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A method based on the principles of electrochemistry has been applied for the first time with indigenous equipment in the search for base-metal sulphides, following a field exploration technique known as ‘CHIM — 10’, which is in use in the U.S.S.R. for the last few years. The technique utilizes the electro-positive property of the metallic ions. When a large section of the ground is artificially electrolyzed by the introduction of a direct current, the metallic ions within the moist soil profile close to the mineralized zone tend to move towards the energizing cathodes of a powerful widely spaced electrode array. A laboratory model experiment was conducted first which showed encouraging results. Subsequently, a prototype field unit was fabricated and employed to examine its effectiveness in the field on a soil profile over the base-metal sulphide zones of Aladahalli area, Hassan District, Karnataka, where the geology of the deposit is well known.The results obtained during the field trials were quite good and in full conformity with the known geology. However, detailed evaluation of those data after applying necessary corrections for the different variable parameters of the system is yet to be done. Work is in progress to refine the technique with a view to standardizing and developing its use for qualitative and quantitative assessment of a concealed base-metal deposit in a given area, specially where conventional geochemical exploration methods are not suitable.The paper deals with the details of the technique and discusses the results obtained during the trial run in the field. 相似文献
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Lithospheric structure below transantarctic mountain using receiver function analysis of TAMSEIS data 总被引：1，自引：0，他引：1
P. Kumar Karabi Talukdar Mrinal K. Sen 《Journal of the Geological Society of India》2014,83(5):483-492
The lithospheric structure of Antarctica has been investigated from P- (PRF) and S- receiver functions (SRF) using the seismological data from Trans-Antarctic Mountain Seismic Experiment (TAMSEIS). For the stations deployed on the thick ice sheet, estimation of crustal parameters from PRF may be erroneous as the Moho conversions may interfere with the reverberations within the thick ice sheet. However, the free surface multiples are well observed in PRF. On the other hand, in SRFs, the primary conversions of interest and multiples are separated by the mother S-phase. Therefore, it is advantageous to interpret PRF and SRF jointly for the regions where we have thick low velocity layer at the top such as ice or sediments. The crustal structure and corresponding parameters have already been estimated by various workers, but here we interpret the PRF and SRF jointly to minimize the ambiguity and map the lithospheric architecture below TAM. Our analysis reveals that the average crustal thickness beneath the east Antarctica craton is ～44 km with Vp/Vs ranging between ～1.7 and 1.9. Below Trans-Antarctic Mountain (TAM), the average crustal thickness is ～36 km with higher Vp/Vs of ～1.8–2.0. The rift and the volcanic affected coastal region show erratic depths and Vp/Vs, primarily due to the absence of either primary conversion or multiples in the receiver functions. A small number of stations far from the volcano show that the crust is thinnest (～26 to 34 km thick) in the coastal part. The contribution of this study is the mapping of the lithospheric configuration, not done so far using SRF. The SRF section along a profile spanning E-, W- Antarctica and TAM reveals that the lithospheric thickness in the coast is ～80 km and below TAM it is ～120 km. In the central thick ice cover region, the lithosphere thickens upto ～150 km towards Vostok highlands. The most intriguing feature in our SRF section is that the crust and lithosphere are shallow below TAM compared to the E- Antarctica. Further, we observe a mid-lithospheric low velocity layer confined mostly below TAM, suggesting that the thermal buoyancy could be the prime cause for the upliftment of TAM. 相似文献
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Histograms of echo peaks from three different topographic regions in the outer beams of a Sea Beam sonar show distinct variation as the topography changes from the North Cleft ridge to the Cascadia abyssal plain in the Pacific Ocean. Parameter estimation of probability density functions (pdfs) shows significant departure from Rayleigh pdf for the nonabyssal plain sites. The spectral character of the sea-floor roughness from an acoustic backscatter model suggests that the ridge area is dominated by large-scale roughness and the abyssal plain by small scale. It appears that change in roughness magnitude effects the observed histogram characteristics. 相似文献
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Frequent flood is a concern for most of the coastal regions of India. The importance of flood maps in governing strategies for flood risk management is of prime importance. Flood inundation maps are considered dependable output generated from simulation results from hydraulic models in evaluating flood risks. In the present work, a continuous hydrologic-hydraulic model has been implemented for mapping the flood, caused by the Baitarani River of Odisha, India. A rainfall time-series data were fed into the hydrologic model and the runoff generated from the model was given as an input into the hydraulic model. The study was performed using the HEC-HMS model and the FLO-2D model to map the extent of flooding in the area. Shuttle Radar Topographic Mission (SRTM) 90 m Digital Elevation Model (DEM) data, Land use/Land cover map (LULC), soil texture data of the basin area were used to compute the topographic and hydraulic parameters. Flood inundation was simulated using the FLO-2D model and based on the flow depth, hazard zones were specified using the MAPPER tool of the hydraulic model. Bhadrak District was found to be the most hazard-prone district affected by the flood of the Baitarani River. The result of the study exhibited the hydraulic model as a utile tool for generating inundation maps. An approach for assessing the risk of flooding and proper management could help in mitigating the flood. The automated procedure for mapping and the details of the study can be used for planning flood disaster preparedness in the worst affected area.
