Return to page

Academic Staff


Professor Chris MacLeod

Chris’s principal scientific interests centre on the processes of formation and deformation of ocean lithosphere at mid-ocean ridges. He is presently focusing his research on detachment fault processes at slow-spreading ridges and on the mechanisms of accretion of the lower crust at fast-spreading ridges. His work is mostly based around meso-scale geological and geophysical investigations of modern ocean floor, and field-based studies of ophiolite complexes (principally Oman and Cyprus).

Before coming to Cardiff in 1995 Chris worked at the Institute of Oceanographic Sciences in Wormley (now relocated to the National Oceanography Centre in Southampton) and University of Leicester on the structural geological applications of borehole geophysical data. Before that he had held post-doctoral research fellowships at the Open University and the Université de Montpellier 2 in France, studying ocean-floor processes as recorded in ophiolite complexes.

Since 2005 Chris has been seconded from the School of Earth, Ocean & Planetary Sciences to run the European science planning office of the Integrated Ocean Drilling Program (IODP). He is returning to normal university duties in October 2007. He teaches courses in plate tectonics and geodynamics at second, third and fourth year undergraduate level, and leads the Year 3 fieldcourse to Cyprus.

Accretion of the lower oceanic crust at fast-spreading ridges: a rock drill and near-bottom seafloor survey in support of IODP drilling in Hess Deep (with Dr. Damon Teagle, National Oceanography Centre, Southampton). NERC grant NE/C509023/1 (£332,992). Generation of ocean lithosphere by seafloor spreading at the 60,000km-long chain of mid-ocean ridges is one of the fundamental geological processes operating on Earth. One of the most important problems is to understand how magma generated in the mantle beneath ridges builds the ocean crust, which floors 60% of the surface of the Earth. Studying the deeper part of the crust (formed in a sub-seafloor magma chamber) is difficult as it is usually blanketed by submarine lava flows. This is particularly acute for crust formed at fast spreading rates. The only known exception is a 5400m-deep submarine rift valley in the eastern Equatorial Pacific known as Hess Deep, where the valley walls expose a complete cross-section through the ocean crust into the underlying mantle. This unique section has previously been the subject of several piecemeal submersible investigations, and an IODP project to carry out deep-penetration drilling in Hess Deep has been proposed; however, far more detailed knowledge of the background geology is required before resources can be committed.

In January 2008 Chris will lead a NERC-funded cruise to Hess Deep in the UK’s new research ship RRS James Cook. The aim of the expedition is to make a detailed sonar and optical survey of the lower crustal section in Hess Deep using the UK’s ISIS remotely-operated vehicle in order to support future IODP operations. In addition the survey will be used as the basis for a sampling programme using the British Geological Survey’s ‘BRIDGE’ seabed rock drill. With this unique device Chris and colleagues will attempt to obtain large numbers of short (1m-long) orientated cores to construct a transect through the lower crust. To these samples a variety of geochemical and geophysical measurements will be made, with the intention of (for example) constraining heat and mass flux from the Earth’s mantle to crust and crust to ocean, and testing competing models for the functioning of mid-ocean ridge magma chambers.

Prof Chris MacLeod - Cardiff School of Earth and Social Sciences
Launching the TOBI deep-towed
sidescan sonar vehicle. 

Geological and Geophysical Studies of the Mid-Atlantic Ridge, 12º30’N to 14º30’N (with Prof. R.C. Searle, Durham University and Dr. B.J. Murton, National Oceanography Centre, Southampton). NERC grant NE/B500058/1 £147,575 (Cardiff award; total £268,067).

In March-April 2007 Chris took part in cruise JC007, the maiden scientific voyage of RRS James Cook. During this NERC-funded expedition a deep-towed TOBI sidescan sonar survey of the Mid-Atlantic Ridge axis in the 13°N region was conducted, and the region sampled by dredging and by using the British Geological Survey’s BRIDGE seabed rock drill. The project aims to provide constraints on the processes of lithospheric accretion and mechanisms of plate separation at a magma-starved mid-ocean ridge, including further insights into the development of oceanic core complexes.

Prof Chris MacLeod - Cardiff School of Earth and Ocean Sciences
Chris separating volcanic glass
from pelagic mud in a dredge haul,
Mid-Atlantic Ridge, 14°N 45°W. 

The expedition received extensive media coverage worldwide (e.g. http://news.bbc.co.uk/1/hi/wales/6405667.stm), and was followed live by the general public via the cruise web site http://www.classroomatsea.net/JC007/

Ongoing/recent Research Projects

The British Geological Survey’s ‘BRIDGE’ rock drill, as depicted on the November 2002 cover of ‘Geology’.

