EAS Seminar: Hector Lamadrid (Missouri)

Kinetics of the serpentinization and carbonation reactions in the oceanic lithosphere: a geologist baby steps towards the energy transition

The hydrothermal alteration of the oceanic lithosphere is a critical geologic process that occurs when ultramafic minerals (mantle rocks) interact with aqueous fluid circulation. The chemical and petrological processes (serpentinization, hydrogen production, and carbonation reactions) have become one of the most important subjects in the scientific literature, and are key to understanding the physical, chemical, and biological evolution of the Earth’s system, and are central to the current origin of life hypotheses, as well as the search for microbial life on the icy moons of Jupiter and Saturn. Serpentinization and carbonation reactions play an important role in the deep volatile cycle on Earth due to the subduction of hydrothermally altered ultramafic rocks, transporting a significant amount of carbon and other volatiles to the deep mantle. Carbonation of ultramafic rocks is also considered a suitable option for long-term geological storage of CO2. Understanding the effect of different PTX conditions on these reactions can contribute to making industrial CO2 more economically feasible and advance our understanding of oceanic hydrothermal systems that are believed to be essential places for early biological evolution. In this talk, we will present different applications of a recently developed experimental technique that uses the combination of synthetic fluid inclusions as microreactors and various non-destructive analytical techniques that allows us to obtain kinetic data at various environmental conditions. The method has been successfully used to study the rates of both olivine and pyroxene serpentinization, hydrogen production, dehydration rates, and olivine carbonation reactions at different temperatures, pressures, and fluid compositions. Serpentinization reaction rates were determined by measuring the increase in salinity of the aqueous fluid inside the fluid inclusion as H2O was gradually removed from the solution and incorporated into the hydrous reaction products. Carbonation rates of olivine were determined at temperatures ranging from 50 to 200°C using Raman spectroscopy by monitoring the decrease of CO2 density (indicated by the decrease in the so-called Fermi diad splitting of CO2 peaks) in fluid inclusions as a proxy for the reaction progress. The advantage of this method over more traditional experimental approaches is that it allows detailed micron-scale investigations of fluid-rock interactions and the determination of reaction products and reaction rates in situ, in real-time, with various fluid compositions at elevated temperatures (and pressures) in tens to hundreds of individual microreactors simultaneously. This technique provides new avenues to obtain detailed kinetic and thermodynamic information at different conditions relevant to natural processes, the degree to which we can produce hydrogen from ultramafic rocks for green energy, and carbon capture and sequestration.

Hector Lamadrid’s research interests span a wide range of geological and geochemical problems that focus on the role of fluids in crustal processes, how fluids interact with the surrounding rocks, and how these interactions evolve through time and space. In particular, he is interested in process driven studies that relate together fluid-rock interactions, the associated alteration assemblages, the fluids and melts trapped during these processes, and the equilibrium and disequilibrium reactions (and their kinetic and thermodynamic mechanisms) to reconstruct the sequences of events and understand the evolution of the Earth’s system. In his research he integrates information obtained from field observations, analytical techniques (fluid inclusions, Raman spectroscopy, SEM-EMPA, TOF SIMS), high pressure and temperature experiments (cold seal pressure vessels, piston cylinder) and computational modeling to investigate the role fluids, and their interactions with the host rocks.

Professor Lamadrid’s main research line focuses on understanding the dissolution and precipitation mechanisms (hydration, dehydration, carbonation, etc.) that occur during serpentinization of the oceanic lithosphere near mid-ocean ridges (MOR) and later during subduction, as well as the geochemical evolution of the associated fluids. Additionally, he is interested in a myriad of petrological problems including volcanic systems, deep metamorphism, hydrothermal systems and ore deposits, as well the diagenesis of carbonate rocks.

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