2012-2014 Postdoctoral research fellow, Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington D.C.
2012-2014 Research associate, Geology Department, University of Maryland
2012-2009 Ph.D., Laboratoire Magmas et Volcans, Université Blaise Pascal, Clermont-Ferrand, France
2007-2009 MSc Laboratoire Magmas et Volcans, Université Blaise Pascal, Clermont-Ferrand, France
Unités de recherche
Projets de recherche en cours
What is the nature and timing of the major events affecting the chemistry of the early Earth's mantle?
Understanding early Earth's differentiation entails the interrogation of the oldest rocks that can be sampled on the Earth's surface. Rocks older than 3.8 Ga are rarely preserved, leaving many open questions about the earliest differentiation events experienced by Earth. The Saglek-Hebron gneiss complex in Northern Labrador comprises gneisses with zircons dated as old as 3.8 Ga (Collerson et al., 1991; Schiotte et al., 1989) and metaperidotites as old as 4 Ga (Collerson et al., 1991), yet is still relatively uncharacterized. This gneiss complex includes multiple enclaves of volcano-sedimentary sequences over an area of ~2500 km2. During the summer of 2014, together with Dr. J. O'Neil (University of Ottawa), we have performed a first sampling of the area, collecting over 150 rocks from various lithologies (metasedimentary rocks, metabasalts, metaperidotites and gneisses). We will perform a study of the metasedimentary rock collections from different greenstone belts in the Saglek-Hebron complex. Analysis of the petrological features of the metasediments will help determining their metamorphic history, in particular the maximum pressure and temperature at which the rocks were buried. We will also conduct U-Pb and Hf isotopic analyzes on zircons to constrain the source and the age of the metasedimentary rocks. This project will be performed in collaboration with Dr. M. Garçon (Laboratoire Magmas et Volcans), who has extensive experience working with Archean sediments. Samples with indigenous W will be selected to perform high precision measurements of 182W, coupled with the measurement of highly siderophile element abundances. The results of these analyses will help to constrain the differentiation history of the Northern Labrador mantle, and these results will be compared with the differentiation history of the southwest Greenland mantle. This study will further provide the opportunity to evaluate the extent of the W isotopic heterogeneities in the Archean mantle.
Survival of primitive heterogeneities in the mantle
How planets formed and how they evolved through time is a fundamental question in Earth and planetary sciences. However, our planet has been geologically active for over four and a half billion years. This geologic activity has overprinted much of the direct evidence for processes involved in the Earth's formation and its initial chemical differentiation into core, mantle, crust and atmosphere. Geochemical and numerical models and planetary analogs suggest that Earth accreted from complex processed materials and then evolved rapidly after its formation. Early events such as core segregation, mantle differentiation and crust formation seem to have occurred shortly after the Earth's accretion. The composition of the Earth's mantle was further modified by the addition of meteoritic material at the last stages of its formation. In the past few years, new opportunities to learn about early Earth history have opened up with the development of analytical techniques that allow high-precision analysis of various short-lived radioactive isotopic systems. Observations from these systems suggest that mantle domains formed during the initial differentiation of the Earth's interior have survived to the present day. These primordial mantle domains hold important information about the Earth's formation, and timing of their survival in the convective mantle help constraining the dynamics of the Earth during its early stages of development.
First stages of planetary formation and evolution
Sequestration of the highly siderophile elements (HSE) to the Earth's core during primary differentiation explains the low concentrations of these elements in the Earth's mantle. However, abundances of HSE in the terrestrial mantle actually are higher than predicted based on low-pressure experimental data, and their relative abundances are very similar to chondrites - the meteorites that are thought to be the building blocks of planets. The current hypothesis that best explains the higher than expected abundances of HSE in the mantle is that they were added by late accreted planetesimals after chemical communication between the core and the mantle ceased. Ancient mantle domains have recently been recognized with excesses of 182W compared to modern mantle compositions, and could represent mantle reservoirs that had not received their full late accretionary component. Recently, differences in 182W between the Earth and the Moon were also discovered (Touboul et al., 2015; Kruijer et al., 2015) , corroborating the presumption that the isotopic compositions of both bodies diverged after lunar formation as a result of disproportional late accretion to the Earth and to the Moon. Clues to the origin of HSE abundances in Earth's mantle and the late accretion hypothesis can come from comparisons of the Earth with the differentiated asteroid Vesta. The asteroid Vesta is believed to represent the first stage of formation of planetary building blocks. Apparent chondritic relative abundances of HSE in Vesta's mantle (Day et al., 2012), as for the Earth's mantle, are inconsistent with core-mantle equilibrium after core segregation. Howardites, eucrites and diogenites (HED) are a suite of meteorites that, based on spectroscopic data, may have originated from the differentiated asteroid Vesta (e.g. Scott et al., 2009). From this suite of meteorites, diogenites are cumulative orthopyroxenites from mafic melts or mantle materials, and are the main focus of this project.
