a depth of 5 km in the south in response to the regional faulting of the Seulimeum segment. Based on the MT research, we concluded that the volcano has the geothermal potential to be tapped into power plant energy in the future.

A sedimentological, biostratigraphic, and petrographical investigation was conducted on exposed sedimentary rocks in the Seulimeum Formation in the Northwest Aceh Basin, Sumatra. Sedimentary facies analysis suggests a deep-marine depositional environment consists of an inner fan, middle fan, and outer fan to basin plain deposits. New foraminiferal data designated a late Miocene to early Pleistocene age for the studied rock unit, equivalent to N17 to N21 zone, with paleobathymetry in the bathyal environment. Petrographically, the sandstone of the Seulimeum Formation is included as subarkose, sublithic arenite, and lithic arenite, or classified as litho-quartzose, feldspatho-litho-quartzose, and litho-feldspatho-quartzose. Provenance analysis suggests that the origin of the sandstones is from the arc orogen sources. Furthermore, it is concluded that the development of the GSF zone in the late Neogene controls the formation of the deep-marine depositional setting. The west-south-west part of the fault is the footwall part (the Barisan Mountains), as the main high area of sedimentary source material consisting dominantly of the Woyla Group, with some contributions from Bentaro volcanic and Paleogene to early Neogene sediments. Our findings also suggest that the beginning of the Great Sumatran Fault, which corresponds with the uplift of the Barisan Mountains in the northern part of Sumatra, took place in the late Miocene, between 8.6 and 5.9 Ma.

Lambada Lhok is one of the coastal areas with the most severe water crisis in Aceh Besar, Aceh. Clean water crisis happening in the area because of their breach of saltwater into freshwater aquifers and also due to the large decrease in ground water level that resulted in seawater intrusion. This research was conducted on four lines at two locations, namely: 3 (three) lines in the village of Lambada Lhok and 1 (one) line in the village of Kajhu. Kajhu village was used as comparative data for areas that are free from the intrusion of sea water. The research method using 2D resistivity Wenner-Schlumberger configuration, while the data acquisition using the ARES equipment. Data analysis using Res2Dinv software to make 2-dimension (2-D) cross section model. Lambada Lhok village is an alluvial deposition with an average height of 0-5 meters above sea level (dpl). The subsurface lithology of the village lambada lhok consists of clay sand, sandy clay and clay. Based on the results of the analysis of resistivity values indicate that the suspected sea water intrusion in the village of Lambada Lhok reaches a depth of 29 meters. It can be concluded that the spread of sea water intrusion in Lambada Lhok beginning of the line LL 1, LL 2 to LL 3. Distribution of seawater intrusion are most severe in the trajectory LL 2 and began to decrease at LL 3 trajectory.

Seulawah volcano, located in Sumatra, Indonesia, is renowned for its geothermal potential, a crucial source of cleaner energy for Indonesia’s future growth and security. Available studies of Seulawah volcano primarily focus on its general geological, geochemical, and regional characteristics, with limited research on its shallow subsurface conditions. This study aimed to fill this research gap and enhance our understanding of the geothermal system of Seulawah volcano. There are two objectives of this study: (1) to conduct a transient electromagnetic (TEM) survey across the study area and (2) to better visualize and characterize the shallow subsurface conditions of the geothermal system of Seulawah volcano. The TEM method, which employed 60 stations (with distances between stations ranging from 0.5 to 1 km) and intersected several geothermal manifestations as well as local and regional faults, was used to achieve the objectives of this study. The Occam algorithm was applied for 1D inversion of TEM data, which was then validated using magnetotelluric data. The results of this study indicate that the geothermal system of Seulawah volcano has the potential to generate up to 230 Mwe of electrical energy. Moreover, the shallow depth (10 Ωm. At a depth of 500 m, a conductive layer with resistivity values <10 Ωm was observed, interpreted as a clay cap where fluids from the reservoir layer accumulate. Validation with magnetotelluric data shows results consistent with the TEM data, confirming that the findings of this study are reliable. These findings contribute to a deeper understanding of the geothermal system of Seulawah volcano and are expected to support the development of greener, renewable energy sources for Indonesia.

The Tamiang region in Aceh, Indonesia, is geologically complex and underexplored, with limited baseline geochemical data. This study conducted a reconnaissance geochemical survey to evaluate spatial variations in metal concentrations and their geological controls. Forty stream sediment samples from various drainage systems across the region were analyzed for 22 elements (Al, As, Ba, Ca, Co, Cr, Cu, Fe, K, La, Li, Mn, Na, Ni, Pb, Sc, Sr, Ti, V, Y, Zn, Zr) using ICP-OES. Nineteen elements exhibited anomalous concentrations, with Cu, Ca, Li, and Na showing particularly high anomalies, whereas Al, Sc, and Y remained within background levels. Based on their geochemical behaviour, the elements can be grouped into major lithogenic elements such as Al, Fe, Ca, K, Na, Ti, Sr, and Zr, which reflect lithology and weathering intensity, and ore-related elements including Cu, Pb, Zn, As, Co, Ni, and Cr, which may indicate localized metal enrichment. Rare earth and high field strength elements such as La, Y, Sc, Li, Zr, and Ti provide insight into source rock composition and magmatic or weathering processes, while miscellaneous elements including Mn, Ba, and Sr show mixed lithological or secondary origins. The spatial distribution of these anomalies may suggest localized metal enrichment associated with specific lithological zones. Despite the reconnaissance scale and limited sampling density, these results provide a preliminary geochemical framework for the Tamiang region, supporting future geological and geochemical investigations and contributing to a robust scientific assessment of the area.

This study investigates the geochemical distribution of rare earth elements (REEs) in stream sediments from the Aceh Tamiang Regency, Aceh Province, Indonesia, an area characterized by a complex geological framework and potential lanthanide-bearing source rocks. Rare earth elements such as lanthanum (La), scandium (Sc), and yttrium (Y) are essential to modern high-technology and clean-energy applications, yet baseline data from this region remain limited. A total of forty stream sediment samples were collected from the Simpang Kanan, Simpang Kiri, Tamiang, and Tenggulun rivers to determine the spatial distribution and concentration levels of La, Sc, and Y. All three elements were detected in the riverbed sediments in the study area, with La showing higher concentrations (average 11 ppm) compared to Sc (2 ppm) and Y (3 ppm). Higher values are observed in upstream sediments underlain by igneous and metamorphic rocks, while lower values occur in downstream sedimentary zones. This distribution pattern indicates that the enrichment of REEs is primarily derived from the weathering of upstream source rocks. Additionally, the presence of active tectonic structures in the region may have contributed to the mobilization and accumulation of these elements. This study establishes a baseline of REE distribution in stream sediments of Tamiang and provides valuable data that may support broader regional geochemical investigations.