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Coherent structures entailing the existence of double layers have been studied in magnetised plasma contaminated with dust
charging fluctuations. It has been shown that the dust charging in magnetic plasma leads to complexity in the derivation of
the Sagdeev wave equation, but under way new procedure enable one to study the nature of double layers showing the effective
role of the constituents of the plasma. A parametric analysis is a subject of interest in laboratory and space plasmas, and
it has been explained with the input of various typical plasma numerics. The proposed mathematical mechanism has shown the
success to yield plasma acoustic modes in a dusty plasma which, in turn, has been solved convincingly for double layers. Observations
have been evaluated in an appropriate model with a view to agree with the observations in astrophysical problems dealing with
present new findings. 相似文献
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R. K. Majumdar S. Kar D. Talukdar T. Duttagupta 《Journal of the Geological Society of India》2014,83(1):21-30
Integrated geoelectric and geochemical investigation were carried out in the Canning and adjoining areas to assess the prevailing groundwater conditions and chemical quality of groundwater. Geologically, the area is constituted of alluvial sediments of Quaternary age. Vertical electrical soundings (VES) in the area of investigation mostly show six layers consisting of top soil, saline water, clay layer, brackish water, clay layer and fresh-water bearing zone of appreciable thicknesses at depths of 137 to 182 meter at six locations and from 370 to 430 meter for other two locations under confined conditions. The result of VES studies significantly correspond with the borehole litholog and well log data. A litho-resistivity relationship is established for this area of investigation A Fence diagram is constructed to show the spatial variation of the sub-surface lithology and hydrological characteristics. Chemically the ground water is fresh and mixed cation and anion type as revealed from Piper-Trilinear diagram with TDS ranging from 699 to 1547 mg/l. The geochemical parameters like Total hardness (TH), Sodium absorption ratio (SAR), Soluble sodium percentage (SSP), Percentage of sodium (PS), Kelley’s ratio (KR), Residual sodium carbonate (RSC), Corrosivity ratio (CR), Gibbs ratios (GR), Chloro alkaline indices (CAI), Sea water contamination (SWC) are also calculated for examining the quality of groundwater in the area. The depth of occurrences of freshwater bearing ground water zones for drinking and irrigation purposes are occurring at depths from 137 meter to 430 meter in this area. 相似文献
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Landscape Dynamics in North East Region of India (Meghalaya State) Using Spatial Decision Tree Model
Abstract India has figured with two hotspots ‐ the Western Ghats and the Eastern Himalayas ‐ in an identification of 8 ‘hottest’ biodiversity hotspots (Myers et. al. 2000). The Meghalaya state (study area) in North Eastern India lies within the “Indo‐Burma” area, which is one of the 8 ‘hottest’ biodiversity hotspots. Timber extraction, the age‐old practice of shifting cultivation and mining has been a major cause of extensive changes in this landscape. Human induced disturbance differs from natural disturbance especially in extension, severity and frequency. Spatial presentation of landscape dynamics can be used to infer disturbance regimes horizontally. Disturbance regimes are mostly dominated by landuse practices in Meghalaya and these landuse practices are important contributors for overall interpretation of ecological processes operating within the landscape. In this scenario, the development of models to study landscape dynamics using remote sensing and GIS would be of great importance to ecologists. In this paper, we make an attempt to characterize landscape dynamics using a decision tree based approach. The varying impacts of human interventions reflected in three zones at landscape level have been brought out in the present study. The physiographic zones of Meghalaya (viz. Garo hills, Khasi hills and Jaintia hills) manifest different landscape characteristics and present varying degree of degradation status. Garo hills, experiences maximum shifting cultivation and has shown highest dynamism in the study area followed by Jaintia and Khasi hills. Characterization of landscape dynamics is important in the perspective of decision makers and policy makers in order to prioritize conservation strategies, so that urgent and necessary action can be taken. 相似文献
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Assam–Arunachal forest fringed foothill area is endemic for malaria incidence. The present study deals with the temporal analysis of malaria incidence and determines its association with deforestation in 24 villages along the Assam–Arunachal forest fringed foothill area of Sonitpur district of Assam. Malaria epidemiological survey has been carried out in the study area from the year 1994 to 2005. Remote sensing (RS) technique has been used to map the areas of forest changes from the year 2000 to 2005. Geographical information system (GIS) was used to map the malaria incidence and forest cover. The study villages are endemic to malaria infections and there was increasing trend of malaria incidence over the years. The slide positivity rate (SPR) ranged from 5.1% in 1997 to 44.4% in 2005. The percentage forest cover decreased significantly from 23.6% during 2000 to 15.4% during 2005, whereas SPR was increased during 2000–2005. The present study is the first attempt to understand the role of deforestation in malaria incidence using RS and GIS in the north-eastern region of India at a micro-geographic level. The study suggests that the area is endemic to malaria transmission. The decrease in forest cover is a serious ecological concern besides its role in elevating the malaria incidence in the study area. 相似文献
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