Affiliations externes principales
- "Memories of Earth Formation in the Modern Mantle: W Isotopic Composition of Flood Basalt Lavas". AGU Fall Meeting 2015 San Francisco
- "Memories of Earth Formation in the Modern Mantle: W Isotopic Composition of Flood Basalt Lavas". 25th annual V.M. Goldschmidt Conference 2015, Prague, Czech Republic
- "Early differentiation processes recorded by 142Nd and 182W in Eoarchean rocks from Isua". Joint GACMAC-Spring AGU Meeting 2015, Montreal.
- "Early differentiation processes recorded by 142Nd and 182W in Eoarchean rocks from Isua". AGU Fall Meeting 2014, San Francisco.
- "Reconciling 182W/184W variability in the Archean mantle with W partition coefficients for metal-silicate differentiation". The Geochemical Society of America Meeting 2014, Vancouver.
- "Multiple early Earth differentiation events revealed by 142Nd, 182W, and HSE abundances in Isua samples". 24rd annual V.M. Goldschmidt conference 2014, Sacramento, USA.
- "Early mantle composition and evolution inferred from 142Nd and 182W variation in Isua samples". AGU Fall Meeting 2013 San Francisco.
- "Early mantle composition and evolution inferred from 142Nd and 182W variation in Isua samples". 23rd annual V.M. Goldschmidt conference 2013, Florence, Italy.
- "Early mantle dynamics inferred from 142Nd variations in Archean rocks from southwest Greenland". 22nd annual V.M. Goldschmidt conference 2012, Montreal, Canada.
- "Variation in 142Nd/144Nd of Archean rocks from southwest Greenland: Implications for early Earth mante dynamics". EGU General Assembly 2012.
- "A coupled Nd and Hf isotopic study of Isua Archean rocks and the differentiation of the Hadean mantle". AGU Fall 2010 San Francisco.
- Outstanding Young Scientist Award 2013 given by the city of Clermont-Ferrand
- Excellence scholarship from CONACyT for graduate studies (Mexico, 2009)
Organization of seminars Geotop-UQAM
Représentante du Doyen
- O’Neil, J., Rizo, H., Boyet, M., Carlson, R.W. et Rosing, M.T. Geochemistry and Nd isotopic characteristics of Earth’s Hadean mantle and primitive crust. Earth and Planetary Science Letters.
Notes: Article accepté
- Rizo, H., Walker, R.J., Carlson, R.W., Mukhopadhyay, S., Francis, D. et Jackson, M. Memories of Earth Formation in the Modern Mantle : W Isotopic Composition of Flood Basalt Lavas. Science.
- Rizo, H., Walker, R.J., Carlson, R.W., et al. (2016). Early Earth differentiation investigated through 142Nd, 182W, and highly siderophile element abundances in samples from Isua, Greenland. Geochimica et Cosmochimica Acta, 175, 319–336. http://dx.doi.org/10.1016/j.gca.2015.12.007.
- Jackson, M.G., Shirey, S.B., Hauri, E.H., Kurz, M.D. et Rizo, H. (2016). Peridotite xenoliths from the Polynesian Austral and Samoa hotspots: Implications for the destruction of ancient 187Os and 142Nd isotopic domains and the preservation of Hadean 129Xe in the modern convecting mantle. Geochimica et Cosmochimica Acta. http://dx.doi.org/10.1016/j.gca.2016.02.011.
- Rizo, H., Boyet, M., Blichert-Toft, J. et Rosing, M.T. (2013). Early mantle dynamics inferred from 142Nd variations in Archean rocks from southwest Greenland. Earth and Planetary Science Letters, 377-378, 324–335. http://dx.doi.org/10.1016/j.epsl.2013.07.012.
- Rizo, H., Boyet, M., Blichert-Toft, J., O'Neil, J., Rosing, M.T. et Paquette, J.-L. (2012). The elusive Hadean enriched reservoir revealed by 142Nd deficits in Isua Archaean rocks. Nature, 491(7422), 96–100. http://dx.doi.org/10.1038/nature11565.
- Gannoun, A., Boyet, M., Rizo, H. et El Goresy, A. (2011). 146Sm-142Nd systematics measured in enstatite chondrites reveals a heterogeneous distribution of 142Nd in the solar nebula. Proceedings of the National Academy of Sciences of the United States of America, 108(19), 7693–7697. http://dx.doi.org/10.1073/pnas.1017332108.
- Rizo, H., Boyet, M., Blichert-Toft, J. et Rosing, M. (2011). Combined Nd and Hf isotope evidence for deep-seated source of Isua lavas. Earth and Planetary Science Letters, 312(3-4), 267–279. http://dx.doi.org/10.1016/j.epsl.2011.10.014.
- Carlson, R.W., Boyet, M., O’Neil, J., Rizo, H. et Walker, R.J. (2015). Early differentiation and its long term consequences for Earth evolution. Dans J. Badro et M. M. Walter (dir.). The Early Earth.
Notes: AGU Geophysical Monograph Series