Multiple-mineral inclusions in diamonds from the Snap Lake/King Lake kimberlite dike, Slave craton, Canada: a trace-element perspective     

Prinya Promprated  Lawrence A. Taylor  Mahesh Anand  Christine Floss  Nikolai V. Sobolev  Nikolai P. Pokhilenko 《Lithos》2004,77(1-4):69-81

Multiple inclusions of minerals in diamonds from the Snap Lake/King Lake kimberlites of the southeastern Slave craton in Canada have been analyzed for trace elements to elucidate the petrogenetic history of these inclusions, and of their host diamonds. As observed worldwide, the harzburgitic-garnet diamond inclusions (DIs) possess sinusoidal REE patterns that indicate an early depletion event, followed by metasomatism by LREE-enriched, HREE-depleted fluids. Furthermore, these fluids appear to contain appreciable concentrations of LILE and HFSE, based on the increasing abundances of these elements in the olivine inclusion that occurs at the outer portion of a diamond compared to that near the core. The compositions of these fluids are probably a mixture of hydrous-silicic melt, carbonatitic melt, and brine, similar to the compositions of micro-inclusions in diamonds reported by Navon et al. (2003). Comparison between the compositions of majoritic and normal harzburgitic garnets shows that the former are more depleted in terms of major/minor elements (higher Cr#) but significantly more enriched in the REE (up to 10×). This characteristic may indicate the higher susceptibility for metasomatic enrichment of previously more depleted garnets. Garnets of eclogitic paragenesis show strong LREE-depleted patterns, whereas the coexisting omphacite inclusion has relatively flat light- and middle-REE but depleted HREE. Whole-rock reconstruction from coexisting garnet and omphacite inclusions indicates that the protolith of these inclusions was probably the extrusive section of an oceanic crust, subducted beneath the Slave craton.  相似文献   

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   

Isotopic evidence of middle proterozoic magmatism from bombay high field: Implications to crustal evolution of western offshore of India     

S. S. Rathore  A. R. Vijan  M. P. Singh  B. N. Prabhu  Anand Sahu 《Journal of Earth System Science》2004,113(1):27-36

Precambrian granitic basement rocks obtained from well BH-36 of Bombay High Field, western offshore of India has been studied both by Rb-Sr and K-Ar dating methods. Seven basement samples chosen from two cores have yielded whole rock Rb-Sr isochron age of 1446 ± 67 Ma with an initial⁸⁷Sr/⁸⁶Sr ratio of 0.7062 ± 0.0012. This age has been interpreted as the formation/emplacement time of the granite. Two biotite fractions of different grain size separated from a sample CC6B2T have yielded Rb-Sr mineral isochron age of 1385 ± 21 Ma. However, these fractions when studied by K-Ar dating method have yielded slightly higher but mutually consistent ages of 1458 ± 43 Ma and 1465 ± 43 Ma, respectively. Further, two biotites separated from additional samples CC5B9T and CC6B3B have yielded K-Ar ages of 1452 ± 42 Ma and 1425 ± 40 Ma with an overall mean age of 1438 ± 19 Ma. This mean K-Ar age is indistinguishable from whole rock Rb-Sr isochron as well as mineral isochron age within experimental error. The similarity in the whole rock and biotite ages obtained by different isotopic methods suggests that no thermal disturbance has occurred in these rocks after their emplacement/formation around 1450 Ma ago. The present study provides the evidence for the existence of an important Middle Proterozoic magmatic event around 1400-1450 Ma on the western offshore of India which, hitherto, was thought to be mainly confined to the eastern Ghats, Satpura and Delhi fold belt of India. This finding may have an important bearing on the reconstruction of Proterozoic crustal evolution of western Indian shield.  相似文献   

Relationship Between the Momentum and Scalar Fluxes Close to the Ground During the Indian Post-monsoon Period     

Subharthi Chowdhuri  Thara V. Prabha  Anand Karipot  T. Dharamraj  M. N. Patil 《Boundary-Layer Meteorology》2015,154(2):333-348

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Remote sensing GIS-based landslide susceptibility & risk modeling in Darjeeling–Sikkim Himalaya together with FEM-based slope stability analysis of the terrain     

Nath  Sankar Kumar  Sengupta  Arnab  Srivastava  Anand 《Natural Hazards》2021,108(3):3271-3304

