METEOMOD: A numerical model for the calculation of melting- crystallization relationships in meteoritic igneous systems
The METEOMOD model is a computer program designed to calculate melting-crystallization relationships in igneous systems compositionally similar to ordinary chondrites and basaltic achondrites. The core of METEOMOD is a set of empirically calibrated equations, called geothermometers, which describe equilibria between silicate melt and minerals such as olivine, orthopyroxene, pigeonite, augite, plagioclase, and metallic iron in terms of pressure, temperature, and liquid compositions. The silicate mineral geothermometers are calibrated from a database containing the compositions of melts and minerals produced in melting experiments on 113 meteoritic and 141 synthetic systems. The metallic iron-silicate melt geothermometer is calibrated from a database of 396 melting experiments. METEOMOD calculates crystallization temperatures and contents of major end-members in mineral solid solutions with accuracies of +/-10-15 degC and +/-1-2 mole %, respectively. Input parameters for the program are (1) increment in crystallization degree; (2) one of 12 fO2 buffers routinely used in petrology; (3) shift from the buffer in log units, if any; (4) a choice of equilibrium or fractional crystallization trajectory; (5) terminal crystallization degree; (6) contents of 10 major elements in wt.%; (7) a set of minor and trace elements in ppm; (8) the number of initial compositions to be modeled in a single computation run. The output consists of a series of tables which list equilibrium temperatures, oxygen fugacities, and proportions of melt and minerals and their compositions, as a function of the degree of crystallization. The results of application of METEOMOD to modeling of melting-crystallization of the St.Severin LL chondrite are compared with the experimental data of Jurewicz et al. (1995).