MAFIC ENCLAVES IN GRANITOID INTRUSIONS - A CATASTROPHIC MODEL OF RHEOLOGICAL BEHAVIOR

The significance of mafic enclaves as indicators of magma mixing proce sses between juxtaposed felsic and mafic magmas is evaluated from a th eological point of view. A qualitative model for explaining strain and morphological changes in the enclaves has been developed on the basis of the catastrophe theory. Mafic enclaves in intrusive granitoids com monly behave as physical systems that can be described using a cusp ca tastrophe model. Their behaviour is characterized by bimodality, diver gence and sudden changes, which are properties typical of this model. Accordingly, the presence of mafic enclaves showing variable strain an d morphology within the same granitoid intrusion would be indicative o f mutual interaction and mingling between mafic and felsic magmas. Due to the characteristics of these precesses, it is not possible to esta blish unambiguous age relationships between the two magmatic component s.