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Journal : Journal of Geoscience, Engineering, Environment, and Technology

Petrochemistry of Ultramafic Rock in Baula - Pomalaa Ophiolite Complex, Southeast Sulawesi, Indonesia Cendrajaya, Rio Irhan Mais; Juarsan, Laode Ihksan; Masri; Rubaiyn, Al; Syahrul; Neni; Ramadani, Suci; Hasria
Journal of Geoscience, Engineering, Environment, and Technology Vol. 9 No. 1 (2024): JGEET Vol 09 No 01 : March (2024)
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25299/jgeet.2024.9.1.14491

Abstract

Baula and Pomalaa Ophiolitic Complexes are part of East Sulawesi Ophiolite (ESO). The ultramafic rocks in the Baula and Pomalaa Ophiolite Complex mainly is peridotite and consist of harzburgite, lherzolite and olivine websterite, mostly serpentinized. Chemical and petrological research has focused on minerals, such as olivine, pyroxene, and spinel. This study examines the tectonic setting and temperature of ultramafic rock formation. Twelve ultramafic rock samples were examined using geothermometers made of pyroxene, petrographic examination, and coexisting olivine and spinel analyses. SEM and petrographic analysis of pyroxene lamellae and mylonite-ultramylonite structures allowed for the measurement of the geothermometer of ultramafic rocks. Using SEM-EDS, the coexistence of olivine and spinel was analyzed to determine the type of ultramafic tectonic setting. In the coexistence of olivine and spinel, olivine and spinel oxide compounds as tectonic setting markers in the form of Fo and Cr# values. Ultramafic rocks have different temperature levels, based on pyroxene thermometer, and the first one starts at a high temperature of 1000-1200ºC. It is characterized by thin, elongated augite lamellae. Instead, large lamellae characterize augite at medium temperatures (800–1000ºC). Irregular, anhedral, and broader forms of enstatite lamellae are typical of low temperatures (500–800ºC). Different generations of exsolution lamellae indicate that magma cooling was gradual. The distribution of #Fo ranged from 0.87 to 0.92, and Cr# values ranged from 0.13-0.19. According to coexisting olivine and spinel analysis. On the Olivine-Spinel Mantle Array (OSMA), the Fo and Cr# plot indicates that the peridotites tectonic setting was from the ocean floor and the magmatism was from MORB (Mid Oceanic Ridge Basalt). The Al2O3 vs. TiO2 pattern in spinel lherzolite also similar with Ampana and Kabaena peridotites magmatism.
Assessing the Carbon Sequestration Potential of Ultramafic Rocks in the Kolaka Ophiolite Complex, Southheastern Sulawesi: A Petrographic, Geochemical, and Mineralogical Study Syahrul; La Ode Dzakir; Riska; Rio Irhan Mais Cendra jaya; Masri
Journal of Geoscience, Engineering, Environment, and Technology Vol. 10 No. 1 (2025): JGEET Vol 10 No 01 : March (2025)
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25299/jgeet.2025.10.1.19484

Abstract

Climate change has prompted significant global interest in carbon sequestration technologies, particularly using geological formations. This study investigates the potential of ultramafic rocks from the Kolaka Ophiolite Complex in Southeast Sulawesi for carbon sequestration, focusing on the mineralogical, petrographic, and geochemical characteristics that enhance their reactivity with CO₂. The research involved petrographic and mineragraphic analyses of 15 peridotite samples, geochemical measurements via X-ray fluorescence (XRF), and mineral characterization using scanning electron microscopy (SEM). The results revealed that Kolaka's ultramafic rocks, particularly harzburgite and lherzolite, exhibit moderate to high serpentinization, which enhances their reactivity with CO₂. Key minerals such as olivine, pyroxene, and serpentine, rich in magnesium, calcium, and iron oxides, demonstrate significant potential for mineral carbonation. Secondary minerals like magnesite and brucite were identified as products of carbonation, reinforcing the rocks' ability to act as carbon sinks. The discussion highlights that serpentinized peridotites are more effective for carbon sequestration than unaltered ones due to increased mineral reactivity. The presence of magnesite and Cr-Fe-rich carbonates, alongside serpentine veins, indicates that fluid-rock interactions have promoted ongoing carbonation processes. The Kolaka ultramafic rocks, therefore, hold strong potential for long-term carbon storage, offering a promising solution for reducing atmospheric CO₂ levels
Influence of Laterite Bedrock on Ni Content in Langgikima District, North Konawe Regency, Southeast Sulawesi, Indonesia Hasria; Okto, Ali; Rio Irhan Mais Cendra Jaya; Alamyah, Wa Ode Nur; Safar, Muhamad; Septiana, Sara; Syahrul
Journal of Geoscience, Engineering, Environment, and Technology Vol. 10 No. 4 (2025): JGEET Vol 10 No 04 : December (2025)
Publisher : UIR PRESS

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.25299/jgeet.2025.10.4.24735

Abstract

This study investigates the influence of bedrock on nickel (Ni) content in laterite deposits in the Lameruru Region, Langgikima District, North Konawe Regency, Southeast Sulawesi Province, Indonesia. The research area is dominated by ultramafic rocks, which are potential sources of laterite nickel. The study employs literature review, field surveys for lithological data collection and representative sampling, petrographic analysis to determine mineral composition and rock types, and geochemical analysis using X-Ray Fluorescence (XRF) to determine nickel content in the rocks. The results show that the bedrock in the study area consists of harzburgite and olivine pyroxenite. Harzburgite, occupying approximately 72.72% of the area, is composed of 54-78% olivine, 15-45% orthopyroxene, 6% clinopyroxene, and accessory minerals, while olivine pyroxenite, occupying about 27.28% of the area, is composed of 27% olivine, 49% orthopyroxene, 17% serpentine, and 7% spinel. Geochemical analysis reveals that harzburgite has higher Ni content (0.10-0.16%) compared to olivine pyroxenite (0.03-0.10%). The distribution of Ni in the bedrock and saprolite is directly proportional, with higher Ni content in harzburgite in both zones. The study concludes that the type of bedrock greatly influences the nickel content in laterite deposits, with harzburgite having a higher Ni content due to its higher percentage of olivine minerals, which are the main hosts of nickel in ultramafic rocks.