Filtering of hydraulically significant lineaments from lineament map of precambrian metamorphic terrain in NE India using set theory

Abstract

Identification of hydraulically potential lineaments directly from lineament map required for studies of groundwater resource development in crystalline metamorphosed rock terrain, which is considered as a poor groundwater province area, is a big challenge. Lineament study from satellite image gives all available lineaments present in the location including the hydraulically potential lineaments. But there are no existing methods present at our disposal which can detect only the hydraulically potential lineaments. This study attempts to delineate the hydraulically significant lineaments those are actively promoting groundwater flow in Purulia district, West Bengal, NE India, where the exposed rock-types are porphyritic granite gneisses, quartzite, mica schist, garnetiferous-sillimanite-biotite schist and phyllite, using Set theory. For the study, standard FCC image setup has been used to view the satellite imagery on computer screen within Erdas Imagine software and lineaments are examined visually on-screen, without taking any print out of the map. The azimuth directions of the lineaments are diagrammed using GEOrient software. Azimuth rose diagrams of the trend of foliation planes and fracture planes, obtained from direct measurement at rock exposures, are compared with the lineament trends to yield hydraulically significant lineaments, concordant to the trends of hydraulically significant fractures. Hydraulically significant lineaments are filtered from the total lineament map by using the laws of set theory, like universal set, sub-set, union, intersection, subtraction and equality. Validation of the obtained result with ground truth reveals that intense deformation of brittle rocks, that allow fluid movement, have a significant role in the development of hydraulically significant lineaments. This study successfully distinguishes the hydraulically significant lineaments, exhibiting a directional concurrence to hydraulically significant fractures, implying that set theory can be successfully used to extract hydraulically significant lineaments directly from lineament map.