Oxygen isotope systematics of magnetite in hydrated Antarctic micrometeorites: new water reservoir

• Main Authors: Dobrica, Elena, Ogliore, R, Engrand, Cecile, Nagashima, K, Brearley, A. J.
• Other Authors: Centre de Sciences Nucléaires et de Sciences de la Matière (CSNSM), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDU]Sciences of the Universe [physics]; Antarctic; Jupiter; Antarc*
• Online Access: https://hal.science/hal-02360861; https://hal.science/hal-02360861/document; https://hal.science/hal-02360861/file/Dobrica_2018_MMs_Oiso_hydrated_Mt-LPSC.pdf

International audience Introduction: Secondary phases in hydrated Antarctic micrometeorites (AMMs) will show an oxygen isotopic signature from their likely formation by aque-ous processes, in either a comet or asteroid parent body. Asteroidal water may be distinguishable from cometary water in its oxygen isotopic composition. The oxygen isotopic composition of water in asteroi-dal-derived hydrated AMMs should be close to Δ 17 O ~ 0 if their parent body is carbonaceous chondrite (CC)-like (similar to the hydrated interplanetary dust particles (IDPs) measured so far [1]) or Δ 17 O ~ +6.6‰ if their parent body is ordinary chondrite (OC)-like [e.g. 2-4]. Any hydrated AMMs with significantly different Δ 17 O values would be evidence that these particles formed from non-asteroidal water. If Jupiter-family comets (JFCs) accreted outer nebular water, the O composition of their secondary minerals could be similar to the cosmic symplectites (COSs) from Acfer 094 [5-6]. Here we present the mineralogy and oxygen isotope compositions of magnetite grains and a magnetite-dolomite assemblage that were identified in five AMMs. The purpose of these measurements is to investigate the diversity of the water reservoir from which hydrated AMMs formed and the temperature at which these minerals co-precipitated.