Synthetic fluid inclusions XXIII. Effect of temperature and fluid composition on rates of serpentinization of olivine

Synthetic Fluid Inclusions XXIV. In situ Monitoring of the Carbonation of Olivine Under Conditions Relevant to Carbon Capture and Storage Using Synthetic Fluid Inclusion Micro-Reactors: Determination of Reaction Rates

“…Similarly, the difference between an SFI with a spherical shape and an SFI with the same total volume but a tabular shape with a thickness of 1 µm is ∼0.5 log unit. The error introduced by assuming that all SFI studied are spherical and have a diameter of 10 µm is within the range of the dispersion observed in our data (±0.5 log J) for experiments conducted at 50 • C. We conclude that variations in size and shape of the SFI studied are likely the biggest contributor to the dispersion in our data, however, similar uncertainties are commonly reported in other reaction rate studies (Rimstidt et al, 2012;Rimstidt, 2014), including reaction rate studies using fluid inclusions as microreactors (Lamadrid et al, 2017b(Lamadrid et al, , 2021.…”

“…In this study, we present experimentally determined rates of olivine carbonation at temperatures ranging from 50 to 200 • C in the presence of an aqueous solution with salinity similar to that of seawater, using synthetic fluid inclusions (SFI) as micro-reactors. The use of SFIs as micro-reactors applies non-destructive analytical techniques to follow the reaction in situ and in real time, and has been used successfully to monitor rates of serpentinization of olivine (Lamadrid et al, 2017b(Lamadrid et al, , 2021 as a function of temperature and fluid composition using changes in salinity as a proxy. In the present study, we use Raman spectroscopy to monitor reaction progress of olivine carbonation at elevated temperatures and pressures by quantifying the amount of CO 2 consumed in the reaction as a function of time.…”

Decreasing extents of Archean serpentinization contributed to the rise of an oxidized atmosphere

“…Therefore, for serpentinization to be a significant source of reduced gas throughout most of the Archean, the rate of serpentinization should be at least 10 −6 km yr −1 . While this represents an upper limit on rates perceived to occur in modern low-temperature ultramafic aquifers 55 , such a rate could have been normal under warmer and more dynamic Archean surface conditions.…”

“…2 . In these calculations, we assume a serpentinization rate ( ) of 10 −6 km yr −1 , a maximum value for low-temperature ophiolitic aquifers with low reactive surface area 55 . For the extents of ultramafic rocks in continents ( , km 2 ), we used the average distribution and continental presence calculated by Greber et al 53 and Dhuime et al 56 , respectively.…”

“…Reaction extents can be quantified through high-temperature experiments where reaction rates are considerably faster. Extrapolation of high-temperature laboratory experiments simulating olivine serpentinization to low temperatures (25 °C) reveals that it takes between 10 6 and 10 8 Myrs to completely serpentinize a km 3 of ultramafic rock 55 , assuming reactive surface areas (e.g., 6 × 10 6 –6 × 10 3 km 2 (km 3 rock) −1 ) common in low-temperature continental systems 55 . Multiplying laboratory-determined rates, usually depicted as mole mineral m −2 s −1 that can be converted to km 3 rock km −2 yr −1 , with the reactive surface area (km 2 (km 3 rock) −1 ) will yield the rate (yr −1 ) required to totally alter a given volume (e.g., 1 km 3 ) of reacting material.…”