Petrology and Geochemistry of Volcanic Rocks of Kaba Volcano, Bengkulu

Muhammad Eval Juni Wijaya, Sakila Gia Mentari, Ridho Ramadhan Pratama, Victor Ranson Sitohang

Abstract


Mount Kaba is an active stratovolcano in Bengkulu Province, Indonesia, characterized by explosive magmatic eruptions and the presence of monogenetic volcanic centers, reflecting complex magmatic processes. This study focuses on the northern sector of the Mount Kaba area to investigate magma evolution and its relationship to volcanic development and hazard mitigation. Fifteen representative lava and pyroclastic rock samples were analyzed using petrographic observations and ICP-MS geochemical methods to determine major, trace, and rare earth element (REE) compositions. Petrographic results indicate basaltic to andesitic rocks with hypocrystalline textures, dominated by plagioclase, pyroxene, olivine, hornblende, and displaying porphyritic, trachytic, sieve, zoning, intersertal, and reaction rim textures that reflect disequilibrium processes and multi-stage magma evolution. Geochemically, rocks range from basanite/tephrite to dacite and belong mainly to calc-alkaline to high-K calc-alkaline magma affinities, forming two magma groups (Danau Mas and Kaba). Major element Harker diagrams show decreasing MgO, CaO, FeO, TiO₂ with increasing SiO₂ and increasing Na₂O + K₂O, indicating progressive differentiation. Trace element diagrams display positive trends of LILE and HFSE with SiO₂ and dual magma trends, suggesting multiple differentiation histories. Spider diagrams reveal LILE enrichment, HFSE depletion, and LREE enrichment relative to HREE, consistent with subduction-related magma sources. Integration of petrographic and geochemical data indicates that magma evolution was dominated by fractional crystallization, with additional influences from assimilation and magma mixing that produced compositional diversity and disequilibrium textures. Overall, the Mount Kaba magmatic system reflects a dynamic subduction zone environment characterized by multiple magma sources, progressive differentiation, and complex interactions within the crust, with implications for understanding volcanic processes and hazard potential in the northern sector.

Keywords


Petrology; Geochemistry; Volcanic Rocks; Kaba Volcano; Bengkulu.

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Permana, S., Lubis, D. P., Marbun, S. F., & Amelia, P. (2025). The Meaning of Place in Historic Building (Case Study: Three Urban Heritage Tourism Destinations at Kesawan Medan). Jurnal Penelitian Geografi, 13(2), 223-242.

Westerveld, J. (1952). Quaternaky volcanism on Sumatra. Geological Society of America Bulletin, 63(6), 561-594.

Sieh, K., & Natawidjaja, D. (2000). Neotectonics of the Sumatran fault, Indonesia. Journal of Geophysical Research: Solid Earth, 105(B12), 28295-28326.

Sugianto, N., Nukman, M., & Suryanto, W. (2023). Characteristics of Active Volcanoes in Sumatra, Indonesia: From Perspective Seismicity, Magma Chemical Composition and Eruption History. In E3S Web of Conferences (Vol. 468, p. 09002). EDP Sciences.

Kusumadinata, K., Hadian, R., Hamidi, S. and Reksowirogo, L.D., 1979. Data dasar gunungapi Indonesia. Direktorat Vulkanologi, Bandung, 820.

Mibei, G., Bali, E., Geirsson, H., Guðfinnsson, G. H., Harðarson, B. S., & Franzson, H. (2021). Partial melt generation and evolution of magma reservoir conditions at the Paka volcanic complex in Kenya: Constraints from geochemistry, petrology and geophysics. Lithos, 400, 106385.

Sparks, R. S. J., & Cashman, K. V. (2017). Dynamic magma systems: Implications for forecasting volcanic activity. Elements, 13(1), 35-40.

Wijaya, M. E. J., & Setijadji, L. D. (2022). A Preliminary Volcanological Study of North Eastern Kaba Volcano, Bengkulu Province, Indonesia. IOP Conference Series: Earth and Environmental Science (Vol. 1071, No. 1, p. 012018). IOP Publishing.

Wijaya, M. E. J., & Mentari, S. G. (2025). Karakteristik Geokimia Batuan Unsur Jejak dan Unsur Tanah Jarang Gunung Api Kaba untuk Interpretasi Tatanan Tektonik Berdasarkan Analisis ICP-MS. Jurnal Penelitian Inovatif, 5(3), 2311-2320.

Gafoer, S., Amin, T.C. and R.. Pardede, 1992. Peta geologi lembar Bengkulu, Sumatra. Pusat Penelitian dan Pengembangan Geologi.

Heryanto, R. and Suyoko, S., 2007. Karakteristik batubara di Cekungan Bengkulu.

Indonesian Journal on Geoscience, 2(4), pp.247-259.

Rollinson, H. R. (1993). Using geochemical data: evaluation, presentation, interpretation. Routledge.

Zhou, J., & Li, X. (2006). GeoPlot: An Excel VBA program for geochemical data plotting. Computers & Geosciences, 32(4), 554-560.

Janoušek, V., Farrow, C. M., & Erban, V. (2006). Interpretation of whole-rock geochemical data in igneous geochemistry: introducing Geochemical Data Toolkit (GCDkit). Journal of Petrology, 47(6), 1255-1259.

Winter, J. D. (2014). Principles of igneous and metamorphic petrology (Vol. 2). Harlow, UK: Pearson education.

