The Charnockite — A-type Granitoid — Charnockite Cycle in Southwestern India     

H.M. Rajesh  M. Yoshida 《Gondwana Research》2001,4(2):187

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Analysis of Slope-Matching Methods for Aquifer Parameter Determination     

Rajesh Srivastava  Amado Guzman-Guzman 《Ground water》1994,32(4):570-575

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Genetic implications of the trace element distribution pattern in the upper knox carbonate rocks,copper ridge district,East Tennessee     

Habte G. Churnet  Kula C. Misra 《Sedimentary Geology》1981,30(3):173-194

The Lower Ordovician, Upper Knox Group rocks (the Kingsport and Mascot formations) in the Copper Ridge district consist predominantly of fine-grained dolostones, medium and coarser grained dolostones, and limestones. Dolomite crystals of medium and coarser grained dolostones show up to eight cathodoluminescent zones of variable width and intensity. Electron microprobe analyses indicate that the zoning is related to variation in Fe/Mn ratios, the brighter luminescent zones corresponding to lower ratios. Superposed on this growth zoning is a compositional zoning characterized by a general increase in Fe from core to rim of individual dolomite crystals.Field and petrographic studies (Churnet, 1979; Churnet et al., 1981) indicate that the fine-grained dolostones formed in supratidal to upper intratidal environments, whereas the precursor lime muds of the limestones as well as of the medium and coarser grained dolostones formed in shallow subtidal to lower intertidal environments. The large areal extent of the dolostones must have required a regionally abundant source of Mg such as marine water. Yet, both limestones and dolostones have low Na and Sr contents suggestive of their formation in solutions more dilute than normal marine water. It is proposed that the fine-grained dolostones formed by aggradation of initially very fine-grained dolostones in presence of fresh water, and that the limestones stabilized and the medium and coarser grained dolostones formed in environments of mixed marine and fresh waters. Considered in the light of ordering of partition coefficients, such a mixing model can account for the observed correlation pattern of trace elements (especially, SMn and SrFe) as well as the Fe distribution in the zoned dolomite crystals. Variation of the partition coefficient of Mn due to fluctuations in the relative proportions of fresh and marine waters in the diagenetic solution may explain the different Fe/Mn ratios observed in the growth zones (luminescence bands) of zoned dolomite crystals.  相似文献   

Strontium diffusion in feldspars—a laboratory study     

N.K Misra  V.S Venkatasubramanian 《Geochimica et cosmochimica acta》1977,41(6):837-838

Sr⁹⁰ Radiotracer diffusion studies have been carried out on crystals of orthoclase and microcline using an ion implantation method. The activation energies are consistent with calculations based on mineral age data.  相似文献   

On the thermal bending of a thin elastic simply supported rectangular plate resting on an elastic foundation     

Misra  J. C. 《Pure and Applied Geophysics》1974,112(1):83-89

Pure and Applied Geophysics - Deflection and bending moments of a thin isotropic rectangular plate, having its edges simply supported and maintained at zero temperature, have been investigated in...  相似文献   

Age of granitic activity associated with copper–molybdenum mineralization at Malanjkhand, Central India     

Mruganka K. Panigrahi  Brendan R. Bream  Kula C. Misra  Rajesh K. Naik 《Mineralium Deposita》2004,39(5-6):670-677

The Malanjkhand copper–molybdenum deposit in the Bhandara Craton, Central India, is hosted by a granite complex which consists of regionally dominant grey granitoid and pink granitoid confined to the mineralized zone. New SHRIMP RG data on zircons from both granite types are inferred to have crystallized during the same magmatic pulse at ca 2.48 Ga. The discrepancy between zircon age and earlier obtained Rb–Sr whole-rock age is attributed to modification of the Rb–Sr system by hydrothermal overprint. Similarity in petrographic features and chemical affinity in combination with identical age strongly indicate that the pink granite is the hydrothermally altered variety (microclinization and silicification) of the grey granite. The spatially associated, main Cu–Mo mineralization event at Malankhand appears to be broadly contemporaneous with and genetically related to the emplacement of the host granitoids at about 2.48 Ga.  相似文献   

Prediction of Arsenic in Bedrock Derived Stream Sediments at a Gold Mine Site Under Conditions of Sparse Data   总被引：2，自引：0，他引：2  

Navin K. C. Twarakavi  Debasmita Misra  Sukumar Bandopadhyay 《Natural Resources Research》2006,15(1):15-26

Arsenic is often present in gold mining areas. The high sensitivity of arsenic to biogeochemical conditions may lead to catastrophic consequences through contamination of resources such as ground water. Therefore, it is critical to understand the spatial occurrence of arsenic across a given site. Previous studies using traditional pattern recognition techniques such as neural networks and kriging have not been entirely successful in predicting arsenic concentrations across a gold mining area. The methods used in this paper are the support vector machines (SVM) and robust least-square support vector machines (robust LS-SVM). The two techniques were used to predict arsenic concentrations in the sediments of Circle City, Alaska, using the gold concentration distribution present within the sediments. The analysis of the results shows an improved performance and better predictive capabilities of SVM and robust LS-SVM than that of the neural networks and kriging techniques. The robust LS-SVM performed better than the SVM. The performance of the SVM was affected by outliers. The removal of the outliers from the data set and application of SVM showed improved results.  相似文献   

Geochronological constraints on evolution of Singhbhum mobile belt and associated basic volcanics of eastern Indian Shield—reply     

Saumitra Misra 《Gondwana Research》2006,9(4):543-544

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Identification of critical ground motions for seismic performance assessment of structures   总被引：1，自引：0，他引：1  

Rajesh P. Dhakal  John B. Mander  Naoto Mashiko 《地震工程与结构动力学》2006,35(8):989-1008

A method is established to identify critical earthquake ground motions that are to be used in physical testing or subsequent advanced computational studies to enable seismic performance to be assessed. The ground motion identification procedure consists of: choosing a suitable suite of ground motions and an appropriate intensity measure; selecting a computational tool and modelling the structure accordingly; performing Incremental Dynamic Analysis on a non‐linear model of the structure; interpreting these results into 50th (median) and 90th percentile performance bounds; and identifying the critical ground motions that are close to these defining probabilistic curves at ground motion intensities corresponding to the design basis earthquake and the maximum considered earthquake. An illustrative example of the procedure is given for a reinforced concrete highway bridge pier designed to New Zealand specifications. Pseudodynamic tests and finite element based time history analyses are performed on the pier using three earthquake ground motions identified as: (i) a Design Basis Earthquake (10% probability in 50 years) with 90 percent confidence of non‐exceedance; (ii) a Maximum Considered Event (2% probability in 50 years) representing a median response; and (iii) a Maximum Considered Event representing 90 percent confidence of non‐exceedance. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Practical Approximations of the Well Function     

Rajesh Srivastava  Amado Guzman-Guzman 《Ground water》1998,36(5):844-848

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