Les terres rares et les isotopes radiogéniques comme traceurs d'échange et de transfert dans les cycles géochimiques externes

Abstract : This habilitation thesis is entitled "tracing of exchange and transfer processes in surface geochemistry by rare earth elements (REE) and radiogenic isotopes". It presents a summary of my research realized since 1995 as post-doctoral fellow at the "Centre de Géochimie de la Surface" in Strasbourg and since 1998 as lecturer ("Maître de conférences") at the university of Franche-Comté in Besançon. The common topic of all these studies are chemical exchange and transfer processes in surface environments, using as principal tracers the rare earth elements (REE) and the radiogenic isotopes of Sr and Nd.
I have followed a classical formation in geology and sedimentology, that I completed during my PhD thesis with the tools of elementary and isotope geochemistry. The beginning of my post-doctoral years marks a break with my previous research: I abandoned the problems of palegographic and paleotectonic reconstructions and switched completely to surface geochemistry.
This reorientation started with a study of a heavy-metal contaminated soil near Basel (Switzerland), followed by a project on the migration of REE in salt deposits in Germany, within the framework of feasibility studies on the storage of radioactive waste in salt diapirs. I continued my research with projects on interstitial fluid circulation in the barrier reef of Tahiti and on low temperature hydrothermal processes on the Cocos plate. After this incursion to the marine environment, I returned to the continents with projects on REE transport in streams of the Massif Central and REE exchange processes between soils and vegetation. This latter study is actually running on field sites in the Jura and Vosges mountains, and on the inactive volcano of Kaiserstuhl (in the Rhine plain near Freiburg, Germany). All these projects were realized in numerous collaborations.
In spite of the variety of study objects and environments, we regularly found that the chemical exchange and transfer processes were controlled by similar mechanisms. The identification of these mechanisms was based on a combined approach using REE, radiogenic isotopes and complementary tools, such as major elements or mineralogy. In many cases, the mobility of the REE and other trace metals was directly related to the presence and the stability of accessory minerals, such as apatite or Fe-Mn oxyhydroxides. For water samples, we found an important role of colloidal particles and vegetation, in addition to more "classic" parameters such as pH, Eh, solution complexation, or sorption. Therefore, our future research will be focused more precisely on the importance of colloids and vegetation for REE transport and fractionation in surface environments.
The REE are today a powerful geochemical tracer, that can be determined in most samples by ICP-MS without specific preparation procedures and additional costs. Therefore, we think that the REE should systematically be included in routine chemical analyses by ICP-MS. However, in some cases, the REE data should be combined with isotope data in order to eliminate ambiguities in the interpretation of the REE patterns.
Document type :
Habilitation à diriger des recherches
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00349272
Contributor : Marc Steinmann <>
Submitted on : Saturday, December 27, 2008 - 2:50:50 PM
Last modification on : Wednesday, September 5, 2018 - 5:04:02 PM
Long-term archiving on: Saturday, November 26, 2016 - 4:00:17 AM

Identifiers

  • HAL Id : tel-00349272, version 1

Citation

Marc Steinmann. Les terres rares et les isotopes radiogéniques comme traceurs d'échange et de transfert dans les cycles géochimiques externes. Planète et Univers [physics]. Université de Franche-Comté, 2008. ⟨tel-00349272⟩

Share

Metrics

Record views

448

Files downloads

4209