A Sequence of Pan-African and Hercynian Events Recorded in Zircons from an Orthogneiss from the Hercynian Belt of Western Central Iberia-an Ion Microprobe U-Pb Study

H.P. Zeck, Michael Wingate, Gregory Pooley, J.M. Ugidos

    Research output: Contribution to journalArticle

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    Abstract

    Sensitive high-resolution ion microprobe U-Pb dating shows that a biotite orthogneiss from the Hercynian belt of western central Iberia contains 1000-300 Ma zircon. Older, 1000-570 Ma ages within this range represent inherited, detrital material among which four age components may be recognized: similar to980 Ma, similar to830 Ma, 616 +/- 10(2sigma) Ma and 582 +/- 5(2sigma) Ma. This inherited zircon commonly forms cores that are surrounded by rims Yielding Late Pan-African ages, identical to those found in slender, prismatic, and some stubbier, bi-pyramidal, euhedral crystals. This is the predominant hype of zircon with an average age of 546 3(2sigma) Ma, thought to have been formed during the main magmatic crystallization stage of the granitic protolith of the gneiss. Local deuteric replacements of magmatic zircon yield a virtually identical average age of 547 +/- 5(2sigma) Ma, suggesting rapid magmatic cooling, typical of shallow intrusive settings. Many zircon crystals have very thin, low-Th/U rims with an age of similar to315 Ma, suggested to represent the gneissfication of the granitic rock during the Hercynian orogeny. The abundance in the gneiss body of Al-rich restitic material and inherited, detrital zircon suggests that the granitic magma was formed by anatectic melting of a meta-sedimentary source rock complex. The age of the youngest inherited, detrital zircon constrains the sedimentation age of the (youngest parts of the) analectic source rock complex to the Late Neoproterozoic ( < 582 +/- 5 Ma) and leaves a maximum period of similar to40 Myr for metamorphism and anatexis of the source rock complex, and migration and intrusion of the granitic magma. Among the inherited, detrital zircon the 616 +/- 10(2sigma) Ma and 582 +/- 5(2sigma) Ma ages are by far the most abundant, and might be derived from the West African craton, where such ages are common for main-stage Pan-African complexes. The older, similar to980 Ma and similar to830 Ma inherited zircon ages are absent or rare in the West African craton and a derivation from the Amazon craton (Grenvillian, Sunsas orogens), where such ages are common, is an alternative.
    Original languageEnglish
    Pages (from-to)1613-1629
    JournalJournal of Petrology
    Volume45
    Issue number8
    DOIs
    Publication statusPublished - 2004

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    orthogneiss
    ion microprobe
    cratons
    zircon
    rocks
    Ions
    gneiss
    rims
    magma
    ions
    Rocks
    biotite
    dating
    intrusion
    leaves
    source rock
    crystals
    craton
    derivation
    melting

    Cite this

    @article{e2cf3524071f44bea43e114a5ce2326b,
    title = "A Sequence of Pan-African and Hercynian Events Recorded in Zircons from an Orthogneiss from the Hercynian Belt of Western Central Iberia-an Ion Microprobe U-Pb Study",
    abstract = "Sensitive high-resolution ion microprobe U-Pb dating shows that a biotite orthogneiss from the Hercynian belt of western central Iberia contains 1000-300 Ma zircon. Older, 1000-570 Ma ages within this range represent inherited, detrital material among which four age components may be recognized: similar to980 Ma, similar to830 Ma, 616 +/- 10(2sigma) Ma and 582 +/- 5(2sigma) Ma. This inherited zircon commonly forms cores that are surrounded by rims Yielding Late Pan-African ages, identical to those found in slender, prismatic, and some stubbier, bi-pyramidal, euhedral crystals. This is the predominant hype of zircon with an average age of 546 3(2sigma) Ma, thought to have been formed during the main magmatic crystallization stage of the granitic protolith of the gneiss. Local deuteric replacements of magmatic zircon yield a virtually identical average age of 547 +/- 5(2sigma) Ma, suggesting rapid magmatic cooling, typical of shallow intrusive settings. Many zircon crystals have very thin, low-Th/U rims with an age of similar to315 Ma, suggested to represent the gneissfication of the granitic rock during the Hercynian orogeny. The abundance in the gneiss body of Al-rich restitic material and inherited, detrital zircon suggests that the granitic magma was formed by anatectic melting of a meta-sedimentary source rock complex. The age of the youngest inherited, detrital zircon constrains the sedimentation age of the (youngest parts of the) analectic source rock complex to the Late Neoproterozoic ( < 582 +/- 5 Ma) and leaves a maximum period of similar to40 Myr for metamorphism and anatexis of the source rock complex, and migration and intrusion of the granitic magma. Among the inherited, detrital zircon the 616 +/- 10(2sigma) Ma and 582 +/- 5(2sigma) Ma ages are by far the most abundant, and might be derived from the West African craton, where such ages are common for main-stage Pan-African complexes. The older, similar to980 Ma and similar to830 Ma inherited zircon ages are absent or rare in the West African craton and a derivation from the Amazon craton (Grenvillian, Sunsas orogens), where such ages are common, is an alternative.",
    author = "H.P. Zeck and Michael Wingate and Gregory Pooley and J.M. Ugidos",
    year = "2004",
    doi = "10.1093/petrology/egh026",
    language = "English",
    volume = "45",
    pages = "1613--1629",
    journal = "Journal of Petrology",
    issn = "0022-3530",
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    }

    A Sequence of Pan-African and Hercynian Events Recorded in Zircons from an Orthogneiss from the Hercynian Belt of Western Central Iberia-an Ion Microprobe U-Pb Study. / Zeck, H.P.; Wingate, Michael; Pooley, Gregory; Ugidos, J.M.

