Earliest rock fabric formed in the Solar System preserved in a chondrule rim
MetadataShow full item record
Rock fabrics – the preferred orientation of grains – provide a window into the history of rock formation, deformation and compaction. Chondritic meteorites are among the oldest materials in the Solar System1 and their fabrics should record a range of processes occurring in the nebula and in asteroids, but due to abundant fine-grained material these samples have largely resisted traditional in situ fabric analysis. Here we use high resolution electron backscatter diffraction to map the orientation of sub-micrometre grains in the Allende CV carbonaceous chondrite: the matrix material that is interstitial to the mm-sized spherical chondrules that give chondrites their name, and fine-grained rims which surround those chondrules. Although Allende matrix exhibits a bulk uniaxial fabric relating to a significant compressive event in the parent asteroid, we find that fine-grained rims preserve a spherically symmetric fabric centred on the chondrule. We define a method that quantitatively relates fabric intensity to net compression, and reconstruct an initial porosity for the rims of 70-80% - a value very close to model estimates for the earliest uncompacted aggregates2,3. We conclude that the chondrule rim textures formed in a nebula setting and may therefore be the first rock fabric to have formed in the Solar System.
Showing items related by title, author, creator and subject.
Bland, Phil; Travis, B. (2017)Carbonaceous asteroids may have been the precursors to the terrestrial planets, yet despite their importance, numerous attempts to model their early solar system geological history have not converged on a solution. The ...
Emmerton, S.; Muxworthy, A.; Hezel, D.; Bland, Philip (2011)We have conducted a detailed magnetic study on 45 chondrules from two carbonaceous chondrites of the CV type: (1) Mokoia and (2) Allende. Allende has been previously extensively studied and is thought to have a high ...
Impact-induced compaction of primitive solar system solids: The need for mesoscale modelling and experimentsDavison, T.; Derrick, J.; Collins, G.; Bland, Phil; Rutherford, M.; Chapman, D.; Eakins, D. (2017)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 ...