Office Phone: 307-721-5082
Fax Phone: (307) 766-6679
P.O. Box 3006 Laramie, Wyoming 82071-3006
Office Room No: GE 221
Geophysics, PhD, Cambridge University, UK, 1989 Geophysics, MS, Cornell University, 1984 Geology, BA, Oxford University, UK, 1981
I have on-going projects to study:
- Processes at slow spreading ridges: How is mantle deformed and exposed at these ridges? What is the origin of anomalous uplift seen at inside corner highs and along transverse ridges? How does magmatism occur at ultraslow spreading ridges? How deep does water penetrate down oceanic detachment faults? And how do oceanic core complexes form? Slow spreading ridges are 'arguably' one of the last frontiers of plate tectonics, and there are lots of fascinating questions to investigate. Professor Barbara John and I have a group who use all techniques (structure, petrology, geochemistry & geophysics) to study these problems. In particular, we are applying geo-chronologic and thermochronologic methods to help solve these problems. We are one of the first groups on the world to do this. Put simply, uranium bearing minerals, such as zircon are much more common in oceanic crust than conventionally thought (see pubs. below) and this is allowing us to apply all the techniques developed for continental crust to the study of cooling rates, accretion rates and faulting rates at Mid Oceanic Ridges. We have NSF funding for this research and much of the geochronologic work is done in conjunction with Joe Wooden at the Stanford/USGS SHRIMP facility. An important component of work is “going to sea” to collect samples and explore the seafloor; our students have enjoyed cruises to the Pacific, Atlantic and Indian Oceans. Current research areas: the Mid Cayman Rise, the South-West Indian Ridge, the Mid Atlantic Ridge and the Gakkel Ridge.
- Processes at fast spreading ridges: How does oceanic crust form? How fast does it accrete? How is the deformation associated with plate spreading accommodated? How do the gabbro fabrics form? My group is working on gabbros recovered from two of the three explored localities that expose significant sections of gabbroic lower crust in the Pacific Ocean: Hess Deep and Pito Deep. I’ll be sailing on IODP Leg 345 in 2012-13.
- Processes in intrusions: How big are magma chambers? How do igneous cumulates form? What processes occur in magma chambers? For example, is compaction or porous media convection more important? And where and how do platinum deposits form? I have a NSF funded project in collaboration with Jeff Gee at Scripps to study the Dufek Intrusion in Antarctica; arguably the second biggest layered intrusion in the world. In January 2007, we spent 5 weeks collecting over 900 samples from the lower part of the intrusion. All of these samples are oriented and we have a whole series of projects to look at the petrology, fabrics and magnetics of these samples. I’m also looking to start work on the Laramie Anorthosite which is just a few miles away from the University. Current research areas: Laramie Anorthosite, Wyoming; Dufek, Antarctica; Stillwater, Montana; Rum, N.W. Scotland; Bushveld, South Africa.
- The microstructure of rocks: The Department has two SEM’s with Electron Back Scatter Diffraction (EBSD) systems, which allows us to quickly quantify the crystallographic fabrics of rocks. We can use EBSD to study deformation mechanisms in rocks and therefore to understand how rocks can flow, and fault. We’ve looked at the deformation mechanisms of the Kane Oceanic Core Complex Detachment Fault. Chris Christofferson, a Masters student, has recently compared gabbroic crust from fast and slow spreading ridges with gabbros from layered mafic intrusions and has found them all to be different. Other students have looked at the clustering and organization of crystals in rocks. We can also use the EBSD system to understand how igneous cumulates are formed. I currently have projects to look at the fabrics, deformation and accumulation processes of oceanic gabbros and mantle peridotites. Current research areas: All those listed in the projects above.
Recent Publications (2012-2005)
* denotes student first author
Schoolmeesters, N., Cheadle, M.J., John, B.E., Reiners, P.W., Gee, J. and Grimes, C.B.,, The cooling history and the depth of detachment faulting at the Atlantis Massif oceanic core complex: Geochem. Geophys. Geosyst. (accepted),
Holness, M.B., Sides, R. Prior, D.J., Cheadle, M.J., & Upton, B. G. The peridotite plugs of Rum: crystal settling and fabric development in magma conduit, Lithos, Volumes 134–135, March 2012, Pages 23-40 .
