Nature of diamonds in Yakutian eclogites: views from eclogite tomography and mineral inclusions in diamonds   总被引：1，自引：0，他引：1  

Mahesh Anand  Lawrence A. Taylor  Kula C. Misra  William D. Carlson  Nikolai V. Sobolev 《Lithos》2004,77(1-4):333-348

We have performed dissections of two diamondiferous eclogites (UX-1 and U33/1) from the Udachnaya kimberlite, Yakutia in order to understand the nature of diamond formation and the relationship between the diamonds, their mineral inclusions, and host eclogite minerals. Diamonds were carefully recovered from each xenolith, based upon high-resolution X-ray tomography images and three-dimensional models. The nature and physical properties of minerals, in direct contact with diamonds, were investigated at the time of diamond extraction. Polished sections of the eclogites were made, containing the mould areas of the diamonds, to further investigate the chemical compositions of the host minerals and the phases that were in contact with diamonds. Major- and minor-element compositions of silicate and sulfide mineral inclusions in diamonds show variations among each other, and from those in the host eclogites. Oxygen isotope compositions of one garnet and five clinopyroxene inclusions in diamonds from another Udachnaya eclogite (U51) span the entire range recorded for eclogite xenoliths from Udachnaya. In addition, the reported compositions of almost all clinopyroxene inclusions in U51 diamonds exhibit positive Eu anomaly. This feature, together with the oxygen isotopic characteristics, is consistent with the well-established hypothesis of subduction origin for Udachnaya eclogite xenoliths. It is intuitive to expect that all eclogite xenoliths in a particular kimberlite should have common heritage, at least with respect to their included diamonds. However, the variation in the composition of multiple inclusions within diamonds, and among diamonds, from the same eclogite indicates the involvement of complex processes in diamond genesis, at least in the eclogite xenoliths from Yakutia that we have studied.  相似文献   

Biostratigraphy and floristic evolution of coal swamp floras of a part of Talcher Basin,India: a window on a Permian temperate ecosystem     

Shreerup Goswami  Kamaljyoti Das  Mrutyunjaya Sahoo  Soumyaranjan Bal  Sanghamitra Pradhan  Kamal Jeet Singh  Anju Saxena 《Arabian Journal of Geosciences》2018,11(17):524

The present megafloral assemblage recorded from the Barakar sediments of Dholpahar section along Singda rivulet near Gopal Prasad Village in Talcher Basin comprises of equisetaceous stems, Gangamopteris buriadica, Palaeovittaria kurzii and 19 species of the genus Glossopteris. Record of Gangamopteris, Palaeovittaria and many narrow mesh forms of Glosspteris viz., G. angustifolia, G. churiensis, G. communis, G. recurva, G. spatulata, G. stenoneura, G. tenuifolia, G. vulgaris and G. zeilleri from two older fossiliferous horizons demonstrates that these fossils were preserved during Lower Barakar sedimentation. The report of middle and broad mesh forms of Glossopteris viz., G. barakarensis, G. browniana, G. indica, G. intermittens, G. karharbariensis, G. nakkarea, G. oldhamii, G. taeniensis and G. retifera in the youngest fossiliferous horizons reveals that these fossils were preserved during the deposition of Upper Barakar sediments. The continuation of some of the Karharbari plant fossils in the early phase of Barakar Formation and their disappearance in the flora of Late Barakar suggests a shift in the climatic setup. Palaeoclimate and palaeovegetation of this area are also summarised in this study. Moreover, the fossil assemblages of different fossiliferous beds of Dholpahar section demonstrate the evolution of midrib and meshes in different reticulate leaves.  相似文献   

Assessing flood inundation mapping through estimated discharge using GIS and HEC-RAS model     

Ernieza Suhana Mokhtar  Biswajeet Pradhan  Abd Halim Ghazali  Helmi Zulhaidi Mohd Shafri 《Arabian Journal of Geosciences》2018,11(21):682

