Dating long thrust systems on Mercury: New clues on the thermal evolution of the planet

• Published in: Di xue qian yuan. Vol. 11; no. 3; pp. 855 - 870
• Main Authors: Giacomini, L., Massironi, M., Galluzzi, V., Ferrari, S., Palumbo, P.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier B.V 01.05.2020; Elsevier Science Ltd; INAF-IAPS,Istituto di Astrofisica e Planetologia Spaziali,Via Fosso Del Cavaliere 100,Rome,00133,Italy%Dipartimento di Geoscienze,University of Padova,Via G. Gradenigo 6,Padova,35131,Italy%Center of Studies and Activities for Space (CISAS)"G. Colomb?,University of Padova,Via Venezia 15,Padova,35131,Italy%Dipartimento di Scienze e Tecnologie,University of Naples"Parthenop?,Centro Direzionale,Isola C4,Napoli,80143,Italy
• Subjects: Buffers; Crater counting; Craters; Fault lines; Geological faults; Landforms; Mercury; Mercury (planet); Planetary evolution; Planetary geology; Plate tectonics; Ridges; Spatial distribution; Stratigraphy; Structural geology; Tectonics; Thermal evolution; Thermophysical models; Thrust systems; Crater counting; Structural geology; Thrust systems; Thermal evolution; Planetary geology; Mercury
• ISSN: 1674-9871; 2588-9192
• DOI: 10.1016/j.gsf.2019.09.005

The global tectonics of Mercury is dominated by contractional features mainly represented by lobate scarps, high relief ridges, and wrinkle ridges. These structures are the expression of thrust faults and are linear or arcuate features widely distributed on Mercury. Locally, these structures are arranged in long systems characterized by a preferential orientation and non-random spatial distribution. In this work we identified five thrust systems, generally longer than 1000 ​km. They were named after the main structure or crater encompassed by the system as: Thakur, Victoria, Villa Lobos, Al-Hamadhani, and Enterprise. In order to gain clues about their formation, we dated them using the buffered crater counting technique, which can be applied to derive the ages of linear landforms such as faults, ridges and channels. To estimate the absolute age for the end of the thrust system’s activity, we applied both Le Feuvre and Wieczorek Production Function and Neukum Production Functions. Moreover, to further confirm the results obtained with the buffered crater counting method, the classic stratigraphic approach has been adopted, in which a faulted and an unfaulted craters were dated for each system. The results gave consistent ages and suggested that the most movements along major structures all over Mercury most likely ended at about 3.6–3.8 ​Ga. This gives new clues to better understand the tectonics of the planet and, therefore, its thermal evolution. Indeed, the early occurrence of tectonic activity in the planet’s history, well before than predicted by the thermophysical models, coupled with the orientation and spatial distribution of the thrust systems, suggests that other processes beside global contraction, like mantle downwelling or tidal despinning, could have contributed to the first stage of the planet’s history. [Display omitted] •Activity along thrust systems all over Mercury has most likely ended at about 3.6–3.7 ​Ga.•Dating thrust systems gave new clues to better understanding the thermal evolution of the planet.•Tidal despinning and/or mantle convection may have contributed to Mercury evolution.