Francisco J. Martínez

GPT: an Excel spreadsheet for thermobarometric calculations in metapelitic rocks

GPT takes advantage of Excel spreadsheet utilities (e.g. the possibility of entering a large number of data) to calculate 72 thermometers, 59 barometers, two fO2-meters, thirteen fH2O-meters and fourteen XH2O-meters, as well as the equations for the calculation of the H2O fugacity coefficient corresponding to different mineral assemblages. Each calibration uses expressions by different authors. Because these calibrations are two-variable expressions, one of them needs to be assumed to obtain the other (e.g. a pressure needs to be assumed in a thermometer and a temperature in a barometer). GPT, however, allows the simultaneous solution of two two-variable expressions through iteration, provided the mineral assemblage studied contains any of the sub-assemblages used in the calibration. The P and T values thus obtained can easily be represented through spreadsheet graphics as a formatted P-T chart. In this way, for instance, probe sites of a garnet profile can be represented by symbols and linked by lines representing the P-T path followed by the sample, assuming that the right mineral compositions are used. In order to make GPT easier to use it has been divided into four different spreadsheets that cover the whole P-T geological range. The spreadsheet can be divided easily into smaller sheets adapted to the users purposes.

Petrology of garnet — cordierite — sillimanite gneisses from the El Tormes thermal dome, Iberian Hercynian foldbelt (W Spain)

AbstractThe core of the El Tormes thermal dome, situated in the central part of one of the main metamorphic belts of the Iberian Peninsula, is formed by garnet-cordierite-biotite-sillimanite pelitic gneisses. These rocks, that very often are cut by minor intrusions of Al-rich S-type granites, are metatexitic gneisses in which there exists garnet showing different stages of resorption and transformation into an aggregate of cordierite±plagioclase±biotite. The garnet, mantled and corroded mainly by cordierite, has never been found to occur in contact with the prismatic sillimanite of the matrix, thus indicating that the continuous reaction Gr+Sill+Q = Cd has taken place. The presence of corroded biotite inside the garnet-rimming cordierite of the aggregates as well as inside the cordierite of the matrix, which usually includes remmants of sillimanite, indicates that the continuous reaction Bi+Sill+Q = Cd+FK+H2O has occurred too. Therefore, a realistic net reaction for these aggretates should be represented by the univariant, at a given

Provenance, age, and tectonic evolution of Variscan flysch, southeastern France and northeastern Spain, based on zircon geochronology

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Dimensioning storage and computing clusters for efficient high throughput computing

, equilibrium: Biotite+Sillimanite+Garnet+Quartz = Cordierite+K-feldspar+H2O (1)The important garnet resorption near the anatectic granitic veins implies that this process is favoured by a decrease in

The use of soil-flushing to remediate metal contamination in a smelting slag dumping area: Column and pilot-scale experiments

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U–Pb Shrimp-RG zircon ages of Variscan igneous rocks from the Guilleries massif (NE Iberia pre-Mesozoic basement). Geological implications

, this factor being otherwise buffered by the reaction (1) assemblage.The most probable P-T path, assuming these conditions, consistent with the AFM projection of the former (inferred) and present assemblages in the aggregates and in the matrix, implies a decrease in P coeval with a decrease in T (Fig. 4, path 2).The most reliable P-T determination for the final stage of garnet breakdown through reaction (1), based on the coexistence of the seven phase assemblage garnet — cordierite — biotite — sillimanite — plagioclase — potash feldspar — quartz plus melt, gives 695° C, 4.3 kbar,