In the High Himalayan Crystalline Series of Northwest India, numerous peraluminous
granites intruded the metasediments of the late Proterozoic to early late Cambrian Haimanta Group.
Nd and Sr isotope systematics confirm that they were derived from heterogeneous crustal sources.
New geochronological data from two plutons range in age from late Precambrian to early Ordovician:
single zircon U–Pb dating yielded an age of 553 ± 2 (2σ) Ma for the Kaplas granite, whereas mineral
Sm–Nd isotope systematics define a crystallization age of 496 ± 14 (2σ) Ma for the tholeiitic mafic
rocks in the Mandi pluton, where evidence of magma mingling documents a close association between
mafic and granitic melts. The end of this period of magmatic activity coincides with the depositional
gap below the Ordovician transgression, caused by surface uplift and erosion, that is an important
feature in the stratigraphy of the Northwest Himalaya. In Spiti, the transgression of the Ordovician
basal conglomerates on a normal fault indicates pre-Ordovician extensional faulting. Therefore, the
early Palaeozoic magmatic activities in the Northwest Himalaya could be correlated with a late extensional
stage of the long-lasting Pan-African orogenic cycle which ended with the formation of the
Gondwana supercontinent.