Deformation patterns of icy satellite crusts: Insights for tectonic balancing and fluid migration through structural analysis of terrestrial analogues

Abstract

The icy satellites of the Solar System, such as Europa and Ganymede, show widespread evidence for tectonic structures that provide insights to infer the kinematics and the mechanical properties of their crusts. Their investigation is pivotal for the understanding of the regimes responsible for their formation and the connection with subsurface layers. Icy satellite tectonics is dominated by extension and shear regimes, while paucity evidence for compression represents an open issue. Structural investigation is constrained at regional-scale coverage of the remote sensing imagery. The study of analogues on Earth represents a strong support for the geologic analysis of the icy satellites. Glaciers represent optimal terrestrial analogues, showing deformation styles at multiple scale similar to those in the icy satellites, and being the excellent sites to further explore, verify and confirm what observed through remote sensing on the icy satellite geology. Although the formation processes differ, the similarity of their structures at surface allows quantifying and predicting the state of deformation in the icy satellites at different scales of investigation. Moreover, glacier deformation shows corridor-like pattern (i.e., shear zone with internal associated deformation), analogous to the main tectonic setting recognized in the icy satellites. This work aims to investigate and compare the tectonic structures of the glaciers with those on the icy satellites, by means of multi-scale approach of both remote-sensing and field survey. We present a structural investigation in the Russell and Isunguata Sermia glaciers, located at the western margin of the Greenland Ice Sheet, where field campaign has been conducted by the UPSIDES project under the Europlanet 2024 RI's Transnational Access field analogue in Kangerlussuaq. This project aims i) to achieve knowledge of the ice tectonic setting at local-scale, ii) to compare with that at regional-scale, and in turn iii) to better understand the tectonic styles and to characterize structures that are exclusively identified at regional-scale (such as in the icy satellites). Field measurements of brittle structures (fractures/faults), concerning the quantification of their azimuth, dip, length, width, throw and spacing, have been performed. In parallel, remote sensing analysis, concerning structural mapping on areas including the locations of the investigated outcrops, allowed to derive the same quantities at regional-scale. In this way, both local- and regional-scale tectonic setting has been investigated, and the stress analysis has been performed. Obtained results have been compared and in turn related with areas that show similar tectonic setting on Ganymede. In particular, the lack of detection of the regional-scale counterpart of the low-angle structures, and in particular the compressional ones that have been recognized at local-scale in the investigated glaciers, has been related to the lack of evidence of such structures in the icy satellite's surfaces. Such comparison allows us to infer a tectonic model that accounts for the existence of deep zones of balanced deformation depicted by diffuse and low-angle structures, and can explain their limited detection at surface and regional-scale investigations.