Formation and dispersal of pyroclasts on the Moon: Indicators of lunar magma volatile contents

The Long Sinuous Rille System in Northern Oceanus Procellarum and Its Relation to the Chang'e‐5 Returned Samples

“…Based on our reanalysis of the Rima Sharp/Mairan source vents, rille characteristics and stratigraphic relationships, and their relationship to Em4/P58, we call on the paradigm of basaltic magma ascent and eruption (see Figure S12 for the definition of eruption phases) outlined by Wilson and Head (2018) to reconstruct their emplacement (Figures 1c-1f). Following the short-lived Phase 1 as the dike reached the surface, Phase 2 involved a high-volume-flux Hawaiian eruptive phase as the magma degassed, forming a hemispherical pyroclastic fountain and attendant lava pond, the scale of which was dictated by the magma volatile content (Morgan et al, 2021). The initial high-flux stages of the eruption of both Rima Sharp and Rima Mairan (Phase 1) are likely to have involved the emplacement of sheet flows, rapidly flooding the surrounding topography.…”

Determining the Effect of Varying Magmatic Volatile Content on Lunar Magma Ascent Dynamics

“…Future developments could involve utilizing the magma ascent model results in the context of the Morgan et al. (2021) work.…”

“…This would be also important to elucidate the role of the initial volatile content on magma fragmentation within a gas cloud. The link between initial volatile content and pyroclastic deposit morphology has recently been explored by Morgan et al (2021), using measurements of volatile abundance and release patterns from experiments to estimate pyroclast grain size distributions and their subsequent ejection distances. Their results predicted a bimodal pyroclastic grain size distribution, a maximum pyroclast ejection distance of 20 km (a distance that encompasses 79% of all observed lunar pyroclastic deposits), and that a wide range of volatile contents are responsible for producing the wide range of deposit sizes observed.…”

“…Pyroclastic material has been found on the surface of the Moon in many of the returned lunar soil samples (Delano, 1986; Heiken et al., 1974) and via remote sensing data (Carter et al., 2009; Gaddis et al., 1985; Hawke et al., 1989). Not only do these pyroclastic glass beads provide evidence that the Moon experienced explosive volcanism, rather than solely effusive volcanism (Coombs & Hawke, 1992; Morgan et al., 2021; Wilson & Head, 1981), they have also been important samples for researching the volatile content of the Moon's mantle (Hauri et al., 2011; Saal et al., 2008). These pyroclasts are picritic in composition (containing <52 wt % SiO 2 and >12 wt % MgO [Le Bas, 2000]), spherical to ovoid in shape, occasionally host olivine phenocrysts (Hauri et al., 2011), have a glassy or devitrified texture, and are analogous to terrestrial Pele's tears (Moune et al., 2007).…”

The Identification and Analysis of Gas-Related Volcanic Features within Chang’e-5 Landing Region

“…Although the volatile content in the primitive magma is low, basaltic eruptions were always accompanied by different degrees of explosive processes due to the low gravity and vacuum environment of the Moon. These volatile components are mostly composed of the carbon monoxide (CO) generated at a depth of ~50-300 km in dikes as well as the water vapor and sulfides that dissolved within a few hundred meters of the top of the dikes [10,11]. According to the volatile content of the magma, volcanic eruptions on the moon can be divided into different stages, corresponding to the formation of various volcanic morphologies [12].…”