Non-linear deformation and break up of enclaves in a rhyolitic magma: A case study from Lipari Island (southern Italy)

A dome from Lipari Island (Southern Italy) consists of 12 vol.% of circular, elongated and folded latitic enclaves hosted in a rhyolitic matrix. The dm- to cm-scale enclaves are more deformed than the mm-scale blobs. The critical value of the ratio between the viscous forces, which allow deformation and eventually break up blobs of latitic magma, and the interfacial tension forces is larger than 0.29. The Reynolds number is <5.3. The equivalent radius and the axial ratio of the enclaves follow power-law distributions. This feature suggests that the break up and stretching of magmas are non-linear, scale-invariant, probably cyclic processes. The coexistence of enclaves of different shape and the self-similar size distributions suggest that chaotic advection plays a major role in the formation of mingled magmas. Caution must be used when measuring the finite strain from enclave shapes because they may break apart during the deformation. Copyright 2004 by the American Geophysical Union.