Tephra-stratigraphy and Ash Componentry Studies of Proximal Volcanic Products at Mount Tangkuban Parahu, Indonesia: An Insight to Holocene Volcanic Activity

Abstract

Tangkuban Parahu Volcano is one of the most active volcanoes in West Java, Indonesia, although most of the recent eruptions were relatively mild (e.g. 2013 eruption). However, there is still little information from the volcanic products in the proximal area. Here, a new documentation from the proximal volcanic succession is provided, including tephra-stratigraphy, componentry analysis, and petrography of volcanic products. Detailed mapping of the proximal area shows that the volcanic products are predominantly composed of alternating fine-clay and coarse ash, lapilli tuff, and pyroclastic breccia within ten tephra units. Componentry of ash particles revealed the presence of five components, associated with hydrothermally altered lithics, oxidized lithics, coherent crystalline lithics, magmatic juvenile, and free crystal in entire eruptive products. These indicate that the subvolcanic hydrothermal system has been developed since the Holocene and associated with a continual introduction of magmatic intrusion. Petrographic observation shows the presence of hydrothermal minerals of quartz or silica accompanied by alunite and kaolinite, representing acidic alteration within the crater-conduit. The existence of a silicified zone indicates that the subvolcanic hydrothermal system played an essential role as a cap-rock of pressurized gas and steam at depth (200-500 m), whereas magmatic injection caused the vapour plume expansion. The observation concluded that the proximal volcanic succession captured the evidence of coupled phreatic and phreatomagmatic activities during the latest development of Mount Tangkuban Parahu.

Exploring magmatic gas and subvolcanic hydrothermal system interactions: Mineralogy and sulfur isotope characteristics of the Holocene volcanic products at Mt. Tangkuban Parahu, Indonesia.

“…Graph showing the plot of the sulfur isotopic composition of alunite, pyrite, and jarosite against the studied stratigraphic unit in Angkasa et al, 2019. The δ34S values are compared to δ34S values from sul de and sulfate samples at Mt. Muine (Watanabe and Ohta, 2005) and Kawah Ijen (Scher et al, 2013).…”

“…Historical eruptions at Tangkuban Parahu were documented in 1929in , 1961in , 1969in , 1971in , 1983in , 1986in , 2004in (Kusumadinata, 1976CVGHM, 2016), andrecently in 2019 (www.magma.vsi.go.id). Most of the eruptions are relatively small-scale explosion associated with phreatomagmatic and phreatic or hydrothermal activities (Kartadinata et al, 2005;CVGM, 2016;Angkasa et al, 2019). The distribution of Holocene volcanic products is limited in about 1-1.5 kilometers around the craters (Angkasa et al, 2019).…”

“…Holocene volcanic activities of Tangkuban Parahu are mostly still understudied in the sense of the eruption process as well as the characteristic of volcanic products. The Holocene eruptive products are composed of ne-coarse fall-out and base surge deposits (Kartadinata et al, 2002;Angkasa et al, 2019), which covered a total of 20 km 2 area of the summit area of Tangkuban Parahu volcano (CVGHM, 2016). The volcanic products consist of various proportions of lithics, magmatic juveniles, and isolated free crystals in the tephra layers from several episodic eruptions (Angkasa et al, 2019).…”

“…The present work focused on volcanic products from the proximal area of Tangkuban Parahu volcano, Indonesia, which has an established tephra-stratigraphy (cf. Angkasa et al, 2019). The volcano has been active within the Holocene epoch.…”

“…The volcano has been active within the Holocene epoch. During Holocene, the activities are magmatic-hydrothermal and phreatic explosive eruptions, along with several magmatic intrusion in contact with water bodies (e.g., crater lake) to explode as a common phreatomagmatic eruption (CVGHM, 2016;Angkasa et al, 2019). In this context, Holocene volcanic products from this volcano are good examples to understand interactions between magma and a hydrothermal system.…”