Physics
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p11a1578b&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P11A-1578
Physics
[1060] Geochemistry / Planetary Geochemistry, [3630] Mineralogy And Petrology / Experimental Mineralogy And Petrology, [3924] Mineral Physics / High-Pressure Behavior, [5430] Planetary Sciences: Solid Surface Planets / Interiors
Scientific paper
Over 12 new high pressure Mo metal-silicate partitioning experiments were performed in the pressure (P) and temperature (T) range of 3-8 GPa and 2173-2373 K. Parameterization of our data and literature data, limited to experiments with an Fe-rich metal phase and no light elements, produces a PT solution set that is compatible with the magma ocean hypothesis, and can be used to further constrain core formation models. The goal of these models is to reproduce the siderophile element abundances observed in Earth's mantle. The mantle is depleted in siderophile elements relative to chondrites as a result of their affinity for the metal phase during core formation. Metal-silicate partitioning experiments on the siderophile elements Ni and Co have provided valuable constraints on the PT conditions of core formation. Li and Agee (1996) showed that at 2273 K and pressures above 28 GPa, equilibrium core formation, such as in a magma ocean, can explain the observed mantle depletion of Ni and Co. Compared to Ni and Co, there is a paucity of data on the siderophile element Mo, especially at high pressure. Only 15 partitioning experiments have been performed at pressures above 1.5 GPa, which leads to large errors when the results are extrapolated to the higher pressure conditions of core formation. Consequentially, Mo has been left out of most core formation models such as those proposed by Rubie et al. (2011) and Wade and Wood (2005). Increasing the number of Mo partitioning data points will provide much needed additional constraints on core formation. All of our experiments were performed on a Walker-type multi-anvil press at the Institute of Meteoritics. Run products were analyzed by EPMA with a 20 μm broad beam. Crushable MgO capsules were used in all experiments. With this capsule material there is significant MgO infiltration into the silicate; however, MgO is already part of the system so it is more ideal than graphite capsules which impart a significant carbon component to the metal phase. We examined multiple silicate compositions, all of which were ultramafic, and used either a FeMo or FeNiMo metal phase. The oxygen fugacity of our experiments ranged from -2.53ΔIW to -1.37ΔIW. The molybdenum partition coefficients we determined are between 99 and 1050, which are lower than those determined in previous work on basaltic compositions. We found that silicate composition has a large effect on molybdenum partitioning, with D(Mo) decreasing as melt polymerization increases. P and T have only a slight effect over the range of conditions investigated. We parameterized our results, along with previous partitioning work, using the multiple linear regression method of Righter et al. (1997). When all the data is parameterized, no coherent trends are observed, presumably because of large variations in metal phase compositions. This demonstrates one of the pitfalls of trying to parameterize a large data set with many variables and how a smaller, relevant data set can be more insightful.
Agee Carl B.
Burkemper L. K.
Garcia K. A.
No associations
LandOfFree
High Pressure Metal-Silicate Partitioning of Molybdenum and Constraints on Core Formation 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 High Pressure Metal-Silicate Partitioning of Molybdenum and Constraints on Core Formation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High Pressure Metal-Silicate Partitioning of Molybdenum and Constraints on Core Formation will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-867432