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Title: Understanding the origin of meteoritic magnetism : implications for protoplanetary disk accretion
Author: Shah, Jay
ISNI:       0000 0004 6496 9646
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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Chondritic meteorites largely formed 4.6 billion years ago, and can range from being metamorphosed as a result of processing on their asteroid parent bodies to entirely unaltered since their formation in the protoplanetary disk. The magnetic grains within these meteorites can potentially record and retain the magnetic conditions on the parent body and the conditions in the protoplanetary disk during the formation of our planetary system. However, the complex history of these meteorites can make their magnetic records difficult to interpret, and their age prompts the question of whether a magnetic remanence can be retained for so long. In this thesis, to help identify the origin of the magnetic remanence, a new method for the palaeomagnetic conglomerate test that uses micro-CT scans to accurately mutually orient chondrules from chondrites was developed. When applied to Vigarano (CV3) and Bjurböle (L/LL4), a more in-depth understanding of parent body processing was achieved that provides evidence for magnetic dynamo activity on their parent bodies. To understand the magnetic record of CK chondrites, a palaeomagnetic analysis of Karoonda (CK4) was conducted, and found no evidence of a significant magnetic field recording, supporting the solar radiative heating model for the CV-CK chondrites. To determine whether magnetic remanence can be retained from the early Solar System, the high thermal stability of single and multi-vortex kamacite grains from Bishunpur (LL3.1) was demonstrated by performing in-situ temperature-dependent nanometric magnetic measurements using electron holography and numerical micromagnetic energy barrier calculations. This study found that the majority of kamacite grains in dusty olivines are capable of retaining magnetic field information from the early Solar System, a key finding in our quest to understand the formation of our Solar System.
Supervisor: Muxworthy, Adrian R. ; Genge, Matthew J. ; Russell, Sara S. Sponsor: Science and Technology Facilities Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral