Imperial College London

Dr. Adrian Muxworthy

Faculty of EngineeringDepartment of Earth Science & Engineering

Reader in Earth and Planetary Magnetism
 
 
 
//

Contact

 

+44 (0)20 7594 6442adrian.muxworthy

 
 
//

Location

 

4.48Royal School of MinesSouth Kensington Campus

//

Summary

 

Overview

Geomagnetic Field Variation

The Earth's magnetic is constantly changing. To understand variations on long geological timescales, we need to examine the magnetic signal recorded by rocks during their formation. Extracting directional magnetic recording from rocks is relatively straightforward, but extracting the intensity of the ancient field is much more problematic. Reliable intensity data is required if we are to construct accurate geomagnetic field models and understand the long-term behaviour of the fluid motions deep within the earth where the field originates. With several colleagues, I am working on several new methods of determining accurate ancient geomagnetic field intensity (palaeointensity) determination.

Magnetotactic bacteria

Magnetotactic bacteria contain chains of magnetic crystals (usually magnetite), which are termed magnetosomes. The bacteria use these chains of magnetosomes as magnetic compasses to help navigate towards their optimal environment, which is in the oxic-anoxic transition zone. This affect is termed magnetotaxis. To maximize magnetotaxis the magnetosomes should be large to increase the magnetic signal, but not so large that the magnetization in the individual magnetosomes becomes non-uniform and less efficient. With Wyn Williams at the University of Edinburgh, we have used numerical micromagnetic models to determine optimal grain and spatial geometries for chains of magnetotactic bacteria.  

Unravelling complex magnetic signalsDirect measurement of magnetisation

The magnetic signature of most natural magnetic materials is highly complex. To interpret such signals in geological or environmental terms requires a good understanding of fundamental magnetic processes, such as magnetic hysteresis, and a knowledge of chemical effects such as diagenesis, which can strongly alter mineralogy. With a number of colleagues, I examine a range of fundamental mineral magnetic properties and develop new methods of extracting meaningful information from rocks. We employ several of approaches from examining well-characterized rocks, to synthesizing magnetic mineralss to constructing numerical models.

Evolution of Vomt. st. helenslcanic Processes

Violent pyroclastic volcanic eruptions such as the famous "Pompeii" eruption of Mt. Vesuvius in 79 AD, can be highly destructive . To assess the risk for the today's local inhabitants it is important to have a knowledge of the historical behaviour of such geohazards. Pyroclastic density currents generated during eruptions can move at high speeds in excess of 100 km per hour, but more importantly can vary in temperature from ambient up to 1000 C. Obviously the temperature strongly affects the danger to local inhabitants and livestock. The only method of estimating the emplacement temperature of past pyroclastic deposits, is through examination of the magnetic signature acquired by lithic clasts during the eruption. With colleagues, I employ palaeomagnetic techniques to study the evolution of volcanic processes

Collaborators

Yongxin Pan, Chinese Academy of Scienes, Beijing

Dominik Weiss, Imperial College London

Richard Harrison, University of Cambridge

David Dunlop, University of Toronto

Phil Bland, Imperial College London

Rafal Dunin-Borkowski, Technical University of Denmark

Greig Paterson, Chinese Academy of Sciences, Beijing

Liao Chang, University of Southampton

Conall Mac Niocaill, University of Oxford

Wyn Williams, University of Edinburgh

John MacLennan, University of Cambridge

Claire Carvallo, IMPMC, Paris

Andrew Roberts, Australian National University, Canberra

Dave Heslop, Australian National University, Canberra

Guest Lectures

Magnetic interactions: Love thy neighbour?, University of Durham, 2011

Micromagnetic modelling of magnetostatic interactions, University of Botswana, Gaborone, Botswana, 2003

An introduction to FORC diagrams, Chinese Academy of Sciences, Beijing, 2005

Understanding viscous magnetisation in multidomain minerals, Moscow State University, Moscow, 2004

Low-temperature techniques in rock magnetism: background and applications, Chinese Academy of Sciences, Beijing, 2005

Viscous behaviour of multidomain magnetite, Chinese Academy of Sciences, Beijing, 2005

Magnetostatic Interactions:Palaeomagnetic signals and magnetotactic bacteria, Chinese Academy of Sciences, Beijing, 2006

Palaeomagnetic signals and Magnetotactic Bacteria, University of Liverpool, Liverpool, 2005

Palaeomagnetic signals and Magnetotactic Bacteria, University of Oxford, Oxford, 2005

Magnetic dating of megafloods, NGU, Trondheim, Norway, 2010

Magnetic interactions: Love thy neighbour?, ANU, Canberra, 2011

Research Staff

Almeida,T

van Ginneken,M

Research Student Supervision

Penny,C, Nanoparticles in meterorites: the contribution of surfaces to the magnetic curie temperature and magnetic recording fidelity (2015 - )

Badejo,SA, Application of magnetic techniques to lateral hydrocarbon migration - Lower Tertiary reservoir systems, UK North Sea (2015 - )

Supakulopas,R, Deviations from the Geocentric Axial Dipole hypothesis: High-latitude study of the palaeomagnetic field (2014 - )

Nagy,L, Parallelisation of Micromagnetic Simulations (2011 - 2014)

Valdez Grijalva,M, A numerical investigation of hydrocarbon magnetic signatures (2014 - )

Shah,J, Understanding the origin of meteoritic magentism: Implications for the proto-planetary disk formation (2013-)

Berndt,T, Viscous Remanent Magetization (VRM) Dating of Cataclysmic Floods and Palaeotsumanis (2013 -)

Abubakar,R, Mapping petroleum migration pathways using magnetics, geochemistry and seismic interpretation. Case study: Wessex Basin, southern England, UK (2011 - )

Dodd,S, Constraining the timing and duration of Large Igneous Province Volcanism: magnetostratigraphic constraints from the Etendeka traps, Namibia. (2011-2014 )

Emmerton,S, A new magnetic mineral based technique for detecting hydrocarbons. (2009-2012)

Chang,L, Determining the fundamental properties of greigite (Fe3S4). (2005-2009)

Paterson,GA, A new approach to determining the ancient geomagnetic field intensity using pyroclastic deposits. (2005-2009)

Barron,L, How do magnetic intergrowths in nanoscale intergrowths affect palaeomagnetic interpretations? (2006-2011)