Amphibole-rich polycrystalline clots in calc-alkaline granitic rocks and their enclaves

A. Castro, W. E. Stephens

    Research output: Contribution to journalArticlepeer-review

    Abstract

    A petrological study of amphibole-rich polycrystalline aggregates (clots), including field relationships, textures, mineral chemistry, and compositional zoning has been carried out to constrain possible origins and petrogenetic significance. The two plutons chosen, the Quintana pluton in the Hercynian belt of Iberia and the Strontian pluton in the Caledonides of Scotland, differ in age and tectonic setting. In both, amphibole-rich clots are present in microgranular enclaves and in the host granitic rocks. The clots are generally zoned. In general terms, the core is actinolite, and the rim, magnesian hornblende. This "reverse' zoning can be explained by a complex reaction with early pyroxene. The origin of the pyroxene precursors to these amphibole clots is not well constrained by this study, but the prismatic form of these clots in the enclaves suggests that those preserved in enclaves were originally idiomorphic magmatic phenocrysts, whereas those in the host granite could also have a restitic origin. -from Authors

    Original languageEnglish
    Pages (from-to)1093-1112
    Number of pages20
    JournalCanadian Mineralogist
    Volume30
    Issue number4
    Publication statusPublished - 1992

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