Comment on “Application of Analytical Diffusion Models to Outcrop Observations: Implications for Mass Transport by Fluid Flow Through Fractures” by Antonellini et al. (2017)

Abstract

AbstractAntonellini et al. (2017, https://doi.org/10.1002/2016WR019864) presented a detailed analysis of alteration halos observed in outcrops of a fractured rock system. We point out here the need for a critical discussion on the low value of dissolved oxygen concentration used in the boundary water of their analytical models. Moreover, we argue that the model used by Antonellini et al. (2017) to evaluate the time for fracture filling is not consistent with the hypotheses used by the same authors to analyze the alteration halos. We propose here an alternative explanation along with an alternative model for fracture filling by precipitation of hydroxide minerals. Unlike the model used by Antonellini et al. (2017), in the model presented here, the time for fracture filling, defined as the time when the relative fracture aperture is equal to a given minimum threshold, does not depend on the initial fracture aperture.