Natural Hazards - Landslide susceptibility (LSI) modeling of Darjeeling–Sikkim Himalaya is performed by integrating 28 causative factors on 28C28 combinations on Geographical Information...  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   

Tree Crown Detection,Delineation and Counting in UAV Remote Sensed Images: A Neural Network Based Spectral–Spatial Method     

Ramesh Kestur  Akanksha Angural  Bazila Bashir  S. N. Omkar  Gautham Anand  M. B. Meenavathi 《Journal of the Indian Society of Remote Sensing》2018,46(6):991-1004

UAVs are fast emerging as a remote sensing platform to complement satellite based remote sensing. Agriculture and ecology is one of the important applications of UAV remote sensing, also known as low altitude remote sensing (LARS). This work demonstrates the use and potential of LARS in agriculture, particularly small holder open field agriculture. Two UAVs are used for remote sensing. The first UAV is a fixed wing aircraft with a high spatial resolution visible spectrum also known as RGB camera as a payload. The second UAV is a quadrotor UAV with an RGB camera interfaced to an on-board single board computer as the payload. LARS was carried out to acquire aerial high spatial resolution RGB images of different farms. Spectral–spatial classification of high spatial resolution RGB images for detection, delineation and counting of tree crowns in the image is presented. Supervised classification is carried out using extreme learning machine (ELM), a single hidden layer feed forward network neural network classifier. ELM was modelled for RGB values as input feature vectors and binary (tree and non-tree pixels) output class. Due to similarities in spectral intensities, some of the non-tree pixels were classified as tree pixels and in order to remove them, spatial classification was performed on the image. Spatial classification was carried out using thresholded geometrical property filtering techniques. Threshold values chosen for carrying out spatial classification were analysed to obtain optimal values. Finally in the delineation and counting, the connected tree crowns were segmented using Watershed algorithm performed on the image after marking individual tree crowns using Distance Transform method. Five representative UAV images captured at different altitudes with different crowns of banana plant, mango trees and coconut trees were used to demonstrate the performance of the proposed method. The performance was compared with the traditional KMeans spectral–spatial method of clustering. Results and comparison of performance parameters of KMeans spectral–spatial and ELM spectral–spatial classification methods are presented. Results indicate that ELM performed better than KMeans.  相似文献   

Seismic bearing capacity of strip footing on partially saturated soil using modal response analysis     

Anand  Abhijit  Sarkar  Rajib 《地震工程与工程振动(英文版)》2022,21(3):641-662

The present study proposes a novel and simplified methodology to assess the seismic bearing capacity (SBC) of a shallow strip footing by incorporating strength non-linearity arising due to partial saturation of a soil matrix. Furthermore, developed methodology incorporates the modal response analysis of soil layers to assess SBC. A constant matric suction distribution profile has been considered throughout the depth of the soil. The Van Genuchten equation and corresponding fitting parameters have been considered to quantify matric suction in the analysis. SBC has been obtained for three different geomaterials; viz. sand, fly ash and clay, based on their predominant grain size and diverse soil water characteristics curve (SWCC) attributes. Variation of SBC with different modes of vibration and damping ratio are reported for ranges of matric suction pertinent to the geomaterials considered in the study. The relative significance of matric suction on SBC has been reported for suction values within the transition zone of each geomaterial. It is observed that the SBC of sand is drastically reduced, with matric suction reaching beyond the residual suction value. The SBC of fly ash remains constant beyond the residual suction value, whereas the SBC of clay shows an increasing trend toward the practical range of matric suction values.

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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

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Estimation of Sea Ice Freeboard from SARAL/AltiKa Data     

Megha Maheshwari  C. Mahesh  Kamaljit Singh Rajkumar  J. Pallipad  Sandip R. Oza 《Marine Geodesy》2015,38(3):487-496

An attempt has been made to derive sea ice freeboard from Ka-band Altimeter (SARAL/AltiKa) over Arctic region for 15 March–15 April 2013 (spring) and 15 September–15 October 2013 (autumn). A waveform template matching technique is employed for classification of leads and floe pixels. The estimated sea ice freeboards were found in close agreement with “Operation IceBridge quick look” freeboards (RMSD = 0.30 m). The differences between the two freeboards were largely due to snow layer over sea ice (R = 0.8). The estimated freeboards were of the order of 0.08–0.15 m during the two seasons.  相似文献