Alteration geochemistry and fluid inclusion characteristics of the greenstone-hosted gold deposit of Hutti, Eastern Dharwar Craton, India

Gold mineralization of the Hutti mine, southern India, is situated in closely spaced laminated quartz veins and associated alteration haloes along steeply dipping shear zones within a sequence of rather uniform amphibolites. Intense shearing has resulted in large-scale mylonitization of the wall rocks. Anastomosing shear zones, with intervening lensoid bodies of unsheared amphibolites, are characteristic features of the deposit. The general pattern of symmetrical alteration comprises a distal zone of chlorite-rich rock, with a proximal biotite-rich zone adjacent to laminated quartz veins. Arsenopyrite thermometry yielded a temperature range of 350-477 °C for the biotite alteration zone, which preceded the formation of the laminated quartz veins. Mass balance calculations on the alteration zones indicate a gradual mass and volume loss during alteration. The alteration is accompanied by intense potash metasomatism and addition of sulfur, which resulted in the formation of arsenopyrite, pyrrhotite, and pyrite. Results of fluid inclusion studies suggest that low salinity (3.9-13.5 wt% NaCl equivalent) H₂O-CO₂ rich fluids were responsible for gold-rich laminated quartz vein formation in the Hutti deposit. These fluids constituted a later counterpart of the protracted fluid activity that first formed the biotite alteration zone. The estimated P-T values range from 1.0 to 1.7 kbar at 280-320 °C. These data, along with the alteration assemblages and the characteristic gold-sulfide association, both in the altered wall rock and laminated quartz veins, suggest that gold, transported as reduced bisulfide complexes, was deposited in response to sulfidation reactions in the wall rocks. Comparison of P-T conditions of formation of gold-quartz veins at Hutti with two other large gold deposits in the eastern Dharwar Craton, namely Kolar (1.8 kbar/280 °C) and western Ramagiri (1.45-1.7 kbar/240-270 °C), indicates broadly similar lode-gold forming conditions in the Dharwar Craton.     

Tectonics and crustal structures related to Bhuj earthquake of January 26, 2001: based on gravity and magnetic surveys constrained from seismic and seismological studies

Gravity and magnetic data of the Kachchh basin and surrounding regions have delineated major E–W and NW–SE oriented lineaments and faults, which are even extending up to plate boundaries in the north Arabian Sea and western boundary of the Indian plate, respectively. The epicentral zone of Bhuj earthquake and its aftershocks is located over the junction of Rann of Kachchh and median uplifts viz. Kachchh mainland and Wagad uplifts, which are separated by thrust faults. Gravity data with constraints from the results of the seismic studies along a profile suggest that the basement is uplifted towards the north along thrust faults dipping 40–60° south. Similarly gravity and magnetic modeling along a profile across Wagad uplift suggest south dipping (50–60°) basement contacts separating rocks of high susceptibility and density towards the north. One of these contacts coincides with the fault plane of the Bhuj earthquake as inferred from seismological studies and its projection on the surface coincides with the E–W oriented north Wagad thrust fault. A circular gravity high in contact with the fault in northern part of the Wagad uplift along with high amplitude magnetic anomaly suggests plug type mafic intrusive in this region. Several such gravity anomalies are observed over the island belt in the Rann of Kachchh indicating their association with mafic intrusions. The contact of these intrusives with the country rock demarcates shallow crustal inhomogeneities, which provides excellent sites for the accumulation of regional stress. A regional gravity anomaly map based on the concept of isostasy presents two centers of gravity lows of −11 to −13 mGal (10⁻⁵ m/s²) representing mass deficiency in the epicentral region. Their best-fit model constrained from the receiver function analysis and seismic refraction studies suggest crustal root of 7–8 km (deep crustal inhomogeneity) under them for a standard density contrast of −400 kg/m³. It is, therefore, suggested that significant amount of stress get concentrated in this region due to (a) buoyant crustal root, (b) regional stress due to plate tectonic forces, and (c) mafic intrusives as stress concentrators and the same might be responsible for the frequent and large magnitude earthquakes in this region including the Bhuj earthquake of January 26, 2001.     