Water discharge is the main parameter in hydraulic modeling for flood hazard assessment. However, the unavailability of data on discharge and observed river morphologies resulted in erroneous calculations and irregularities in flood inundation mapping. The objectives of this study are (i) to investigate uncertainties of hydraulic parameters (width, cross-sectional depth, and channel slope) used in discharge equation and (ii) to examine the influence of estimate discharge on water extent and flood depth with different boundary conditions on interferometric synthetic aperture radar (IFSAR) and modified IFSAR DEMs. Sensitivity analysis was conducted with the Monte Carlo simulation method to generate random data combinations. Bjerklie’s equation was used to calculate discharge based on the three variables, and Manning’s n was substituted into the Hydrologic Engineering Center River Analysis System (HEC-RAS) model. TerraSAR-X was used to distinguish existing flood water bodies and normal water extent. The uncertainty of the combined variables was assessed with the likelihood measures such as F-statistic, mean absolute error, root mean square error, and Nash–Sutcliffe efficiency which compares observed and predicted inundated area as well as flood water depth simulated using the HEC-RAS model.  相似文献   

A review on the effect of rubber membrane in triaxial tests     

Mavinakere?Eshwaraiah?RaghunandanEmail author  Jitendra?S.?Sharma  Biswajeet?Pradhan 《Arabian Journal of Geosciences》2015,8(5):3195-3206

This paper presents a review on the effect of rubber membranes on the measured stress and volume change data during the triaxial tests. In many instants, the error associated due to membrane penetration is measured to be close to the total sample volumetric strains. Hence, in addition to precise measurements, adopting an appropriate correction to the measured data is pivotal. This paper provides a detailed review on the methods used to estimate and reduce the influence of rubber membrane on the measured triaxial test results. The discussion therefore clearly highlights the stiffness, thickness, and diameter of the membrane used, to have significant influence on the measured deviatoric stress and the volume change data. The mean grain size of sample has an equally significant influence on the volume change. The methods in general are limited to test conditions, and therefore, it is practically uncertain to have a generalized correction procedure. Effectively, the outcome from this review work enhances the understanding of the reader towards the effect, methods, and corrections to be considered in triaxial testing due to rubber membrane and membrane penetration effects.  相似文献   

Geospatial modeling to identify the effects of anthropogenic processes on landscape pattern change and biodiversity   总被引：1，自引：0，他引：1  

Saeideh maleki najafabadi  Alireza Soffianian  Vahid Rahdari  Fazel Amiri  Biswajeet Pradhan  Tayebh Tabatabaei 《Arabian Journal of Geosciences》2015,8(3):1557-1569

This research used geospatial data to quantify biodiversity changes and landscape pattern change to track anthropogenic impacts of such changes at the Mouteh Wildlife Refuge (MWR), Isfahan, Iran. Satellite image duration of four decades, LandSat_1-5, and IRS-P6 data were used to develop land cover classification maps for 1971, 1987, 1998, and 2011. The number and size of land cover patches, the degree of naturalness, and the diversity indices were calculated and compared for a 40-year period. The results showed an increasing concern with regard to unplanned human activities. Some improvements of the natural landscape also occurred in the core protected zone of the study area. The number and size of land cover patches, the degree of naturalness, and the diversity indices were calculated. Overall changes in natural land use between 1971 and 1998 at MWR showed that the number of patches for natural land use has increased, but it also showed a decrease in 2011. Similar changes were observed for seminatural land use. Within the artificial classes, the number and area of patches were higher and the largest patch occurred in 2011. The maximum variation of diversity is related to the year 2011. The results showed an increasing concern with regard to unplanned human activities. Some improvements of the natural landscape also occurred in the core protected zone of the study area. Remote sensing and geographic information system offers an important means of detecting and analyzing temporal changes occurring in our landscape.  相似文献   

Flood susceptibility prediction using four machine learning techniques and comparison of their performance at Wadi Qena Basin,Egypt     

El-Haddad  Bosy A.  Youssef  Ahmed M.  Pourghasemi  Hamid R.  Pradhan  Biswajeet  El-Shater  Abdel-Hamid  El-Khashab  Mohamed H. 《Natural Hazards》2021,105(1):83-114

Natural Hazards - Floods represent catastrophic environmental hazards that have a significant impact on the environment and human life and their activities. Environmental and water management in...  相似文献   

Experimental Studies and its Application using PLAXIS-2D for Lithomargic Clay Stabilized by GBFS and Lime     

Mahesh Bhat  K.  Nayak  Sitaram 《Geotechnical and Geological Engineering》2021,39(7):4901-4915

Geotechnical and Geological Engineering - Lithomargic clay is found along the Eastern and Western coasts of Southern India. Presence of weak soils like lithomargic clay below the foundations, cause...  相似文献   

Semi-empirical model for retrieval of soil moisture using RISAT-1 C-Band SAR data over a sub-tropical semi-arid area of Rewari district,Haryana (India)     

