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

Abstract

Mixing between magmas is thought to affect a variety of processes, from the growth of continental crust to the triggering of volcanic eruptions, but its thermophysical viability remains unclear. Here, by using high-pressure mixing experiments and thermal calculations, we show that hybridization during single-intrusive events requires injection of high proportions of the replenishing magma during short periods, producing magmas with 55-58 wt% SiO 2 when the mafic end-member is basaltic. High strain rates and gas-rich conditions may produce more felsic hybrids. The incremental growth of crustal reservoirs limits the production of hybrids to the waning stage of pluton assembly and to small portions of it. Large-scale mixing appears to be more efficient at lower crustal conditions, but requires higher proportions of mafic melt, producing more mafic hybrids than in shallow reservoirs. Altogether, our results show that hybrid arc magmas correspond to periods of enhanced magma production at depth.

Final Closure of the Paleo‐Asian Ocean and Onset of Subduction of Paleo‐Pacific Ocean: Constraints From Early Mesozoic Magmatism in Central Southern Jilin Province, NE China

“…First, coeval Naozhigou Formation felsic rhyolites (222 Ma) and granites occur in southern Jilin Province (Lu et al, ; Wu et al, ; Yu et al, ). Furthermore, the analyzed Late Triassic igneous rocks display a bimodal range of compositions (Cao et al, ; Tang et al, ; Yu et al, , and references therein), which was likely generated through magma mixing (Laumonier et al, ). Second, the Late Triassic trachyandesites are crystal‐rich and contain abundant phenocrysts (~30% of the rock volume; Figure b) that likely formed through magma mixing/mingling, which typically induces crystallization of the hotter mafic liquid.…”

Geochemical and isotopic evidence for magma mixing/mingling in the Marshenan intrusion: Implications for juvenile crust in the Urumieh–Dokhtar Magmatic Arc, Central Iran

“…However, if it is introduced slightly later, then the viscosities of two magmas may be sufficiently contrasting to only allow comingling and MMEs form as a result and (or) incomplete mixing of more acidic and basic components (e.g., Barbarin & Didier, ; Didier, ; Didier & Barbarin, ; Vernon, ). Distribution of enclaves will be controlled by the viscosity contrast and is dominant if the mafic globule has a viscosity higher by >0.3 log unit relative to felsic host rocks (Laumonier et al, ). The mafic magma breaks up into blobs and can be scattered in the felsic magma to form enclaves.…”

Effects of chaotic advection on the timescales of cooling and crystallization of magma bodies at mid crustal levels

“…Understanding the dynamics occurring during the thermochemical evolution of igneous bodies at mid to lower-crustal level is of crucial importance in both petrology and volcanology since the possible behaviors of a magmatic mass strongly depend on the development of thermal and compositional heterogeneities, which, in turn, can influence the way a magmatic mass differentiates and/or erupts [Bachmann and Bergantz, 2008;Cooper and Kent, 2014;Caricchi and Blundy, 2015;Laumonier et al, 2014].…”