To D or not to D? Re-evaluating particle-size distributions in natural and experimental fault rocks

Cataclasis is a first-order mechanism shaping fault-rock development in the brittle crust. The most accepted model for cataclasis is constrained comminution which predicts a power-law distribution of particle size described by the fractal dimension, D. In this paper, we statistically test for the presence of power-law scaling in 61 naturally and experimentally deformed fault rocks, thereby assessing the validity of the constrained comminution model. We find that no data set exhibits compelling evidence for power-law scaling, even when a lower threshold is applied to promote the appearance of power-law scaling. Log-normal distributions provide better fits to statistically conclusive test cases, both when using a lower threshold (91% of cases) and when examining the full data sets. Thus, our results are not consistent with constrained comminution. We propose that log-normal distributions provide a more useful description of fault-rock particle-size distributions and discuss the implications for the mechanisms of cataclasis. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study statistically tests for the presence of power-law scaling in 61 naturally and experimentally deformed fault rocks, finding that log-normal distributions provide better fits to the data sets compared to power-law distributions. The results contradict the constrained comminution model and suggest that log-normal distributions offer a more useful description of fault-rock particle-size distributions, with potential implications for the mechanisms of cataclasis.