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Impact-Induced Subduction and Slab Rollback for the Tectonic Origin of the Tharsis Rise on Mars
| Content Provider | Semantic Scholar |
|---|---|
| Copyright Year | 2011 |
| Abstract | Introduction: The Tharsis rise occupying 25% of Mars surface is the largest and youngest tectonic feature on Mars. Its formation has been attributed to (1) activity of a stationary or migrating hotspot, (2) magmatic underplating of the lower crust due to partially molten mantle, (3) protracted volcanic construction initiated by the Late Heavy Bombardment, and (4) impact-induced deep mantle plumes. Delamination of mangle lithosphere was also advocated local uplift of the Tharsis rise. Since the early mapping by Scott and Tanaka (1986) and more recently the compilation of a newly renovated global geologic map of Mars by Skinner et al. (2006), it has been known that the initial development of individual large volcanic fields was approximately linear trending in the NE-SW direction. The age of initiation of Tharsis volcanism has become younger from southeast to northwest, starting in the Late Noachian and ending in the Late Amazonian. Associated with the migration of Tharsis volcanic chains is a change in the style of volcanism, from early effusive eruption in the southwest to central-volcano construction in the northwest. Within each volcanic zone, central volcanoes change styles along strike from thin and tall geometry in the southwest (i.e., Tharsis Montes and Olympus Mons) to wide and flat geometry in the northeast (e.g., Alba Patera) across a NE-trending linear boundary. This observation implies an abrupt decrease in lava viscosity across the boundary. Recent work also shows that after the initiation of zonal volcanic fields such as the Tharsis Montes, Late Amazonian small and younger volcanoes were widely developed and are closely related to NE-trending fissures across the Tharsis Montes and Syria Planum. The Tharsis rise is also dominated by NE-trending grabens that extend >1500 km away from the margins of the rise. Their wide spatial distribution beyond the topographic high region of therise has been a major mechanical obstacle to all the existing Tharsis models advocating vertical loading for its origin, either by a plume from below or by a large load of volcanic construct from above. Hypothesis: A crucial observation with regard to Tharsis formation is its initial development coinciding spatially and temporally with a volcanic zone along its southeastern margin (i.e., Thaumasia Highland), after which zonal volcanism sequentially swept northwestward across the tectonic province. Examination of the spatial relationship between major impact basins on Mars (Utopia, Hellas, Isidis, and Argyre) and their nearby volcanism suggests that the initial volcanism along the southeast side of the Tharsis rise may have been induced by Argyre impact. This and observations from the Tharsis rise mentioned above leads to a hypothesis that involves three steps of reasoning (Fig. 1): (1) vertical load (ejecta deposits, crustal shortening, and injection of pyroclastic sills) from Argyre impact had produced flexural stresses guiding the impactinduced melts to migrate to the surface; (2) accumulation of volcanic flows and its positive feedback with lithospheric bending caused rupture and later subduction of the Tharsis lithosphere; (3) continuous subduction through slab rollback drove trench retreat and northwestward migration of zonal volcanism; (4) backarc extension induced scattered volcanism and the development of NE-trending grabens across the Tharsis rise, and (5) delamination of mantle lithosphere dragged down by the sinking slab to the southwest may have led to the development of flat but wide central volcanoes (Alab Patera and Uranius Patera) in the NW Tharsis rise (Fig. 2). |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www.lpi.usra.edu/meetings/lpsc2011/pdf/1525.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
