Magmatic Processes

Magmatic systems are a key pathway connecting the deep Earth to the climate and the biosphere. The spatio-temporal scale of magma transport in the crust and the lithosphere sets the rate of volcanic eruptions and controls volcanic gas fluxes, hydrothermal activity, and crustal density and rheology. Consequently, my research focuses on two key questions: What are the primary processes controlling magma transport from source (melt generation) to eruption, and associated timescales? How do these change in different tectonic environments? 

I create coupled models and combine them with observations to greatly increase our understanding of magma transport in the asthenosphere (melt channelization in plume-ridge systems, Mittal & Richards 2017), lithosphere (fracture-mechanics and analog dike experiments, Mittal & Richards 2018), and the crust (multiply connected thermo-mechanical magma chambers, Mittal & Richards 2020b; data-driven parameterizations of high-velocity fault friction, Saltiel, Mittal, et al., 2020).

I developed a new thermo-mechanical model for magma reservoirs interacting with crustal hydrothermal systems. Using this framework, I demonstrated for the first time that non-eruptive magmatic gas emissions strongly affect the likelihood of an eruption [Mittal & Richards, 2019]. In collaboration with a geochemist, I created a new petrological method to determine eruption initiation timescales and used it to show that both mafic and silicic systems can be primed for eruption on similar time periods, contrary to previous assumptions [Antonelli, Mittal 2019].

Using the Deccan Traps as an archetype for CFB systems, I created an extensive data compilation comprising geochronology, paleomagnetism, geochemistry, volcanology (lava flows, eruptive vents), and geophysics (seismic, gravity, magnetotelluric) [Mittal & Richards 2020a]. Integrating this compilation with my magmatic model toolkit, I definitively showed that the conventional model of one/a few large magma chambers cannot explain the frequent, large individual CFB eruptions. Instead, CFBs have a trans-crustal magmatic system with multiple smaller (∼ 102 - 103.5 km3) magma bodies that stochastically connect to feed eruptions [Mittal & Richards 2020b]. 

My current research focuses on two key areas: (i) understanding the primary processes controlling magma transport from source (melt generation) to the formation of crustal magma bodies and (ii) the role of crystal-rich mushes in the thermochemical evolution of magma reservoirs. To investigate magma transport, I use the interaction of mantle plumes with mid-ocean ridges (e.g., in the Galápagos islands) as a case study because the two magma sources are chemically distinct and, thus, geochemically traceable. Based on a statistical analysis of a newly compiled mid-ocean ridge geochemistry dataset, I found that mantle plumes influence ridges up to ~ 500 km away, and that plume-derived melts contribute ~ 30-40% to water and CO2 flux from mid-ocean ridges globally. Next, I plan to image mantle melt transport in the Galápagos region using seafloor electromagnetic imaging to validate numerical models and have recently been awarded NSF support for a ship-based expedition.  

Since volcanology has recently shifted to a new consensus perspective of trans-crustal magmatic systems dominated by crystal-rich mushes, assessing how these mushes affect the evolution of magmatic systems and eruption dynamics is critical. I investigate outcrop to thin section scale crystal texture and geochemical properties using theoretical magma reservoir models (constrained by observations) and lab experiments (analog and rock deformation experiments) and models for reactive transport and non-linear porous media flow. My work in this domain is specifically focused on the dynamics of basaltic lavas and basaltic calderas - both in terms of effusion rate histories from long-lived eruptions as well as long term magma recharge history (inferred from gas and deformation data).