Hydrochemical signatures of deep groundwater circulation in a part of the Himalayan foreland basin

Groundwater samples were analyzed from 71 springs and wells as part of a larger study in a region of compressional tectonic regime. The study site covers the Peshawar basin and surroundings in the Himalayan foreland of Pakistan. The northern portion is mountainous and the water table is discontinuous in different intermontane valleys, with abundant springs (with normal and anomalous temperatures and composition). The southern part is divided into isolated basins with a number of drilled (“deep”) and dug (“shallow”) wells. Hydrochemical signatures of elevated strontium (Sr), SiO₂, boron (B)—and the geothermometric signatures—all indicate a deep circulation of the emerging groundwater. Moreover, for several of the sample sites, water chemical compositions, measured spring and water well temperatures, and reservoir temperatures calculated for spring waters, all point to origin from deep horizons within the basin. Remarkable proximity of all the thermal and hydrochemical anomalies to major faults suggests that the waters ascended along these faults from greater depths. The area is a natural western extension of the Himalayan Geothermal Belt described in earlier literature for the eastern and central Himalayas.