Leucogranites in Zanskar make no exception to the rule and their mineralogical composition is remarkably constant. As for the other Himalayan regions, the leucogranites in the studied area can be grouped in two categories, the tourmaline facies and the biotite facies, depending essentially on the presence or absence of biotite or garnet and the amount of tourmaline and muscovite. The texture of both leucogranitic facies is equigranular.
The tourmaline facies is formed of quartz (30 - 35 %), plagioclase (35 - 40 %), K-feldspar (15 - 25 %), muscovite (~ 5 %) and tourmaline (~ 5 %).
The biotite facies is formed of quartz (30 - 35 %), plagioclase (35 - 40 %), K-feldspar (15 - 25 %), muscovite (10 - 15 %), biotite (5 - 10%) and tourmaline (~1 %).
In general both type of leucogranites are exceptionally fresh in thin sections and sericitisation of the F-feldspar or chloritisation of the biotite is very rarely observed.
Pegmatites and aplites belong to the tourmaline facies because they have all the mineralogical characteristics of this category of leucogranites. As the pegmatites and aplites are often undeformed by extensional movements, they are among the last intrusives.
Consequently we interpret the tourmaline facies as intruding chronologically later than the biotite facies and representing a later stage of the magmatic evolution.
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