SPS Seminar - Geological and geophysical analysis of Mercury’s tectonic and crustal structures

When:  Monday 3 April at 14.00

Where:  CMR01 and Microsoft Teams -Online

Speaker:  Salvatore Buoninfante – University of Naples Federico II

Hosted by: Alexander Barrett

Abstract:

This study blends a geological and a geophysical approach to better understand the link between surface and internal tectonic structures of Mercury. The main target is represented by the relation between regional thrust system and large impact basins. It is commonly thought that the arrangement of thrust systems on Mercury is strongly influenced by old impact basins, due to their reactivation (see Fegan et al., 2017). Beethoven basin (20.8°S–236.1°E) and Vincente-Yakovlev basin (52.6°S–197.9°E) can represent clear examples of tectonic inversion. The reactivation structures can be the result of previous impact-related normal faults reactivated by the compressive tectonic regime deriving from the global contraction.

Preliminary results concerning the geological cartography of the Michelangelo quadrangle (H-12) of Mercury and gravity data modelling for the interpretation of crustal structures will be presented. The cartography analysis 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 (Galluzzi et al., 2021). Linear features (crater rims, faults, pits) and geological contacts have been recognized from the photointerpretation of the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) Mercury Dual Imaging System (MDIS) imagery, characterized by an average resolution of 166 m/pixel. Linear features define crater rims, faults and pits, while geological contacts delimit geological units (crater materials and plains). Main regional thrust systems have NW-SE strike.

The NW-SE system seems to border the southwestern edge of the high-Mg region, although the accuracy of XRS data at these latitudes is much lower than the accuracy of data acquired in the Northern hemisphere, where a better spatial correlation between faults and high-Mg region edges is noted (e.g., Galluzzi et al., 2019). Frequently, thrust segments interact with volcanic vents (e.g., Thomas et al., 2014). These vents are often located along lobate scarps or in soft-linkage zones between thrust segments. Indeed, as also observed on Earth, curved thrust surfaces or linkage areas between fault segments represent weakness zones acting as preferential pathways for magma uprising.

MESS160A gravity field (Konopliv et al., 2020) is used to calculate Mercury’s isostatic gravity anomalies and model intra-crustal sources. According to the flexural isostatic response curve, the lithospheric flexure occurs in the spherical harmonic degree range 5-80, and the mean elastic lithosphere thickness is 30  10 km. These parameters can be used to model the crust-mantle interface, which varies from 19 to 42 km depth according to a regional compensation model and show the presence of crustal heterogeneities in density. Indeed, the isostatic gravity anomalies mainly represent the gravity effect of intra-crustal sources. Isostatic gravity highs mostly correspond to large-impact basins (e.g., Caloris basin, Sobkou basin) suggesting intra-crustal magmatic intrusions as the main origin of these anomalies. Isostatic gravity lows prevail, instead, above intercrater plains and may represent the signature of a heavily fractured crust. Moreover, the enhancement techniques applied on isostatic gravity data can be useful for identifying crustal structures that can be compared with tectonic structures. In this talk the example of the Victoria quadrangle structures will be shown.

References:

Fegan E. R. et al., (2017). Icarus, 288, 226-234.
Galluzzi et al. (2019). J. Geophys. Res. Planets, 124, 2543-2562.
Galluzzi et al. (2021). LPI Contrib., 2610.
Konopliv, A. S., et al., (2020). Icarus 335.
Thomas R. J. et al., (2014). J. Geophys. Res. Planets, 119, 2239-2254.

BIO:

Salvatore Buoninfante received the B.Sc. and M.Sc. degrees in Applied Geophysics from the University of Naples Federico II, Naples (Italy), in 2018 and 2021, respectively. Currently he is a Ph.D. student in Earth, Environment and Resources Sciences at the University of Naples Federico II, associated to the Institute of Astrophysics and Space Planetology – INAF, Rome, Italy. He is leading the 1:3M geological mapping of Michelangelo (H-12) quadrangle of Mercury. His research interests include structural analysis of Mercury’s faults; satellite gravity data modelling for the interpretation of Mercury’s crustal structures; spectral, multiscale, enhancing potential fields analysis for modelling Mercury’s upper crust. He is involved as ECR in the ISSI project “Wide-Ranging Characterization of Explosive Volcanism on Mercury: Origin, Properties, and Modifications of Pyroclastic Deposits”. He also studies Earth structural analogues to investigate Mercury’s tectonics. He is member of the ESA/JAXA BepiColombo GGWG and SCWG working groups.