Paragenesis and thermobarometry of Ca-amphiboles in the Barcroft granodioritic pluton, central White Mountains, eastern California
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W.G. Ernst
Abstract
Mid-Mesozoic to Tertiary igneous activity reflects arc evolution along the Sierra + White-Inyo sector of the continental margin. The Ca-amphibole + biotite ± augite-bearing Middle Jurassic Barcroft pluton consists of intergradational, quartzose gabbro-diorite, metadiorite, voluminous mafic-to-felsic granodiorite, and rare alaskite-aplite. It was emplaced along the Barcroft structural break-a major ENE-striking suture juxtaposing mid-Mesozoic bimodal metavolcanics on the north against metamorphosed Lower Cambrian platform strata on the south. The Cretaceous, two-mica McAfee Creek Granite intruded both wall rocks and the Barcroft granodioritic pluton on the east. Geologic mapping and petrochemical studies have documented the structure and metaluminous geochemistry of the Barcroft body.
Analyses of Ca-clinoamphiboles from 16 Barcroft rocks allow the assignment of P-T conditions of crystallization/recrystallization based on experimentally determined and calculated clinoamphibole thermobarometers. Combined with earlier studies of country-rock metamorphism, and oxygen isotopic investigations of mineral assemblages in both plutons and wall rocks, four stages in the P-T evolution of the Barcroft pluton have been identified: Stage 1, partial melting of a mafic protolith at ~25 km or greater depth, then onset of crystallization of refractory hornblende and other ferromagnesian phases at ~915 ± 25 °C attending magma ascent. Stages 2 → 3, crystallization of progressively more actinolitic hornblende during decompression cooling and stalling of the pluton at a depth of 10-12 km, as temperature declined over the interval ~760-650 °C. Stage 4, subsolidus recrystallization/ exsolution of nearly stoichiometric actinolite ± grunerite attending deuteric alteration over the range ~395-545 °C at a depth of 4-5 km. Mineral assemblages of stages 1 → 4 are disposed progressively inward, indicating that the Barcroft pluton lost heat along intrusive contacts with the wall rocks, cooling, annealing, and re-equilibrating in the process. The Cretaceous McAfee Creek Granite transected this ENE-trending thermal zonation, but exerted little effect on Ti + Al contents (and δ18O values) of Barcroft amphiboles.
© 2015 by Walter de Gruyter Berlin/Boston
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- Coexisting andalusite, kyanite, and sillimanite: Sequential formation of three Al2SiO5 polymorphs during progressive metamorphism near the triple point, Sivrihisar, Turkey
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- Stability of corundum + quartz relative to kyanite and sillimanite at high temperature and pressure
- Andalusite-sillimanite replacement (Mazarrón, SE Spain): A microstructural and TEM study
- Hydroxyl-rich topaz in high-pressure and ultrahigh-pressure kyanite quartzites, with retrograde woodhouseite, from the Sulu terrane, eastern China
- Coesite exsolution from supersilicic titanite in UHP marble from the Kokchetav Massif, northern Kazakhstan
- Composition of synthetic tremolite-tschermakite solid solutions in amphibole + anorthiteand amphibole + zoisite-bearing assemblages
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- B and Li in Proterozoic metapelites from the Black Hills, U.S.A.: Implications for the origin of leucogranitic magmas
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Articles in the same Issue
- Titanium in biotite from metapelitic rocks: Temperature effects, crystal-chemical controls, and petrologic applications
- Local equilibrium in polymetamorphic gneiss and the titanium substitution in biotite
- The enthalpy of formation and internally consistent thermodynamic data of Mg-staurolite
- Coexisting andalusite, kyanite, and sillimanite: Sequential formation of three Al2SiO5 polymorphs during progressive metamorphism near the triple point, Sivrihisar, Turkey
- Co-existing aluminum silicates in quartz veins: A quantitative approach for determining andalusite-sillimanite equilibrium in natural samples using oxygen isotopes
- Stability of corundum + quartz relative to kyanite and sillimanite at high temperature and pressure
- Andalusite-sillimanite replacement (Mazarrón, SE Spain): A microstructural and TEM study
- Hydroxyl-rich topaz in high-pressure and ultrahigh-pressure kyanite quartzites, with retrograde woodhouseite, from the Sulu terrane, eastern China
- Coesite exsolution from supersilicic titanite in UHP marble from the Kokchetav Massif, northern Kazakhstan
- Composition of synthetic tremolite-tschermakite solid solutions in amphibole + anorthiteand amphibole + zoisite-bearing assemblages
- Paragenesis and thermobarometry of Ca-amphiboles in the Barcroft granodioritic pluton, central White Mountains, eastern California
- B and Li in Proterozoic metapelites from the Black Hills, U.S.A.: Implications for the origin of leucogranitic magmas
- The role of Fe and cation order in the crystal chemistry of surinamite, (Mg,Fe2+)3(Al,Fe3+)3O[AlBeSi3O15]: A crystal structure, Mössbauer spectroscopic, and optical spectroscopic study
- Fe3+ and Fe2+ partitioning among silicates in metapelites: A synchrotron micro-XANES study
- Thermodynamic and structural behavior of analcime–leucite analogue systems
- In-situ synchrotron study of the kinetics, thermodynamics, and reaction mechanisms of the hydrothermal crystallization of gyrolite, Ca16Si24O60(OH)8·14H2O
- The crystal structures of grossular and spessartine between 100 and 600 K and the crystal chemistry of grossular-spessartine solid solutions
- The structures of becquerelite and Sr-exchanged becquerelite
- Elasticity and equation of state of orthoenstatite, MgSiO3
- Reidite: An impact-produced high-pressure polymorph of zircon found in marine sediments
- A new polymorph of eucryptite (LiAlSiO4), ε-eucryptite, and thermal expansion of α- and ε-eucryptite at high pressure
- Disordering during melting: An 17O NMR Study of crystalline and glassy CaTiSiO5 (titanite)
- Characterization of Mn oxides in cemented streambed crusts from Pinal Creek, Arizona, U.S.A., and in hot-spring deposits from Yuno-Taki Falls, Hokkaido, Japan
