Côme Lefebvre
My general interest about rock exhumation processes
My researches mainly focus in provinces affected by regional extension. In this geodynamical context, “deep rocks” may be exhumed and reach the surface. Timing, deformation structures and metamorphism associated with this large scale phenomena are my principal interests. Since a couple of years, I concentrated my studies on two distinct research topics:
- Exhumation of ultramafites in context of Oceanic Spreading and Ocean/Continent Transition
- Exhumation of crystalline rocks involved in Alpine North South shortening in Central Turkey
Current research projects:
- Tectono-metamorphic evolution, timing and mechanism of Cenozoic exhumation of the Central Anatolian Crystalline Complex, Central Turkey . Supervisors: Prof. Dr. Reinoud Vissers and Dr. Douwe Van Hinsbergen
Current Phd project in Utrecht University – The Netherlands
The Alpine-Himalayan orogen essentially formed in response to northward subduction of the Neotethyan Ocean along the southern margin of Eurasia during Late Mesozoic - Cenozoic convergence. In the eastern Mediterranean part of the orogen there is widespread evidence for mostly Neogene collapse of this mountainbelt as a result of roll-back and slab break-off. Widespread extension, however, has also affected the orogen as early as the late Cretaceous, leading to e.g. the opening of the Black Sea generally interpreted as a back-arc basin. The Central Anatolian Crystalline Complex (CACC) (see illustration below) shows late Cretaceous regional high-temperature metamorphism and widespread felsic intrusion before pre-Lutetian exhumation, suggesting that exhumation of the CACC and the opening of the Black Sea were associated with an orogen-scale process involving an abnormally hot mantle. The proposed project aims to add not only to the recognition of this geodynamic processes in Anatolia and the Black Sea, but to a general and largely unrecognised problem of orogenic collapse well before ocean closure.
This field-based project is focussed on three main aspects of the CACC as follows.
(1) The PTt evolution of the crystalline rocks of the CACC will be studied to place the metamorphism with estimated climax conditions of 6-7 kbar and 750°C, and the subsequent intrusion by syentic-monzonitic and/or granodioritic plutons, in the context of a tectono-metamorphic evolution of the CACC. A field- and microscale structural study allied with thermobarometry and chemical Monazite U-Th-Pb age dating is proposed to reveal details of this evolution with time.
(2) A prime aim of the project is to test whether the CACC was exhumed along one or more extensional detachments and if so, to determine rate and direction of exhumation and the large-scale extensional geometry.
(3) Post-Eocene deformation, evidenced by thrusts and folds affecting the Eocene and younger sediments overlying the CACC, will be studied to estimate in how far the CACC was a coherent large-scale continental block during the early Tertiary, or since when the CACC obtained its present-day geometry. To this end a strong interaction is proposed with current paleomagnetic studies within the ISES context, to reveal since when the CACC became a more or less coherent continental fragment.
- Microstructural characteristics and metamorphic changes of deformed serpentinite rock-type in context of oceanic exhumed ultramafites in Corsican ophiolite
In collaboration with Alain Chauvet Chargé de Recherche CNRS- Geosciences Montpellier – France, and Muriel Andréani Maître de Conférence – UCB Lyon - France Msc in Geosciences Montpellier
- Sedimentary reworking of peridotites and mantle exhumation setting in Lherz - The Pyrenees
In collaboration with Yves Lagabrielle Chargé de Recherche CNRS- Geosciences Montpellier – France) Hobby project
Geodynamic model of mantle exhumation in the peculiar context of the Pyrenean belt. (a) Timing of rotation of Iberia after Olivet et al., 1995), thick green lines indicate zones of active mantle exhumation. (b) Cartoon showing the locus of possible mantle exhumation in pull-apart basins. (c) Details of the exhumation zone and evolution of the zone of exhumed mantle during basin inversion due to the Pyrenean orogeny.
From Yves Lagabrielle and Jean-Louis Bodinier, Submarine reworking of exhumed subcontinental mantle rocks: field evidence from the Lherz peridotites, French Pyrenees,Terra Nova, 20, 11-21, 2008
Research funding
My research in Turkey is funded by 
Integrated Solid Earth Science (ISES)
My research in the Pyrenees and Corsica is funded by
Groupe De Recherche MARGES
Past and present
- Since Sept. 2007 PhD student Utrecht University, The Netherlands
- 2006-2007 MSc (M2) Earth Research Environment Geoscience Montpellier, France
- 2005-2006 MSc (M1) Physics and Chemistry of the Earth and Planets ENS Lyon, France
- 2004-2005 BSc (L3) Physics and Chemistry of the Earth and Planets ENS Lyon, France
- 2002-2004 Diploma of Higher Education (L1 & L2) Earth and Universe Sciences UCB Lyon University, France
- June 2002 A levels Scientific option Jean Moulin College LYON 5e, France
Publications
(in process…)
Publications submitted/in preparation
1. Lefebvre C., Chauvet A., Andréani M., Meresse F., LagabrielleY., Serpentinites tectono-metamorphic evolution in oceanic detachment fault system: Contribution from the study of the Inzecca ophiolite (Alpine Corsica) [Writing in process]
Refereed Conference Proceedings
C6. C. Lefebvre, D. van Hinsbergen, R. Vissers, Tectonic denudation of the high-grade Kırşehir block, Central Anatolian Crystalline Complex, Turkey, 9th Nederlands Aardwetenschappelijk Congres, 18 and 19 March 2008 at Koningshof, Veldhoven
C5. E. Gülyüz, A. Peynircioğlu, A. Koç, D. van Hinsbergen, C. Lefebvre, N. Kaymakci, R. Vissers, Eo-Oligocene compression following exhumation of the Central Anatolian Crystalline Complex: detailed basin analysis around the Çiçekdağ anticline, 9th Nederlands Aardwetenschappelijk Congres, 18 and 19 March 2008 at Koningshof, Veldhoven
C4. C. Lefebvre, A. Chauvet, M. Andréani, F. Meresse, Y. Lagabrielle, E. Masini, Relics of oceanic detachment-related structures within the Corsican ophiolites : witnesses of possible Tethyan OCT, «Ocean Continent Transition / Transition Océan Continent », Institut océanographique de Paris, 19-21 septembre 2007 Colloque de l’Académie des sciences
C3. Y. Lagabrielle, J.-L. Bodinier, J.-M. Dautria, V. Vignon, M. Neumaier, C. Lefebvre, Ultramafic debris flows in the Lherz region and the exhumation of the subcontinental Pyrenean mantle, «Ocean Continent Transition / Transition Océan Continent », Institut océanographique de Paris, 19-21 septembre 2007 Colloque de l’Académie des sciences
C2. P. H. Leloup, C. Sassier, D. Rubatto, C. Lefebvre, Y. yue, l. Ding (AGU 2006), Comparison between direct and indirect estimates of ductile strain rates in a major lithospheric continental shear zone: the Ailao Shan Red River, American Geophysical Union, Fall Meeting 2006, 2006AGUFM.T31C0471L
C1. C. Sassier, C. Lefebvre and P.H. Leloup (EGU 2006), Testing paleo-piezometers: constraints from a natural example, Geophysical Research Abstracts, Vol. 8, 01698, 2006 SRef-ID: 1607 7962/gra/EGU06-A-01698