Late Amazonian dike-fed distributed volcanism in the Tharsis volcanic province on Mars

Abstract

Tharsis is the largest volcanic province on Mars and in the solar system. This region includes major volcanoes (Olympus Mons, Alba Mons, Arsia Mons, Pavonis Mons, and Ascraeus Montes) and hundreds of small volcanic cones and vents, whose origin is not yet fully understood. Although the main Tharsis' edifices plumbing system has been extensively studied, smaller volcanoes' origin remains unknown. The formation of those minor volcanic landforms may be related to the large volcanic edifices' evolution, and/or controlled by the fault systems through which magma migrates towards the Martian surface. In this study, we analyzed the central part of the Tharsis volcanic province using satellite images with a resolution of ~6 m/px from the Context Camera onboard the Mars Reconnaissance Orbiter (CTX/MRO). We identified and mapped 659 volcanic edifices >1 km in diameter. We analyzed (1) their spatial distribution, (2) alignment of summit craters, and (3) surface model ages derived from crater counting. We found that volcanic edifices are unevenly distributed across the Tharsis province and proposed that their formation is controlled by at least six individual magma-plumbing systems associated with major edifices: Olympus Mons, Alba Mons, Arsia Mons, Pavonis Mons, Ascraeus Mons, and Uranius Mons. Their summit alignment orientations indicate they were controlled by radial and circumferential dikes originated from magma sources beneath the six central volcanoes, either magma chambers in the crust or other magmatic underplates at the base of the crust. Volcano flanks of distributed volcanoes are of similar age or younger than the summit calderas of the associated central volcano indicating a common magmatic system. Magma migration and eruptions from distributed volcanoes may thus extend beyond the magma waxing periods when magma supply was high enough to sustain summit eruptions. The relatively young age of documented volcanic activity within the Tharsis province may imply recently active hydrothermal systems triggered by magma-water interaction.