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Not AvailableFifteen water abstraction structures along the two streams adjacent to the NIASM site were selected for studying the geochemistry of the groundwater and abiotic factors responsible for their distribution. The results indicated that the groundwater is alkaline with high electrical conductivity (EC). The Total Hardness is below the prescribed drinking water limit whereas Na concentrations are far below the permissible limit. The sodium absorption ration (SAR) distribution pattern indicated downstream increase in the areas due to surfacial obstruction of the natural drainage system. EC of water shows a positive correlation with major cations Ca + Mg (R2= 0.63) and Na + K (R2= 0.61) which indicates a strong lithological control on the major oxide cations of the groundwaters. There is a strong positive correlation between EC and Cl (R2= 0.96) while the correlation between EC and HCO3 is weak (R2= 0.12) indicating that the amount of chloride in the groundwater controls the EC. The samples showed considerable scatter with a weak correlation (R2= 0.19) between NO3-N and EC. Such variation in the NO3-N concentration from the groundwaters reflects the role of physical process such as evaporation and /or anthropogenic additions to the groundwater. The SO4 concentration showed no distinct correlation with EC (R2= 0.07) indicating that its concentration did not contribute to the conductivity of groundwaters from the NIASM site. Based on the SAR values, the groundwater for irrigation purposes are classified as ‘good’ and most of them belong to the Ca+Mg>Na+K; HCO3+CO3>Cl+SO4 facies.Not Availabl

First Annual Report 2009-10

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Not AvailableGeochemical variability in rocks collected from profile section, drilling core and random samples from NIASM site has been studied using x-ray fluorescence spectrometry. The sum total of all the major oxide analyses show variable degrees of weathering and range from highly weathered samples to fresh rock. Analyses were used on an anhydrous basis in the SINCLAS programme to recalculate major oxides and normalise the geochemical analyses to 100. The programme also gives a rock name following the TAS diagram as well as fixes the Fe2O3: FeO ratio and then calculates the norm. Based on the normative mineralogy and SiO2 vs. Na2O+K2O content in the TAS diagram the present samples were classified into sub-alkaline basalts, basaltic andesites and andesite. Major oxide variation diagram in the Main Pit indicated silica and alumina oxides tend to accumulate towards the upper parts whereas TiO2 and FeO tend to be mobile in an oxidizing environment and get leached towards the lower parts of the weathering profile. The unique lobate geometry of the lava flow does not weather uniformly resulting in a rather jagged oxide variation diagram which is predominantly a function of the lobe geometry and the porosity and permeability of the lobe sub-units. The Mg# of the subalkaline basalt indicates moderately evolved magmas. The trace element Cu and Ni have a distinctly opposite signature as compared to Zr, V, Cr, Zn, and Co. Concentration of Ba, Sr and Rb are invariably high in the upper and lower parts of the Main Pit which is due to modal variations in the plagioclase content or due to the variable mobility of these elements in response to differential weathering across the Main Pit profile. Anomalous concentration of different major oxides and trace elements at 50 cm and 70 cm depth is due to presence of the thin clay horizons related to weathering of glassy rind of a single 20 cm thick pahoehoe toe. Such anomalous accumulations could suggest that the clays provide suitable sites for their adsorption or that considerable enrichment of these elements takes place due to deposition of soluble salts in an oxidizing environment.Not Availabl