Impact-induced compaction of primitive solar system solids: The need for mesoscale modelling and experiments
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Primitive solar system solids were accreted as highly porous bimodal mixtures of mm-sized chondrules and sub-µm matrix grains. To understand the compaction and lithification of these materials by shock, it is necessary to investigate the process at the mesoscale; i.e., the scale of individual chondrules. Here we document simulations of hypervelocity compaction of primitive materials using the iSALE shock physics model. We compare the numerical methods employed here with shock compaction experiments involving bimodal mixtures of glass beads and silica powder and find good agreement in bulk material response between the experiments and models. The heterogeneous response to shock of bimodal porous mixtures with a composition more appropriate for primitive solids was subsequently investigated: strong temperature dichotomies between the chondrules and matrix were observed (non-porous chondrules remained largely cold, while the porous matrix saw temperature increases of 100's K). Matrix compaction was heterogeneous, and post-shock porosity was found to be lower on the lee-side of chondrules. The strain in the matrix was shown to be higher near the ch ondrule rims, in agreement with observations from meteorites. Chondrule flattening in the direction of the shock increases with increasing impact velocity, with flattened chondrules oriented with their semi-minor axis parallel to the shock direction.
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Davison, T.; Collins, G.; Bland, Phil (2016)We have developed a method for simulating the mesoscale compaction of early solar system solids in low-velocity impact events using the iSALE shock physics code. Chondrules are represented by non-porous disks, placed ...
Forman, L.; Bland, Phil; Timms, Nicholas Eric; Collins, G.; Davison, T.; Ciesla, F.; Benedix, G.; Daly, L.; Trimby, P.; Yang, L.; Ringer, S. (2016)The CV3 Allende is one of the most extensively studied meteorites in worldwide collections. It is currently classified as S1—essentially unshocked—using the classification scheme of Stöffler et al. (1991), however recent ...
Forman, Lucy; Bland, Phil; Timms, Nicholas Eric; Daly, L.; Benedix, Gretchen; Trimby, P.; Collins, G.; Davison, T. (2017)The Allende meteorite, a relatively unaltered member of the CV carbonaceous chondrite group, contains primitive crystallographic textures that can inform our understanding of early Solar System planetary compaction. To ...