Lithologic Controls on Silicate Weathering Regimes of Temperate Planets

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.3847/PSJ/abe1b8. This is version 2 of this Preprint.

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Authors

Kaustubh Hakim, Dan J. Bower , Meng Tian , Russell Deitrick , Pierre Auclair-Desrotour , Daniel Kitzmann , Caroline Dorn , Klaus Mezger , Kevin Heng 

Abstract

Weathering of silicate rocks at a planetary surface can draw down CO2 from the atmosphere for eventual burial and long-term storage in the planetary interior. This process is thought to provide essential negative feedback to the carbonate-silicate cycle (carbon cycle) to maintain clement climates on Earth and potentially similar temperate exoplanets. We implement thermodynamics to determine weathering rates as a function of surface lithology (rock type). These rates provide upper limits that allow the maximum rate of weathering in regulating climate to be estimated. This modeling shows that the weathering of mineral assemblages in a given rock, rather than individual minerals, is crucial to determine weathering rates at planetary surfaces. By implementing a fluid-transport-controlled approach, we further mimic chemical kinetics and thermodynamics to determine weathering rates for three types of rocks inspired by the lithologies of Earthʼs continental and oceanic crust, and its upper mantle. We find that thermodynamic weathering rates of a continental crust-like lithology are about one to two orders of magnitude lower than those of a lithology characteristic of the oceanic crust. We show that when the CO2 partial pressure decreases or surface temperature increases, thermodynamics rather than kinetics exerts a strong control on weathering. The kinetically and thermodynamically limited regimes of weathering depend on lithology, whereas the supply-limited weathering is independent of lithology. Our results imply that the temperature sensitivity of thermodynamically limited silicate weathering may instigate a positive feedback to the carbon cycle, in which the weathering rate decreases as the surface temperature increases.

DOI

https://doi.org/10.31223/X52P66

Subjects

Astrophysics and Astronomy, Earth Sciences, Geochemistry, Planetary Geochemistry, Planetary Sciences

Keywords

Carbon cycle, Exoplanets, Habitable zone, Exoplanet surface composition, Geochemical cycles

Dates

Published: 2021-03-12 11:27

Last Updated: 2021-03-12 19:27

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License

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:
None

Data Availability (Reason not available):
https://doi.org/10.3847/PSJ/abe1b8

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