Origins of felsic magmas in Japanese subduction zone: Geochemical characterizations of tephra from caldera‐forming eruptions <5 Ma

Abstract

Dacitic to rhyolitic glass shards from 80 widespread tephras erupted during the past 5 Mys from calderas in Kyushu, and SW, central, and NE Japan were analyzed. Laser ablation inductively coupled plasma mass spectrometry was used to determine 10 major and 33 trace elements and A few tephras from SW Japan were identified as adakite and alkali rhyolite and were regarded to have originated from slab melt and mantle melt, respectively. The Pb isotope ratios of the tephras are comparable to those of the intermediate lavas in the source areas but are different from the basalts in these areas. The crustal assimilants for the intermediate lavas were largely from crustal melts and are represented by the rhyolitic tephras. A large heat source is required for forming large volumes of felsic crustal melts and is usually supplied by the mantle via basalt. Hydrous arc basalt formed by cold slab subduction is voluminous, and its heat transfer with high water content may have melted crustal rocks leading to effective felsic magma production. Coincidence of basalt and felsic magma activities shown by this study suggests caldera-forming eruptions are ultimately the effect of a mantle-driven cause.

Depositional setting, provenance, and tectonic-volcanic setting of Eocene–Recent deep-sea sediments of the oceanic Izu–Bonin forearc, northwest Pacific (IODP Expedition 352)

“…In contrast, the mid-Pliocene to Holocene downslope sediments are more similar to volcanic ash from Honshu (e.g. Kimura et al 2015). These relationships are supported by comparison with the average compositions of the discrete tephra layers (Figure 12(d)) (see also Kutterolf et al 2017).…”

Tephra without Borders: Far-Reaching Clues into Past Explosive Eruptions

“…With recent advances in microanalytical techniques, the composition of micronsized individual ash particles can be characterized. Electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) permit the determination of major, minor and trace-element abundances and lead (Pb) isotope data (Tomlinson et al, 2010;Kuehn et al, 2011;Hayward, 2012;Pearce et al, 2014;Kimura et al, 2015;Maruyama et al, in press). These techniques allow characterization of glass, minerals, and melt inclusions in minerals to support correlations between widely dispersed locations as well as to the source areas (e.g., Lowe, 2011;Matsu'ura et al, 2011;Smith et al, 2011c).…”

Marine tephra in the Japan Sea sediments as a tool for paleoceanography and paleoclimatology

“…Major marine tephra studies around the Japanese islands in locations other than in the Japan Sea include the following: general: Machida and Arai (1983, 1988, 2003 and Furuta et al (1986); NW Pacific: Fujioka (1983), Cambray et al (1990), Aoki and Arai (2000), Aoki et al ( , 2008, Aoki and Machida (2006), Aoki and Ohkushi (2006), Suganuma et al (2006), Aoki (2008), and Ikehara et al (2013); Izu-Bonin: Fujioka et al (1992aFujioka et al ( , 1992b and Nishimura et al (1992); South of Japan: Ikehara et al (2006Ikehara et al ( , 2011 and Kutterolf et al (2014); East China Sea: Cambray et al (1990) and Moriwaki et al (2011). Recently, Kimura et al (2015) determined 10 major and 33 trace elements and Pb isotope ratios for dacitic to rhyolitic glass shards from 80 widespread tephras erupted during the past 5 Ma.…”