Characterizing the Magmatic Evolution of the Elysium Volcanic Province on Mars

The stagnant lid tectonic paradigm of Mars posits that regional volcanism is almost exclusively plume-driven. Understanding the evolution of the immense, ~2000-km-in-diameter, isolated Elysium volcanic province, and its underlying crust-mantle interface is essential for examining the stagnant lid tectonic style. Disparate models of Martian mantle evolution also exist, including heterogeneous mantle caused by overturning magma ocean cumulates, secularly drying mantle with increasing crustal thickness, and single source mantle model predicting a secular depletion of large ion lithophile elements (LIL), such as Th and K. We evaluated the feasibility of these models with a working hypothesis that individual provinces like Elysium also experience melt zone migration, causing spatiotemporal changes in the melt formation. We estimated the degree of partial melting, lithospheric thickness, and mantle potential temperature with chemical maps derived from Gamma spectroscopy and petrological modeling of regional magmatic processes. Comparable K/Th mass ratios across regions and the bulk crust suggested that the landscape is dominated by primary mineralogy with negligible secondary products from processes like aqueous alteration. We find that the delineated regions in Elysium do not show a clear relationship between Th and K depletion with age indicating more than one magma source, or that regional-scale processes possibly subsume the secular LIL depletion within individual provinces like Elysium. Furthermore, the absence of depletion of Si and the major enrichment of S and Cl in southern Elysium echoed the recent proposed volcanic pyroclastic deposit at Cerberus Fossae. As greater sulfur and chlorine concentration pointed to Martian dust component and exclusion of airfall dust evidenced by the lack of eolian sorting of Si-poor phases, the pyroclastic deposit is volcanic in origin.