Kishan Singh Rawat  Vinay Kumar Sehgal  Sanatan Pradhan  Shibendu S Ray 《Journal of Earth System Science》2018,127(2):18

We have estimated soil moisture (SM) by using circular horizontal polarization backscattering coefficient (\(\sigma ^{\mathrm{o}}_{\mathrm{RH}}\)), differences of circular vertical and horizontal \(\sigma ^{\mathrm{o}} \, (\sigma ^{\mathrm{o}}_{\mathrm{RV}} {-} \sigma ^{\mathrm{o}}_{\mathrm{RH}})\) from FRS-1 data of Radar Imaging Satellite (RISAT-1) and surface roughness in terms of RMS height (\({\hbox {RMS}}_{\mathrm{height}}\)). We examined the performance of FRS-1 in retrieving SM under wheat crop at tillering stage. Results revealed that it is possible to develop a good semi-empirical model (SEM) to estimate SM of the upper soil layer using RISAT-1 SAR data rather than using existing empirical model based on only single parameter, i.e., \(\sigma ^{\mathrm{o}}\). Near surface SM measurements were related to \(\sigma ^{\mathrm{o}}_{\mathrm{RH}}\), \(\sigma ^{\mathrm{o}}_{\mathrm{RV}} {-} \sigma ^{\mathrm{o}}_{\mathrm{RH}}\) derived using 5.35 GHz (C-band) image of RISAT-1 and \({\hbox {RMS}}_{\mathrm{height}}\). The roughness component derived in terms of \({\hbox {RMS}}_{\mathrm{height}}\) showed a good positive correlation with \(\sigma ^{\mathrm{o}}_{\mathrm{RV}} {-} \sigma ^{\mathrm{o}}_{\mathrm{RH}} \, (R^{2} = 0.65)\). By considering all the major influencing factors (\(\sigma ^{\mathrm{o}}_{\mathrm{RH}}\), \(\sigma ^{\mathrm{o}}_{\mathrm{RV}} {-} \sigma ^{\mathrm{o}}_{\mathrm{RH}}\), and \({\hbox {RMS}}_{\mathrm{height}}\)), an SEM was developed where SM (volumetric) predicted values depend on \(\sigma ^{\mathrm{o}}_{\mathrm{RH}}\), \(\sigma ^{\mathrm{o}}_{\mathrm{RV}} {-} \sigma ^{\mathrm{o}}_{\mathrm{RH}}\), and \({\hbox {RMS}}_{\mathrm{height}}\). This SEM showed \(R^{2}\) of 0.87 and adjusted \(R^{2}\) of 0.85, multiple R=0.94 and with standard error of 0.05 at 95% confidence level. Validation of the SM derived from semi-empirical model with observed measurement (\({\hbox {SM}}_{\mathrm{Observed}}\)) showed root mean square error (RMSE) = 0.06, relative-RMSE (R-RMSE) = 0.18, mean absolute error (MAE) = 0.04, normalized RMSE (NRMSE) = 0.17, Nash–Sutcliffe efficiency (NSE) = 0.91 (\({\approx } 1\)), index of agreement (d) = 1, coefficient of determination \((R^{2}) = 0.87\), mean bias error (MBE) = 0.04, standard error of estimate (SEE) = 0.10, volume error (VE) = 0.15, variance of the distribution of differences \(({\hbox {S}}_{\mathrm{d}}^{2}) = 0.004\). The developed SEM showed better performance in estimating SM than Topp empirical model which is based only on \(\sigma ^{\mathrm{o}}\). By using the developed SEM, top soil SM can be estimated with low mean absolute percent error (MAPE) = 1.39 and can be used for operational applications.  相似文献   

Thermally altered coals from bore core EBM-1, East Bokaro coal field,Damodar Valley,India: A petrographic inference     

S. Mahesh  Srikanta Murthy  Vikram Partap Singh  Jyoti Shankar Roy 《Journal of the Geological Society of India》2015,86(5):535-546

  相似文献   

Remote sensing-based studies coupled with field data reveal urgent solutions to avert the risk of flash floods in the Wadi Qus (east of Jeddah) Kingdom of Saudi Arabia     

Youssef  Ahmed M.  Pradhan  Biswajeet  Sefry  Saleh A. 《Natural Hazards》2015,75(2):1465-1488

Natural Hazards - On November 25, 2009, heavy amount of rainfall precipitated in the city of Jeddah that led to floods causing unexpected loss of life (113 person died), and damaged public and...  相似文献