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Moore, Gordon
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Moore, Gordon
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gmmoore@umich.edu
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- PublicationRestrictedA K-feldspar–liquid hygrometer specific to alkaline differentiated magmas(2015)
; ; ; ; ; ; ; ; ; ; ;; ;We present a K-feldspar-liquid hygrometer specific to alkaline differentiated magmas that is calibrated through the regression analysis of sanidine and anorthoclase crystals coexisting with trachyte and phonolite melts. Partial-regression leverage plots were used to determine the minimum number of regression parameters that closely describe the variance of the dataset. The derived model was tested using K-feldspar-liquid pairs not included into the calibration dataset in order to address issues of systematic errors. When K-feldspar and plagioclase crystals coprecipitate from the same alkaline liquid under identical P-T-X-fO(2)-H2O conditions, the ability prediction of the new hygrometer is comparable to that of previous plagioclase-liquid models. To minimize the error of H2O estimate caused by the inadvertent use of disequilibrium data in natural samples, we have also calibrated a new test for equilibrium based on Or-Ab exchange between K-feldspar and coexisting melt. As an immediate application for both equilibrium and hygrometer models, we used as input data K-feldsparliquid pairs from alkaline explosive eruptions at the Phlegrean Fields. The estimates of H2O dissolved in natural trachyte and phonolite magmas closely match those determined by melt inclusion analysis and H2O solubility modeling. This leads to the conclusion that our new models can significantly contribute to a better quantitative characterization of the H2O content in differentiated alkaline magmas feeding large-volume explosive eruptions. (C) 2014 Elsevier B.V. All rights reserved.65 1 - PublicationRestrictedClinopyroxene–liquid thermometers and barometers specific to alkaline differentiated magmas(2013)
; ; ; ; ; ;Masotta, M.; Bayerisches Geoinstitut ;Mollo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Freda, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Gaeta, M.; Università Sapienza ;Moore, G.; University of Michigan; ; ; ; We present new thermometers and barometers based on clinopyroxene–liquid equilibria specific to alkaline differentiated magmas. The new models were calibrated through the regression analyses of experimental datasets obtained by merging phase equilibria experiments from the literature with new experiments performed by using trachytic and phonolitic starting compositions. The regression strategy was twofold: (1) we have tested previous thermometric and barometric equations and recalibrated these models using the new datasets; (2) we have calibrated a new thermometer and a new barometer including only regression parameters that closely describe the compositional variability of the datasets. The new models yield more precise estimates than previous thermometers and barometers when used to predict temperatures and pressures of alkaline differentiated magmas. We have tested the reliability of the new equations by using clinopyroxene–liquid pairs from trachytes and phonolites erupted during major explosive eruptions at the Phlegrean Fields and Mt. Vesuvius (central Italy). The test yielded crystallization conditions comparable to those determined by means of melt and fluid inclusion analyses and phase equilibria studies; this validates the use of the proposed models for precise estimates of crystallization temperatures and pressures in differentiated alkaline magmas. Because these magmas feed some of the most voluminous, explosive, and threatening volcanic eruptions in the world, a better understanding of the environmental conditions of their reservoirs is mandatory and this is now possible with the new models provided here.280 50 - PublicationRestrictedLow pressure experiments in piston cylinder apparatus: calibration of newly designed 25 mm furnace assemblies to P = 150 MPa(2012)
; ; ; ; ; ; ; ;Masotta, M.; Sapienza Università Roma ;Freda, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Paul, T. A.; Depths of the Earth co ;Moore, G.; Arizona State University ;Gaeta, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Scarlato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Troll, V. R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; We present new pressure calibration experiments demons trating that the piston cylinder apparatus is suit-able for experiments at pressure as low as 150 MPa. Two newly designed 25 mm furnace assembly have been developed and calibrated using two differe nt calibration methods: the NaC l melting curve and the sol-ubility of H2 O in albitic and rhyolitic melts. The NaCl calibration experiments performed in the pressure range 150 –500 MPa yield the pressure correction that has to be applied to the nominal pressure in order to have the equivalent (real) pressure on the sample. This correction varies as a function of the experime ntal pressure as follows: Pcorrection MPaðÞ¼ −0 :115xP nominal MPaðÞþ 78 : 23 The H 2O solubility experiments in albitic and rhyolitic melts con firm the corrections determined using the NaCl calibration method. Moreover, because these experiments are performed at temperatures higher than those used for NaCl calibration, they demonstrate that the pressure correction is not affected by temperature in the range 800– 1000 °C. The accuracy of the pressure estimate associated wi th the calibration methods is ± 25 MPa. The major advantage of using the new assemblies is that low pressure experiments, which require rapid heating and quenching rates (e.g. volcanic and hydrothermal systems), can be performed with the same ease and precision as standard high pressure experiments for which piston cylinder is routinel y used.583 92