Research

Water and volatile contents of the magma can play an important role in ultimately regulating how explosive or effusive a volcanic eruption will be. In addition to that, understanding the partitioning and diffusive behavior of water in nominally anhydrous volcanic minerals can be very useful in producing a picture of the storage and ascent of magma under a volcano. Studying the equilibrium partitioning behavior of water between the magma and a widespread mineral like plagioclase (feldspar) can inform us about the magma storage depths even without having to find and analyze melt inclusions. On the other hand, diffusion profiles of water concentrations across a feldspar crystal can shed light on the timescales of ascent of the magma, which can also influence the eruptive style of the volcano. As a first step along this direction, I am starting to characterize water concentrations in plagioclase phenocrysts from different volcanic systems by Fourier Transform Infrared (FTIR) spectroscopy. I intend to perform dehydration experiments using a 1-atm gas-mixing furnace on these natural crystals to investigate the diffusive behavior of H at volcanic conditions.

Ordinary chondrites (OCs) account for over 85% of observed meteorite falls in our collections, and are thought to come from parent bodies that are thermally like onion shells with differing degrees of metamorphism (according to which samples are classified into petrologic types). Previous work (e.g., Peterson et al., 2023a, b, 2024; Newcombe et al., 2023) has revealed nominally anhydrous minerals in partially to fully differentiated meteorite parent bodies to be very dry. This work attempts to make similar in situ measurements using Secondary Ion Mass Spectrometry (SIMS) on a suite of OC samples of varying degrees of thermal metamorphism and parent body chemical affinities. Preliminary work on equilibrated OCs reveal them to be dry and likely insufficient to account for the Earth's water inventories solely from the accretion of OC-like material from the inner solar system. More investigations are underway on unequilibrated OC samples.

The Southern Granulite Terrane (SGT) of India is a key piece in the reconstructions of the Neoproterozoic eastern Gondwana supercontinent. Moreover, it exposes rocks metamorphosed at ultrahigh-temperatures (over 900°C at mid- to lower crustal depths, without melting completely) in the roots of an orogen at the surface today, and preserves over 3 billion years of crustal history from the Archean to the early Phanerozoic. I worked on tracing the pressure-temperature evolution of sapphirine-bearing metapelites and charnockites from the Kodaikanal Massif, which sits close to a shear zone that separates one of largest the crustal blocks of the SGT into domains with different evolutionary histories. Petrography and electron probe microanalysis of mineral chemistry were used to perform phase equilibrium modeling and geothermobarometry to estimate pressures and temperatures of formation of the various mineral assemblages. A clockwise P-T evolution was recovered from the studied rocks, consistent with a continental collisional tectonic setting.