| Auteur(s) supplémentaire(s) | James W. Head1, Christian Huber1, Laura H. Lark1, Stephen W. Parman1, E. M. Parmentier1, Lionel Wilson1,2. |
| Institution(s) supplémentaire(s) | 1Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, RI 02912 USA, 2Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK. |
Abstract | Planetary exploration has provided insight into variation of volcanic-tectonic records, global lithospheric stress states/magnitudes, and mantle convection patterns with increasing planetary radius:
(1) The Moon’s tectonic-magmatic history is dominated by a thick primary crust whose magma oceanography and aftermath dictated a volumetrically insignificant secondary crust generated from deeper mantle sources through a low-density crust/thickening lithosphere that precluded formation of magmatic-volcanic-tectonic (MVT) rises; relatively rapid conductive cooling changed global lithospheric stress state to modest contraction at ~3.5 Ga; the role of subsequent mantle convection is still debated.
(2) Mercury’s magma oceanography suggests a distinctly different primary crust (sulfur and carbon-rich). There is little evidence of mantle convection patterns (MVT rises/mantle plumes). Regional flood basalt volcanism from now-buried fissures dominated early volcanic history. The syn-post volcanism global lithospheric stress state implies significant radial contraction over the last several BY (widely distributed wrinkle ridges, huge tectonic arches). Evolution of the lithosphere was also affected by the presence of sulfides (possibly >10 vol%), which could reduce viscosity and concentrate radiogenic heat production.
(3) Mars magma oceanography suggests basaltic primary and secondary crusts; secondary crustal volcanism was near-global early on but rapidly focused to mantle-plume-like upwellings (MVT rises Tharsis/Elysium). The global lithospheric stress state implies decreasing modest contraction for the last several BY (widely distributed post-regional plains wrinkle ridges).
(4 and 5) Geological records of the first 80% of Venus and Earth histories are poorly known. Venus is currently (and for the last 0.5-1.0 BY) a one-plate planet losing heat conductively, and displaying a wide range of features implying both global-scale flood volcanism (regional plains) and vigorous mantle convection at several scales (rises, rift zones, coronae, large volcanoes). Earth currently displays bimodal MVT patterns: plate recycling and vigorous mantle convection at a range of scales (mantle plumes, hot spot, rises, LIPs).
Differences in planetary core-mantle radius ratios (Moon ~0.29, to Mercury ~5.2?) are clearly an important evolutionary factor. As an endmember on this spectrum, Mercury offers insights into planetary geodynamic evolution. We currently focus on 3 questions: 1) Magma oceanography aftermath and predictions for mantle composition, fO2, sulfide distribution, volatile content parameter space; 2) How magnitude and timing of global contraction can help constrain the nature of heat sources/timing for mantle melting (relative roles of mantle internal heating and core heat flux mantle bottom-heating); & 3) How the observed volcanic record of magma generation, ascent & eruption is related to Mercury’s thin mantle, sulfur-rich lithology and convection patterns & scale. |
