WATER-GAS-ROCK INTERACTIONS
WATER-GAS-ROCK INTERACTIONS
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Most rocks on Earth originally form at high temperatures during the cooling of magma. At lower temperatures and in the presence of water and the atmosphere, the magmatic minerals that originally composed rocks are not stable and will subsequently alter into new minerals. Rock alteration is a major geological process as it changes the physical properties of rocks, converts rocks into soils, facilitates the chemical exchanges between rock and water that result in the mobilization of critical elements and nutrients, and consequently supports all life on our planet. Different rocks on Earth alter differently, given the temperature and pressure conditions, resulting in diverse compositions of alteration minerals, fluids, and volatiles.
We study water-gas-rock interactions, wherever and whenever they occur. Current research interests include mass transfer processes in subductions zones deep beneath the Earth's surface to low-temperature chemical reactions occurring in other planetary bodies. We are interested in exploring the contributions of water-gas-rock interactions in the surface redox conditions of the Early Earth as well as processes that enables habitable environments in present-day, rock-hosted aquifers and springs.
We investigate water-gas-rock interactions through a combination of field, analytical, experimental and theoretical techniques in mineralogy and aqueous geochemistry .
We investigate water-gas-rock interactions through a combination of field, analytical, experimental and theoretical techniques in mineralogy and aqueous geochemistry .
Picture: A microscope image of a very thin slice of a rock from the mantle. The bright colored-minerals are water-free minerals formed in the Earth's mantle called olivine. The dark veins cutting the mantle minerals are hydrous minerals called serpentine. Serpentine forms because olivine, a mantle mineral that is not stable in the Earth's surface, breaks down.
Geochemistry and mineralogy of aqueously altered rocks
Geochemistry and mineralogy of aqueously altered rocks
We study rocks and minerals, and how their chemical composition changes when they break down and transform into new minerals in the presence of water. Altered minerals are valuable records of the aqueous and redox conditions that led to their formation. In addition, studying their compositions provides insights into the mobilization of elements and nutrients critical to life and the clean energy transition.
Recent interests include:
(1) Carbon mineralization and critical element mobilization during ultramafic alteration.
(2) Subsurface redox conditions informed by variably altered, low-temperature serpentinites.
Geochemistry of extreme aqueous environments
Geochemistry of extreme aqueous environments
We investigate water seeping out from rocky outcrops. The composition of these rock-hosted fluids provides clues on subsurface chemical exchanges between minerals and fluids. In particular, we study highly alkaline (pH >11!) fluids generated during serpentinization of ultramafic rocks.
Aside from studying their compositions, we also quantify energy available for various chemotrophic microbes that may inhabit these environments. These extreme fluids can also occur outside our own planet as ultramafic rocks may be present in contact with water at other rocky bodies in our solar system. As such, these extreme environments are attractive Earth analogs and model ecosystems to study how geochemical reactions provide habitable environments beyond our planet such as in ice-covered ocean worlds in the outer solar system.
Pictures: Highly alkaline stream water in the mountains of Northern Oman. These unique fluids are formed when groundwater reacts with olivine-rich rocks uplifted from Earth's mantle.
Picture: Gas bubbling out from a stream in the mountains of Northern Oman.
Formation of reduced volatiles during water-rock interactions
Formation of reduced volatiles during water-rock interactions
Aside from water and rocks, we also study gas! Gases such as hydrogen and methane are generated during water-rock interactions.
Like water chemistry, gas compositions can also provide clues on the chemical reactions accompanying subsurface water-rock interactions. These volatiles also fuel chemotrophic microorganisms. Thus, knowing the compositions, origins, and movements of these gases can provide insights into the habitability of rock-hosted ecosystems on Earth and beyond!
Using thermodynamic calculations to simulate water-gas-rock interactions
Using thermodynamic calculations to simulate water-gas-rock interactions
Our study of natural samples (water, rock, gas) is complemented by thermodynamic calculations that simulate and predict outcomes of interactions between materials that are not in equilibrium with each other (e.g., rock and water). Conversely, we ground truth model results with analysis of natural fluids, and investigate processes that can cause deviation from equilibrium expectations.
We simulate consequences of water-rock-gas interactions wherever and whenever they occur. Below are some current and past modeling interests:
(1) Formation of hyperalkaline fluids during present-day serpentinization of ultramafic aquifer host rocks and how model outcomes fare with actual, natural samples.
(2) Stability of Fe-rich olivine in the Martian surface
(3) H2 generation potential of thousands of Fe-bearing igneous rocks during the Archean eon, and their implications for the Great Oxidation event.
(4) Carbon mineralization in ultramafic bodies.
(5) Element mobilization and carbon mineralization in subduction zones.
Picture: Predictions vs Reality. The red curve depicts predicted pH in equilibrium with the minerals serpentine, brucite, and diopside. Black circles are measured pH from several alkaline springs in the world.
Picture: A portable Picarro gas analyzer actively measuring CH4 and CO2 concentrations above a hyperalkaline pool in Oman.
Gas emission and sequestration rates in the field and the lab
Gas emission and sequestration rates in the field and the lab
We measure emission and sequestration rates of gases (H2, CH4, CO2) in the field and the laboratory to constrain flux of reduced volatiles into the atmosphere, CO2 sequestration and carbon mineralization rates, and subsurface habitability.
Recent interest include:
(1) Rates of outgassing of reduced volatiles (H2, CH4) in ultramafic-hosted environments.
(2) Rate of carbonation of common alkaline household and waste materials.
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