DefinePK

Abstract

The Manserah pluton is a very typical example of the discontinuous belt of two mica-cordierite granites of the “Lesser Himalaya”. It is aluminous, quartz rich but feldspar and sodium deficient, and igneous "microgranular" inclusions are frequent. Severely deformed to the North, the Manserah pluton has been metamorphosed and gneissified during the Himalayan orogeny. Rb-Sr whole rock isotopic data give a well defined seven point isochron with a Cambrian age of 516+ 16 m.y. The high initial ratio of 0.7189 +- 6 implies derivation from a source containing a major and very old crustal contribution. The geodynamic framework for the genesis of this huge belt of similar plutons could be that of a simple thinning of a Precambrian shield or that of a late Pan African orogeny.