HYDRASA Team

General presentation

Managers: Richard GIOT et Fabien HUBERT

The general theme of the HydrASA team (Hydrogeology, Clays, Soils, Alterations) focuses on understanding and modeling transfers in reactive geosystems.

These reactive geosystems refer to a wide variety of natural objects of very different characteristic dimensions:

Clay minerals and their aggregates (from nanometers to hundreds of micrometers)
Clay soil profiles (from centimetre to ten metres)
Large geological systems (from 100 metres to 100 kilometres)

HydrASA, two strong cognitive challenges:

Connect the different space scales involved through these objects. To understand the implementation of large geological systems and their transfer properties, it is also necessary to (a) understand the physico-chemical processes operating at the solid (mineral) –liquid (electrolyte) and (b) interface and the organization (microstructure) the geological materials involved.
Integrate large time scales (geological time) into our approaches. It is an imperative specificity when geological or soil objects are studied. Transfers concern the transport of masses (fluids or elements in solution) but also the transfer of energy (heat transfer).

The advantages: international visibility thanks to an ability to mobilize multiple skills (mineralogical, crystalllochemical, microstructural and geomechanical) for the study of clay environments and materials. It is undoubtedly this skill set that enabled the team to host in Poitiers the Master National Argiles and the Master Erasmus Mundus IMACS (International Master in Clay Science) under the responsibility of HydrASA.

The existence of a Hydrogeological Experimental Site (SEH) in Poitiers, which is one of the 7 sites of the National Network of Hydrogeological Sites (Observation Service H+ labelled by the INSU) also contributes to the national and even international visibility of the team.

The international visibility of the team has also increased since 2010 by the discovery by a core of researchers of HydrASA, fossils of the oldest known pluricellular organisms (2.1 Billion years) in a Gabonese sedimentary basin. Since then, HydrASA has been piloting an international program on the study of palaeoenvironments related to these primitive living organisms, the characterization of which will help to better understand the appearance of life on Earth.

Research Axis

Axis 1: Functioning of reactive geosystems (soils, sedimentary basins, aquifers, hydrothermal systems and more broadly systems of alteration)

1. understand the establishment and past functioning of geological systems involving fluid/rock/living interactions (organisms or microorganisms)
2. specify the response of these environments to anthropic activity.

The objective of the research is to integrate numerous data and observable of various origins (outcrops or soil pits, petrographic, petrophysical and mineralogical data, drilling/pumping data etc.) in order to describe and/or predict the transformations of the studied rocks and more broadly the functioning of the geosystem in which they are located.

Axis 2: Properties and reactivity of solutions/clay mineral systems

Axis 3: Spatialization and multi-scale modeling of reactive transfer

The studies of distribution and identification of reactive phases (axis 1) and their reactive properties (axis 2) must be supplemented by a fine analysis of the organization of porous media (grains and pores) All these data constitute essential information for scale transfer.

Research in this area aims to develop:

Tools for mineral and poral mapping of natural thin-blade systems (mesoscopic scale)
numerical modeling tools (e.g., homogenization models, finite volume models, inverse-approach models)

allowing the scaling of elementary processes at the solution/mineral interfaces to the spatial scales of interest (soil profile, aquifer, weathered rock).

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