Evidence for a Locally Thinned Lithosphere Associated With Recent Volcanism at Aramaiti Corona, Venus. Issue 8 (29th July 2021)

• Record Type: Journal Article
• Authors: Russell, M. B.; Johnson, C. L.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-29
• Subjects: Venus -- lithospheric flexure -- remote sensing -- volcanism -- planetary science; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1029/2020JE006783
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: Heat flow estimates of terrestrial planets and icy satellites are important for exploring their thermal evolution. Topographic signatures of flexure can be used to estimate the effective elastic lithospheric thickness, h e, and heat flow. Here, we use high resolution stereo topography and axisymmetric elastic flexure models to investigate lithospheric flexure around Narina Tholus, a steep‐sided volcanic dome ∼40 km across that superposes the tectonic annulus of Aramaiti Corona. Our results indicate a best‐fit elastic thickness h e = 3.9–9.1 km, for values of Young's modulus, E, ranging from 65 to 5 GPa respectively. This suggests a thinned lithosphere locally around Narina Tholus, compared to regional estimates for h e . The lower values of E are appropriate to the heavily fractured environment of the corona annulus, and we find that they predict flexural stresses compatible with the limited fracturing observed around Narina Tholus. A global survey yielded 13 additional tholi (or tholi groups) at coronae and with stereo coverage, none of which showed evidence for flexure. We find, that locally at Narina Tholus, the heat flow is elevated by a factor of 2–4 relative to that inferred from a previous study of flexure at Aramaiti, consistent with late‐stage, possibly recent, volcanism focused at, and facilitated by, the fracture annulus. Our results further strengthen arguments for a currently volcanically active planet and demonstrate the role that high‐resolution stereo topography can play in elucidating the current thermal state of Venus. Plain Language Summary: Estimates of heat flow provide important constraints on the volcanic and tectonic evolution of Venus, and can be obtained by studying large geologic features, such as volcanoes, that cause the surface to flex beneath them. The thickness of the flexing layer can be estimated by comparing the surface topography to the predictions of models for bending of an elastic plate. This thickness can then be related to the subsurface heat flow at the time the surface was flexed; specifically, higher heat flow can cause thinning of the layer. In this study, we use data from the Magellan mission to Venus (1990–1994), to investigate flexure seen in high‐resolution topography around a steep‐sided volcano (∼40 km across). The volcano is located on a ring of faults at the edge of a corona, a type of feature on Venus characterized by concentric fracturing and volcanism. Our results indicate heat flow at the volcano that is larger by a factor of 2–4 than that the previous regional estimate at the corona. Our results, taken together with previous geological studies of the corona and recent modeling, suggest the volcano is geologically young. Key Points: We use thin elastic plate models to investigate flexure at Narina Tholus, a small volcanic dome on the annulus of Aramaiti Corona, Venus Locally thin lithosphere and high heat flow reflect late stage, possibly recent, magmatism, facilitated by the annulus fractures We find that the local heat flow enhancement at Narina is unusual but could be detected elsewhere with global high‐resolution topography