Le Maitre, R. W., Streckeisen, A., Zanettin, B., Le Bas, M. J., Bonin, B., & Bateman, P. (Eds.). (2005). Igneous rocks: a classification and glossary of terms: recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks. Cambridge University Press.

Best, M. G. (2002). Igneous and metamorphic petrology. John Wiley & Sons.

Philpotts, A. R., & Ague, J. J. (2009). Principles of igneous and metamorphic petrology. Cambridge University Press.

Jerram, D. A., Dobson, K. J., Morgan, D. J., & Pankhurst, M. J. (2018). The petrogenesis of magmatic systems: Using igneous textures to understand magmatic processes. In Volcanic and igneous plumbing systems (pp. 191-229). Elsevier.

Gill, R., & Fitton, G. (2022). Igneous rocks and processes: a practical guide. John Wiley & Sons.

Dietrich, V. J., & Popa, R. G. (2017). Petrology and geochemistry of lavas and pyroclastics. In Nisyros Volcano: The Kos-Yali-Nisyros Volcanic Field (pp. 103-144). Cham: Springer International Publishing.

Putnis, A. (2009). Mineral replacement reactions. Reviews in mineralogy and geochemistry, 70(1), 87-124.

Koyaguchi, T., & Kaneko, K. (1999). A two-stage thermal evolution model of magmas in continental crust. Journal of Petrology, 40(2), 241-254.

Marsh, B. D., & Watts, A. B. (2007). Magmatism, magma, and magma chambers. Treatise on Geophysics: Crust and Lithosphere Dynamics; Watts, AB, Ed, 275-333.

Caceres, F., Scheu, B., Colombier, M., Hess, K. U., Feisel, Y., Ruthensteiner, B., & Dingwell, D. B. (2022). The roles of microlites and phenocrysts during degassing of silicic magma. Earth and Planetary Science Letters, 577, 117264.

Streck, M. J. (2008). Mineral textures and zoning as evidence for open system processes. Reviews in Mineralogy and Geochemistry, 69(1), 595-622.

Stewart, M. L., & Pearce, T. H. (2004). Sieve-textured plagioclase in dacitic magma: Interference imaging results. American Mineralogist, 89(2-3), 348-351.

Bas, M. L., Maitre, R. L., Streckeisen, A., Zanettin, B., & IUGS Subcommission on the Systematics of Igneous Rocks. (1986). A chemical classification of volcanic rocks based on the total alkali-silica diagram. Journal of petrology, 27(3), 745-750.

Ewart, A. (1982). The Mineralogy and petrology of Tertiary-Recent orogenic volcanic rocks; with special reference to the andesitic-basaltic compositional range. Andesites: orogenic andesites and related rocks, 26-87.

Parat, F., Streck, M. J., Holtz, F., & Almeev, R. (2014). Experimental study into the petrogenesis of crystal-rich basaltic to andesitic magmas at Arenal volcano. Contributions to Mineralogy and Petrology, 168(2), 1040.

Brenna, M., Ubide, T., Nichols, A. R., Mollo, S., & Pontesilli, A. (2021). Anatomy of intraplate monogenetic alkaline basaltic magmatism: clues from magma, crystals, and glass. Crustal Magmatic System Evolution: Anatomy, Architecture, and Physico‐Chemical Processes, 79-103.

Harker, A. [32] . The natural history of igneous rocks. Methuen & Company.

Jagoutz, O., & Klein, B. (2018). On the importance of crystallization-differentiation for the generation of SiO2-rich melts and the compositional build-up of arc (and continental) crust. American Journal of Science, 318(1), 29-63.

Jamali, H. (2017). The behavior of rare-earth elements, zirconium and hafnium during magma evolution and their application in determining mineralized magmatic suites in subduction zones: constraints from the Cenozoic belts of Iran. Ore Geology Reviews, 81, 270-279.

McDonough, W. F., & Sun, S. S. (1995). The composition of the Earth. Chemical geology, 120(3-4), 223-253.

Vural, A. (2020). Investigation of the relationship between rare earth elements, trace elements, and major oxides in soil geochemistry. Environmental Monitoring and Assessment, 192(2), 124.

Perugini, D., & Poli, G. (2012). The mixing of magmas in plutonic and volcanic environments: analogies and differences. Lithos, 153, 261-277.

Kirchenbaur, M., Schuth, S., Barth, A. R., Luguet, A., König, S., Idrus, A., ... & Münker, C. (2022). Sub-arc mantle enrichment in the Sunda rear-arc inferred from HFSE systematics in high-K lavas from Java. Contributions to Mineralogy and Petrology, 177(1), 8.

Fyfe, W. S. (2012). Fluids in the earth's crust: Their significance in metamorphic, tectonic and chemical transport process (Vol. 1). Elsevier.

Harry, D. L., & Green, N. L. (1999). Slab dehydration and basalt petrogenesis in subduction systems involving very young oceanic lithosphere. Chemical Geology, 160(4), 309-333.

Münker, C., Wörner, G., Yogodzinski, G., & Churikova, T. (2004). Behaviour of high field strength elements in subduction zones: constraints from Kamchatka–Aleutian arc lavas. Earth and Planetary Science Letters, 224(3-4), 275-293.

Kent, A. J. (2008). Melt inclusions in basaltic and related volcanic rocks. Reviews in mineralogy and geochemistry, 69(1), 273-331.

Kumar, S. (2014). Magmatic processes: review of some concepts and models. Modelling of magmatic and allied processes, 1-22.




DOI: https://doi.org/10.31284/j.jemt.2025.v6i1.8571

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