Mineral Potential of the Dhanjori Metavolcanics, East Singhbhum, Jharkhand

摘要

Deep Electrical Profiling (DEP) has proved to be very useful in identifying buried conductive anomalies in Dhanjori basin. 2-D modeling of such anomalies indicated a near vertical conductive body (80 ohm m) within the metabasics of Dhanjoris. A deep stratigraphic cum structural borehole drilled vertically upto a depth of 768 m over this anomaly zone revealed flat lying metavolconic assemblages grading from acidic to ultra basic in composition with interlayering of tuff and sediments. At least four different flows have been identified following the classical top and bottom criteria followed in stratigraphy. The bore hole lithology is in itself a revealation as it is different from the expected lithostratigraphy of Dhanjori basin. The metabasics are highly sheared and striated and the propensity of shearing increases with depth. Deep Electrical Sounding (DES) has been successful in estimating the thickness of the lithopackage which is within 1 km. SP, resistance, natural gamma ray logs run up to 750 m deptindicate 37 distinct conductive zones, varying from a fraction of a meter to several meters. Some of these are sulphides with pyrite, chalcopyrite, covellite and arsenopyrite assemblages. Density and chargeability values measured in the laboratory on selected core samples corroborate the above findings.