83-6 Percolative Sulfide Core Formation in Oxidized Planetary Bodies

Session: Asteroid Observations, Return Missions, and Meteoritics: Interweaving Perspectives and Data

Presenting Author:

Samuel Crossley

Authors:

Crossley, Samuel Dean¹, Setera, Jacob B.², Anzures, Brendan A.³, Iacovino, Kayla⁴, Buckley, Wayne P.⁵, Eckley, Scott A.⁶, O'Neal, Evan W.⁷, Maisano, Jessica A.⁸, Simon, Justin Ibrahim⁹, Righter, Kevin¹⁰

(1) Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, USA, (2) University of Texas at El Paso - Amentum JETS at Johnson Space Center, Houston, TX, USA, (3) NASA/Amentum Johnson Space Center, Houston, TX, USA, (4) NASA/Amentum Johnson Space Center, Houston, TX, USA, (5) NASA/Amentum Johnson Space Center, Houston, TX, USA, (6) NASA/Amentum Johnson Space Center, Houston, TX, USA, (7) NASA/Amentum Johnson Space Center, Houston, TX, USA, (8) Jackson School of Geosciences, University of Texas, Austin, TX, USA, (9) NASA Johnson Space Center, Houston, TX, USA, (10) University of Rochester, Rochester, NY, USA,

Abstract:

The process of core formation in planetary bodies is often described by one of two mechanisms: (1) percolative flow of core-forming melts prior to silicate melting or (2) rainout of immiscible FeNiS from silicate melts in a magma ocean setting. Metal-rich cores are thought to form through the latter process due to the inability of molten metal to efficiently wet silicate grain boundaries, which is required for percolative flow. However, many oxidized meteorites preserve mineralogical and geochemical evidence for a dearth of Fe,Ni-metals in their parent bodies. Instead, their core-forming phases were dominated by Fe,Ni-sulfides. The melts generated from these materials may be capable of wetting silicate grain boundaries and facilitating rapid percolative core formation, but this mechanism has not yet been tested under appropriate mineralogical and textural constraints of oxidized meteorites.

We conducted partial melting experiments in evacuated silica tubes using chips of oxidized chondritic meteorites and scanned the experiments with X-ray computed microtomography (µ-XCT) to investigate the percolative potential of sulfide-dominated melts below silicate solidus temperatures (< 1,040 °C). Three-dimensional renderings of experiments show rapid migration of molten sulfides due to percolative flow between unmelted silicate grains. This process should be expected for planetary bodies differentiating at conditions more oxidizing than approximately two log units below the iron-wustite oxidation buffer (i.e., IW-2), at or above the iron-troilite (IT) sulfidation buffer, and at pressures up to ~20 GPa. Thus, this process may be applicable to the formation of the Martian core. Rapid formation of a low-density, sulfur-rich core can explain many otherwise anomalous physical and geochemical aspects of the Martian interior.

Finally, using complementary trace element partitioning experiments under similar conditions, we demonstrate that some primitive achondrites (i.e., oxidized brachinites) and their basaltic counterparts both possess platinum-group element proportions that are best explained by percolative sulfide core formation prior to silicate melting. These results provide the first meteorite-based evidence for the occurrence of percolative sulfide core formation in the solar system.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7063

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