Long‐term volumetric eruption rates and magma budgets

Abstract

[1] A global compilation of 170 time-averaged volumetric volcanic output rates (Q e ) is evaluated in terms of composition and petrotectonic setting to advance the understanding of long-term rates of magma generation and eruption on Earth. Repose periods between successive eruptions at a given site and intrusive:extrusive ratios were compiled for selected volcanic centers where long-term (>10 4 years) data were available. More silicic compositions, rhyolites and andesites, have a more limited range of eruption rates than basalts. Even when high Q e values contributed by flood basalts (9 ± 2 Â 10 À1 km 3 /yr) are removed, there is a trend in decreasing average Q e with lava composition from basaltic eruptions (2.6 ± 1.0 Â 10 À2 km 3 /yr) to andesites (2.3 ± 0.8 Â 10 À3 km 3 /yr) and rhyolites (4.0 ± 1.4 Â 10 À3 km 3 /yr). This trend is also seen in the difference between oceanic and continental settings, as eruptions on oceanic crust tend to be predominately basaltic. All of the volcanoes occurring in oceanic settings fail to have statistically different mean Q e and have an overall average of 2.8 ± 0.4 Â 10 À2 km 3 /yr, excluding flood basalts. Likewise, all of the volcanoes on continental crust also fail to have statistically different mean Q e and have an overall average of 4.4 ± 0.8 Â 10 À3 km 3 /yr. Flood basalts also form a distinctive class with an average Q e nearly two orders of magnitude higher than any other class. However, we have found no systematic evidence linking increased intrusive:extrusive ratios with lower volcanic rates. A simple heat balance analysis suggests that the preponderance of volcanic systems must be open magmatic systems with respect to heat and matter transport in order to maintain eruptible magma at shallow depth throughout the observed lifetime of the volcano. The empirical upper limit of $10 À2 km 3 /yr for magma eruption rate in systems with relatively high intrusive:extrusive ratios may be a consequence of the fundamental parameters governing rates of melt generation (e.g., subsolidus isentropic decompression, hydration due to slab dehydration and heat transfer between underplated magma and the overlying crust) in the Earth.

On the conditions of magma mixing and its bearing on andesite production in the crust

“…Analyses at various tectonic settings show that long-term magma fluxes are on the order of 10 À 3 -10 À 4 km 3 yr À 1 (ref. 59), although considerable variations between and within systems are documented. Figure 9 shows the time needed for the assembly of a felsic reservoir in the upper crust, depending on magma fluxes.…”

Crustal redistribution, crust–mantle recycling and Phanerozoic evolution of the continental crust

“…In continental arcs it is impossible to resolve older from new magmatic additions in most circumstances and the volumes of lavas erupted are quite low (Atherton and Petford, 1996;White et al, 2008). Volcanic production rates represent a lower limit to the total production.…”

“…However, this approach is only suitable in areas with good geophysical coverage and this is not universally available, especially in continental interiors, where there is also no Schubert and Sandwell (1989), except that data for the Kerguelen Plateau is from Gladczenko et al (1997) and Coffin et al (2002), for the Ontong Java Plateau from Coffin and Eldholm (1994) and for Shatsky Rise is from Sager et al (1999). Two volumes are shown for the continental LIPs, an eruptive volume, derived from mapping and an estimated total magmatic volume assuming that 75% of the true magma volume is emplaced within the underlying crust (White et al, 2008). Data for the continental LIPs is provided in Table 7.…”

“…North Atlantic province comprises East and West Greenland, the Faeroes, together with the British Isles, including the Faeroe-Shetland Basin and the Rockall Trough. (Fedorenko et al, 1996;Wignall, 2001;Reichow et al, 2002) (Brown, 1963;Boldreel and Andersen, 1998;Escher and Watts, 1976;Larsen et al, 1992;Emeleus and Bell, 2005;Waagstein, 1988;White et al, 2003) White et al (2008), who examined a range of igneous provinces estimating the ratios of extrusive versus intrusive products. Although ratios ranged wildly in some of the small examples, many of the extrusive: intrusive ratios lie in the range 1:2 to 1:5.…”

The habitability of a stagnant-lid Earth

“…However, r ie is difficult to constrain as it could vary with time according to the thickness of the lithosphere below which partial melt is generated and would be influenced by the porosity of the upper crust. For simplicity, we assume here r ie = 2.5 (Grott et al 2011b); this value is intermediate between values as low as 1, typical of some basaltic shields, and 5 or even more, characteristic of mid-ocean ridges and other volcanic complexes (White et al 2006). Whether the water contained in the extruded melts is outgassed into the atmosphere or retained in the solidifying melt depends on its solubility in surface lavas at the evolving pressure and temperature conditions of the atmosphere (Gaillard & Scaillet 2014), whereby the effect of pressure dominates.…”