.....for young melts within the Nanga Parbat massif. Further details are provided by Butler et al. (1997).
The leucogranites are characterised by very high 87-86 strontium isotopic ratios (values of up to 0.88 in the main bodies and over 1.0 in some pegmatitic sheets). The Rb-Sr ratio and rare earth geochemistry argues for these being very small-volume batch-melts generated from the breakdown of muscovite without the presence of appreciable volumes of fluid. Low-vapour melting is supported by field relations - because the leucogranites have migrated away (?up several km) from their source migmatites. In contrast, wet melts tend to crystallise more readily as they rise in the crust.