Ciremai Volcano is the youngest active volcanic system within the Ciremai Volcanic Complex (CVC), located on the northern coast of West Java. This study aims to further investigate the characteristics of the magmatic system as part of the Sunda Arc. The activity of the CVC is divided into four periods: Putri Volcano, Gegerhalang Volcano, Wurung Crater, and Ciremai Volcano with its parasitic cones. The magmatic evolution of the CVC is reflected in the characteristics of its lava throughout its volcanic history. Petrographic analysis reveals that the volcanic rocks of the CVC are predominantly composed of plagioclase, pyroxene, olivine, hornblende, and opaque minerals as phenocrysts. The magma exhibits calc-alkaline affinity, with Fe enrichment during the early stages of magma formation. The enrichment of incompatible elements (Sr, K, Rb, Ba, and Th), depletion of HFSE (Nb, P, and Ti), and the presence of xenoliths suggest a convergent margin setting, with a continental-derived sediment enrichment in the magmatic source. Both petrological and geochemical analyses indicate that the magmatic evolution of the CVC has an interconnected open-system magma dynamic. Major basaltic injections and mixing of basaltic magma likely triggered a significant eruption at the end of Gegerhalang and contributed to the development of new magma conduits. Besides fractional crystallization, the post-caldera magmatism of Wurung Crater, Ciremai, and its parasitic cones is affected by a prolonged basaltic influx and magma reheating.
The Yogyakarta region is one of the most seismically vulnerable areas in Indonesia, so detailed subsurface fault characterization is crucial for effective disaster mitigation strategies. Previous studies have recognized the Opak Fault as the main structure controlling seismicity in this area, but the geometry and existence of other fault systems remain less constrained. This study aims to delineate the subsurface density variations associated with fault zones and rock deformation. This study develops a two-dimensional gravity inversion model to refine the subsurface configuration of faults in southern Yogyakarta. Gravity data were processed through standard corrections and anomaly separation to generate a complete Bouguer anomaly and residual anomalies. The results show that residual anomalies (-60 to 100 mgal) successfully delineate lithological variations, where older volcanic units (Semilir, Nglanggeran, and Sambipitu Formations) produce positive density contrasts (0.4-0.85 g/cm³), while younger Merapi deposits display negative contrasts (-0.5 to -0.05 g/cm³). Importantly, the 2D model highlights not only the Opak Fault but also the Ngalang Fault to the east, spatially coinciding with the 26th May 2006 earthquake epicentre. This finding provides new evidence of the structural complexity in southern Yogyakarta and emphasizes the role of the Ngalang Fault in regional seismicity, offering an updated basis for seismic hazard assessment in the area.
One transformative, inexpensive (~$0.5-1/kg), and low-carbon energy source is natural hydrogen produced by serpentinization and other geochemical processes. Global data on its accumulation, migration, and geological mechanisms have been collected in the present study. Temperature, pressure, and mineralogy all affect the rate at which hydrogen is generated. While very limited hydrogen is produced at low temperatures (0.01-1 mmol/kg), significant production (1-100 mmol/kg) is made possible by ideal hydrothermal conditions (200-315° C), with extremely high rates (100-360 mmol/kg) possible under extreme experimental conditions. The evaluation of Indonesia's enormous potential, situated within the vast East Sulawesi Ophiolite Belt, is a primary focus. The country's tectonic environment offers the three necessary components for a significant hydrogen play: a steady geochemical engine, a large supply of source rock, and efficient migration routes. Consequently, Indonesia stands poised to emerge as a potential leader in the regional hydrogen economy. To realize this potential, specific exploration and regulatory support must be initiated, and technical issues related to gas purity must be resolved. This work presents the scientific and financial justification for prioritising natural hydrogen in the global energy transition.
This study presents a comprehensive geochemical and hydrogeological characterization of the Wayang Windu Geothermal System in West Java, Indonesia. The research aims to identify water and gas chemistry patterns, to determine fluid origins, and to estimate reservoir temperatures to support conceptual modeling of the geothermal field. Field sampling was conducted on hot and cold springs and fumarolic gases, complemented by laboratory analyses of major ions (Cl⁻, SO42⁻, HCO3⁻; Na⁺, K⁺, Mg2+), stable isotopes (δ2H, δ18O), and gas compositions (CO2, N2, Ar). Data interpretation employed standard geochemical tools, including Cl-SO4-HCO3 and Na-K-Mg diagrams for water classification, δ2H-δ18O plots for recharge source identification, and N2-CO2-Ar ternary diagrams for gas origin assessment. The results indicate that sulphate-type hot springs mark upflow zones, while bicarbonate-type warm and cold springs reflect lateral outflow and mixing processes. The isotopic signatures confirm predominantly meteoric recharge with localized steam-heated and magmatic influences. The gas geothermometers estimate reservoir temperatures between 225° and 286° C, and Cl-Li-B relationships reveal three distinct reservoir clusters: Gambung, Wayang, and Windu. These findings provide critical insights into fluid pathways, reservoir structure, and recharge dynamics, forming a robust basis for sustainable geothermal resource management in volcanic settings.
work improves seismic hazard evaluation for the Lampung region in Sumatra by tackling the precision in magnitude conversion, attenuation of seismicity, and area-source modelling. Considering the variety magnitude. The magnitude conversion equations were initially validated using scales from historical earthquake data. And, if required, enhanced to guarantee their dependability for the area. Utilizing maximum likelihood estimation Maximum Likelihood Estimation (MLE) and ordinary. Ordinary least squares (OLS) regression was employed to compute parameters for frequency-magnitude distributions. Facilitating a comprehensive comparison that acknowledges OLS's sporadically superior alignment with observed data. Gaussian distribution smoothing was utilized diverse bandwidths (25, 50, 75, and 100 km) to illustrate spatial seismicity patterns, disclosing a distance of 50 kilometers. Bandwidth provides the most consistent model performance, especially in terms of accuracy in the Molchan illustration. The area skill score (ASS) validates the superior forecasting capacity of the smoothed seismicity models. Using bandwidths of 25, 50, and 75 kilometers producing competitive outcomes. Furthermore, the region was partitioned into discrete seismic zones predicated on fault characteristics and seismicity density, further augmenting localized hazard assessments. This is polished. multi-method approach encompassing magnitude conversion, spatial smoothing, and area-specific analysis. Modelling offers a comprehensive framework for seismic hazard preparedness in Lampung, providing useful insights for infrastructure strategic planning and disaster mitigation.
