HR: 09:30h
AN: P31A-07    [PDF]
TI: Martian Mantle Analogues - Properties of Fe-Rich Silicate Melts
AU: * Potuzak, M
EM: potuzak@min.uni-muenchen.de
AF: University of Munich, Earth and Environmental Sciences, Theresienstrasse 41/III, MUNICH, 80333 Germany
AU: Courtial, P
AF: University of Munich, Earth and Environmental Sciences, Theresienstrasse 41/III, MUNICH, 80333 Germany
AU: Dingwell, D B
AF: University of Munich, Earth and Environmental Sciences, Theresienstrasse 41/III, MUNICH, 80333 Germany
AB: Data from Mars missions have revealed that the planet has a very active igneous history and that it may still be volcanically active. To improve and understand the hypotheses regarding the formation and evolution of Mars a model for its interior must be developed. This requires a knowledge of the physico-chemical properties of Martian magmas that control their dynamics. Two different simple Fe-bearing systems have been studied to date: (i) anorthite-diopside eutectic composition (AnDi) with variable amount of Fe (up to 30 wt%) as a basalt analogue and (ii) sodium disilicate (NS2 up to 10 wt% Fe). In addition, the compositional range has been extended to include the more complex SNC meteorite composition (more relevant to Mars). The high-T viscosities (1594-1200$\deg$C) have been measured using the concentric cylinder method in air. The low-T viscosities (817-711$\deg$C) have been measured using the micropenetration method in an Ar atmosphere for samples that could be quenched to glasses. High-T density measurements (1026-1567$\deg$C) have been performed on investigated Fe-bearing melts using the Pt-based double-bob Archimedean method. The oxidation state of Fe has been determined on quenched glasses at regular T steps by wet chemistry method. Differential scanning calorimetry (DSC) measurements have been performed on glassy samples at heating and cooling rates of 5, 10, 15 and 20 K/min in order to define the glass transition temperature (Tg). Isothermal viscosity decreases from 0.15 to 0.22 log Pa.s (high-T) and from 0.8 to 1.2 log Pa.s (low-T) with the addition of each 5 wt% Fe into the AnDi eutectic system. The viscosity of all these melt compositions shows non-Arrhenian behaviour across the whole T-range investigated. The density of the melts increases by about 0.05 g.cm$^{-3}$ with each addition of 5 wt% of Fe. Fe$^{3+}$ content decreases with increasing T (i.e., about 10% between 1300-1600$\deg$C). The DSC measurements suggest that the Tg decreases about 19$\deg$C with the addition of each 5 wt% Fe at a given cooling/heating rate. Low viscosities, which result from the high Fe content of Martian magmas, promote highly fluid lava behaviour, with implications for lava runout distances, eruptive styles and the landforms produced.
DE: 5134 Thermal properties
DE: 5480 Volcanism (8450)
DE: 6225 Mars
DE: 8429 Lava rheology and morphology
DE: 8439 Physics and chemistry of magma bodies
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting