An episodic slab-rollback model for the origin of the Tharsis rise on Mars: Implications for initiation of local plate subduction and final unification of a kinematically linked global plate-tectonic network on Earth

Abstract

A new tectonic model is proposed for the origin of the Tharsis rise on Mars, which occupies ~25% of the planet. The model invokes initiation of plate subduction by a large impact during the Late Heavy Bombardment at ca. 4.0 Ga. The model explains migration of Tharsis volcanism by slab rollback and the lack of magnetized crust in the bulk of Tharsis by formation of juvenile crust after the Mars dynamo creased to operate. The model also explains (1) the formation of thrust systems as a result of impact-generated crustal thickening (i.e., Thaumasia thrust), retro-arc contraction (i.e., Solis-Lunae fold belt), and plate subduction (Lycus and Ulysses thrusts), (2) the development of dominantly NEtrending grabens and a major east-facing V-shaped conjugate strike-slip system across the Tharsis rise as a result of backarc extension, and (3) crustal thickening of the Tharsis rise as a result of magmatic accretion during protracted construction of arcs above an episodically stalled and thus stationary subducting slab. The model has several implications for the way in which a unifi ed global plate-tectonic network may have been established on early Earth. First, large impacts were common during the Late Heavy Bombardment (ca. 4.2-3.9 Ma), and thus impact-induced plate subduction would have been highly likely in the Hadean period. Such subduction systems must be local in scale and associated only with trench retreat and slab rollback. Localized plate subduction permits other modes of tectonic processes to have occurred simultaneously on early Earth, reconciling confl icting observations for plate-tectonic and non-plate-tectonic processes. Second, the presence of water at the surface of Hadean Earth would have allowed rapid transformation of basaltic crust to eclogite, allowing a sustainable plate subduction process once it started. The Hadean and possibly Archean Earth may only have had localized subduction systems, all characterized by slab rollback and trench retreat. Trench advance and related shallow-angle plate subduction probably did not begin on Earth until Proterozoic time, when a single and united global plate-tectonic network was established. This may have been accomplished by gradual coalescence of formerly independent subduction systems over a signifi cant period of geologic time (>1 b.y.). Incorporation of trench-advance and shallow-angle plate subduction in the Proterozoic may have been induced by complex interactions of multiple subduction systems in a single and kinematically linked global tectonic network. This in turn led to the beginning of the formation of the crustal structures and petrologic assemblages of modern Earth. Based on a simple conductive cooling model, it appears that the most critical factors that control whether plate subduction could have been initiated in a rocky planet during the Late Heavy Bombardment in the inner solar system are its initial crustal thickness and the cooling rate/thickening rate of the lithosphere.

Gravitational spreading, bookshelf faulting, and tectonic evolution of the South Polar Terrain of Saturn’s moon Enceladus

“…This effort results in a structural map of the SPT (Fig. 2B) that contrasts with most planetary geologic maps that display mostly geomorphic features with little or no emphasis on determining the kinematics of major faults (e.g., Figueredo and Greeley, 2000;cf., Schultz et al, 2010;Yin, 2012aYin, , 2012bCrowWillard and Pappalardo, 2015). We determine structural kinematics using minor structures within and next to major deformation zones and minor structures that terminate major structures.…”

Topographic Expressions of Large Thrust Faults on Mars

“…Mountain building on Earth is, either directly or indirectly, related to plate tectonics. Whether some primitive form of plate tectonics occurred on Mars is debated (e.g., Yin, ; also see detailed discussion in Barlow, , p. 48–50), but there is no evidence for globally distributed, Earth‐style plate tectonics preserved in its geologic record (e.g., Zuber, ). Mountain building on Mars, if related to some form of plate tectonics, would likely involve structural styles of faulting comparable to thrust belts on Earth, including multiple, long, sinuous thrust fault traces and complex landform morphology.…”

Principles of structural geology on rocky planets

“…Mars is a geologically diverse planet, displaying many large-and small-scale physiographic features that have been shaped by volcanic, glacial, fluvial, eolian, and tectonic processes. With the insight that plate tectonics has long operated on Earth, many researchers hypothesized and tested whether similar tectonics also operate or operated on other rocky bodies (e.g., Anderson 1981;Sleep 1994;Yin 2012). Processes with phenomena similar to those accompanying plate tectonics on Earth have also been invoked to explain many peculiar large-scale physiographic Martian features, such as the dichotomy boundary separating the comparatively lightly cratered northern lowlands from the heavily cratered and thus older southern highlands, the Tharsis large igneous province with its many volcanic shields, or Valles Marineris as the largest canyon system known in our solar system.…”