Geothermal studies at Tattapani hot spring area, Sarguja district, central India (original) (raw)

Abstract

Tattapani area, Sarguja district, M.P. (Madhya Pradesh), is one of the strongest thermal manifestations in central India, comprising several hot springs (50-98°C) in marshy land with a cumulative discharge of about 60 1/min, and hydrothermal incrustations over an area 0.10 km 2. Thermal activity is controlled by the ENE-WSW Tattapani fault and NE-SW cross faults. Tattapani fault also forms the southern boundary of the coal-bearing Gondwana basin with its Proterozoic basement comprising a sequence of gneisses, granites, pegmatites and granulites.

The hot springs are of the low discharge, alkaline, NaHCO 3ClSO 4 type with high fluoride, low HCO 3 and TDS. Gas activity is moderate. Silica deposits occur around the vents of the hot springs. The chemically computed base-temperature for these thermal waters is 155 ± 15° C . Common hydrothermal alteration minerals are chalcedony, cryptocrystalline silica, stilbite, cristobalite, montmorillonite and pyrite with traces of clinoptilolite and platy calcite. This mineral assemblage is in equilibrium in a temperature range of 100° C ± 10° C , which is actually recorded in boreholes.

A conductive temperature gradient of 100 ± 20° C/km is measured in 300-350 m deep boreholes drilled in an area of 4 × 0.5 km . The average heat flow is computed to be around 290 ± 50 mW/m 2 . Maximum possible heat generation due to radioactive decay around Tattapani could be in the region of 75 ± 15 mW/m 2 .

Saturated hot water (105-108°C) under pressure was encountered in two boreholes, and a 5000-6000 1/min flow was more or less maintained for about 6 months in one of these holes which is being deepened after controlling the blow-out.

A model is proposed for such an anomalous geothermal regime which cannot be explained by the contemporary understanding of the known magmatic history of the Indian shield.