Finding of high-grade tectonic blocks from the New Idria serpentinite body, Diablo Range, California: Petrologic constraints on the tectonic evolution of an active serpentinite diapir

Tatsuki Tsujimori, Juhn G. Liou, Robert G. Coleman

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    26 Citations (Scopus)

    Abstract

    Three high-grade tectonic blocks, including jadeite-bearing retrograded eclog-ite, pumpellyite-rich retrograded eclogite, and clinopyroxene-bearing garnet-amphibolite, are newly described in the jadeitite-bearing New Idria serpentinite body. Petrologic analyses reveal two contrasting peak metamorphic stages-eclogite-facies metamorphism (M1 E) characterized by garnet + omphacite (∼48 mol% jadeite) + rutile ± epidote + quartz, and amphibolite-facies metamorphism (M1 A characterized by garnet + hornblende + augite (∼14 mol% jadeite) + rutile + quartz. Both peak metamorphic events are overprinted by very low-T blueschist-facies minerals (M2), which include glaucophane, lawsonite, pumpellyite, jadeitite (up to 94 mol% jadeite), chlorite, and titanite. Garnet-clinopyroxene geothermometry yields T = ∼580-620 °C at P > 1.3 GPa for the M 1 E stage and T = ∼630-680 °C at P = ∼0.8-1.0 GPa for the MJ1 A stage. The jadeite-and lawsonite-bearing phase equilibria constrain metamorphic conditions of P > 1.0 GPa at T = ∼250-300 °C for the M2 stage that is probably synchronous with the formation of nearby jadeitite within serpentinite. The presence of eclogite blocks suggests that the New Idria serpentinite diapir was initiated at mantle depths. The wide range of P-T conditions of tectonic blocks supports the idea that the New Idria serpentinite diapir rose from mantle depths and enclosed tectonic blocks at various mantle-crustal levels during diapiric upwelling and extrusion.

    Original languageEnglish
    Pages (from-to)67-80
    Number of pages14
    JournalSpecial Paper of the Geological Society of America
    Volume419
    DOIs
    Publication statusPublished - 2007

    Fingerprint

    jadeite
    diapir
    serpentinite
    tectonic evolution
    garnet
    tectonics
    eclogite
    lawsonite
    pumpellyite
    rutile
    mantle
    clinopyroxene
    metamorphism
    quartz
    blueschist facies
    glaucophane
    omphacite
    geothermometry
    augite
    P-T conditions

    Keywords

    • Diablo Range
    • HP metamorphism
    • P-T path
    • Serpentinite diaper
    • Tectonic block

    ASJC Scopus subject areas

    • Geology

    Cite this

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    title = "Finding of high-grade tectonic blocks from the New Idria serpentinite body, Diablo Range, California: Petrologic constraints on the tectonic evolution of an active serpentinite diapir",
    abstract = "Three high-grade tectonic blocks, including jadeite-bearing retrograded eclog-ite, pumpellyite-rich retrograded eclogite, and clinopyroxene-bearing garnet-amphibolite, are newly described in the jadeitite-bearing New Idria serpentinite body. Petrologic analyses reveal two contrasting peak metamorphic stages-eclogite-facies metamorphism (M1 E) characterized by garnet + omphacite (∼48 mol{\%} jadeite) + rutile ± epidote + quartz, and amphibolite-facies metamorphism (M1 A characterized by garnet + hornblende + augite (∼14 mol{\%} jadeite) + rutile + quartz. Both peak metamorphic events are overprinted by very low-T blueschist-facies minerals (M2), which include glaucophane, lawsonite, pumpellyite, jadeitite (up to 94 mol{\%} jadeite), chlorite, and titanite. Garnet-clinopyroxene geothermometry yields T = ∼580-620 °C at P > 1.3 GPa for the M 1 E stage and T = ∼630-680 °C at P = ∼0.8-1.0 GPa for the MJ1 A stage. The jadeite-and lawsonite-bearing phase equilibria constrain metamorphic conditions of P > 1.0 GPa at T = ∼250-300 °C for the M2 stage that is probably synchronous with the formation of nearby jadeitite within serpentinite. The presence of eclogite blocks suggests that the New Idria serpentinite diapir was initiated at mantle depths. The wide range of P-T conditions of tectonic blocks supports the idea that the New Idria serpentinite diapir rose from mantle depths and enclosed tectonic blocks at various mantle-crustal levels during diapiric upwelling and extrusion.",
    keywords = "Diablo Range, HP metamorphism, P-T path, Serpentinite diaper, Tectonic block",
    author = "Tatsuki Tsujimori and Liou, {Juhn G.} and Coleman, {Robert G.}",
    year = "2007",
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    T1 - Finding of high-grade tectonic blocks from the New Idria serpentinite body, Diablo Range, California

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    AU - Tsujimori, Tatsuki

    AU - Liou, Juhn G.

    AU - Coleman, Robert G.

    PY - 2007

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    AB - Three high-grade tectonic blocks, including jadeite-bearing retrograded eclog-ite, pumpellyite-rich retrograded eclogite, and clinopyroxene-bearing garnet-amphibolite, are newly described in the jadeitite-bearing New Idria serpentinite body. Petrologic analyses reveal two contrasting peak metamorphic stages-eclogite-facies metamorphism (M1 E) characterized by garnet + omphacite (∼48 mol% jadeite) + rutile ± epidote + quartz, and amphibolite-facies metamorphism (M1 A characterized by garnet + hornblende + augite (∼14 mol% jadeite) + rutile + quartz. Both peak metamorphic events are overprinted by very low-T blueschist-facies minerals (M2), which include glaucophane, lawsonite, pumpellyite, jadeitite (up to 94 mol% jadeite), chlorite, and titanite. Garnet-clinopyroxene geothermometry yields T = ∼580-620 °C at P > 1.3 GPa for the M 1 E stage and T = ∼630-680 °C at P = ∼0.8-1.0 GPa for the MJ1 A stage. The jadeite-and lawsonite-bearing phase equilibria constrain metamorphic conditions of P > 1.0 GPa at T = ∼250-300 °C for the M2 stage that is probably synchronous with the formation of nearby jadeitite within serpentinite. The presence of eclogite blocks suggests that the New Idria serpentinite diapir was initiated at mantle depths. The wide range of P-T conditions of tectonic blocks supports the idea that the New Idria serpentinite diapir rose from mantle depths and enclosed tectonic blocks at various mantle-crustal levels during diapiric upwelling and extrusion.

    KW - Diablo Range

    KW - HP metamorphism

    KW - P-T path

    KW - Serpentinite diaper

    KW - Tectonic block

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