A GIS approach in Mineral Targeting with Narayanpet Kimberlite Spatial Dataset

A GIS approach in Mineral Targeting with Narayanpet Kimberlite Spatial Dataset

Praveen Kumar Sinha
Geologist (Jr.), AMSE Wing , Project INDIGEO, Training Institute, Geological Survey of India, Banglore
E-mail : gsitihyd@hd2.dot.net.in

Dr. M. Surendra Nath
Geologist (Sr.), Address:Project INDIGEO, Training Institute, Geological Survey of India,Bandlaguda,Hyderabad-500068
E-mail : gsitihyd@hd2.dot.net.in

Sikhendu De
Geophysicsist (Sr.), AMSE Wing, Project INDIGEO, Training Institute, Geological Survey of India,Banglore

Dr. P. K. Murlidharan
Director (Geol.), Project INDIGEO, Training Institute, Geological Survey of India, Bandlaguda, Hyderabad-500068
E-mail : gsitihyd@hd2.dot.net.in

Ravi Shankar Misra
Geophysicsist (Sr.), Project INDIGEO, Training Institute, Geological Survey of India, Bandlaguda, Hyderabad-500068
E-mail : gsitihyd@hd2.dot.net.in

Introduction
Diamond, as a lustrous precious stone, has human fascination since historical times. In India, well known epics - the Ramayana and the Mahabharata have mention of ornaments of diamonds. India continued to have dominant position in diamond mining and trade till beginning of the 18th century. But, mining of the diamond on large scale started with real 'rush' in the last quarter of the 19th century in South Africa. The 'rush' in gradual process founded the basis for the modern scientific methods of exploration. Kimberlite was identified as the primary source. Index minerals were identified as exploration tools. Thermodynamics of diamonds and host-rock-mineral-entities and association helped in re-establishing the relation between the host rock and diamonds. Mineralogical assemblage, geophysical signatures and geochemical attributes of the primary rock become the implements for integrated approach in prospecting. Airborne surveys and remote sensed data were inducted in the search process. By now, there are sufficient numbers of discoveries world-over to establish the pattern of distribution in tectonic set-up and localisation in plate-tectonics model. The broad outlines used in exploration for primary source of diamonds can be summarised in the following lines :

Kimberlite Emplacement Model: Theoritical facts

World over, majority of the kimberlites are emplaced in ancient cratonic blocks (Clifford,1966) or where Archaean basement is underlain by deep lithospheric keels (Haggerty, 1986) .
Productive or diamond bearing kimberlites are emplaced in areas where surface heat flow is generally less than 40 Mw/m². This condition is suitably available in majority of the cratonic blocks.
Ascent of kimberlite melt is from upper mantle but below the graphite-diamond stability surface (i.e., where pressure >45 to 60 Kb = 150-200 km depth and temperature from 900º to 1300º C ).
The melt intrudes through pre-existing deep-seated faults / fractures, which have their roots in upper mantle.
The deep-seated faults and deep-seated fractures are well depicted on the imageries in the form of lineaments traversing hundreds of kilometers.
After reaching the lower level of the upper crust, the melt finds a number of shallow faults / fractures in its way. The melt intrudes into these weak zones of varied orientation in the form of cones and dykes.
The kimberlites are usually localised in zones of high magmatic permeability and repetitive basic and ultrabasic magmatic activity (Kaminsky et al., 1995).
The kimberlites occur in clusters and such clusters make a field (of 1 to 50 or more bodies Janse,1984, Mitchell,1986) and a set of fields a province.
Mantle-xenoliths and xenocrysts, along with diamonds, are inducted into the accelerated-ascent of melt from the upper mantle environment and diamond stability zone.

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