Research Overview
I am a geochemist, experimentalist, petrologist, and thermodynamicist. I use a variety of analytical and modeling tools to learn more about the chemistry of planetary materials.
Critical Element Recovery & Carbon Capture
I am worked on a U.S. Department of Energy (DOE) funded project titled "Mining Red Mud Waste fro Carbon Dioxide Capture and Storage and Critical Element Recovery" led by Xin Zhang at Pacific Northwest Nation Laboratory (PNNL) with co-PI's Alex Navrotsky (ASU) and Xiaofeng Guo (WSU). The overarching goal to this project is to recover critical elements from red mud (a common industrial waste product rich in REE's) while capturing carbon as stable carbonates.
My role in this project was to develop a database of rare earth compounds. Where datasets are lacking, students in the Navrotsky group will synthesize and measure thermodynamic properties of REE compounds and solutions. These data are needed to understand the REE extraction from red mud.
My role in this project was to develop a database of rare earth compounds. Where datasets are lacking, students in the Navrotsky group will synthesize and measure thermodynamic properties of REE compounds and solutions. These data are needed to understand the REE extraction from red mud.
Infograph from the International Aluminum Institute.
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Red mud near Stade, Germany (photo credit Wikipedia). Read more about red mud basics here.
Aerial view of bauxite processing facility showing red mud ponds. Photo credit
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The Deep Carbon Cycle
Carbon in the Mantle Lithosphere
The shallow, conductively cooled mantle lithosphere is believed to be a significant reservoir for carbon storage (e.g., Lee et al., 2019; Kelemen and Manning, 2015; Dasgupta, 2013; Shcheka et al., 2006). However, these estimates of carbon in the mantle lithosphere, based on ‘back of the envelope’ mass balance calculations. Only a few studies (e.g., Créon et al., 2017) present direct measurements of sources and distribution of carbon in the lithospheric mantle. Currently, I am characterizing the carbon stored in mantle xenoliths, as carbonates and fluid inclusions, from the Colorado Plateau. I am (1) using carbon and oxygen isotopic analyses of carbonate from lithospheric mantle xenoliths to infer source provenance; (2) determining the entrapment temperature and composition of fluid inclusions to quantify the forms of aqueous carbon contributing to the mantle lithospheric carbon reservoir; and (3) modeling the fluid inclusion chemistry at lithospheric mantle conditions to investigate the complete aqueous carbon speciation at the determined entrapment temperatures. Collectively these investigations will provide constraints on the distribution and sources of carbon in the Proterozoic lithospheric mantle underlying the southwestern United States, adding to the few direct measurements of the carbon in the mantle lithosphere.
This work is funded through the NSF GeoPRISMS Program.
This work is funded through the NSF GeoPRISMS Program.
Predictive Fluid Speciation Calculations
Fluids in subduction zones are invoked to trigger partial melting and to oxidize and metasomatize the mantle wedge but the detailed geochemistry of said fluids lacks full characterization. However, recent advances in theoretical thermodynamic modeling, namely the development of the Deep Earth Water (DEW) Model (Sverjensky et al., 2014), facilitate calculations at pressures-temperatures relevant for subduction zones; a regime that was previously inaccessible. A limited number of studies have set the precedent for the exploration of subduction fluid chemistry via new thermodynamic modeling techniques, (e.g., Guild & Shock, 2020; Huang et al., 2017; Sverjenksy et al., 2014) pioneering the field of high pressure-temperature aqueous geochemistry. Here we use the DEW model to characterize the organic and inorganic carbon speciation in high pressure-temperature fluids with applications to subduction zones.
Studying "Fossil" Fluids
Hydrous minerals are "footprints" of a fluid that is no longer present. I use these trace fossils to learn more about the chemistry of the fluid.
To do this, I integrate geochemical observations of hydrous minerals with thermodynamic modeling. For example, I show that natural chlorite can form under a broad range of pressure-temperature conditions in a subduction zone, previously only observed in experimental studies (e.g., Till et al., 2012). I do this by using traditional thermobarometric techniques, together with boron isotopic composition of chlorite, and thermodynamic modeling. These thermodynamic modeling results show that pH and pressure-dependent speciation of trigonally and tetrahedrally coordinated boron species in a high pressure-temperature fluid are ultimately preserved in the high-pressure chlorite.
To do this, I integrate geochemical observations of hydrous minerals with thermodynamic modeling. For example, I show that natural chlorite can form under a broad range of pressure-temperature conditions in a subduction zone, previously only observed in experimental studies (e.g., Till et al., 2012). I do this by using traditional thermobarometric techniques, together with boron isotopic composition of chlorite, and thermodynamic modeling. These thermodynamic modeling results show that pH and pressure-dependent speciation of trigonally and tetrahedrally coordinated boron species in a high pressure-temperature fluid are ultimately preserved in the high-pressure chlorite.
Water-Undersaturated Melting in Subduction Zones
I am interested in how water influences the chemistry of mantle melts in subduction zones. Previous experimental studies have established the chemistry of anhydrous mantle melts (Grove & Juster 1989; Kinzler & Grove, 1992; Baker & Stopler, 1994; Falloon et al., 1997; Till et al., 2012) and water-saturated mantle melts (Mysen & Boettcher, 1975; Till et al., 2012; Grove & Till, 2019) but only a handful of studies have characterized water-undersaturated mantle melting (Hirose & Kawamoto, 1995; Gaetani & Grove, 1998).
Recycling Processes in Subduction Zones
During my Ph.D. I have conducted a detailed petrologic, geochemical, and thermobarometric study to determine the origin and history of an ultramafic suite, the Higashi-Akaishi body, from the Sanbagawa metamorphic belt in southwest Japan. Major element and mineral chemistry suggests the garnet pyroxenite and dunite originated in the sub-arc crust as a cumulate. However, slab signature overprinting and thermobarometric estimates support its removal from the lower crust and incorporation in the subduction channel. A warming of the paleo subduction setting and hydration of the lithologies leads to the exhumation of the Higashi-Akaishi suite. The Higashi-Akaishi cumulate likely represents a piece of the subduction system that is rarely preserved, as well as key component in the compositional evolution of the continental crust.
Check it out here!
Check it out here!