Himalaya (Geological Aspects)

The volume is mainly focussed on structural and metamorphic characteristics of the Himalayan rocks exposed in various sectors of the Himalaya. The peridotites in the Spongtang nappe of Ladakh are mylonitised and occur in superposed imbrications. The regionally metamorphosed pelitic rocks of a part of Kashmir show low pressure, intermediate and medium pressure of metamorphism. The Buniyar granite is an intrusive plunton in the Dogra Slates (Precambrian) in the Western part of Kashmir. The NE-SW compressional stress was responsible for development of multiple folds in metamorphics of Chamba area. The radiometric date of granites in Chor mountain is Pre-Tertiary (1000 m.y and 525 m.y.). The metamorphic and folding processes of the Chor pelites were terminated by the Jutogh thrusting phenomena. The crystallines of Palampur (Himachal) are characterised by the Chail thrust and contain about 12 types of garnet texturally. The Manali-Rohtang Pass area forms a part of an overturned limb of the Crystalline nappe. The thrusts in the Kumaun region developed from the hinterland to foreland. The total displacement of the Munsiari, Krol and Berinag Sheets was about 330 km. The Purola area in Garhwal is located between the Main Central Thrust and the Tons Thrust. Metamorphics in the Bhagirathi valley were formed at the temperatures ranging from 479° to 666° C. The uranium mineralisation in the granite-gneisses and the footwall quartzite took place after the formation of the Main Central Thrust III in Tehri Garhwal. The rock-fabric (b-c girdles of quartz) in rocks of Lansdowne Crystalling nappe developed along the thrust-transport direction with rotation which is exhibited by triclinic symmetry. The fracture and lineament patterns were formed in the frontal parts of the Himalaya. The Lesser Himalaya region in Himachal Pradesh has overlapping crystalline thrust. The Chail nappes are traceable throughout the length of the Lesser Himalaya. The nappe thrusting in two phases occurred in Eastern Nepal during middle Tertiary and Quaternary times. Simple shear type of deformation affected the rocks in Eastern Nepal. The high heat flow in rocks of Darjiling region was responsible for the first phase of metamorphism which was followed by overturning and thrusting during the second phase of deformation. The metapelites in Eastern Sikkim are characterised by Kyanite-sillimanite isograd with associated quartzofeldspathic melt during pre-and syn-kinematic deformation. The reflected Aravalli trends are present in Arun transanticline and Tista Dome in Bhutan. The Central Tibetan region was possibly the homeland for the nappes in the Eastern Himalaya.

These volumes would be useful to earth scientists, academicians, research scholars and for those interested in complex problems of the geology of the Himalaya.

Dettagli