¹Marc Monnereau,^1,2Jérémy Guignard,^1,3Adrien Néri,¹Michael J.Toplis,¹Ghylaine Quitté
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115294]
¹IRAP, University of Toulouse, CNRS, Toulouse, France
²ICMCB, CNRS, Université de Bordeaux, Bordeaux, France
³BGI, University of Bayreuth, Bayreuth, Germany
Copyright Elsevier

The petrologic and geochemical diversity of meteorites is a function of the bulk composition of their parent bodies, but also the result of how and when internal differentiation took place. Here we focus on this second aspect considering the two principal parameters involved: size and accretion time of the body. We discuss the interplay of the various time scales related to heating, cooling and drainage of silicate liquids. Based on two phase flow modelling in 1-D spherical geometry, we show that drainage time is proportional to two independent parameters: , the ratio of the matrix viscosity to the square of the body radius and , the ratio of the liquid viscosity to the square of the matrix grain size. We review the dependence of these properties on temperature, thermal history and degree of melting, demonstrating that they vary by several orders of magnitude during thermal evolution. These variations call into question the results of two phase flow modelling of small body differentiation that assume constant properties. For example, the idea that liquid migration was efficient enough to remove 26Al heat sources from the interior of bodies and dampen their melting (e.g. Moskovitz and Gaidos, 2011; Neumann et al., 2012) relies on percolation rates of silicate liquids overestimated by six to eight orders of magnitude. In bodies accreted during the first few million years of solar-system history, we conclude that drainage cannot prevent the occurrence of a global magma ocean. These conditions seem ideal to explain the generation of the parent-bodies of iron meteorites. A map of the different evolutionary scenarios of small bodies as a function of size and accretion time is proposed.

^1,2Jiří Mizera
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13912]
¹Nuclear Physics Institute, Czech Academy of Sciences, Řež 130, 250 68 Husinec-Řež, Czech Republic
²Institute of Rock Structure and Mechanics, Czech Academy of Sciences, V Holešovičkách 41, 182 09 Praha 8, Czech Republic
Published by arrangement with John Wiley & Sons

The quest for the parent impact structure for Australasian tektites (AAT) has remained without solution for almost a century. The present paper doubts the plausibility of the recently proposed location of the impact site at the Bolaven volcanic field in Southern Laos by showing problems with most of the presented lines of evidence. The geochemical incompatibility of the AAT composition with a mixture of weathered basalts and Mesozoic sandstones that were proposed as source materials of AAT is demonstrated by a two-component mixing calculation for major element oxides and the Nd-Sr isotopic system. Deficiency of the basaltic component as a source of Ni, Co, Cr, and 10Be in AAT and inconsistency with trends observed for O and Pb isotopes are shown. The size of the putative crater, conclusiveness of a gravity anomaly identification, signs of complete crater burial by postimpact lava flows, and identification of proximal ejecta blanket are doubted. Remarks on the shortcomings of the current consensus location of an impact site for AAT in Indochina are presented.