Structural control of the distribution of trace elements between silicates and hydrothermal solutions |
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| Authors: | Marcel Volfinger Jean-Louis Robert |
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| Institution: | Centre de Recherche sur la Synthèse et Chimie des minéraux, C.N.R.S., 1A, rue de la Férollerie, 45045 Orléans Cedex, France |
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| Abstract: | Over several years many partition coefficients have been measured between framework silicates, sheet silicates and hydrothermal solutions. Only trace alkaline cations are considered in the present work. It is well known that the difference between ionic radii of the trace cation and the major cation is replaces is not satisfactory for a good correlation with the partition coefficients PX. A structural parameter δc is therefore defined, taking into consideration the adaptation of the trace cation to the cavity in which it occurs. This cavity may be the entire site of the major element, or a part of this site in the case of small cations, or a structural cavity located out of the alkali-ion site. The adaptation parameter δc is the difference between the ionic radius of the trace cation and the radius of that cavity. This paper shows that the partition coefficient PX of the trace alkali-ion from the hydrothermal solution is an exponential function of the adaptation parameter δc, whatever the silicate may be. |
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