Volume and composition relationships between granites and their lower crustal source regions: An example from central Victoria, Australia

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Abstract
The widespread occurrence of S‐type granites and volcanic rocks in central Victoria requires the lower crust (deeper than 17 km) to contain a metasedimentary layer 2–14 km in thickness. The remainder of the crust must consist of mafic granulites. Some of this mafic lower crust is probably the restitic remnants of the sources for I‐type granites and the balance is inferred to be non‐restitic metagabbros and cumulates formed from the magmatic heat source which initiated the crustal fusion event. In this region, the Late Devonian was a great period of crustal growth (through basaltic underplating) and differentiation (through partial fusion and the ascent of felsic magmas). The generation of granitic batholiths need not involve partial fusion of large fractions of the underlying crust.