Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

A. K. Padhi ¹, S. K. Jain ¹, V. J. Katti ²

Affiliations
1 AMD, Department of Atomic Energy, Central Region, Nagpur - 440 001, IN
2 AMD, Department of Atomic Energy, Western Region, Jaipur - 302 030

Abstract

Satpura Gondwana Basin around Polapathar contains feldspathic and subfeldspathic quartz arenites of the Motur Formation, with minor intercalations of shale and conglomerate, resting over the Barakar Formation. These sediments are intruded by a number of dolerite dykes trending NE-SW and E-W. The arenites, when close to the contact of dolerite dykes, are reddish brown coloured, rich in heavy minerals like ilmenite, monazite and zircon, have higher concentration of REE, especially LREE and devoid of uranium mineralization (<50 ppm uranium); hence, they are designated as non-mincralized arenaceous rocks (NMARs). The alteration of plagioclase to a mixture of sericite, calcite and clay minerals, and pronounced negative europium anomaly in these samples indicate europium fractionation in a high-temperature condition, possibly related to dolerite intrusion. The reddish grey coloured arenaceous rocks away from the contact of these dykes are rich in hematite, biotite and pyrite, host uranium mineralization (≥100 ppm U) and are termed as uranium mineralized arenaceous rocks (UMARs). These rocks contain a few grains of ilmenite, monazite and zircon, and, therefore, have low concentration of TiO₂, and REE. The relatively flat chondrite-normalized REE pattern with slightly negative to positive europium anomaly in UMARs indicates preferential mobilization of other LREE in comparison to europium. Uraninite, brannerite, U-Ti complex, traces of coffinite and pitchblende are the uranium minerals. Besides, uranium is in adsorbed state on goethite, limonite and organic matter. The localized concentration of uranium in UMARs, confined between two NE-SW trending dykes, is suggestive of the re-mobilization of uranium from the sediments by heated groundwater and its concentration in suitable locales, with the dolerite dykes supplying the required thermal gradient for such re-mobilization.

Keywords

U-mineralization, Satpura Basin, Motur Formation, Dolerite dykes, Thermal gradient, Polapathar, Madhya Pradesh.

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S. P. Rai ¹, Vijay Kumar ¹, Omkar Singh ¹, Bhishm Kumar ², S. K. Jain ²

Affiliations
1 National Institute of Hydrology, Western Himalayan Regional Centre, Satwari Jammu Cantt (J&K) 180 003, IN
2 National Institute of Hydrology, Jalvigyan Bhawan, Roorkee (U A ) - 247 667, IN

Abstract

An attempt has been made to workout the bathymetry, determine the rate of sedimentation and the physico-Chemical characteristics of the Mansar lake of Jammu region. The bathymetric survey conducted using Range-Line method shows present lake surface area is 0 59x10⁶ m² and volume to be 11 57x10⁶ m³. The rate of sedimentation determined using ¹³⁷Cs and ²¹⁰Pb radiometric dating technique in the lake varies between 0 14 cm/y to 0 37 cm/y with a mean rate of 0 23 cm/y±0 002 cm/y. The variation of temperature, pH, electrical conductivity, dissolved oxygen, hardness and alkalinity suggest that Mansar lake undergoes two distinct stages, viz complete mixing stage in the months of January and February and stratified stage in other months. The catchment lithology contributes a large part of the major constituents in lake water, Ca and Mg account 70 to 85% of the cations and HCO₃ accounts for 77 to 91% of the total anion, and equivalent ratio of Ca Mg varies from 0 45 to 6 40. The average (Ca+Mg)/HCO₃ equivalent ratio of 1 04, major contribution of (Ca+Mg) to total cations and high (Ca+Mg)/(Na+K) ratio indicate that weathering of calcareous sandstones and mudstones of the Siwalik Group could be the primary source of major ions in the lake water. Results of phosphorous show that Mansar lake has entered the eutrophic stage.

Keywords

Bathymetry, Sedimentation Rate, ¹³⁷Cs and ²¹⁰Pb Dating, Stratification, Hydrochemistry, Mansar Lake, Jammu and Kashmir.

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