Origin of oceanic core complexes In 2001 Chris led a NERC-funded expedition (with Dr. J. Escartin, IPG Paris) on RRS James Clark Ross to investigate the origin of oceanic core complexes: flat-topped massifs with prominent spreading-direction-parallel striations recently discovered at slow-spreading mid-ocean ridges. Mantle and lower crustal lithologies are associated with these massifs, which have been interpreted as representing the footwalls of major detachment faults. Using the BRIDGE rock drill 63 sites were successfully cored on one such massif at 15°45’N, providing the first substantive in situ sampling of an oceanic core complex. Chris and colleagues showed that the striated surface of the massif is composed predominantly of low-temperature talc-bearing schistose fault rock formed within a major detachment fault zone. They were able to demonstrate that dramatic strain localisation occurred as water penetrated along the detachment and formed weak scaley hydrous minerals on the fault plane. Continuing studies of the small-scale structure and palaeomagnetism of the geographically orientated cores (with Dr. J. Carlut, ENS Paris, and Dr. Escartin) are helping to unravel the kinematics of core complex formation and mantle exhumation at the mid-ocean ridge axis.

Prof Chris MacLeod - Cardiff School of Earth and Ocean Sciences
The British Geological Survey’s
‘BRIDGE’ rock drill, as depicted on
the November 2002 cover of ‘Geology’. 

Previously, Chris co-led (with Dr. H. Dick, Woods Hole) an expedition on RRS James Clark Ross to Atlantis Bank, a gabbro massif on the Southwest Indian Ridge. This is an oceanic core complex also, though the deformation mechanisms are different from the 15°45’N example. In conjunction with ODP drilling this study is helping in our understanding of the relationship between magmatism and deformation in slow-spreading environments.

Orientated BRIDGE drill core of mylonitic gabbro, SW Indian Ridge

Oman ophiolite Since 1988 Chris has been conducting field-based investigations of the ophiolite of the Sultanate of Oman. The Semail nappe in Oman and the United Arab Emirates is the largest and best-preserved ophiolite in the world, and offers a unique opportunity to study mid-ocean ridge processes in detail. It is believed to have formed at a fast-spreading ridge and, until we can learn more about Hess Deep (see above), has guided most of our ideas about crustal accretion at fast spreading rates. Chris has conducted a study of sheeted dyke-gabbro relationships across the ophiolite with the aim of understanding the spreading structure of the Oman palaeo-ridge and the nature of the top of the axial magma chamber. By means of coupled structural and petrological and geochemical studies of intact lower crustal sections he and his research students/post-docs have been able to document some of the physical and chemical processes operating in the magma chamber and place important constraints on the mechanisms of crustal accretion.

Prof Chris MacLeod - Cardiff School of Earth and Ocean Sciences

Orientated BRIDGE drill core of mylonitic gabbro, SW Indian Ridge 

Chris in the field in the Oman ophiolite. The crust-mantle boundary - the 'Moho' - lies below the mountain top on the extreme right of the picture.

 

 

 

 

Summary of external activities:ESSAC Chair and head of the ESSAC Office, 2005-2007, Chris is currently the Chair of ESSAC, the ECORD Science Support and Advisory Committee (http://www.essac.ecord.org). The European Consortium for Ocean Research Drilling (ECORD) is the organisation through which 16 European nations (plus Canada) participate in IODP. ESSAC provides science advice to ECORD and coordinates ECORD’s scientific activities in IODP (http://www.iodp.org). ESSAC is responsible for the selection of European scientists for IODP expeditions and for IODP’s Science Advisory Structure panels. The ESSAC Office, based in Cardiff, organises or sponsors outreach activities such as the ECORD Distinguished Lecturer Programme, annual IODP-themed summer schools in Urbino and Bremen, and a scholarship scheme for outstanding young IODP scientists.

Prof Chris MacLeod - Cardiff School of Earth and Ocean Sciences

Chris in the field in the Oman
ophiolite. The crust-mantle
boundary - the 'Moho' - lies
below the mountain top on the
extreme right of the picture. 

ECORD representative, IODP Science Planning Committee, 2003-2007 Chris is one of four ECORD scientists serving on the highest level committee of the IODP Science Advisory Structure, which deals with all scientific coordination and planning within IODP, including ranking of proposals and scheduling of IODP cruises. Responsibilities include ensuring that European rights and interests are met within IODP.

NERC UKIODP Grants Committee and Strategy Group member, 2003-present Responsible for overseeing the UK’s contribution to IODP (through ECORD), which is supported by the Natural Environment Research Council. Chris is also a member of the committee that reviews IODP-themed NERC grant proposals.

InterRidge Deep Earth Sampling Working Group member, 2004-present