Are granitic intrusions scale invariant?

K. J W Mccaffrey*, N. Petford

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    174 Citations (Scopus)


    Published length (L) and thickness (T) data on 135 laccolith and 21 granite intrusions define power-law relationships of the form L=kTa typical of systems exhibiting scale invariant (fractal) behaviour. Both data sets are characterised by an exponent a<1 (0.88 ± 0.1 for laccoliths and 0.80 ± 0.20 for plutons) that reflects an inherent preference for scale invariant tabular-sheet geometries. These power-law size relationships can be explained in mechanical terms by the need for an incoming magma sheet to travel laterally some distance before vertical thickening can occur. Sheet thickness is a function of available magma pressure which for an intrusion fed by a feeder dyke is proportional to the vertical magma transport distance.

    Original languageEnglish
    Pages (from-to)1-4
    Number of pages4
    JournalJournal of the Geological Society
    Issue number1
    Publication statusPublished - Jan 1997


    • Fractals
    • Granites
    • Intrusions
    • Magmas
    • Shape


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