Ganguly 2001 modelado termodinámico de las soluciones sólidas

Ganguly 2001 modelado termodinámico de las soluciones sólidas

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Thermodynamic modelling of solid solutions J IBAMITRA GANGULY Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA; e-mail: Introduction One of the major goals of petrology is to retrieve values of the intensive parameters, such as pressure ( P ), temperature ( T ) and fluid composition, under which the major mineralogical properties of a rock were established, along with the time scales of evolution of the mineralogical properties. The basic approach in the retrieval of the intensive properties involves comparison of the mineralogical assemblages and the mineral compositions of the rock with the phase equilibrium constraints. The latter are calculated from the internally consistent thermochemical properties of the stoichiometric end members or determined in the laboratory on relatively simple systems, usually involving only the end-member phases, and then corrected for the effects of the compositional departures as observed in a specific natural assemblage. In addition, many mineral pairs ( e.g . garnet and biotite) respond to changes of P–T conditions, especially temperature, by continuous ion exchange reactions, and thus register the P–T condition or P–T history of the rock in their compositions. The ion- exchange reactions are also calibrated in the laboratory on relatively simple systems, but require corrections for the effects of additional components that enter into solid solution in the minerals in natural environments. The corrections for the compositional effects rely critically on the thermodynamic mixing properties of the components in the mineral solid solutions and fluid phase which are involved in a specific reaction ( e.g. Ganguly & Saxena, 1987). There has, thus, been a sustained effort over the last few decades on the determination of thermodynamic mixing properties of phases in geologically important systems. In this review, I will summarise the general concepts of thermodynamic solution theory and a number of macroscopic models that have been used in the treatment of experimental data on mineral solid solutions. Some of the solution models were originally developed for polymer and liquid solutions, but are also applicable to oxide and solid solutions. For reasons of both time and space, I have not included order- disorder theory specifically, although some aspects of the thermodynamics of minerals showing such behaviour may also be treated within the framework of the models discussed in this review, as will be pointed out in the appropriate sections. I have assumed that the reader has a working knowledge of thermodynamics, including the fundamentals of thermodynamic solution theory. Thus, only a brief discussion of the EMU Notes in Mineralogy, Vol. 3 (2001), Chapter 3, 37–69
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solution theory has been included in this review in the spirit of recapitulation and re- emphasis of some of the important points. The presentation of the topics follows a systematic order in that the concepts presented in a particular section builds on what has been presented in the preceding sections. The primary aim here has been to convey the
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This note was uploaded on 03/19/2012 for the course GEOLOGY 6 taught by Professor Rm during the Spring '12 term at UNAM MX.

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Ganguly 2001 modelado termodinámico de las soluciones sólidas

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