A Geophysical and Petrophysical Appraisal of a Possible Origin of Himalayan Rivers and Glaciers

Recent investigations of the seismic, electrical conductivity and rheological structures of the continental crust favours the presence of a fluid-rich layer at the mid and lower crustal levels. Such layers may exhibit high electrical conductivity, seismic reflectivity and ductility. In the light of this observation the results of (i) geomagnetic depth sounding (GDS) experiment carried out by means of a magnetometer array (MMA) spread over a large area along the Delhi-Aravalli belt (DA-B) and (ii) petrological investigations to recover the (P,T) regimes of the Vaikrita formation near the Main Central Thrust (MCT) are examined. It is suggested, on combining the findings of these studies. that owing to the-(a) thrusts and consequent uplifts of the crustal block and (b) intense compressive zones due to collision, the deeper crustal layer may be exposed or lie close to surface in the Himadri region. The metamorphic characteristics of the crystalline complex near the MCT and the high Himalayan topographic front corroborates this. The uparching (folding) and uplift of these (ductile) layers may, in turn release, with great force, the fluid (including free water) and volatiles. Such a thermotectonic mechanism may have significantly contributed in the development of the water regimes of the Himalayas. The mechanism involves (a) development of fluid (water) rich deep crustal layer and (b) intensely compressive regime as exists in the convergent boundary. The former may take place when the continental crust is thermally treated which may be the case, if the Reunion hotspot has carved out a trace (from Vaikrita to Cambay via DA-B) as has been recently suggested.