Mantle hydration and the role of water in the generation of large igneous provinces

Abstract

The genesis of large igneous provinces (LIP) is controlled by multiple factors including anomalous mantle temperatures, the presence of fusible fertile components and volatiles in the mantle source, and the extent of decompression. The lack of a comprehensive examination of all these factors in one specific LIP makes the mantle plume model debatable. Here, we report estimates of the water content in picrites from the Emeishan LIP in southwestern China. Although these picrites display an island arc-like H2O content (up to 3.4 by weight percent), the trace element characteristics do not support a subduction zone setting but point to a hydrous reservoir in the deep mantle. Combining with previous studies, we propose that hydrous and hot plumes occasionally appeared in the Phanerozoic era to produce continental LIPs (e.g., Tarim, Siberian Trap, Karoo). The wide sampling of hydrous reservoirs in the deep mantle by mantle plumes thus indicates that the Earth’s interior is largely hydrated.

Weak Vertical Surface Movement Caused by the Ascent of the Emeishan Mantle Anomaly

“…Although the variation in Fe/Mn ratios of olivine can alternatively be interpreted by partial melting of a peridotite source under different pressure and temperature conditions (Matzen et al, ; Niu et al, ). Nevertheless, recent geochemical studies conclude that the Emeishan mantle source must have been enriched supporting our hypothesis of an involvement of a fertile pyroxenite mantle source for the Emeishan LIP (e.g., Ali et al, ; Liu et al, ; Ren et al, ). We therefore argue that the Fe/Mn ratios of olivine can be used to calculate a maximum proportion of pyroxenite‐derived melt in the source through equation (S2) of Sobolev et al ().…”

Melt Diversity and Magmatic Evolution in the Dali Picrites, Emeishan Large Igneous Province

“…These are compared for olivine‐hosted melt inclusions and clinopyroxene equilibrium melts, with respect to host olivine Fo content and clinopyroxene Mg# value, in Figure . The ranges of Ce/Y and Ce/Yb ratios of clinopyroxene equilibrium melts are relatively constant and are identical to those of the melt inclusions (Liu et al, ) for clinopyroxene Mg# <88 (Figure ). Thus, these clinopyroxene macrocrysts have crystallized from the same range of melts as the olivine macrocrysts.…”

“…Olivine Fo and clinopyroxene (Cpx) Mg# versus (a) Ce/Y and (b) Ce/Yb ratios of olivine‐hosted melt inclusions and clinopyroxene equilibrium melts. Olivine‐hosted melt inclusion data are from Liu et al (). To be able to plot olivine Fo and clinopyroxene Mg# data on the same axis, the Fe‐Mg exchange coefficient between clinopyroxene and olivine, was calculated using the ratio of to (Fe‐Mg exchange coefficient between olivine and melt), which was derived from the reverse crystallization model with compositional dependent and values determined from Danyushevsky () and Herzberg and O'Hara (), respectively (Figure ).…”

Deep open storage and shallow closed transport system for a continental flood basalt sequence revealed with Magma Chamber Simulator

“…Another unknown but potentially significant factor is the water content of the parental melt. Because the ultimate source of the Vestfjella lavas likely resided in moderately water-enriched depleted mantle (Heinonen et al 2016(Heinonen et al , 2018, we constrained H 2 O contents using H 2 O/Ce ratio of 600 (PM H 2 O = 1.2 wt% before normalization; Table 1), which is the average between MORB and Karoo CFBs derived from enriched mantle sources (Liu et al 2017). Again, for testing the effect of H 2 O on phase equilibria, we also ran models that correspond to H 2 O/Ce of average MORB (200, PM H 2 O = 0.4 wt%) and average Karoo LIP (1000, PM H 2 O = 2 wt%) as defined by Liu et al (2017) on the basis of a specific set of samples (Online Resource 1).…”