Subsequent to migmatization, the leptynitic gneisses were intruded by garnet-bearing leucogranitic melts (L2), forming veins parallel and subperpendicular to the foliation. The leucogranites are rich in potassium (K2O ~ 5.5 wt %), Ba (~ 400 ppm) and Sr (~ 300 ppm) and exhibit low concentrations of Zr (~ 40 ppm), Th (< 1 ppm) and Y (< 10 ppm). The chondrite-normalized REE spectra show low abundances (LaN ~ 20, LuN ~ 3) and are moderately fractionated (LaN/LuN ~ 7). A Eu anomaly is absent or weakly negative. The higher 87Sr/86Sr ratio at 550 Ma (0.7345) compared to the migmatite (0.7164) precludes a direct genetic relationship between leptynitic gneisses and leucogranites at Manali. Nevertheless, the chemical and mineralogical composition of the leucogranites strongly favour a derivation through fluid-absent biotite melting of isotopically distinct but chemically comparable Manali-type gneisses. The undersaturation of Zr, Th and REE, a typical feature of leucogranitic melts generated during granulite facies anatexis of psammo-pelitic lithologies and attributed to disequilibrium melting with incomplete dissolution of accessory phases (zircon, monazite), is weakly developed in the leucogranites of Manali. It is concluded that this is mainly due to the sluggish migration of the melts at static conditions which facilitated equilibration with the restitic gneisses.
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