The Group on Crystal Growth and Experimental Aqueous Geochemistry of the
Department of Geology of the University of Oviedo is involved in a research network
sponsored by the European Commission. The objective of the research to
be performed by this network is the study of the dissolution and
precipitation behaviour of solid solutions. The understanding of
mineral-water reactions involving solid solutions and their quantification
through rate equations is essential for the accurate chemical modelling of
natural systems. A major result of this effort will be development of
equations and algorithms that allow for the calculation of the dissolution
and precipitation rates of natural solid solutions as a function of
temperature, pressure and fluid composition. The resulting algorithms
can be incorporated into comprehensive chemical mass-transfer algorithms
to allow predictions of the fate and consequences of chemical transport
during both natural and industrial processes.
Laboratorie de Géochimie, Université Paul
Sabatier-CNRS, Toulouse, France (Project Co-ordinator).
(Scientist in charge: Eric Oelkers. Transition state theory, bulk
measurement of dissolution/precipitation rates).
- Departamento de Geología, Universidad
de Oviedo, Oviedo, Spain. (Scientist in charge: Manuel Prieto.
Crystal growth and
experimental aqueous geochemistry
Institute, University of Iceland, Reykjavik, Iceland. (Scientist
in charge: Sigurdur Gislason. Experimental aqueous geochemistry).
- Institut fur
Mineralogie, Universitat Munster, Munster, Germany. (Scientist
in charge: Andrew Putnis. Mechanisms of dissolution/crystallisation
- Department of Geology,
University of Oslo, Oslo, Norway. (Scientist in charge: Bjorn Jamveit.
Growth and dissolution processes in hydrothermal systems).
- Department of Earth Sciences,
University of Bristol, Bristol, U.K. (Scientist in charge: Vala
Ragnarsdottir. Dissolution kinetics and mineral surface chemistry).
The project is supported by the European Commission in the framework of the
programme Improving the Human Research Potential. The total cost of
the project is 1,139,352 Euro (189.816.043 Ptas.), including the personnel
costs for six young post-doctoral researchers (one for each group). From this
total, 184,440 Euro (30.688.234 Ptas.) correspond to the group of the
University of Oviedo.
The approach to be adopted by this network is to focus in several distinct
fluid-solid solution systems of particular relevance to natural and industrial
- Characterisation of the dissolution rates of volcanic-basaltic
Because of its widespread occurrence on the ocean floor and in volcanic
terrains, its emission during volcanic eruptions, and its relatively
rapid dissolution rate, basaltic glass plays a major role in the global
flux and cycling of numerous metals and nutrients. Moreover, industrial
produced glass has been proposed as a host for storing high level
- Dissolution and precipitation of sulphate solid solutions as a
function of temperature
The project will begin on the system barite/celestite which forms
massive scale deposits in wells of both hydrothermal energy plants and
producing oil fields, resulting from the mixing of injected
sulphate-rich seawater with barium rich pore fluids. Barite/celestite
precipitation also controls the Ba/Sr budget in the oceans.
- Rates and mechanisms of metal-calcium carbonate solid solution
precipitation and dissolution
Crystallisation of metal-carbonate solid solutions represents a
potentially significant metal-scavening process in aqueous phases.
Divalent metals (M) including Cd, Zn, Co, Ni, Mn, and Pb can be removed
from the aqueous solution by precipitation of (M,Ca)CO3 solid solutions
or by growing an adherent solid solution layer on the carbonate surface.
The dissolution and precipitation of such toxic metal bearing mineral
phases can affect greatly the quality of fresh water found in rivers,
lakes, and aquifers.
- Dissolution and precipitation of illite at sedimentary basin
The precipitation of this mineral during diagenesis lowers the
permeability of petroleum reservoirs by up to two orders of magnitude,
leading to a decreased production. Similarly such processes can also
decrease the permeability of fresh water aquifers reducing drinking
water supplies. Detailed knowledge of the dissolution and precipitation
mechanisms of this mineral are therefore a prerequisite for accurate
oil field reservoir and aquifer modelling.
- Determining the effect of leached layers and the presence of
secondary mineral formation on amphibole dissolution
Amphibole dissolution on the surface of the Earth is one of the main
sources of plant nutrients such as Mg, Ca, K, and Fe in soils. The
release of these cations to soils and their replacement by protons from
groundwater can significantly enhance the acid neutralisation capacity
of soils, and thus act as a buffer against the effects of acid rain.
Long-term studies show that the release of these cations is more and
more influenced by the presence of leached layers with time.
- Coupled dissolution/precipitation reactions
Numerous reactions in natural systems occur by dissolution of a parent
phase and the subsequent precipitation of a product phase on its
surface. As the parent phase dissolves, the aqueous solution becomes
supersaturated with respect to the product phase, which then
precipitates on the surface of the parent phase. This precipitation can
greatly enhance the dissolution rate of the parent phase and in turn
can increase the growth rate of the product phase.
- Dissolution/precipitation in porous media
Understanding the effects of porous media on dissolution/precipitation
processes is essential to applying the results of the previous studies
to natural systems. Because the fluid saturation state in a porous
medium may vary with pore size due to the volume-dependent nucleation
probability, the spatial distribution of dissolution/precipitation
will depend on factors such as pore size distributions and flow rates.
The research to be performed by this network is interdisciplinary. Each
research task outlined above will be directed by one of the teams (R) but
other network teams will act as contributing partners. The structure of this
overall work plan is given in the table bellow.
16 de Septiembre de 2002