Mantle plumes, flood basalts, and thermal models for melt generation beneath continents: Assessment of a conductive heating model and application to the Paraná

Abstract

Growing evidence suggests that there is more than one type of continental flood basalt (CFB). Many CFB, such as the Deccan, were probably derived by decompression melting of asthenospheric peridotite in a mantle plume resulting in high eruption rates (∼1 km3 yr−1) and geochemical signatures of uncontaminated basalt which are similar to ocean island basalts. However, several geochemical studies have concluded that other CFB were derived from the subcontinental lithospheric mantle. This requires that melting occurs via heating of lithospheric peridotite above a mantle plume instead of melting within the plume itself. The feasibility of this model is tested with a simple one‐dimensional, time‐dependent thermal model. The results show that 1–2 km thick CFB may be derived from the lithospheric mantie without melting occurring within the underlying mantle plume if (1) the mantle potential temperature of the plume is between 1380 and 1580°C; (2) the lithospheric mantle is composed of volatile‐enriched peridotite; (3) the overlying lithosphere is >100 km thick; (4) eruption occurs over 10–15 Myr; and (5) melting occurs over an area similar to the surface distribution of basalt. Small volumes of alkalic basalt may precede the eruption of tholeiites and if higher plume temperatures prevail, or extension/thermal erosion leads to lithospheric thicknesses ≤100 km, melts from the plume will rapidly dominate those from the lithosphere and eruption rates will increase (magmatic underplating may reduce the strength of the lithosphere sufficiently to initiate or focus rifting if the lithosphere is already under tension). These predictions can be used to discriminate between different CFB and are illustrated by application to the Paraná CFB using published data along with new geochemical data from a borehole through the thickest section of basalt.

The Early Permian Tarim Large Igneous Province: Main characteristics and a plume incubation model

“…Whether the~290 Ma basalts were formed by whole-scale 'wet' melting of heterogeneous SCLM by heat supplied from an underlying mantle plume (Gallagher and Hawkesworth, 1992;Turner et al, 1996) or by mixing of mantle plume-derived melts with SCLMderived melts (e.g., lamproitic melt) as they rise through the SCLM (Ellam and Cox, 1991;Gibson et al, 1995a) is an open question. White and McKenzie (1995) argued that the timescales for heat conduction were too long to explain the rapid production of a large volume of magma by melting of hydrous lithospheric mantle.…”

“…On the other hand, lithospheric mantle melts can contribute directly to flood basalt magmatism (Ellam and Cox, 1991;Gibson et al, 1995a;Gallagher and Hawkesworth, 1992;Turner et al, 1996). Local melting of the SCLM is possibly triggered by heating of upwelling mantle plume and by melt percolation, especially when water and fusible components are present (Gibson et al, 2006;Gallagher and Hawkesworth, 1992;Turner et al, 1996).…”

“…Local melting of the SCLM is possibly triggered by heating of upwelling mantle plume and by melt percolation, especially when water and fusible components are present (Gibson et al, 2006;Gallagher and Hawkesworth, 1992;Turner et al, 1996). When the SCLM undergoes extension and/ or heating, some of the earliest melts to be generated are mafic and rich in volatiles and potassium (McKenzie, 1989).…”

“…Specifically, flood basalts generated by adiabatic melting in a convecting mantle regime generally have rapid eruption rates (over a few million years) (Campbell, 2001(Campbell, , 2005Gibson et al, 2006). In contrast, magmatism related to melting Lithos 204 (2014) [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] of the sub-continental lithospheric mantle (SCLM) due to conductive heating by an incubating mantle plume (Gibson et al, 1995a,b;Gallagher and Hawkesworth, 1992;Kent et al, 1992;Turner et al, 1996) commonly have a relatively low eruption rate (over tens million years) and display a lithospheric geochemical fingerprint. Investigations into LIPs thus provide information as to vertical transfer of mantle materials/heat.…”

Geochemistry of basaltic flows from a basalt ring structure of the Serra Geral formation at Água Vermelha dam, Triângulo Mineiro, Brazil: implications for the magmatic evolution of the Paraná-Etendeka Province

“…10C) is a characteristic chemical signature for some continental flood basalt (e.g., Arndt & Christensen 1992, Pik et al 1999, reflecting the source composition and melt conditions (Turner & Hawkesworth 1995). The PEMP model for melt generation suggests the partial fusion of peridotite on the subcontinental lithospheric mantle (SCLM), chemically modified due to previous subduction processes which generated the negative Nb anomaly (Turner et al 1996, Reichow et al 2005, Wang et al 2008.…”