    In: Journal of Petrology, Vol. 45, No. 8, 2004, p. 1613-1629.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - A Sequence of Pan-African and Hercynian Events Recorded in Zircons from an Orthogneiss from the Hercynian Belt of Western Central Iberia-an Ion Microprobe U-Pb Study

    AU - Zeck, H.P.

    AU - Wingate, Michael

    AU - Pooley, Gregory

    AU - Ugidos, J.M.

    PY - 2004

    Y1 - 2004

    N2 - Sensitive high-resolution ion microprobe U-Pb dating shows that a biotite orthogneiss from the Hercynian belt of western central Iberia contains 1000-300 Ma zircon. Older, 1000-570 Ma ages within this range represent inherited, detrital material among which four age components may be recognized: similar to980 Ma, similar to830 Ma, 616 +/- 10(2sigma) Ma and 582 +/- 5(2sigma) Ma. This inherited zircon commonly forms cores that are surrounded by rims Yielding Late Pan-African ages, identical to those found in slender, prismatic, and some stubbier, bi-pyramidal, euhedral crystals. This is the predominant hype of zircon with an average age of 546 3(2sigma) Ma, thought to have been formed during the main magmatic crystallization stage of the granitic protolith of the gneiss. Local deuteric replacements of magmatic zircon yield a virtually identical average age of 547 +/- 5(2sigma) Ma, suggesting rapid magmatic cooling, typical of shallow intrusive settings. Many zircon crystals have very thin, low-Th/U rims with an age of similar to315 Ma, suggested to represent the gneissfication of the granitic rock during the Hercynian orogeny. The abundance in the gneiss body of Al-rich restitic material and inherited, detrital zircon suggests that the granitic magma was formed by anatectic melting of a meta-sedimentary source rock complex. The age of the youngest inherited, detrital zircon constrains the sedimentation age of the (youngest parts of the) analectic source rock complex to the Late Neoproterozoic ( < 582 +/- 5 Ma) and leaves a maximum period of similar to40 Myr for metamorphism and anatexis of the source rock complex, and migration and intrusion of the granitic magma. Among the inherited, detrital zircon the 616 +/- 10(2sigma) Ma and 582 +/- 5(2sigma) Ma ages are by far the most abundant, and might be derived from the West African craton, where such ages are common for main-stage Pan-African complexes. The older, similar to980 Ma and similar to830 Ma inherited zircon ages are absent or rare in the West African craton and a derivation from the Amazon craton (Grenvillian, Sunsas orogens), where such ages are common, is an alternative.

    AB - Sensitive high-resolution ion microprobe U-Pb dating shows that a biotite orthogneiss from the Hercynian belt of western central Iberia contains 1000-300 Ma zircon. Older, 1000-570 Ma ages within this range represent inherited, detrital material among which four age components may be recognized: similar to980 Ma, similar to830 Ma, 616 +/- 10(2sigma) Ma and 582 +/- 5(2sigma) Ma. This inherited zircon commonly forms cores that are surrounded by rims Yielding Late Pan-African ages, identical to those found in slender, prismatic, and some stubbier, bi-pyramidal, euhedral crystals. This is the predominant hype of zircon with an average age of 546 3(2sigma) Ma, thought to have been formed during the main magmatic crystallization stage of the granitic protolith of the gneiss. Local deuteric replacements of magmatic zircon yield a virtually identical average age of 547 +/- 5(2sigma) Ma, suggesting rapid magmatic cooling, typical of shallow intrusive settings. Many zircon crystals have very thin, low-Th/U rims with an age of similar to315 Ma, suggested to represent the gneissfication of the granitic rock during the Hercynian orogeny. The abundance in the gneiss body of Al-rich restitic material and inherited, detrital zircon suggests that the granitic magma was formed by anatectic melting of a meta-sedimentary source rock complex. The age of the youngest inherited, detrital zircon constrains the sedimentation age of the (youngest parts of the) analectic source rock complex to the Late Neoproterozoic ( < 582 +/- 5 Ma) and leaves a maximum period of similar to40 Myr for metamorphism and anatexis of the source rock complex, and migration and intrusion of the granitic magma. Among the inherited, detrital zircon the 616 +/- 10(2sigma) Ma and 582 +/- 5(2sigma) Ma ages are by far the most abundant, and might be derived from the West African craton, where such ages are common for main-stage Pan-African complexes. The older, similar to980 Ma and similar to830 Ma inherited zircon ages are absent or rare in the West African craton and a derivation from the Amazon craton (Grenvillian, Sunsas orogens), where such ages are common, is an alternative.

    U2 - 10.1093/petrology/egh026

    DO - 10.1093/petrology/egh026

    M3 - Article

    VL - 45

    SP - 1613

    EP - 1629

    JO - Journal of Petrology

    JF - Journal of Petrology

    SN - 0022-3530

    IS - 8

    ER -