Grimes, C. B., M. J. Cheadle, B. E. John, P. W. Reiners, and J. L. Wooden (2011), Cooling rates and the depth of detachment faulting at oceanic core complexes: Evidence from zircon Pb/U and (U-Th)/He ages, Geochem. Geophys. Geosyst., 12, Q0AG01, doi:10.1029/2010GC003391.
John, B.E., and Cheadle, M.J., 2010, Deformation and alteration associated with oceanic and continental detachment fault systems: are they similar?: in Rona, Devey, Dyment, and Murton, eds., Diversity of Hydrothermal Systems on Slow-spreading Ocean Ridges, AGU Monograph 188, p. 175-206.
Cheadle M.J. & Grimes, C.B., 2010. To Fault or Not to Fault, Nature Geosciences, News & Views, vol 3 454-456.
John, B.E., and Cheadle, M.J., 2010 Deformation and alteration associated with oceanic and continental detachment fault systems: are they similar?: in Rona, Devey, Dyment, and Murton, eds., Diversity of Hydrothermal Systems on Slow-spreading Ocean Ridges, AGU Monograph p 175-205.
Schwartz, J.J., John, B.E., Cheadle, M.J., Wooden, J., Mazdab, F., Swapp, S, and Grimes, C.B., 2010, Dissolution-Reprecipitation of Igneous Zircon in Mid-Ocean Ridge Gabbro, Atlantis Bank, Southwest Indian Ridge: Chemical Geology, vol 274, p68-81.
Michael, P.J. & Cheadle, M.J., 2009, Making Crust. Science. (Perspectives) Vol. 323. no. 5917, pp. 1017 – 1018 DOI: 10.1126/science.1169556.
*Schwartz, J.J., John, B.E., Cheadle, M.J., Reiners, P., & Baines, A.G., The cooling history of Atlantis Bank oceanic core complex: evidence for hydrothermal activity 2.6 Myr off-axis. Geochemistry, Geophysics, Geosystems (G3), 2009.
*Baines, G., Cheadle, M.J., John, B.E., Grimes, C.B., and Wooden, J., Rapid accretion of gabbroic crust at Atlantis Bank on the ultra-slow-spreading SW Indian Ridge: EPSL, 2009 .
*Grimes, C.B., John, B.E., Cheadle, M.J., Mazdab, F.K., Wooden, J., Swapp, S., and Schwartz, J., On the occurrence, trace element geochemistry, and crystallization history of zircon from in situ ocean lithosphere: Contributions to Mineralogy and Petrology. 2009
*Baines, A.G., Cheadle, M.J., John, B.E., and Schwartz, J.J., 2008. Rate of detachment faulting at Atlantis Bank, South-west Indian Ridge: evidence for 100% asymmetry during the formation of oceanic core complexes. Earth and Planetary Science Letters, vol. 273, 105–114. doi:10.1016/j.epsl.2008.06.013.
*Grimes, C.B., John, B.E., Cheadle, M.J., and Wooden, J.L., 2008. Evolution and timescales for accretion of slow-spreading oceanic crust: constraints from high resolution U-Pb zircon dating of a gabbroic crustal section at Atlantis Massif, 30º N, MAR: Geochemistry, Geophysics, Geosystems, vol. 9, no. 8, Q08012, doi:10.1029/2008GC002063.
*Fletcher, R.; Kusznir, N.J., Cheadle, M.J., 2008 (in press). Melt initiation and mantle exhumation at the Iberian rifted margin: Comparison of pure-shear and upwelling-divergent flow models of continental breakup. (Geophysical Journal of the Royal Astronomical Society)
*Baines, A.G., Cheadle, M.J., Dick, H.J.B., Hosford-Scheirer, A., John, B.E., Kusznir, N.J., & Matsumoto. T., 2007,The evolution of the Southwest Induan Ridge and the implications of major changes in the ridge axis geometry since 25Ma. Geochemistry Geophysics Geosystems, vol. 8, doi:10.1029/2006GC001559.
