Wed 18th September @ noon, Rm 312.222

Abstract:

The meteorite Allende fell in 1969 in Mexico, and remains one of the most heavily studied meteorites to date. Due to the large volume of material that fell, many different analyses have been carried out on the meteorite as technology has developed all over the world. Allende is a carbonaceous chondrite (CV subclass) that is presumed to originate from the same parent asteroid that all CV chondrites came from. Allende has undergone a relatively small amount of thermal and aqueous alteration when compared with many other meteorites, therefore textures observed in this rock may be considered relatively primitive. Extensive investigation of the various meteoritic components, i.e. chondrules, matrix grains, and calcium-aluminium inclusions, using EBSD, led to finding some of the first evidence of the process of asteroid compaction in this meteorite. Low-porosity components, i.e. chondrules, show a very small amount of crystal-plastic deformation when compared with small matrix grains, which would have been highly porous prior to compaction. These findings align with modelling predictions of impact-induced compaction as the driver for asteroid compaction. Further fabric analyses of the small matrix grains across a large area revealed an asymmetrical flattening of the matrix grains against low-porosity objects, such as chondrules, and enabled the direction of compaction to be estimated. Finally, we used EBSD data from 3 CV chondrites, including Allende, to compare matrix grain morphology and crystallography. Grain size, shape and alignment were assessed and considered in the context of the differing thermal and aqueous alteration that each meteorite has experienced based on prior work. At present, it is not common to measure the chondritic matrix grain sizes and shapes during classification. This approach may be a useful tool in the future for quantifying the physical properties of meteoritic matrices. The comparison across and between different meteorite classes may allow for patterns to be observed and correlated with accretionary or alteration processes, leading to a better understanding of how the chondritic parent bodies evolved.

Short bio:

Lucy is a postdoctorate researcher working with Prof. Gretchen Benedix in the Space Science and Technology Centre (SSTC), here at Curtin. The focus of her postdoc is investigating Martian meteorites to gather a better understanding of the formation and origin of these rocks on the Martian surface, using electron backscattered diffraction (EBSD). She completed her PhD in Planetary Geology in 2017 exploring early impacts in the solar system, and found evidence of deformation induced by impacts, also using EBSD techniques. She is a passionate science outreach advocate and enjoys sharing her love of science with the public.