Revised Thermobarometry of Alpe Arami and other Garnet Peridotites from the Central Alps |
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Authors: | NIMIS P; TROMMSDORFF V |
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Institution: | 1DIPARTIMENTO DI MINERALOGIA E PETROLOGIA, UNIVERSITÀ DI PADOVA, CORSO GARIBALDI 37, 35137 PADOVA, ITALY
2INSTITUT FÜR MINERALOGIE UND PETROGRAPHIE, ETH ZENTRUM, SONNEGGSTRASSE 5, 8092 ZÜRICH, SWITZERLAND |
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Abstract: | The four, currently best constrained, independent thermobarometersfor garnet peridotites, namely Taylors (Neues Jahrbuchfür Mineralogie, Abhandlungen 172, 381408, 1998)pyroxene solvus and Kroghs (Contributions to Mineralogyand Petrology 99, 4448, 1988) clinopyroxenegarnetFeMg exchange thermometers, and Taylors (1998)Al-in-orthopyroxene and Nimis & Taylors (Contributionsto Mineralogy and Petrology, 139, 541544, 2000) Cr-in-clinopyroxenebarometers, have been applied to garnet lherzolites from theCentral Alps. Analyses from the literature, as well as new in-houseanalyses, all pertaining to core compositions of first-generation,garnet lherzolite minerals, have been selected for thermobarometriccalculations. The PT data obtained for the three knowngarnet lherzolite occurrences in the Central Alps are tightlyconstrained, consistent with one another, and summarized asfollows: Alpe Arami, 3·2 GPa and 840°C; Monte Duria,3·0 GPa and 830°C; Cima di Gagnone, 3·0 GPaand 740°C. These values are consistent with experimentaldata on pargasite stability and composition in peridotitic systems.Our PT estimates, along with microstructural and fieldgeological observations, indicate that the garnet lherzoliteparageneses form part of the prograde, Alpine, high-pressuremetamorphic sequence of the AdulaCima Lunga unit. Thermobarometryshows that the garnet lherzolites reached a maximum depth ofsubduction of |
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