Flow breccias, formed at the margins of blocky andesite lavas, can be reheated, welded and sometimes deformed to form rocks reminiscent of welded pyroclastic rocks. Reheating occurs due to advection of heat from the flow to the basal breccias. Surface breccias also infill extensional crevasses which are later closed and compressed. Strongly deformed welded breccia bands form within the flow levees. The angular breccia clasts can be deformed into fiamme.
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Sparks et al. (1993) studied this question.
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