Crystallization in a saturated magma Part I (Theory) Three phase segregation laws and saturated magma modelling through trace elements
published: Dec 1, 1995
ArtNo. ESP154017001004, Price: 29.00 €
A sequence of equations is developed to explain the phenomenon of simultaneous three phase segregation, to be applied in a physico-chemical solid-liquid-liquid equilibrium system. As crystallization proceedes in a system saturated with a liquid, the saturated constituent in excess is segregated as an immiscible fluid. The two liquid phases are assumed to be in equilibrium, and the third (solid) fractionates with respect to the two others. Therefore the immiscible fluid grows as a consequence of crystallization from the saturated magma, and remains in contact with it. Since the system involves two liquids in contact with a solid, the differences of interface surface tension between each liquid and the solid are considered. Or in other words, from which of the two liquids crystals are growing. This allows the definition of three new laws of segregation, which are herein named pseudoequilibrium, combined fractionation, and pseudofractionation. These laws describe the behavior of a trace element, when the mineral grows from the residual magma, residual magma and immiscible fluid, or immiscible fluid, respectively. Furthermore, these laws will have a different meaning for F (fraction of remaining liquid), whether the immiscible liquid has moved and evolved into a large drop (additive effect), or it has remained as an emulsion (iterative effect) before crystallization proceedes. In this last situation, a high segregation degree can be achieved by a small crystallization process. These laws can be applied to the most common liquid saturated magma situations, (sulfide, silica-aluminous, or hydrothermal solutions) using trace elements for quantitative modelling.