Influence of analytical operating procedures on particle size distributions in carbonate cataclastic rocks

Abstract

Fractal dimensions of fault core rocks provide a suitable tool to estimate amounts of comminution and describe processes associated with faulting, such as hydraulic sealing, and nucleation and propagation of coseismic ruptures. It is thus important to be aware of possible biases produced by different analytical procedures on given materials, to prevent unsupported interpretations of granulometric data. The aim of this paper is to minimize the method-induced variability in the calculation of fractal dimensions. We present a comparison among different 2D and 3D analytical techniques that are commonly used to calculate grain size distributions, even introducing and discussing new analytical techniques never used before in the study of fault core rocks. The studied samples are loose and coherent carbonate cataclastic rocks collected at the same field site along the Fiamignano Fault in the Central Apennines (Italy). Our results provide further support to the evidence that analytical procedures can significantly influence particle size distributions and related D-values. It follows that direct comparison between different datasets is not straightforward if rigorous analytical protocols are not systematically used and described. Guidelines for fractal analysis of carbonate fault rocks are provided.