Writers : Sharma.Anjana , Ahmad.Talat and Mukherjee.P.K
Refference : Geosciences Scientific Quarterly Journal,No.:8,P.:74

Abstract :

Himalaya has a record of pre-orogenic mafic magmatism widely distributed in space and time. Volcanism during Proterozoic and Ordovician appears to have restricted to the western and central parts of the Lesser Himalaya, the late Permian to Cretaceous magmatism is recorded in the whole region (from east to west), although the focus of magmatism shifted from Lesser to Tethyan Himalaya (Fig 1). In this paper we review the data available on these Himalayan volcanics to put constraints on their genesis, source characteristics and tectonics of their eruption.
Trace element based classification reveal that the Proterozoic volcanics are mostly tholelitic whereas the younger ones are both tholeiitic and alkaline, some being transitional in nature.
We infer predominance ot lithospheric input in the generation of older volcanics and asthenophere appears to have influenced in the generation of younger volcanics. This implies that the magmatism in the Himalayan region essentially started in an interrupted extensional continental environment which caused the attenuation of lithosphere and abrupt ascent of asthenosphere at later stages, resulting in secular variation of basalt chemistry in the Himalayas.

Subject List : Petrogenesis