Modeling weathering pathways and processes of the fragmentation of salt weathered quartz-chlorite schist

The relationship between the rate of rock breakdown and environmental and geological factors must be understood in order to establish the conditions under which weathering limits erosion. In this study qualitative and quantitative models of the rock fragmentation process are fitted to previously published data obtained from laboratory salt weathering trials of quartz-chlorite schist. Weathering was modeled as a combination of (1) a fragmentation event that fragments the parent particle into a number of daughter particles while preserving mass, and (2) a fracture probability, that determines the probability that a fragmentation event will occur in a given time period. We show that observations of the complex breakdown of salt weathered schist are consistent with model assumptions of a simple fracture geometry model and an increase in fracture probability with time. For the fragmentation geometry the best fit to the experimental data was achieved by assuming that each fragmentation event involves splitting of the parent particle into two daughter fragments of equal volume. For the fragmentation rate the data could best be described with a fracture probability, and hence the weathering rate, that increased linearly with time. This paper shows that it is possible to use a physically based fragmentation model to infer the process of fragmentation for individual particles using a time evolving particle size distribution for the weathering rock fragments.