The temperature/pressure conditions of grenville-age granulite-facies metamorphism of the Oaxacan Complex, Southern Mexico.

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dc.contributor.advisorValley, John W.en_US
dc.contributor.committeeMemberBaker, Donald R.en_US
dc.contributor.committeeMemberLallemant, Hans G. Avéen_US
dc.creatorMora, Claudia Inesen_US
dc.date.accessioned2018-12-18T21:18:50Zen_US
dc.date.available2018-12-18T21:18:50Zen_US
dc.date.issued1983en_US
dc.description.abstractCoexisting feldspar thermometry for charnockites and quartzofeldspathic gneisses in the Grenville-age Oaxacan Complex, southern Mexico, yields an average temperature of T=762+5°C at 7kb. Reintegration of coarsely-exsolved perthites yields internally consistent peak temperature estimates. Texturally-homogeneous alkali-feldspar has reequilibrated at low temperature. Unusually extensive solid-solution of albite (Abs to Ab5§) and anorthite (Ang.3 to An^ç) necessitated extrapolation of the Stormer (1975) determinative curves beyond their explicit limits. This results in unreasonably high temperature estimates of up to 975°C for feldspar pairs in which X/yj /^f>.4 and suggests that extrapolation is unwarranted. The distribution of albite between coexisting feldspars is consistent with the shape of the Brown and Parsons (1981) general form for the graphical two-feldspar thermometer. Peak metamorphic pressure was estimated using the Newton and Perkins (1982) anorthite+enstatite=pyrope 2/3 grossular 1/3 + quartz geobarometer which yields P=7.5+lkb. The experimentally determined geobarometer anorthite+ferrosilite=almandine 2/3 grossular 1/3 + quartz (Bohlen et al., 1983) yields P=7.25+lkb. The assemblage dolomite+diopside+forsterlte+calcite restricts the metamorphic temperature to 764°C at PQ) =7kb, calculating from the 5kb experimental reversal of the buffering reaction 3dolomite+ldiopside= 2forsterite+4calcite+2C2 by Kase and Metz (1981). Using the temperature estimated by two-feldspar thermometry, at P=7kb the assemblage buffers the fluid composition to Xco =.8. The estimated pressures and temperatures are consistent with metamorphic conditions indicated by the occurrence of quartz+K-feldspar+garnet +sillimanite+biotite in the pelitic gneisses and orthopyroxene+plagioclase+ garnetjMclinopyroxene in the mafic gneisses of the terrane.en_US
dc.format.digitalOriginreformatted digitalen_US
dc.format.extent90 ppen_US
dc.identifier.callnoThesis Geol. 1983 Moraen_US
dc.identifier.citationMora, Claudia Ines. "The temperature/pressure conditions of grenville-age granulite-facies metamorphism of the Oaxacan Complex, Southern Mexico.." (1983) Master’s Thesis, Rice University. <a href="https://hdl.handle.net/1911/104206">https://hdl.handle.net/1911/104206</a>.en_US
dc.identifier.digitalRICE1834en_US
dc.identifier.urihttps://hdl.handle.net/1911/104206en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.titleThe temperature/pressure conditions of grenville-age granulite-facies metamorphism of the Oaxacan Complex, Southern Mexico.en_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentEarth Scienceen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Artsen_US
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