Petrographic discrimination of low- and high-temperature I-type granites

Allan J R White*, Bruce W. Chappell

*Corresponding author for this work

    Research output: Contribution to journalArticle

    15 Citations (Scopus)

    Abstract

    The existence of two groups of I-type granites, those formed at relatively low- and high-temperatures, has been established using differences in zircon saturation and patterns of bulk compositional variation between those two groups. Granites of these two groups also show some distinctive petrographic differences. The clearest petrographic distinction between the low- and high-temperature granites is seen in the crystals of plagioclase. In all but the most felsic low-temperature granites these crystals are always complex and commonly have corroded cores, which may be as calcic as An80. Core compositions are fairly uniform in composition compared with the outer parts, which display normal and oscillatory zones of varying widths. In the high-temperature granites the crystals of plagioclase are generally better-shaped with a uniform composition and lack the prominent corroded cores of the low-temperature granites. These differences are due to the fact that homogenization of plagioclase proceeds very slowly at low magmatic temperatures.

    Original languageEnglish
    Pages (from-to)215-226
    Number of pages12
    JournalResource Geology
    Volume54
    Issue number3
    Publication statusPublished - 2004

    Keywords

    • Ab-An system
    • High-temperature granite
    • Low-temperature granite
    • Petrography
    • Plagioclase cores
    • Plagioclase zoning
    • Restite
    • Zircon saturation

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    White, A. J. R., & Chappell, B. W. (2004). Petrographic discrimination of low- and high-temperature I-type granites. Resource Geology, 54(3), 215-226.