Abstract

Diapirism is a themomechanically viable ascent mechanism for granitic magmas. However there is very little direct evidence of actual granite diapirs. Many of the characteristics we may expect to use to determine ascent mechanisms are destroyed by changes in the shapes of intrusions resulting from the interaction of buoyancy and tectonic forces during emplacement. Many features of ballooning plutons are identical to those we would expect for diapirs. Notably, patterns of strain deduced from deformed xenoliths and concentric foliations, cannot be used as unambiguous evidence for diapirism. Diapirism can only be proven beyond doubt where it is possible to demonstrate vertical uplift of country rocks in excess of the vertical thickness of the intrusion.

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