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Explosive eruptions at Tandikat volcano, Sumatra (Indonesia): Insights into two temporally proximate eruptions in the last 5000 years

Marcus Phua1,3, Wei-Ran Li1, Xiao-Yu Liu1, Francesca Forni2,3, Steffen Eisele3, Caroline Bouvet de Maisonneuve3, Hamdi Rifai4

  • Affiliations: 1VRock Laboratory, Department of Earth Sciences, The University of Hong Kong, Hong Kong; 2Dipartimento di Scienze della Terra "Ardito Desio", Università degli Studi di Milano, Milan, Italy; 3Earth Observatory of Singapore, Nanyang Technological University, Singapore; 4Departemen Fisika, Universitas Negeri Padang, Sumatera Barat, Indonesia 

  • Presentation type: Talk

  • Presentation time: Monday 10:45 - 11:00, Room R280

  • Programme No: 1.7.2

  • Theme 1 > Session 7

Abstract

The island of Sumatra is home to over 130 active/potentially active volcanoes with explosive eruptive histories. Of particular interest is Tandikat (TDK) volcano that was attributed as the source of two temporally proximate explosive eruptions -- the magnitude ~5.6 Tandikat I (TDK I) at ~4.94 ka and the magnitude ~5.2 Tandikat II (TDK II) at ~4.36 ka. Despite the improved eruption record, little is known about the catalyst for two explosive eruptions occurring only ~580 years apart. Here, we reconstruct the magma plumbing system (composition, pressure (P), temperature (T) and volatile budget) through pyroxene, amphibole and melt thermobarometers, as well as an apatite-based melt hygrometer. Preliminary results indicate bulk rock and glass compositions of basaltic andesite and low-silica rhyolite, respectively. Magma storage P-T estimates from different minerals show consistently higher values for TDK II (T=950-1150°C and P=350-650 MPa from two-pyroxene; T=850-950°C and P=300-500 MPa from amphibole) in comparison to TDK I (T=900-1100°C and P=300-600 MPa from two-pyroxene; T=800-900°C and P=250-450 MPa from amphibole). Syn-eruptive P-T estimates from matrix glass occur within similar ranges for the two eruptions, i.e., 800-900°C (median=850°C) and 200-400 MPa (median=220 MPa). The range of melt water estimates (~3-5 wt.% from apatite) are also analogous for these eruptions. Calculations using the melt water content and existing solubility models indicate that for a magma containing ~5 wt.% H2O to reach volatile saturation at ≥220 MPa, at least ~950 ppm CO2 is required. Further constraints on the volatile budget will be obtained by ongoing work on melt inclusions.