Geology and tectonic structures of the Michelangelo (H12) quadrangle

Geological cartography and structural analysis are essential for understanding Mercurys geological history and tectonic processes. This work focuses on the geological and structural analysis of the Michelangelo quadrangle (H12), located at latitudes 22.5S-65S and longitudes 180E-270E. We present the first geological map of H12 at 1:3,000,000 scale, based on the photointerpretation of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) imagery. The present study is a contribution to the 1:3M geological map series, planned to identify targets to be observed at high resolution during the ESA-JAXA BepiColombo mission 1. We mapped tectonic structures and geological contacts using the MDIS derived basemaps, characterized by an average resolution of 166 m/pixel. Linear features are subdivided into large craters (crater rim diameter > 20 km), small craters (5 km < crater rim diameter < 20 km), subdued or buried craters, certain or uncertain thrusts, certain or uncertain faults, wrinkle ridges and irregular pits. Geological contacts, mapped as certain or approximate, delimit the geological units grouped into three classes of crater materials (c1-c3) based on degradation degree, and plains (smooth, intermediate and intercrater plains). Michelangelo appears as a densely cratered quadrangle dominated by degraded crater materials (c2) and intermediate plains. We identified two main regional thrust system trending NW-SE and NE-SW. We found that many lobate scarps developed at the edges of ancient, large impact basins. Clear examples of such tectonic structures in the Michelangelo quadrangle are provided by the Beethoven basin (20.8S236.1E) or by the Vincente-Yakovlev basin (52.6S197.9E). We propose a thick-skinned tectonic model according to which the lobate scarps were formed after positive reactivation of previous impact-related normal faults, due to the contractional tectonic regime deriving from the global contraction. Evidence of thick-skinned tectonics on Mercury are provided by the presence of fault systems exceeding the basin rim, and by the estimated rooting depth of thrusts bordering large basins (e.g., Discovery Rupes, Soya Rupes). Following 2, we found that the NW-SE system largely borders the southwestern edge of the HMR. We also show that the volcanic vents on Mercury are often associated with impact craters and/or lobate scarps (e.g., 3,4), which can be considered as possible preferential areas for magma uprising. Acknowledgements: We gratefully acknowledge funding from the Italian Space Agency (ASI) under ASI-INAF agreement 2017-47-H.0. References: 1 Galluzzi, V. et al. (2021). LPI Contrib., 2610. 2 Galluzzi, V. et al. (2019). J. Geophys. Res., 124(10), 2543-2562. 3 Thomas, R. J. et al., (2014). J. Geophys. Res., 119, 2239-2254. 4 Jozwiak, L. M. et al., (2018). Icarus, 302, 191-212.