A microchondrule-bearing micrometeorite and comparison with microchondrules in CM chondrites

Suttle, M.D., Genge, M.J., Salge, T., Lee, M. R. , Folco, L., Goral, T., Russell, S.S. and Lindgen, P. (2019) A microchondrule-bearing micrometeorite and comparison with microchondrules in CM chondrites. Meteoritics and Planetary Science, 54(6), pp. 1303-1324. (doi: 10.1111/maps.13279)

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We report the discovery of a partially altered microchondrule within a fine-grained micrometeorite. This object is circular, <10 μm in diameter, and has a cryptocrystalline texture, internal zonation, and a thin S-bearing rim. These features imply a period of post-accretion parent body aqueous alteration, in which the former glassy igneous texture was subject to hydration and phyllosilicate formation as well as leaching of fluid-mobile elements. We compare this microchondrule to three microchondrules found in two CM chondrites: Elephant Moraine (EET) 96029 and Murchison. In all instances, their formation appears closely linked to the late stages of chondrule formation, chondrule recycling, and fine-grained rim accretion. Likewise, they share cryptocrystalline textures and evidence of mild aqueous alteration and thus similar histories. We also investigate the host micrometeorite's petrology, which includes an unusually Cr-rich mineralogy, containing both Mn-chromite spinel and low-Fe-Cr-rich (LICE) anhydrous silicates. Because these two refractory phases cannot form together in a single geochemical reservoir under equilibrium condensation, this micrometeorite's accretionary history requires a complex timeline with formation via nonequilibrium batch crystallization or accumulation of materials from large radial distances. In contrast, the bulk composition of this micrometeorite and its internal textures are consistent with a hydrated carbonaceous chondrite source. This micrometeorite is interpreted as a fragment of fine-grained rim material that once surrounded a larger parent chondrule and was derived from a primitive carbonaceous parent body; either a CM chondrite or Jupiter family comet.

Item Type:Articles
Additional Information:The data presented in this paper were acquired primarily during Martin Suttle’s PhD research while at Imperial College London and the NHM and principally funded by the Science and Technology Council (STFC) under a training grant (ST/M503526/1). However, research continued while Martin Suttle attended a postdoc research position at the University of Pisa, which is funded through two Italian research grants MIUR: PNRA16_00029 (Programma Nazionale delle Ricerche in Antartide—CUP I52F17001050005) and PRIN2015_20158W4JZ7 (CUP I52F15000310001 for the “Meteoriti Antartiche”). Lugi Folco is also supported through the same research grants, while Matthew Genge and Sara Russell are funded by the STFC (ST/J001260/1 and ST/M00094X/1 respectively) and Martin Lee is funded by STFC grants (ST/N000846/1 and ST/H002960/1).
Glasgow Author(s) Enlighten ID:Lee, Professor Martin
Authors: Suttle, M.D., Genge, M.J., Salge, T., Lee, M. R., Folco, L., Goral, T., Russell, S.S., and Lindgen, P.
Subjects:Q Science > QE Geology
College/School:College of Science and Engineering > School of Geographical and Earth Sciences > Earth Sciences
Research Group:Earth Systems
Journal Name:Meteoritics and Planetary Science
ISSN (Online):1945-5100
Published Online:27 March 2019

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
172314A journey from the solar nebula to planetary bodies: cycling of heat, water and organicsMartin LeeScience and Technology Facilities Council (STFC)ST/N000846/1GES - Earth Sciences
190265Follow the water: insights into the martian hydrosphere from nakhlitesMartin LeeScience and Technology Facilities Council (STFC)ST/H002960/1GES - Earth Sciences