New View of the Lunar Silicic Volcanism in the Mons Hansteen: Formation and Origins

Abstract

Silicic volcanos with high‐thorium (Th), low FeO and TiO2 contents are rare on the Moon, but exploring the formation and origins of silicic volcanos can help us to understand the complex process of lunar crustal evolution. The origins of silicic volcanic Mons Hansteen complex on the southern edge of the Oceanus Procellarum (50.2°W and 12.2°S) are enigmatic. Here we use recent high‐resolution topographic data and gravity data to assess the morphology and shallow tectonic features of this complex to investigate its formation and evolution. The results from our crater size‐frequency distribution model show that the silicic volcanism in Mons Hansteen occurred as early as ∼3.8 Ga. A mafic intrusion beneath the Mons Hansteen originated from the Crater Billy impact event. The magma rose to within ∼11 km beneath the lunar surface causing the crust to melt and develop into silicic magma. The silicic magma erupted onto the lunar surface and was eventually covered by younger mare basalt. We conclude that silicic volcanos are older than we previously thought. Geophysical research on the Mons Hansteen area provides a new perspective thus supplementing and extending our knowledge of the silicic volcanism.

Evidence for Fine-grained Material at Lunar Red Spots: Insights from Thermal Infrared and Radar Data Sets

“…Hansteen Alpha) is a steep-sided dome in southern Oceanus Procellarum (50.3°W, 12.1°S). The dome contains three distinct geologic units emplaced in three eruption phases (Hilly Dissected Unit, Pitted Unit, and North Massif Unit; Boyce et al 2017) with absolute model ages ranging from 3.60-3.80 Ga (Qiu et al 2022), and is embayed by mare material from ∼3.0 Ga (Hiesinger et al 2011). The steep-sided morphology again suggests it was formed by viscous lava flows, and the short Christiansen Feature (CF) locations and mid-IR spectral shape indicate it is silicic in composition (Glotch et al 2010).…”