Hydrochemistry deducing basaltic trap thickness for groundwater resource mapping along the Deccan Volcanic Province (DVP) margin in India

摘要

It is hypothesized that hydrochemical parameters can be employed to deduce the basaltic trap thickness and that there exist diverse hydrochemical processes within the existing host rocks along the Deccan Volcanic Province (DVP) margin. Chemical imprints of aquifers, in various flows of flood basalt and fissured zones of granites, had been appraised using major ion chemistry of groundwater in a test site of 623 km~2 at the southern margin of the DVP in India. The wide ranging hydrochemical processes, obtained from empirical data, describe the predominance of carbonate, dolomite, calcite and anorthite weathering in basalts, and alkali feldspar (albite and orthoclase) in granites. Results showed that the elevated concentrations of alkaline earth elements in basaltic aquifers and alkali rich elements in granitic aquifers were useful in tracing the sources of host rock for dissolved mineral reactants. Further, a digital elevation model using Shuttle Radar Topography Mission (90 m) elevation satellite data aided in deciphering trap thickness, vertical transition zone of trap and granitic basement comprising the well depths and hydrochemistry. The mapping of trap thickness is useful to explore the groundwater resources at the vertical transition zone between the basaltic trap and granitic base. The estimated thickness of the basaltic trap is varied from 4 to 98 m at the DVP southern margin, which is further verified with the help of exploratory well lithologs matched closely.