How deceptive are microstructures in granitic rocks? Answers from integrated physical theory, phase equilibrium, and direct observations

M. B. Holness*, J. D. Clemens, R. H. Vernon

*Corresponding author for this work

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    14 Citations (Scopus)
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    Abstract

    In this contribution, we address the vexed question of the extent to which microstructures in granitic rocks reflect their igneous histories or have been masked by later events. The previous works have tended to address the problem either using theoretical or modelling considerations, or by interpretation of observed microstructures. Here, we use an approach that integrates the theory of microstructural development and the results of experimental phase-equilibrium studies with direct observation of natural examples on a variety of scales. We show that the predictions of the theoretical and experimental approaches agree perfectly with the mesoscopic and microscopic evidence from granitic rocks themselves. Our conclusion is that although, in many cases, granitic rock microstructures have been modified by near-solidus reactions and crystallisation, in the absence of tectonic deformation the fundamental elements of their igneous heritage remain intact. This means that it is perfectly in order to infer aspects of crystallisation sequences, magmatic reactions, and magma flow through careful microstructural observations. Thus, our answer to the question of how deceptive granitic textures are is, in most instances, 'not very'. However, some undeformed plutons have undergone fluid-driven alteration, and others have been affected by contact metamorphism. Thus, each case should be examined on its own merits.

    Original languageEnglish
    Article number62
    Pages (from-to)1-18
    Number of pages18
    JournalContributions to Mineralogy and Petrology
    Volume173
    Issue number8
    DOIs
    Publication statusPublished - Aug 2018

    Bibliographical note

    Copyright the Author(s) 2018. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

    Keywords

    • Granitic rocks
    • Textural development
    • Microstructure
    • Textural equilibration
    • Recrystallisation
    • Textural modification

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