Geothermometer calibration

Canil D. (1999) The Ni-in-garnet geothermometer calibration at natural abundances. Contrib. Mineral. Petrol. 136, 240-246. 

O Neill H.St. C. and Wood B. J. (1979). An experimental study of Fe-Mg partitioning between garnet and olivine and its calibration as a geothermometer. Contrib. Mineral Petrol, 70 59-70. 

Method (c) is based on the idea that the calculated/orman on temperature of a rock (calculated from other geothermometers) serves as a calibration to the measured isotopic fractionations, assuming that all minerals were at equilibrium. However, because there is evidence that equilibrium is not always attained or retained in nature, such empirical calibrations should be regarded with caution. 

In general, experimental calibrations of isotope geothermometers have been performed between 250 and 800°C. The upper temperature limit is usually determined by the stability of the mineral being studied or by limitations of the experimental apparatus, whereas the lower temperature limit is determined by the decreasing rate of exchange. 

On the basis of these systematic tendencies of emichment found in nature, significant temperature information can be obtained np to temperatures of 1,000°C, and even higher, if calibration cnrves can be worked ont for the varions mineral pairs. The pnbhshed hterature contains many calibrations of oxygen isotope geothermometers, most are determined by laboratory experiments, althongh some are based on theoretical calcnlations. 

Arnorsson, S. Gunnlaugsson, E. 1985. New gas geothermometers for geothermal exploration -calibration and application. Geochimica et Cosmo-chimica Acta, 49, 1307-1325. 

In principle, isotopic analyses of natural samples can also be used to calibrate fractionation factors. Effective use of the natural sample method, however, requires that several stringent criteria be met. (1) The phases being calibrated first attained isotopic equilibrium at some temperature, and subsequently retained their equilibrium isotopic compositions, (2) equilibration temperatures in the samples of interest are well determined by independent methods, and (3) the geothermometers used to determine... 

Agrinier P (1991) The natnral calibration of geothermometers Application to the quartz-rutile pair. 

Powell and Powell (197 ). In order to calibrate a clinopyroxene -olivine geothermometer, the authors use ternary regular solution theory (Wohl, 19 6 Prigogine and Defay, 195 ) to represent the thermodynamic mixing properties of Mg-Fe -Al (=A1+Ti+Cr+Fe3+) clinopyroxene. Olivine is assumed to be ideal. The crystallization temperatures of several intrusions, xenoliths and lavas are estimated on the basis of the model and known pressures. 

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