Observation versus argument by authority - The origin of enclaves in granites

Ron H. Vernon*

*Corresponding author for this work

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    The essentially human nature of science is well illustrated by the long-standing success of a very unsatisfactory hypothesis for the origin of igneous-looking enclaves ("microgranitoid enclaves," "mafic inclusions") in granite, which effectively stifled progress in understanding their origin for 60 years. The hypothesis stated that solid, commonly metasedimentary rock fragments (xenoliths) undergo "reciprocal reaction" with granitic melt, and are thereby converted to rocks of igneous appearance and composition. It was based on sound chemical principles inferred from experimental data, rather than observation. However, a 100-year-old paper by Phillips made a careful, descriptive distinction between igneouslooking enclaves and xenoliths; and a 50 year-old paper by Pabst hinted that the microgranitoid enclaves may have been magmatic when incorporated in the granite. Both papers were based on careful field and microstructural observations, but were largely ignored, owing to the overwhelming popularity of the theoretical "reciprocal reaction" hypothesis, as argued persuasively by petrologists of high scientific standing. However, a return to field and microstructural evidence is indicating that microgranitoid enclaves in both metaluminous and peraluminous granites most probably have a magmatic origin.

    Original languageEnglish
    Pages (from-to)57-64
    Number of pages8
    JournalJournal of Geoscience Education
    Volume44
    Issue number1
    Publication statusPublished - Jan 1996

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    Keywords

    • Education - graduate
    • Education - undergraduate
    • Geology - general
    • Petrology - igneous and metamorphic
    • Science

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