Thermal demagnetization of Martian crust by magma intrusion

Details Thermal demagnetization of Martian crust by magma intrusion Thermal demagnetization of Martian crust by magma intrusion

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmgp11b0079o&link_type=abstract

American Geophysical Union, Fall Meeting 2006, abstract #GP11B-0079

Biology

5200 Planetary Sciences: Astrobiology, 5400 Planetary Sciences: Solid Surface Planets, 5419 Hydrology And Fluvial Processes, 5440 Magnetic Fields And Magnetism, 5480 Volcanism (6063, 8148, 8450)

Scientific paper

The near absence of magnetic field above large Martian volcanoes provides constraints of their formation and the carrier of magnetization. We consider the ability of magma intrusions to thermally demagnetize the crust through heat conduction and hydrothermal circulation. When magma is intruded into the crust, heat transferred to groundwater in pore spaces causes multi-phase convection. To simulate such gas-liquid hydrothermal convection on Mars, we use the code HYDROTHERM developed by Hayba and Ingebritsen (JGR 1997), which also models supercritical fluids. We consider the effects of intrusion depth, permeability of the crust, and the geothermal temperature gradient. We monitor the highest temperature ever reached at each point in the subsurface in response to the intrusion of the sill. We compare this temperature with the Curie temperature (Tc) of the various minerals that might carry remanent magnetization: pyrrhotite (Tc~320 °C), magnetite (~580 °C), and hematite (~670 °C) (e.g., Dunlop and Arkani-Hamed, JGR 2005) in response to the intrusion of the sill. Thermal demagnetization occurs within a zone that has experienced a temperature above Tc. If magnetization is dominated by magnetite, we find that the fraction of the crust that is thermally demagnetized is similar to the fraction of crust emplaced since the dynamo field disappeared, and the emplacement of most of the crust must thus postdate the termination of the dynamo. If magnetization is dominated by pyrrhotite, volumes of intruded magma similar to those inferred from gravity studies (e.g., Kiefer, EPSL 2004) can thermally demagnetize most of the crust. While we focus on thermal demagnetization, magnetic minerals may also lose their magnetization if they are chemically altered, for example, through oxidation promoted by water circulation. To assess the ability of circulating water to alter magnetic minerals, we monitor the amount of water transported though each part of the crust. We find the water-rock ratio, defined as the ratio of the water mass that passed through the rock to the mass of the rock, increases with k monotonically, exceeding around 10 for k >1014 m2. Without knowing or modeling the composition and oxidation state of the water we are unable to say anything more quantitative about the potential for demagnetization by chemical alteration.

Affiliated with

Also associated with

No associations

Rating

Thermal demagnetization of Martian crust by magma intrusion 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 Thermal demagnetization of Martian crust by magma intrusion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal demagnetization of Martian crust by magma intrusion will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-963645