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Earth Surface Dynamics An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/esurf-2018-1
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
08 Jan 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Earth Surface Dynamics (ESurf).
Impact of grain size and rock composition on simulated rock weathering
Yoni Israeli and Simon Emmanuel Insti tute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
Abstract. Both chemical and mechanical processes act together to control the weathering rate of rocks. In rocks with micrometer size grains, enhanced dissolution at grain boundaries has been observed to cause the mechanical detachment of particles. However, it remains unclear how important this effect is in rocks with larger grains, and how the overall weathering rate is influenced by the proportion of high and low reactivity mineral phases. Here, we use a numerical model to assess the effect of grain size on chemical weathering and chemo-mechanical grain detachment. As grain size increases, the weathering rate initially decreases; however, beyond a critical size no significant decrease in the rate is observed. This transition occurs when the density of reactive boundaries is less than ~ 20 % of the entire domain. In addition, we examined the weathering rates of rocks containing different proportions of high and low reactivity minerals. We found that as the proportion of low reactivity minerals increases, the weathering rate decreases non-linearly. These simulations indicate that for all compositions, grain detachment contributes more than 36% to the overall weathering rate, with a maximum of ~ 50 % when high and low reactivity minerals are equally abundant in the rock. This occurs because selective dissolution of the high reactivity minerals creates large clusters of low reactivity minerals which then become detached. Our results demonstrate that the balance between chemical and mechanical processes can create complex and non-linear relationships between the weathering rate and lithology.

Citation: Israeli, Y. and Emmanuel, S.: Impact of grain size and rock composition on simulated rock weathering, Earth Surf. Dynam. Discuss., https://doi.org/10.5194/esurf-2018-1, in review, 2018.
Yoni Israeli and Simon Emmanuel
Yoni Israeli and Simon Emmanuel
Yoni Israeli and Simon Emmanuel

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We used a numerical model to assess the effect of grain size on chemical weathering and grain detachment. Our simulations showed that grain detachment represents more than a third of the overall weathering rate. We also found that as grain size increases, the weathering rate initially decreases; however, beyond a critical size, the rate became approximately constant. Our results could help predict the sometimes complex relationship between rock type and weathering rate.
We used a numerical model to assess the effect of grain size on chemical weathering and grain...
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