Imperial College London

Professor Gareth Collins

Faculty of EngineeringDepartment of Earth Science & Engineering

Professor of Planetary Science
 
 
 
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Contact

 

+44 (0)20 7594 1518g.collins Website

 
 
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Location

 

4.83Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Muxworthy:2017:10.1111/maps.12918,
author = {Muxworthy, AR and Bland, PA and Davison, TM and Moore, J and Collins, GS and Ciesla, FJ},
doi = {10.1111/maps.12918},
journal = {Meteoritics & Planetary Science},
pages = {2132--2146},
title = {Evidence for an impact-induced magnetic fabric in Allende, and exogenous alternatives to the core dynamo theory for Allende magnetization},
url = {http://dx.doi.org/10.1111/maps.12918},
volume = {52},
year = {2017}
}

RIS format (EndNote, RefMan)

TY  - JOUR
AB - We conducted a paleomagnetic study of the matrix of Allende CV3 chondritic meteorite, isolating the matrix’s primary remanent magnetization, measuring its magnetic fabric and estimating the ancient magnetic field intensity. A strong planar magnetic fabric was identified; the remanent magnetization of the matrix was aligned within this plane, suggesting a mechanism relating the magnetic fabric and remanence. The intensity of the matrix’s remanent magnetization was found to be consistent and low (~6 μT). The primary magnetic mineral was found to be pyrrhotite. Given the thermal history of Allende, we conclude that the remanent magnetization formed during or after an impact event. Recent mesoscale impact mode ling, where chondrules and matrix are resolved, has shown that low-velocity collisions can generate significant matrix temperatures, as pore-space compaction attenuates shock energy and dramatically increases the amount of heating. Non-porous chondrules are unaffected, and act as heat-sinks, so matrix temperature excursions are brief. We extend this work to model Allende, and show that a 1km/s planar impact generates bulk porosity, matrix porosity, and fabric in our target that match the observed values. Bimodal mixtures of a highly porous matrix and nominally zero-porosity chondrules, make chondrites uniquely capable of recording transient or unstable fields. Targets that have uniform porosity, e.g., terrestrial impact craters, will not record transient or unstable fields. Rather than a core dynamo, it is therefore possible that the origin of the magnetic field in Allende was the impact itself, or a nebula field recorded during transient impact heating.
AU - Muxworthy,AR
AU - Bland,PA
AU - Davison,TM
AU - Moore,J
AU - Collins,GS
AU - Ciesla,FJ
DO - 10.1111/maps.12918
EP - 2146
PY - 2017///
SN - 1086-9379
SP - 2132
TI - Evidence for an impact-induced magnetic fabric in Allende, and exogenous alternatives to the core dynamo theory for Allende magnetization
T2 - Meteoritics & Planetary Science
UR - http://dx.doi.org/10.1111/maps.12918
UR - http://hdl.handle.net/10044/1/48604
VL - 52
ER -