000003910 001__ 3910
000003910 005__ 20190125173054.0
000003910 037__ $$aCTALK-2019-0055
000003910 100__ $$aCharlier, Bernard
000003910 245__ $$aMantle melting productivity on Mercury and the relation with crustal thickness
000003910 260__ $$c2018
000003910 269__ $$c2018-12-11
000003910 520__ $$aThe crust of Mercury was built over its first billion years by intense volcanic activity. Mantle melting and emplacement of lava to the surface produced a secondary crust varying spatially and over time in composition and mineralogy. In this study we consider lateral density variations of the crust obtained from global mineralogical mapping (1) to calculate a new map for the thickness of the crust using the MESSENGER gravity and topography data (2-3). The construction of the global map of crustal thickness relies on the inversion of free-air gravity anomalies, which are due to surface topography, relief at the mantle-crust boundary, and lateral variations of crustal and mantle densities. This study focusses on the effect of lateral variations of crustal density. The mineralogy at the surface translates to pore-free crustal densities of 2,800-3,150 kg.m-3. Maximum crustal density (3,100-3,150 kg.m-3) is found in High-Mg regions that are forsterite-dominated and plagioclase-poor. The lightest crust (2,750-2,800 kg.m-3) is found in Al-rich regions such as the North Volcanic Plain that are plagioclase-dominated. We find that local crustal thickness is statistically correlated with the degree of partial melting of the mantle obtained from surface composition measured by MESSENGER. The highest degree of mantle melting in the equatorial ancient High-Mg region (40-55% partial melting of the mantle) produced the thickest crust (52±12km in a model with 35 km mean crustal thickness) and low-degree melting in the polar North Volcanic plain (20-30%) produced a thinner crust (18±3km in the Low-Mg NVP). The thinnest crust is found in the Caloris impact basin. The correlation between variations of crustal thickness with mantle melting productivity should be used to constrain the geodynamics and mantle convection style in the thin silicate shell of Mercury.
000003910 536__ $$aPRODEX/$$c4000120791/$$fPlanetInterior
000003910 594__ $$aNO
000003910 700__ $$aBeuthe, Mikael
000003910 700__ $$aNamur, Olivier
000003910 700__ $$aRivoldini, Attilio
000003910 700__ $$aVan Hoolst, Tim
000003910 773__ $$tAmerican Geophysical Union Fall Meeting, Washington D.C.
000003910 8560_ $$fmikael.beuthe@observatoire.be
000003910 85642 $$ahttps://agu.confex.com/agu/fm18/meetingapp.cgi/Paper/404715
000003910 906__ $$aContributed
000003910 980__ $$aCTALKCONT