Arnaud Agranier

Laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) analyses of B and Li in serpentinized peridotites from the Feather River Ophiolite (California) indicates that B is enriched in serpentine minerals compared to the whole‐rock and less altered olivine grains, while Li in serpentine is depleted or comparable to whole‐rock Li. The high B contents of serpentine minerals correlate with the relatively enriched whole‐rock B contents. The low Li contents of serpentine minerals are consistent with the relatively low Li whole‐rock contents and suggest that only small amounts of Li were added during serpentinization or that some Li was even leached out. A simple model of partial melting shows that Li/Yb increases with increasing melt depletion (and clinopyroxene depletion) in the peridotitic residue because Li is most compatible in olivine while Yb is most compatible in clinopyroxene. Thus, high Li/Yb ratios in peridotites by themselves do not indicate secondary enrichments in Li. However, Li/Yb and Yb contents of many of the Feather River Ophiolites plot above the melt depletion curve in Li/Yb versus Yb space, indicating that these serpentinites experienced subtle and preferential enrichments in Li during serpentinization. If serpentinized oceanic lithospheric mantle, as represented by the Feather River Ophiolite, is important in subduction recycling, then recycled mantle domains having a serpentinite protolith might be characterized by strong B enrichments but only small Li enrichments.

10.1029/2008gc002078

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The internal structure and geodynamics of Mars inferred from a 4.2-Gyr zircon record

Proceedings of the National Academy of Sciences (2020)

M.M. Costa Ninna K. Jensen Laura C. Bouvier James N. Connelly T. Mikouchi

Significance We discovered a zircon record in a Martian meteorite that spans 4.2 Gyr, nearly the entire geologic history of Mars. Ancient zircons define a bimodal distribution with groupings at 4474 ± 10 Ma and 4442 ± 17 Ma, reflecting intense bombardment episodes triggered by the migration of the gas giant planets. A group of younger detrital zircons record ages from 1548.0 ± 8.8 Ma to 299.5 ± 0.6 Ma. The only plausible sources for these grains are the Elysium and Tharsis volcanic provinces that are the expressions of deep-seated mantle plumes. The chondritic-like Hf-isotope compositions of these zircons require the existence of a primitive and convecting mantle reservoir. Thus, these grains provide a tangible record of the deep Martian interior.

Tharsis

10.1073/pnas.2016326117

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Paleoceanographic and paleogeodynamic reconstruction of the Mozambique Channel - contribution of Nd isotopes in ferromanganese crusts

EGU General Assembly Conference Abstracts (2019)

C.D. Charles Ewan Pelleter Sidonie Révillon Philippe Nonnotte Arnaud Agranier

Ferromanganese

paleoceanography

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