Volcanoes of the Diamante cross-chain: evidence for a mid-crustal felsic magma body beneath the Southern Izu–Bonin–Mariana arc

Abstract

Three submarine Diamante cross-chain volcanoes in the southern Mariana arc mark a magma-healed zone of along-arc (north–south) extension that allows either mafic mantle-derived basalts or felsic magmas from the middle of thickened arc crust to erupt. The largest volcano is East Diamante, with a well-developed (5×10 km) caldera that formed via violent felsic submarine eruptions beginning nearly 0.5 Ma. One or more of these eruptions also formed a giant submarine dune field extending 30 km to the NW of the volcano. Felsic igneous activity continues at least as recently as c. 20 000 years ago, with emplacement of resurgent dacite domes, some hot enough to power the only black smoker hydrothermal system known in the Mariana arc. In contrast, felsic eruptions do not occur on the two volcanoes to the west, implying that the mid-crustal felsic zone does not underlie the thinner crust of the Mariana Trough back-arc basin. Diamante cross-chain lavas define a medium K suite; mafic lava phenocryst assemblages show arc-like associations of anorthite-rich plagioclase with Fe-rich olivine. Magmatic temperatures for a basaltic andesite and three dacites are c. 1100 °C and c. 800 °C, respectively, typical for cool, wet, subduction-related felsic magmas. Felsic magmas formed under low-P crustal conditions. The Diamante cross-chain is the southernmost of at least seven and perhaps eight Mariana arc volcanoes in a c. 115 km long arc segment characterized by felsic eruptions. This is the ‘Anatahan Felsic Province’, which may have formed above a mid-crustal tonalite body that formed by fractionation or was re-melted when heated by c. 1200 °C mafic, mantle-derived magmas. Across- and along-arc variations suggest that felsic eruptions and dome emplacement occurred when midcrustal tonalite was remobilized by intrusions of mafic magma, while north–south extension facilitated the development of conduits to the surface.Supplementary material:Detailed Hyperdolphin ROV dive tracks, Cook 7 dredge locations, 40Ar/39Ar analytical data, analytical methods, major and selected trace element analyses of whole rock samples, and compositional data for minerals are available at http://www.geolsoc.org.uk/SUP18611

Evolution of the Earth as an andesite planet: water, plate tectonics, and delamination of anti-continent

“…The presence of plutonic rocks with andesitic compositions in the IBM middle crust is supported by the recovery of intermediate plutonic rock xenoliths in arc lavas, exposures along the IBM and Kyushu-Palau arc systems (e.g., Sakamoto et al, 1999), the exposure of tonalitic plutons in the Tanzawa Mountains where the IBM arc collides with the Japanese islands (Kawate and Arima, 1998;Tani et al, 2010), and the presence of a~150-km-long felsic melt layer in the Mariana arc (Stern et al, 2013). Furthermore, a middle crust layer with a V P of 6.0-6.8 km/s is not unique to the IBM arc; it has also been documented in other intra-oceanic arcs such as the Tonga arc (Crawford et al, 2003) and the Kuriles (Nakanishi et al, 2009).…”

Geological interpretation of volcanism and segmentation of the Mariana back‐arc spreading center between 12.7°N and 18.3°N

“…[] (Figure b). These cross‐arc chains are heavily faulted across most of the back‐arc, with discrete volcanoes observed only along the cross‐arc chains closest to the active volcanic arc (including the Guguan, Diamante, and Pagan cross‐arc chains) [ Stern et al ., ; Stern et al ., ] and those that extend westward from the remnant arc (Figure b).…”

“…A notable feature of the Mariana back-arc is the occurrence of cross-arc chains of volcanoes that extend westward from the presently active volcanic arc and are also present on the remnant arc [Fryer and Hussong, 1982;Dixon and Stern, 1983;Fryer, 1995;Heeszel et al, 2008;Stern et al, 2014]. Several of these ''cross-arc chains'' are seismically active [Heeszel et al, 2008].…”

“…The topographic highs that follow this orientation are thought to be related to cross-arc volcanic chains described briefly by Oakley et al [2009] (Figure 15b). These cross-arc chains are heavily faulted across most of the back-arc, with discrete volcanoes observed only along the cross-arc chains closest to the active volcanic arc (including the Guguan, Diamante, and Pagan cross-arc chains) [Stern et al, 2006;Stern et al, 2014] and those that extend westward from the remnant arc (Figure 15b).…”

An introduction to orogenic andesites and crustal growth

“…Their eruption was ultimately triggered by newly ascending basaltic andesitic melts, which incompletely mingled during ascent, and did not yet produce intermediate andesites. Stern et al (2013) propose a similar scenario in order to account for the strongly bimodal series of basaltic-andesites and dacite -rhyolites erupted at the Quaternary Diamante cross-chain volcanoes, which are part of the 110 km long Anatahan Felsic Province along the southern Mariana Volcanic arc. However, in this model, the silicic series originate from a pre-existing tonalitic middle crust that was reheated by hot and newly ascending mantle-derived magmas.…”