Petrologic evolution of Krakatau (Indonesia): Implications for a future activity |
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| Authors: | G. Camus A. Gourgaud P.M. Vincent |
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| Affiliation: | 1. Dipartimento di Scienze della Terra, Sapienza-Università di Roma, P.le Aldo Moro 5, 00185 Roma, Italy;2. Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata 605, 00143 Rome, Italy;3. School of Earth and Environmental Sciences, The University of Queensland, Brisbane, QLD 4072, Australia;4. Department of Earth Sciences, The Natural History Museum, Cromwell Road, SW7 5BD London, United Kingdom;5. Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, 2 George Street, Brisbane, 4000, QLD, Australia;6. Sezione di Catania, Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Piazza Roma 2, 95125 Catania, Italy;1. University of Kentucky, Department of Mining Engineering, Lexington, KY 40506, USA;2. Schobert International LLC, 22401 Hunter Ridge Circle, Jordan, MN 55352, USA;3. University of Kentucky, Center for Applied Energy Research, 2540 Research Park Drive, Lexington, KY 40511, USA;4. University of Kentucky Department of Earth & Environmental Sciences, Lexington, KY 40506, USA;1. Center for Volcanology and Geologic Hazard Mitigation, Jalan Diponegoro 57, 40122 Bandung, Indonesia;2. Volcano Disaster Assistance Program, U.S. Geological Survey, Cascades Volcano Observatory, Vancouver, WA 98683, USA;3. Sakurajima Volcano Research Center, Disaster Prevention Research Institute, Kyoto University, Kagoshima 891-1419, Japan;4. Volcano Research Center, Earthquake Research Institute, University of Tokyo Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan;1. Université Paris 1 Panthéon-Sorbonne, 1 place du Panthéon, 75005 Paris, France;2. Laboratoire de Géographie Physique, UMR 8591 CNRS, 1 place Aristide Briand, 92195 Meudon, France;3. Institut Universitaire de France, 1 rue Descartes, 75005 Paris, France;4. Universitas Gadjah Mada, Faculty of Geography, Bulaksumur, 55281 Yogyakarta, Indonesia;5. Ternate Khairun University Kampus I (UNKHAIR), Jl. Bandara Babullah, Akehuda, Ternate Utara, Kota Ternate, 97728 Maluku Utara, Indonesia;6. UMR GEOPS, Université Paris-Saclay, CNRS, Orsay 91405, France |
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| Abstract: | Krakatau Volcano is located along a N35E volcanic lineament running through the Sunda straits (Indonesia). Its last activity has been characterized by successive phases, each beginning with the construction of a cone, and ending with its destruction and the formation of a caldera. The two last (pre- and post-1883) cycles are well known, but the more ancient ones are not so clearly defined.Lavas of Krakatau belong to an andesitic series, in which fractional crystallization plays the most important role. The petrologic evolution is characterized by a cyclicity in good agreement with the structural evolution: the succession is regular: basalts, basic andesites, acid andesites, dacites. A gap between acid and basic andesites occurs in each cycle. The destructive stages correspond to the occurrence of dacitic terms.The Anak cycle was characterized from 1927 to 1979 by basalts and basic andesites; the 1981 eruption involved a more differentiated magma (close to dacitic). Detailed study of the petrologic evolution since 1883 emphasizes the predominant role of fractional crystallization. This process occurred during a very short period, between 1979 and 1981. Separation of labradorite, augite, olivine and magnetite from parental basic andesite may generate the dacitic descendant, in a shallow reservoir (PH2O estimated about 0.5 kbar). Implications for a future activity are considered. |
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