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Large silicic ignimbrites commonly erupt from compositionally variable reservoirs. Although ignimbrite compositional architecture is often consistent with evacuation of a single zoned magma body, other examples are better interpreted as the products of amalgamation of multiple discrete subvolcanic melt-rich lenses. For example, multiple populations of pyroxene crystals and glass fragments within single ignimbrites from the central Snake River Plain (Idaho, USA) support the multibatch model. This presents a conundrum in terms of magma generation and storage; if the crystal-poor silicic magma batches are not generated nearly in situ in the upper crust, they must traverse, and reside within, a thermally hostile environment with large temperature gradients, resulting in low survivability in their shallow magmatic hearths. Ubiquitous crystal aggregates in central Snake River Plain rhyolites hint at another model …