Assimilation and mixing of crystal-bearing magmas in the Snake River Plain, NW United States: rheological timescales for magmatism of large silicic provinces
Final Report Abstract
The Snake River Plain (SRP) represents a unique opportunity to study the impact of a thermal anomaly on continental crust and the resulting dynamics in magma reservoirs. Deep, mantle derived mafic melts ascend through the crust, assimilate adjacent country rock, mix and evolve. These processes, along with the composition of the primitive magma, govern the cooling and crystallization dynamics and thus constitute a fundamental contribution to magmatic differentiation. The present project was the continuation of two other previous projects on the same theme and region in the Snake River Plain (SRP) volcanic fields. In this present project our team focused on rheology and mixing enhanced by bubble and crystals especially in acidic melts. As a reservoir forms, primitive magma batches induce crustal melting, assimilation, and mixing. Heating of the reservoir raises temperatures and may obstruct fractionation. Thermal and compositional instabilities caused by recharge of a more primitive magma will trigger convection and mixing. Since mostand least-evolved magmatic end-members (rhyolite and basalt) from the SRP are the most contrasting natural magmas known on Earth, they represent natural materials with extreme viscosity-contrast. Therefore these compositions have been selected for our experiments in order to evaluate a worse case scenario. We performed a series of experiments to systematically characterize the evolution and importance of mixing during the lifetime of reservoirs, additionally taking into account the role of bubbles and crystals. The development of the appropriate experiments has been followed by the search of the best mathematical and thermodynamic tools to measure assimilation and mixing. Chemical processes behind magma mixing provide the pieces of the puzzle portraying the evolution of magmas. Therefore this work aimed to: (1) perform experiments; (2) to study and constrain the nature and timescales of assimilation and mixing, in the SRP magma reservoirs, in such a way to produce deliverables to be applied elsewhere. Our large-scale goal was to look for the appropriate numerical and geochemical tools to be used in volcanology and petrology in general, in small or large igneous provinces; (3) to characterize the composition of recognized end-members (e.g. interstitial melt compositions, volatile and crystal content).
Publications
-
2014. Chaotic Mixing: from lab to nature. Revisiting a deep magma chamber. DMG Conference, Jena
De Campos C.P., Morgavi D., Perugini D., Dingwell D.B.
-
2014. Magma mixing enhanced by bubble segregation. AGU, San Francisco, 2014
Wiesmaier S., Morgavi D., Renggli C., Perugini D., De Campos C.P., Hess K- U., Ertel-Ingrisch W., Lavallée Y., Dingwell D.B.
-
(2015). Chaotic Flow Patterns from a Deep Plutonic Environment: a Case Study on Natural Magma Mixing. Pure and Applied Geophysics. 172, 7: 1815-1833
De Campos C.P.
-
2015. Eruption and emplacement timescales of ignimbrite super-eruptions: a constraint from the thermo-kinetics of glass shards. Frontiers in Earth Sciences. Vol. 3, article 2-1
Lavallée Y., Wadsworth F.B., Vasseur J., Russell J.K., Andrews G.D.M., Hess K-U., von Aulock F., Tuffen H., Dingwell D.B.
-
2015. Magma mixing enhanced by bubble segregation. Solid Earth 6: 1–17
Wiesmaier S., Morgavi D., Renggli C., Perugini D., De Campos C.P., Hess K- U., Ertel-Ingrisch W., Lavallée Y., Dingwell D.B.
-
Concentration variance decay during magma mixing: a volcanic chronometer, Scientific Reports 5(1):14225
Perugini D., De Campos C.P., Petrelli M., Dingwell D.B.
