Integrating exploration dataset in GIS using fuzzy inference modeling Application of fuzzy operators on exploration dataset Brief Geology and Mineralisation The Singhbhum Shear Zone is developed along the southern fringe of the Proterozoic Fold Belt of North Singhbhum. This fold belt is sandwiched between the Early Archean Cratonic Nucleous represented by Singhbhum and Bonai Granite in the south and Proterozoic Chottanagpur Granite Complex to the north. The intervening gap area between the Singhbhum and Chottanagpur crustal province, is occupied by a curvilinear belt of metasedimentaries belonging to Dhanjori and Singhbhum Group of Proteropzoic age. The Singhbhum shear zone which has developed in this Proterozoic belt, is a northery dipping arcuate ductile shear zone (Ghosh and Sengupta, 1987) marked by lenticular mylonite zone. The width and trend of the shear zone is 10 km and SW-NE in the western part , gradually narrows down to 1 km and E-W in the central part and again widens to more than 5 km and NW-SE in southeastern part. In the southeastern part the shear zone splits into a number of N-S trending narrow shear zones (Banerji,1981). In the western part the shear zone branches out and follows the northern and southern boundary of Chakradharpur Granite Gneiss. The rocks within the Singhbhum shear zone form a tectonic mélange comprising of granite mylonite, quartz-mica phyllonite, quart-tourmaline rock and deformed volcanic and volcanoclastic rocks (Mukhopadhyay and Deb, 1995). The shear sense indicator suggests a thrust type of deformation (Mukhopadhyay and Deb, 1995). The copper mineralised zone runs parallel to Singhbhum Shear Zone. The principal ore in this belt consists of chalcopyrite, pyrite and pyrrhotite. The ore zones form a number of parallel to sub-parallel discontinuous lodes aligned along the major tectonic grains of the area. Mode of occurrence varies from massive to braided veins, stringers, dissemination and discordant to sheet like bodies. Volcanic origin of the orebody has been suggested by several workers on the basis of d34 S data. Existence of both structural and stratigraphic control on ore localisation is apparent. The general trend of the orebody is controlled by the local trend of shear bands, these bands also act as a channel for remobilisation (Anon, GSI, 1991). Chloritisation, sericitisation, biotitisation, tourmalinisation and albitisation are common wall rock alteration products (Anon, GSI, 1991). 
Exploration model
GIS data set The GIS data set comprises of following layers Lithology and favourable contacts: Existing field geological map, compiled in 1:50000 scale was digitised. After creating the polygon topology, lithological attributes are updated. Similarly the favourable lithological contacts were also digitised from the same map. Lineament, fault and shear zone: The lineament map interpreted from satellite imagery (courtesy Mr. D.P. Das, Geologist (Sr.), GSI) were digitised. The shear zone and faults were digitised from compiled degree sheet of 73J in 1:2,50,000 scale and 1:50,000 scale compiled geological map respectively. Alteration: The main lithounits underwent alteration mentioned above were digitised from the compiled map. Geophysical: The contours of aeromagnetic map were digitised and converted into polygon topology. The polygon attribute values are updated from contour value. The ground linear anomaly axis of IP,SP,EM and magnetic were digitised from exiting ground geophysical map. Geochemical: Interpreted geochemical anomalies (generated from analytical value of bed rock samples) in the form of available contour maps were digitised into polygon coverage. Generation of fuzzyset The exploration model outlined earlier suggests the importance of each GIS dataset in analysis.The pricipal approaches taken for calculating fuzzy membership values are illustrated below.
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