Insights into collisional magmatism from isotopic fingerprints of melting reactions.

Piston-cylinder experiments in the granite system demonstrate that a wide variety of isotopically distinct melts can arise from progressive melting of a single source. The relation between the isotopic composition of Sr and the stoichiometry, of the observed melting reactions suggests that isotopic signatures of anatectic magmas can be used to infer melting reactions in natural systems. Our results also indicate that distinct episodes of dehydration and fluid-fluxed melting of a single, metapelitic source region may have contributed to the bimodal geochemistry of crustally derived leucogranites of the Himalayan oroge