Hydrated coefficient of clathrates and its applications in determination of aqueous inclusions with multivolatile components

During the microthermometric measurement（cooling）of aqueous inclusions with multivolatile components,solid crystals of gas clathrates often occur with snow-flower-or soft-ice appearances.The structural formula of these solids is M·nH2O（where n≥5.67）.Many hydrocarbons,related compounds and their binary or multi-component mixtures may generate gas clathrates.This phenomenum is of fundamental importance to the study of inclusions with hydrocarbon aqueous solutions,because this is related to the determination of inclusion parameters and the computation of thermodynamic parameters. In the nature most aqueous inclusions contain not merely one volatile component but multi-volatile components.Therefore,the measurement of aqueous inclusions with multivolatile components is of universal significance and great importance.There have been many studies and available formula or figures about the computation of thermodynamic parameters for aqueous inclusions with one volatile component.Nevertheless,there are few studies concerning with muhivolatile components and it is very difficult to computate thermodynamic parameters for aqueous inclusions with these components. In this paper,hydrated coefficient K is introduced.Ki is the ratio of molar fraction of component i in the gas phase to that in the gas clathrate,or Ki=yi/xi.Because K is a function of temperatures and pressures,it can be used to evaluate the temperature-pressure conditions on the phase behavior with muhivolatile components. Based on the regression analysis of available experimental data,the authors have developed computational expression of hydrated coefficients in relation to temperature and pressure for most hydrocarbons and other volatile components,which is helpful to conveniently compute thermodynamic parameters on stability state for elathrates with volatile components.As aqueous inclusions with muhivolatile components are common in the nature,by the use of final melting temperatures of clathrates from mierothermometry and these formula,fluid density of gas phase with valotile components and bulk fluid density of inclusions can be accurately calculated. Furthermore,this method may provide foundations to determine the isochores of inclusions and to calculate trapping temperatures and pressures. Finally,detailed analyses for two computational examples about aqueous inclusions with muhivolatile components are presented.