Qualitative and quantitative analysis of snow parameters using passive microwave remote sensing

Snow cover is an important variable for climatic and hydrologic models due to its effect on surface albedo, energy, and mass balance. Satellite observations successfully provide a global and comprehensive hemispheric-scale record of the short-term, as well as inter-seasonal variations in snow cover. Passive microwave sensors provide an excellent method to monitor temporal and spatial variations in large-scale snow cover parameters, overcoming problems of cloud cover. Using microwave remote sensing data, snow parameters (snow surface temperature, snow water equivalence, scattering index, emissivity, snow depth) have been retrieved to integrate with the snow cover simulation model developed by SASE for avalanche risk assessment on regional basis. Multispectral and multitemporal brightness temperature data obtained from the Special Sensor Microwave Imager (SSM/I), flown onboard the DMSP satellites, for the period November 2000 to April 2001 and from November 2001 to February 2002 have been analysed. A comparative data set on snow measurements and meteorological observations of a region covering large area of Pir-Panjal and the Greater Himalayan range, available on near real time basis from SASE field observatories were also used. Model calculations were carried out to study the effects of atmospheric transmission on the microwave radiation emitted from the snow covered and snow free ground and atmosphere. The sensitivity of combinations of the SSM/I channels at 19, 37 and 85 GHz, in both horizontal and vertical polarizations, in respect to snow depth, surface temperature of the snowpack have been carried out. Decision rule based algorithms are developed to identify snow cover and non-snow area.     

Purification of Drinking Water (Municipal Water Supply) by Activated Charcoal,Potassium Permanganate and Silica Gel Beds Vis a vis to Bleaching Powder and Its Effects on Fish Life

A novel method has been developed to purify the municipal water. A pH of 7.05 has been achieved, which is suitable for the drinking purpose. Heavy metal, Pb²+ ions, have been removed to the extent of 0.074 mg/l. This purified water also saves the life of fishes. At the same time the use of bleaching powder in purifying municipal water has been avoided due to its hazardous effect even on fishes.     

Long wavelength magnetic anomalies from the lithosphere: Indian shield and Himalaya

A few long-range airborne magnetic profiles flown at an altitude of 7.5 km a.s.l. across the Indian shield are analysed and interpreted in terms of magnetization in the lower crust. The wavelengths of the crustal anomalies are in the range of 51–255 km and this is used to separate them from signals originating at shallow depths. Spectral analysis of these profiles provided a maximum depth of 34–41 km for the long-wavelength anomalies and 9–10 km for the shallow sources identified as Mohorovic̆ić discontinuity and the basement respectively. The magnetic “high” recorded in satellite observations over the Indian shield is interpreted as due to a bulge of 3–4 km in the Moho under the Godovari graben, with a magnetization of 200 nT in the direction of the Earth's present-day magnetic field. Similarly the magnetic lows observed over the Himalaya are interpreted in terms of thickening of the granitic part of the crust from 18 to 23.5 km with a magnetization contrast of 200 nT in the direction of the Earth's present-day magnetic field.     

Morphological and strength analysis of PCC bottom ash amended with bentonite

Within the last few years several studies have been completed to evaluate strength, stiffness, and durability properties of pulverized coal combustion (PCC) bottom ash mixed with various admixtures. Studies have shown that strength and stiffness of PCC bottom ash mixed with sodium bentonite changes with the increase in the curing period. Researchers have concluded that this change is due to the chemical composition of the bottom ash and bentonite. In order to understand the reasons for the change in characteristics of bottom ash-bentonite mixtures with time, the strength and structural characteristics of bottom ash-bentonite mixtures cured for various periods was evaluated. Results of the strength testing showed increase in strength and stiffness of the mixtures with curing period. The results of structural analysis using environmental scanning electron microscopy show development of fibrous elements which may cause increase in the unconfined compressive strength and stiffness of the mixtures with the curing period. Selected results from this study are presented herein.