Oxygen isotopic and chemical composition of chromites in micrometeorites: Evidence of ordinary chondrite precursors

• Published in: Meteoritics & Planetary Science
• Main Authors: Rudraswami, N., G, Marrocchi, Yves, Shyam Prasad, M., Fernandes, D., Villeneuve, Johan, Taylor, S.
• Other Authors: CSIR National Institute of Oceanography India (NIO), Centre de Recherches Pétrographiques et Géochimiques (CRPG), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), ERDC Cold Regions Research and Engineering Laboratory (CRREL), USACE Engineer Research and Development Center (ERDC)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology; Indian; South Pole; South pole
• Online Access: https://hal.univ-lorraine.fr/hal-02357526; https://hal.univ-lorraine.fr/hal-02357526/document; https://hal.univ-lorraine.fr/hal-02357526/file/Rudra-final.pdf; https://doi.org/10.1111/maps.13281

International audience We identified 66 chromite grains from 42 of ~5000 micrometeorites collected from Indian Ocean deep-sea sediments and the South Pole water well. To determine the chromite grains precursors and their contribution to the micrometeorite flux, we combined quantitative electron microprobe analyses and oxygen isotopic analyses by high-resolution secondary ion mass spectrometry. Micrometeorite chromite grains show variable O isotopic compositions with δ18O values ranging from –¬¬0.8 to 6.0‰, δ17O values from 0.3 to 3.6‰, and Δ17O values from –0.9 to 1.6‰, seems majority of them are similar to those of chromites from ordinary chondrites. The oxygen isotopic compositions of olivine as a proxy to the chromite in chromite-bearing micrometeorites where we could not measure chromite have Δ17O values suggesting largely related to ordinary chondritic with some having carbonaceous chondrite precursors. Furthermore, the chemical compositions of chromites in micrometeorites are close to those reported for ordinary chondrite chromites, but some contribution from carbonaceous chondrites cannot be ruled out. Consequently, carbonaceous chondrites cannot be a major contributor of chromite-bearing micrometeorites. Based on their oxygen isotopic and elemental compositions, we thus conclude with no ambiguity that chromite-bearing micrometeorites are largely related to fragments of ordinary chondrites with small fraction from carbonaceous chondrites, unlike other micrometeorites deriving largely from carbonaceous chondrites.