Significance of fold and lineament patterns in sulphide mineralization in the northeastern part of the Jabalpur (India) mineralized belt — A photogeological interpretation

Abstract

Photogeological reconnaissance studies in the investigated area of known base-metal occurrences aided in revealing the structural significance of fold and associated shear or lineament patterns in relation to sulphide mineralization. The structural analysis from aerial photographs of complexly folded and faulted, metamorphosed calcareous and argillaceous sediments indicated that the principal fold axis strikes ENE-WSW, which is normal to the theoretical NNW principal stress direction. Syntectonic with this fold deformation, first-order complementary shear or wrench faults (strike-slip faults) developed in N10°E and N50°W directions. The idea of a possible second-order fold system striking nearly parallel to the principal stress direction can be conceived from the development of thrust or longitudinal shears striking parallel or sub-parallel to the principal fold axis. The mineralized quartz veins in the area, the fluorite-bearing quartz porphyry in Imalia (lying outside and WSW of the present area in the mineralized belt) and the chalcopyrite-pyrite bearing, diorite-porphyry dyke exposed in the Mahanadi (a tributary of the Son) river section at Karua Kap (falling outside and ENE of the present area of investigation) mainly follow the N-S shears or wrench faults. Less frequently, the mineralized quartz veins follow the ENE-trending thrust shears which appear to displace the earlier N-S shears.