Multiscale structural context and subsurface evidence supporting crustal-scale faulting in the Kiruna District: a rebuttal to Ulf B Andersson's critique of Veress et al. (2024)

ABSTRACT This paper presents a multiscale rebuttal to the discussion paper by Ulf B. Andersson (Andersson 2025), which critiques the structural interpretations and network of geological structures presented in Veress et al. (2024). We clarify that Veress et al. (2024) is a 3D modeling study, not a traditional mapping study, based on the systematic integration of LKAB's geological subsurface dataset with more than a decade of regional structural fieldwork by our research group. The reply is structured from the regional tectonic framework, through the central Kiruna area, to individual structures questioned in the discussion. We demonstrate that the structures in Veress et al. (2024), many trending NW-SE or NE-SW, fit into a regionally extensive conjugate system formed during late Paleoproterozoic E-W crustal shortening and basin inversion. This deformation regime is well documented by mapping-based studies west, east, south, and north of Kiirunavaara. We further show that the structures under discussion are all supported by LKAB datasets, in particular, drill core logging data and geophysics. Structure D is specifically indicated by drill core data compiled by Ulf B. Andersson himself in a recent report (Andersson 2023), data that include RQD and GSI values that we have now integrated into the updated 3D model, providing additional support for this structure. We also evaluate an alternative cooling-related origin for these structures, previously proposed by Ulf B. Andersson in another report (Andersson & Berglund 2024), and argue that it is inconsistent with the structural context of the wider area.