Buoyant hydrous mantle plume from the mantle transition zone

Abstract

Magmatism at some intraplate volcanoes and large igneous provinces (LIPs) in continental areas may originate from hydrous mantle upwelling (i.e. a plume) from the mantle transition zone (MTZ) at 410–660 km depths in the Earth’s deep interior. However, the ultimate origin of the magmatism, i.e. why mantle plumes could have been generated at the MTZ, remains unclear. Here, we study the buoyancy of a plume by investigating basalts from the Changbaishan volcano, beneath which a mantle plume from the hydrous MTZ is observed via seismology. Based on carefully determined water contents of the basalts, the potential temperature of the source mantle is estimated to be 1310–1400 °C, which is within the range of the normal upper mantle temperature. This observation suggests that the mantle plume did not have a significant excess heat, and that the plume upwelled because of buoyancy resulting from water supplied from the Pacific slab in the MTZ. Such a hydrous mantle plume can account for the formation of extremely hydrous LIP magmatism. The water was originally sourced from a stagnant slab and stored in the MTZ, and then upwelled irrespective of the presence or absence of a deep thermal plume.

Ti-Magnetite Crystallization in Melt Inclusions of Trachytic Rocks from the Dokdo and Ulleung Islands, South Korea: Implications for Hydrous and Oxidized Magmatism

“…With the results of previously reported DUI volcanic rocks, the presence of Ti-magnetite crystals and voids in the melt inclusions of this study indicated that initial melt inclusions might be volatile-rich, reflecting hydrous primary magma. Recently, the formation of a shallow and hydrous mantle plume from the mantle transition zone (MTZ) at 410-660 km depth was suggested for the genesis of the Cenozoic alkaline basalts in northeast China [81,82]. Therefore, we suggest that the hydrous and Fe-rich characteristics of the DUI magma could have also been inherited by a similar process.…”

Hot, volatile‐poor, and oxidized magmatism above the stagnant Pacific plate in Eastern China in the Cenozoic

“…Upwelling mantle beneath Eastern China with low‐ V P , low‐ V S character has commonly been invoked to be hydrous, hydrous and hot, or hot and only weakly hydrous (Chen et al, ; Kimura et al, ; Kuritani et al, , Kuritani et al, , Kuritani et al, ; Wei et al, ). Experimental work has shown that the presence of hydroxyl (dissolved “H 2 O”) does not significantly decrease seismic velocities of peridotite (e.g., by <1% for a 1 wt% increase in dissolved H 2 O), while high temperature (Cline et al, ; Karato, ) and the presence of partial melt or free volatiles do (Aizawa et al, ; Cline et al, ; Karato, ).…”

“…The large-scale geodynamic situation-that is the presence of the stagnant Pacific slab in the mantle transition zone and a big mantle wedge beneath eastern Chinahas thus remained largely unchanged for >10-25 Ma. Upwelling from the mantle transition zone and lower upper mantle or the deep mantle has also been proposed to have been active for >15 Ma, and thus for the entire younger Cenozoic (i.e., Quaternary and Neogene; Kimura et al, 2018;Kuritani et al, 2011Kuritani et al, , 2019Tang et al, 2014;Wang et al, 2017;Xu et al, 2018). The present-day mantle above the stagnant plate, the so-called big mantle wedgeand also the upper mantle beyond it to the west and the lower mantleshows large-scale dV S and dV P anomalies of mostly ≤ ±3% and ±2% (Figure 1b; Chen et al, 2017;Huang & Zhao, 2006;Kimura et al, 2018;Tang et al, 2014;Wei et al, 2019).…”

“…Low S and P wave velocity anomalies extend from the top of the mantle transition zone, and possibly from the deep mantle, to several of the Cenozoic volcanic centers (e.g., at Changbaishan, Wudalianchi, Halaha; Figure a), suggesting a close relation between the mantle transition zone and the wide‐spread volcanism (Chen et al, ; Huang & Zhao, ; Kimura et al, ; Tang et al, ; Wei et al, ; Zhao, ). Many geochemical studies have further shown that enriched mantle components play an important role in the formation of the magmas, which are thought to derive from the stagnant Pacific slab and/or from ancient subducted slabs (Kimura et al, ; Kuritani et al, , ; Tang et al, ; Wang et al, ; Xu et al, ).…”

Evolution of Deformation Fabrics Related to Petrogenesis of Upper Mantle Xenoliths Beneath the Baekdusan Volcano

“…900 km) ( Figure 1), indicating that volcanism here is of intraplate origin [32]. However, recent seismotomographic studies have suggested the presence of a stagnant slab in the mantle transition zone and the possible presence of a hydrous mantle upwelling beneath Baekdusan [33][34][35]; this may have produced subduction-induced hydrous mantle upwelling. The Baekdusan volcano consists of an early-stage basaltic plateau, a middle-stage trachytic cone, and a late-stage explosive comenditic ignimbrite [36,37].…”