Skip to Main content Skip to Navigation
Journal articles

Collisions and compositional variability in chondruleforming events

Abstract : Compound chondrules, i.e. chondrules fused together, make a powerful probe of the density and compositional diversity in chondrule-forming environments, but their abundance among the dominating porphyritic textures may have been drastically underestimated. I report herein microscopic observations and LA-ICP-MS analyses of lobate chondrules in the CO3 chondrites Miller Range 07193 and 07342. Lobes in a given chondrule show correlated volatile and moderately volatile element abundances but refractory element concentrations are essentially independent. This indicates that they formed by the collision of preexisting droplets whose refractory elements behaved in closed system, while their more volatile elements were buffered by the same gaseous medium. The presence of lobes would otherwise be difficult to explain, as surface tension should have rapidly imposed a spherical shape at the temperature peak. In fact, since most chondrules across chondrite groups are nonspherical, a majority are probably compounds variously relaxed toward sphericity. The lack of correlation of refractory elements between conjoined compound chondrule components is inconsistent with derivation of chondrules from the disruption of homogenized melt bodies as in impact scenarios and evokes rather the melting of independent mm-size nebular aggregates. Yet a “nebular” setting for chondrule formation would need to involve not only increased solid concentration, e.g. by settling to the midplane, but also a boost in relative velocities between droplets during chondrule-forming events to account for observed compound chondrule frequencies.
Document type :
Journal articles
Complete list of metadata

https://hal.sorbonne-universite.fr/hal-03187572
Contributor : Hal Sorbonne Université Gestionnaire <>
Submitted on : Thursday, April 1, 2021 - 10:58:06 AM
Last modification on : Friday, April 2, 2021 - 3:30:48 AM

File

 Restricted access
To satisfy the distribution rights of the publisher, the document is embargoed until : 2021-10-01

Please log in to resquest access to the document

Identifiers

Citation

Emmanuel Jacquet. Collisions and compositional variability in chondruleforming events. Geochimica et Cosmochimica Acta, Elsevier, 2021, 296, pp.18-37. ⟨10.1016/j.gca.2020.12.025⟩. ⟨hal-03187572⟩

Share

Metrics

Record views

19