Petromagnetic Study of Lava Flows to Identify Magmatic Processes in the Mount Agung Area, Bali
DOI:
https://doi.org/10.17794/rgn.2027.1.3Keywords:
Mount Agung, rock magnetism, lava, microtextures, magmatic processesAbstract
Mount Agung, an active volcano in Karangasem Regency, Bali, stands at 3,142 meters and is considered one of Bali's primary geological hazards due to its increased volcanic activity, which can affect local social and economic life. To better understand the nature of this volcanic activity and its underlying mechanisms, the development of Mount Agung's magmatic system is studied utilizing rock magnetic, geochemical, and petrographic approaches. This research analyses 15 lava flows spanning from pre-3200 ± 60 BP to post-1040 ± 50 BP, covering four distinct eruptive periods. Rock magnetic investigations reveal systematic variations in magnetic susceptibility, hysteresis parameters, and thermomagnetic curves across these periods. Titanomagnetite is the dominant magnetic phase, with grain sizes primarily in the pseudo-single domain (PSD) state. Thermomagnetic analysis identifies both single and dual Curie temperatures (Tc), where low-titanium magnetite (Tc ~ 520–580°C) is consistently present, while highly Ti-rich titanomagnetite (Tc ~ 270–355°C) appears during periods of intense magma mixing. Geochemically, the lavas are medium- to high-K calc-alkaline basalts to basaltic andesites. Plagioclase microtextures, including fine-sieve, coarse-sieve, and resorbed surfaces, indicate episodes of magma decompression, mixing, and thermal perturbations. Collectively, these multidisciplinary data reveal the cyclic dynamics of Mount Agung's magmatic system, driven by episodic basaltic magma injections and subsequent differentiation. This integrated approach demonstrates that rock magnetic parameters serve as sensitive physical indicators of sub-volcanic processes, providing a unique perspective on the evolution of Mount Agung and its potential magmatic connectivity with neighbouring volcanic centres like Mount Batur.
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Copyright (c) 2026 Ahmad Fadillah, Satria Bijaksana, Aditya Pratama, Lennart Vincent de Groot, Romy Meyer, Putu Billy Suryanata, Wilfridus Ferdinando Supriyadi Banggur, Maria Karatzanou, Khalil Ibrahim, Fathia Matondang, Ulvienin Harlianti
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