The nature of seismic reflections in the lower crust, the demarcation of crustal blocks through identification of shears, mylonite zones and regions of high fluid pressure; the outlining of the stages in crustal growth; the tracing of geochemical trends in crustal evolution; the identification of source of precious and base metal concentration in the lower crust; the dating of major crustal events through geochronological studies - these are some of the items on which much new evidence has still to be gathered. This is possible only through multi- disciplinary and multi-intitutional interactions, involving geologists, geophysicists and geochemists. Seismic profiling, Palaeomagnetism and rock magnetism, aeromagnetic surveys, gravity mapping, electromagnetic studies, geochemistry and geochronological studies, fluid inclusion studies, have a major role to play in this quest for new knowledge.

Advances in our understanding of the lithosphere have been made possible through such interdisciplinary studies. One of the ways in which this understanding can be gained is through the Global Geoscience Transects project (GGT) which aims at constructing crustal "cross-sections" or "lithospheric transacts". as they are called. In the construction of such transacts all available geological, geophysical and geochemical data Pire assembled on equal scale and with identical colour code, in order to allow for global comparison and display of the nature and evolution of the earth's lithosphere.

Through the kind courtesy of the Chairman of the Inter-Union Commission on the Lithosphere (ICL), it has been possible to include the Udupi-Kavali Transect with an explanatory text in this volume. Grateful thanks are due to Dr. T. Radhakrishna and Dr. M. Ramakrishnan for providing the transect and to Prof. Hanz jurgev Gotze for permitting the inclusion of the transect in this volume as a joint publication of the ICL and GSI.

Closely associated with this programme of Deep Continental Studies is a sister project of 'Continental Drilling which several advanced countries have initiated. Holes are to be drilled to a depth of up to 10 km into the crust under this programme. The results of drilling coupled with deep seismic profiling are expected to result in a major contribution to the understanding of continental crust. Progress so far made in this regard has indicated the important role played by fluids. Waters rich in potassium and twice as salty as sea water have been encountered at deep levels. Zones rich in fluids appear to be a causative factor for strong seismic reflection. Deep drillings by the Germans have indicated a rate of increase in temperature higher than that originally assumed. The temperature was stated t6 be 100'C at a depth of 4000 m. The temperature predicted at depths of 7 to 8 km could be as high as 300' C! If temperatures of this order are to be encountered within a depth of 10 km, human ingenuity should be capable of tapping this energy source for the production of electricity, thereby reducing dependence on fossil fuels. We have in our own country an example of a deep hole at Kolar where undergound mine workings have reached a vertical depth of 3 km. Thetemperature at that depth is 150'F. If the shafts were to be deepened by another 1000 m, temperature at that depth should be sufficiently high to produce steam which could be utilized for generation of electric power.

A correct understanding of the nature and action of fluids in the deeper parts of the crust and along shear zones traversing the crust is another aspect of considerable economic importance. Many of the shear zones at intermediate levels show quairtz-carbonate veins enriched in gold. The lodes of Kolar gold field which have produced to date more than 700 tonnes of gold are confined to shear zones and the lodes themselves are full of CO 2-rich fluid inclusions. A relation between CO 2 streaming and concentration of gold is becoming apparent. Deep Continental Studies, therefore, appear to hold promise of exciting new possiblilities.

The Earth Science division of the Department of Science and Technology, Government of Inida has taken the initiative in implementing a multidisciplinary research programme of 'Deep Continental Crustal Studies' (DCS) by concentrating on certain critical transacts of the Indian Lithosphere. Presently a transect running from Jaipur to Raipur is in progress. In addition, it has a proposal to take a N-S transect in the southern region starting from Raichur in the north to Kanyakumari in the south.. As a preliminary to carrying out such a transect programme, DST felt it advisable to collect all the data that was available - geological, geophysical and structural - so that such information becomes readily accessible to all those engaged in this study. DST sought the assistance of the Geological Society of India, in fixing the line of traverse; and in identifying persons and institutions that could get involved in the programme.

The first meeting in this connection was held at Bangalore on 26th March 1991 and was followed by a workshop between the 26th and 27th July of the same year. At the conclusion of the workshop it was decided that the Society should bring together all the pertinent data and publish as a separate volume which could serve as a book of reference for future studies. The present volume is the result of this decision.

I am thankful to the several authors who have contributed review articles specially written for this volume. In order to make the coverage more comprehensive and representative of all aspects, a few original research papers published in outside journal have been reproduced with the kind permission of'the publishers as well as the authors. The papers included in
the volume are expected to bring into focus ma or gaps in our knowledge in understanding the building up of the continental crust of south India.

The Society is under a deep debt of gratitude to the Department of Science & Technology for entrusting to it this responsible work and for funding the meetings and Publication of this volume.