Effect of Sulfur on Siderophile Element Partitioning Between Olivine and Martian Basaltic Melt
Abstract
Nickel and Co variations in primary martian magmas exhibit anomalous incompatible behavior, which has remained an unexplained conundrum. Because martian magmas are S-rich and some trace metals have enhanced solubility in S-bearing magmas, we have carried out a series of experiments to evaluate the effect of S on the olivine/melt partitioning of Ni, Co, Mn, V, and Cr (referred to as D(M); M = Ni, Co, Mn, V, or Cr). Near-liquidus experiments on a synthetic primary (Yamato-980459 [Y98]) martian melt were conducted in a piston-cylinder apparatus at 0.75 GPa. Previous studies in S-free systems were used to calibrate a predictive expression that includes the effects of temperature, melt composition, and oxygen fugacity. These predictive expressions are then used to isolate any effect in D(M) due to dissolved sulfur. The results show that S might have a discernible effect for Co and Cr, but not enough to change Co partitioning from compatible to incompatible in our experiments. Addition of a sulfur term to the D(Co) predictive expressions shows that nearly 8000 ppm of sulfur would be required in the melt at liquidus temperature of Y98 for D(Co) to become <1. These S contents are 2 times higher than those of a sulfide saturated melt at the pressure-temperature conditions of a martian mantle source region. Therefore, the anomalous incompatible behavior observed in martian primary magma suites must be due to another mechanism. High temperature, oxygen fugacity, diffusion are not viable mechanisms, but magma mixing remains a possibility.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMP042.0004U
- Keywords:
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- 1039 Alteration and weathering processes;
- GEOCHEMISTRY;
- 5220 Hydrothermal systems and weathering on other planets;
- PLANETARY SCIENCES: ASTROBIOLOGY;
- 5419 Hydrology and fluvial processes;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS;
- 5455 Origin and evolution;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS