Geochemical prospecting for groundwater in the granitic terrain around Ghatkesar,A.P. (India)

Soil samples collected from a depth of 8 cm near open wells were studied. Finer (minus 80-mesh) fractions of soil from the A-horizon contain more Mn and Fe compared to coarser fractions and these elements show higher concentrations in soils around wells with a deeper water-table. Greater weathering due to percolation of larger volumes of water through soil results in thorough decomposition of all the minerals, liberating the elements. During this process iron hydroxides with very little Mn form large fragile fragments. Higher Fe/Mn ratios in the minus 44 plus 60-mesh fractions of these soils are characteristic of deeper, high-yielding wells and have a positive correlation with depth of water table.