Mathematics – Logic
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p31c0151j&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #P31C-0151
Mathematics
Logic
5475 Tectonics (8149), 8121 Dynamics: Convection Currents, And Mantle Plumes, 8147 Planetary Interiors (5430, 5724, 6024), 8148 Planetary Volcanism (5480, 8450), 8178 Tectonics And Magmatism
Scientific paper
The Tharsis region of Mars displays enigmatic variations in the crustal magnetic field that are correlated with topography and the distribution of volcanism. The southern half of the Tharsis rise is typically characterized by radial magnetic field values (B_r ) greater than 25 nT at elevations less than about 7 km, and by B_r ≍ 0 nT at higher elevations. Previous work (Johnson and Phillips, 2004) has suggested that the magnetic field observations reflect a strongly magnetized annular region that surrounds a core of demagnetized crust at higher elevation. In this study we investigate conditions that can explain the geometry of crustal magnetization. Assuming that the initial uplift of Tharsis postdates the crustal magnetic field we hypothesize that the absence of radial field in the central part of the Tharsis rise is due to enhanced local heat flow from an underlying mantle plume. An observation of B_r at a given spacecraft position reflects the depth-integrated crustal magnetization; consequently the inferred demagnetization can imply that a significant fraction of the (initially magnetized) crust has been heated above its curie temperature. The observed radial extent of the demagnetized region can constrain the structure and heat transfer properties of the proposed mantle plume. However, such a constraint depends on the thickness of lithosphere across which heat is conducted from the plume to the surface of the planet. Under thermally steady-state conditions a reasonable lower bound for this length scale is the depth to the brittle-ductile transition, or the elastic thickness (D_e ) of the region. An independent estimate of D_e can be obtained from analysis of the amplitude and wavelength of the flexurally-supported topography in the Tharsis region. Assuming that the average curie isotherm for magnetic carriers in the Martian crust lies within the elastic lithosphere, a combined analysis of magnetic and topographic observations can uniquely constrain the plume excess temperature (Δ Tplume) and the average D_e in the Tharsis region for a given set of physical properties and thermal conditions for the mantle and crust. Geological and geodynamic studies suggest that the maximum amplitude of the Tharsis bulge at the time of uplift was plausibly greater than is currently observed. Consequently constraints from MOLA topography can provide upper bounds for D_e. The combined MOLA and crustal magnetic observations, together with a model for a long-lived mantle plume, are applied to constrain D_e - Δ Tplume conditions in this region in the early Noachian for a spectrum of plausible conditions. Corresponding estimates of the heat flow as well as the long-term average magma supply at Tharsis are also explored.
Jellinek M.
Johnson Carole
Schubert Gerald
No associations
LandOfFree
Constraints on the elastic thickness and heatflow at Tharsis from topography and magnetic field observations does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Constraints on the elastic thickness and heatflow at Tharsis from topography and magnetic field observations, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Constraints on the elastic thickness and heatflow at Tharsis from topography and magnetic field observations will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-961858