*Grimes, C.B., John, B.E., Kelemen, P.B., Mazdab, F., Wooden, J., Cheadle, M.J.,Hanghoi, K., and Schwartz, J.J., 2007, The trace element chemistry of zircons from oceanic crust: A method for distinguishing detrital zircon provenance: Geology vol. 35, 643–646, doi:10.1130/G23603A.1.
Herzberg, C., Albarede, F., Arndt, N., Asimow, P.D., Lesher, M., Niu, Y., Fitton, J.G., Cheadle, M.J., and Saunders, A.D., 2007. Ultramafic Igneous Rocks: A Challenge for Alternatives to the Plume Hypothesis. Geochemistry Geophysics Geosystems. Volume 8, No. 2, Q02006, doi:10.1029/2006GC001390.
John, B.E., and Cheadle, M.J., 2007, Slow-spreading mid-ocean ridges: McGraw-Hill Yearbook of Science and Technology, Tenth Edition.
Schroeder, T., Cheadle, M.J., Dick, H.J.B., Faul, U., Casey, J.F., and Kelemen, P.B., 2007, Non-volcanic seafloor spreading and corner-flow rotation accommodated by extensional faulting at 15°N on the Mid-Atlantic Ridge: A structural synthesis of ODP Leg 209: Geochemistry Geophysics Geosystems, vol. 8, doi:10.1029/2006GC001567.
Holness, M., Cheadle, M.J., & McKenzie, D.P. 2005 On the use of changes in dihedral angle to decode late-stage textural evolution in cumulates. Journal of Petrology46: 1565-1583; doi:10.1093/petrology/egi026
Jackson, M.D, Gallagher, K. Petford, N. & Cheadle M.J., 2005 Towards a coupled physical and chemical model for tonalite–trondhjemite–granodiorite magma formation: Lithos vol. 79, 43-60.
*Schwartz, J.J., John, B.E., Cheadle, M.J., Miranda, E., Grimes, C., Wooden, J., and Dick, H. 2005. Growth and Construction of Oceanic Crust at Slow-Spreading Ridges, Science, vol 310, p654-658.
Recent Graduate Students:
GEOL1070 - The Earth: Its Physical Environment
GEOL4835 – Applied/Exploration Geophysics
GEOL5217 – Geodynamics
GEOL 5200 – Ocean Tectonics
GEOL 5200 - Hollywood Science, Fact or Fiction?
GEOL 5200 – What’s New in Science & Nature?
I’m a process-oriented Geophysicist/Geologist who believes in a multi-disciplinary approach to solving problems in the Earth Sciences. My primary research aim is to better understand how the Earth’s crust grows and evolves. And to further this aim I study all aspects of magmatic processes from the micro- to the macroscopic scale, both on land and in the oceans. My philosophy is to combine fieldwork (both mapping & field geophysics) with laboratory based studies (geochemistry, microscopy, geochronology etc.) and with mathematical based studies whenever possible, and to go to the best possible location in the world to do this. As an example of this, my students and I have worked on projects ranging from the structural evolution of oceanic crust to mathematical modeling of the origin of granites, to the development of new techniques of textural analysis, to using reflection seismology to look at the sequence stratigraphy of layered intrusions, to doing modern geological field-work and petrologic and geochemical studies. And I’ve worked on mafic intrusions in Antarctica, Scotland, South Africa & North America; on granites in Ireland and France; on komatiites from Zimbabwe and Canada and on the oceanic crust in the Pacific, Indian and Atlantic Oceans and the Caribbean Sea.
Specific interests include:
- physics of magmatic processes
- magma migration & flow
- mantle plumes
- komatiites and the temperature of the Earth
- the application of sequence stratigraphy to mafic intrusions
- the origin of layered intrusions
- the origin of granites
- textural analysis of materials
- physical properties of two-phase systems
- fluid flow in porous media
- the origin and evolution of oceanic crust
- the mechanisms of faulting in oceanic crust
- the origin of oceanic core complexes.
I encourage my graduate students to follow my research philosophy; to tackle problems that require a multidisciplinary approach, and I hope they graduate having learned a broad range of skills that will serve them well in their future careers. If you want to learn more, please go to my personal webpage linked on this this page.