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Maryjo Brounce

mbrounce -at- ucr.edu

Associate Professor, University of California Riverside

Department of Earth Sciences

I am an igneous petrologist and analytical geochemist interested in the composition of the solid Earth and other planetary bodies in this solar system. Explore my webpage to learn more about my active research projects, and to see the inside of my laboratories and classrooms at UCR!

Currently active projects:

Signatures of the water- and oxygen-rich surface of Earth are physically mixed back into the mantle via plate tectonics on geologic timescales.

To what extent does this play a role in the basic rock-forming processes taking place today at island arc and ocean-island volcanoes?

Left: a photomicrograph of a brightly colored, doubly-polished olivine crystal in cross polarized light. An glassy melt inclusion in the center of the olivine crystal appears black.

Apatites are found as an accessory mineral in igneous rocks from a variety of planetary materials in our solar system. Their compositions provide a useful record of the volatile chemistry of the magmas from which they crystallized.

Apatites found in very reduced lunar lavas contain reduced sulfur. Apatites found in more oxidized lavas from Earth contain oxidized sulfur. Can we use apatite as a tool to constrain the bulk oxidation state of igneous rocks from a variety of planetary bodies in our solar system?

Left: a secondary electron image of Apollo rock 12039,4 showing apatites crystallized from a reduced, potassium-rich melt.

The mantle under the East African Rift features one of the most prominent geophysical anomalies observed in Earth's upper mantle. Constraints from lavas erupted along the rift indicate that temperature alone is not sufficient to account for the observed characteristics of seismic waves in this region.

Does the mantle in this region contain elevated water and/or carbon concentrations, also thought to impact seismic wave behaviors? Can we reconcile petrological and geophysical records of the mantle in this region?

Left: a map of the East African Rift, showing a general outline of the position of the geophysical anomaly and the locations of some large rift volcanoes.

The Salton Sea geothermal fields are a primary source of renewable energy in California. Besides being a thermal resource, the brines of these geothermal systems are rich in lithium and other critical raw materials that can be extracted for additional renewable energy demands, like batteries.

Among many outstanding questions surrounding the viability of long-term economic production of raw materials in this area, the distribution of lithium and other critical raw materials in the minerals and rocks through which these brines percolate is unknown.

Left: UCR Postdoctoral scholar J Humphreys examines a section of drilled rock from the Salton Sea region.

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