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- Title
Sulfide Melt Wetting Properties in Earth's Mantle: New Constraints From Combined 2D and 3D Imaging.
- Authors
Beyer, C.; Fonseca, R. O. C.; Bissbort, T.; Schröer, L.; Cnudde, V.
- Abstract
Base‐metal sulfur liquids (mattes) play a crucial role as metasomatic agents and carriers of highly siderophile elements (HSE) within the Earth's mantle. Prior research has predominantly focused on sulfur‐poor metallic liquids involved in core formation scenarios. We conducted high‐pressure experiments using a multi‐anvil apparatus to investigate the effects of pressure, non‐ferrous compounds in mattes, and the mineral composition of the silicate host on matte wetting properties. Specifically, we explored conditions representing both the lithospheric (6 and 7 GPa) and sub‐lithospheric Earth's mantle (13 GPa). We characterized the experiments using the distribution of the dihedral angle in backscattered‐electron sections and the sphericity and network topology of the mattes in tomography scans. Our findings reveal distinct behaviors: while the matte in olivine‐dominated samples exhibited behaviors consistent with previous studies, such as high dihedral angle values (94° and 100°), the majorite‐bearing sample run at 13 GPa formed a disseminated network with a mean dihedral angle of 43°, below the connectivity threshold of 60°. Furthermore, in an experiment involving a garnet‐bearing silicate host, we observed a decrease in the matte's dihedral angle to 72°. Our results suggest that pressure within mafic hosts contributes to increased matte mobility in the sub‐lithospheric Earth's mantle, especially inasmuch as the stability of garnet phases is concerned. Consequently, mattes within subducted oceanic crusts may efficiently transport HSE into surrounding lithologies, while mattes within depleted, more harzburgitic lithologies and the ambient mantle may remain trapped within the silicate host at low melt fractions. Plain Language Summary: Our study focused on how sulfur‐rich liquids percolate in Earth's mantle and carry important elements. Previous research mostly studied how metallic liquids, which are sulfur‐poor, form planetary cores. We did experiments under high pressure and high temperature to see how different factors affect the mobility of sulfur‐bearing liquids in the deep Earth's mantle. We found that the type of rock and pressure levels affect how mattes spread. When rocks contained the high‐pressure polymorph of garnet, called majorite, mattes moved differently compared to rocks that mostly contain the mineral olivine. Our results show that rocks and pressure levels influence matte movement in regions of Earth's mantle that are comprised of subducted oceanic crust. This helps us understand how elements move inside the Earth, especially when oceanic crust sinks into the mantle. Key Points: The mobility of mattes is enhanced by majoritic garnet at sub‐lithospheric depthsThe combination of 2D and 3D methods improves our understanding of liquid percolation in the Earth's mantle
- Subjects
EARTH'S mantle; OLIVINE; GARNET; THREE-dimensional imaging; SILICATE minerals; DIHEDRAL angles; OCEANIC crust
- Publication
Geochemistry, Geophysics, Geosystems: G3, 2024, Vol 25, Issue 5, p1
- ISSN
1525-2027
- Publication type
Article
- DOI
10.1029/2024GC011535