U-Pb sphene dating of metamorphism: the importance of sphene growth in the contact aureole of the Red Mountain pluton, Laramie Mountains, Wyoming
Article Abstract:
Uranium-lead sphene analysis is a powerful tool for dating metamorphic events. Geochronological study of amphibolites and granite gneisses within the contact aureole of the Red Mountain pluton, Laramie anorthosite complex, Wyoming, reveals a 300 million year spread in 207Pb/206Pb ages. This range of ages resulted from two periods of sphene growth, corresponding to phases of regional and contact metamorphism, respectively. The ages were reset by thermal diffusion at high temperatures and the U-Pb ages recorded the new growth of sphene. Textural study distinguished the two phases of sphene.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1996
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Prograde and retrograde fluid flow during contact metamorphism of siliceous carbonate rocks from the Ballachulish aureole, Scotland
Article Abstract:
The mineralogical and stable isotope study of siliceous carbonate rocks from the Ballachulish aureole, Scotland, provides information about retrograde and prograde fluid flow during contact metamorphism. A model describes the infiltration of dolomites and limestones by CO2-H2O fluid and the subsequent alteration modes, reaction textures, and incompatibility between different minerals. Most of the univariant assemblages formed during retrograde metamorphism. The lack of stable isotope alteration of the carbonates explains the small values of prograde and retrograde time-integrated flux.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1996
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Geobarometers involving clinopyroxene, garnet, plagioclase, ilmenite, rutile, sphene and quartz: estimation of pressure in quartz-absent assemblages
Article Abstract:
Andratite's and hedenbergite's entropy and enthalpy of formation were determined using stability relations and experimental data. The findings for hedenbergite was used together with thermodynamic data from related phases to construct geobarometers based on three reactions. The pressure values from two geobarometers, one containing rutile, he other, sphene, corresponds well with data from a geobarometer involving quartz. This implies that geobarometers containing rutile and sphene can be employed in pressure measurement in assemblages without quartz.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1992
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