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NAM2012 - All Presentation Details

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Reading the dynamic compaction of asteroids using mineral microstructures

Author: Paula Lindgren

University of Glasgow

Co-Authors: Martin R. Lee University of Glasgow

Session: PL1: Small bodies in Our Solar System

Presentation type: Talk      12:44  Tuesday 27th 11:45-13:00 

Summary:

Compaction and aqueous alteration were among the earliest processes that took place in the solar system following initial condensation and accretion of material to form planetesimals. Evidence of these early processes is recorded by samples of C-type asteroids that come to Earth as carbonaceous chondrite meteorites. Compaction of their parent bodies probably occurred mostly through impact “gardening”, but also to some extent via static compaction in larger asteroids. Compactional deformation can be seen in carbonaceous chondrites as a rock fabric, e.g. alignment of chondrules and phyllosilicate crystals within their fine-grained matrices, and/or as intracrystalline microstructures such as twinning. Traditionally, olivine microstructures have been used for determining deformation-histories of meteorites, but since the more primitive and aqueousely altered carbonaceous chondrites are depleted in mafic silicates, the mineral calcite can be used here instead. The calcite grains formed during aqueous alteration and their micrometre-sized twins are thought to record dynamic compaction accompanying impacts. In this ongoing study we are using scanning and transmission electron microscopy and electron backscatter diffraction to analyze the twin microstructures of calcite from a range of CM1-CM2 carbonaceous chondrites that have been aqueousely altered to various degrees, to determine their deformation histories during and/or after aqueous alteration.

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