Reports and partecipation to congress
> Result of the Brite project research are described in the following report "Syntesis Report for Pubblication".
> Tenth International Symposium on Water-Rock Interaction - WRI-10, 10-15 July 2001, Villasimus - Italy.
> IGES'20 - International Geochemical Exploration Symposium - Santiago - Chile - 06-10 May - 2001.
Pubblications
Metal concentrations in groundwater around disturbed and undisturbed massive sulfide deposits
R. Castroviejo, J. Samper & A. López
Universidad Politecnica de Madrid, Madrid, Spain
F. Graziottin
Idronaut, Brugherio(Milan), Italy
M-L. Tercier
CABE group, University of Geneva, Switzerland
H.Pauwels, A. Lassin, J-C. Foucher & Y. Deschamps
BRGM, Orléans France
Abstract: A detailed chemical study of groundwater was carried out to elucidate the processes controlling the oxidation and dissolution of sulfide minerals at two massive sulfide deposits in the South Iberian Pyrite Belt: the disturbed La Zarza deposit and the undisturbed Masa Valverde deposit. Metal concentrations were determined by ICP-MS after filtration. Also in some cases, a voltammetric probe was used for in situ metal (Cu, Pb, Zn, Cd) detection where, according to the basic principles of voltammetry on microelectrodes, only the mobile fractions of the trace element are detected (i.e. free metal ions and small labile complexes a few nanometers in size). The results, confirmed by calculations performed with the EQ3/6 geochemical code, indicate an important enhancement of metal solubility through complexing with organic matter and/or adsorption onto colloids and/or small particles. Under very low redox conditions, the attained metal concentrations can be as much as several orders of magnitude greater than those expected from equilibrium with respect to sulfide minerals.
Corresponding author. Fax: +33-2-3864-3518.
E-mail address: h.pauwels@brgm.fr (H. Pauwels)
Chemical characteristics of groundwater around two massive sulphide deposits in an area of previous mining contamination, Iberian Pyrite Belt, Spain
Helene Pauwels a,*, Marie-Lou Tercier-Waeber b, Miguel Arenas c, Ricardo Castroviejo d, Yves Deschamps a, Arnault Lassin a, Flavio Graziottin e, Francisco-Javier Elorza d
aCentre Scientifique et Technique, BRGM Research Division, B.P. 6009, 3 Avenue Claude Guillemin, 45060 Orleans Cedex 2, France
bCABE, Department of Inorganic, Analytical and Applied Chemistry, University of Geneva Sciences II, 30 quai Ansermet,
1211 Geneva 4, Switzerland
cInima S.A., Arturo Soria No. 336, 6a Planta, 28033 Madrid, Spain
dETSI Minas, U.P. Madrid, Rios Rosas No. 21, 28003 Madrid, Spain
eIdronaut Srl, Via Monte Amiata 10, 20047 Brugherio (Mi), Italy
Abstract :A detailed chemical study of groundwater was carried out to elucidate the processes controlling the oxidation and dissolution of sulphide minerals at two massive sulphide deposits in the Iberian Pyrite Belt (IPB), i.e. the mined La Zarza deposit and the unmined Masa Valverde deposit. It was found that major-element compositions varied according to the hydrological regime, La Zarza being in a relatively high area with groundwater recharge (and disturbance due to the human factor) and Masa Valverde being in a relatively low area with groundwater discharge. The variations mainly concern pH, Eh, SO4 and Na concentrations. Metal concentrations were determined (a) by ICP-MS after filtration, and (b) in some cases by voltammetric measurement of Cu, Pb, Zn, Cd and Mn using the Voltammetric In situ Profiling (VIP) System, which allows detection of only the mobile fractions of trace elements (i.e., free metal ions and small labile complexes a few nanometers in size). If one compares the results obtained by each of the two methods, it would appear that the groundwater shows significant enhancement of metal solubility through complexing with organic matter and/or adsorption onto colloids and/or small particles. In areas of sulphide oxidation, however, this solubility enhancement decreases according to Cu > Zn>Cd>Pb. Under very low redox conditions, the attained metal concentrations can be several orders of magnitude (up to 108-109 for Cu and 102-103 for Pb) larger than those expected from equilibrium with respect to sulphide minerals as calculated with the EQ3NR geochemical code; Zn concentrations, however, are close to equilibrium with respect to sphalerite. The implication of these results is discussed with respect both to mineral exploration and to environmental issues. D 2002 Elsevier Science B.V. All rights reserved.
Corresponding author. Fax: +33-2-3864-3518.
E-mail address: h.pauwels@brgm.fr (H. Pauwels).