Erratum to: Summer monsoon rainfall trends in the Indian Himalayan region     

Sandipan Mukherjee  Rajesh Joshi  Ram C. Prasad  Subhash C. R. Vishvakarma  Kireet Kumar 《Theoretical and Applied Climatology》2015,121(3-4):803-805

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Geochemical characteristics and petrogenesis of four Palaeoproterozoic mafic dike swarms and associated large igneous provinces from the eastern Dharwar craton,India     

Rajesh K. Srivastava  Amiya K. Samal  Gulab C. Gautam 《International Geology Review》2015,57(11-12):1462-1484

Palaeoproterozoic mafic dike swarms of different ages are well exposed in the eastern Dharwar craton of India. Available U-Pb mineral ages on these dikes indicate four discrete episodes, viz. (1) ~2.37 Ga Bangalore swarm, (2) ~2.21 Ga Kunigal swarm, (3) ~2.18 Ga Mahbubnagar swarm, and (4) ~1.89 Ga Bastar-Dharwar swarm. These are mostly sub-alkaline tholeiitic suites, with ~1.89 Ga samples having a slightly higher concentration of high-field strength elements than other swarms with a similar MgO contents. Mg number (Mg#) in the four swarms suggest that the two older swarms were derived from primary mantle melts, whereas the two younger swarms were derived from slightly evolved mantle melt. Trace element petrogenetic models suggest that magmas of the ~2.37 Ga swarm were generated within the spinel stability field by ~15–20% melting of a depleted mantle source, whereas magmas of the other three swarms may have been generated within the garnet stability field with percentage of melting lowering from the ~2.21 Ga swarm (~25%), ~2.18 Ga swarm (~15–20%), to ~1.89 Ga swarm (~10–12%). These observations indicate that the melting depth increased with time for mafic dike magmas. Large igneous province (LIP) records of the eastern Dharwar craton are compared to those of similar mafic events observed from other shield areas. The Dharwar and the North Atlantic cratons were probably together at ~2.37 Ga, although such an episode is not found in any other craton. The ~2.21 Ga mafic magmatic event is reported from the Dharwar, Superior, North Atlantic, and Slave cratons, suggesting the presence of a supercontinent, ‘Superia’. It is difficult to find any match for the ~2.18 Ga mafic dikes of the eastern Dharwar craton, except in the Superior Province. The ~1.88–1.90 Ga mafic magmatic event is reported from many different blocks, and therefore may not be very useful for supercontinent reconstructions.  相似文献   

Petrology, geochronology and tectonic implications of Mesozoic high Ba–Sr granites in the Haemi area, Hongseong Belt, South Korea     

Seon-Gyu  Choi  V. J. Rajesh  Jieun  Seo  Jung-Woo  Park  Chang-Whan  Oh  Sang-Joon  Pak  Sung-Won  Kim 《Island Arc》2009,18(2):266-281

Collision between the North and South China continental blocks began in the Korean peninsula during the Permian (290–260 Ma). The Haemi area in the Hongseong collision belt (proposed as the eastern extension in South Korea of the Dabie–Sulu collision zone of China) within the Gyeonggi Massif comprises post-collisional high Ba–Sr granite with intermediate enclaves that intruded into the Precambrian rocks. The intermediate enclaves have a shoshonitic affinity whereas the granite is a high-K calc-alkaline variety. The chondrite-normalized rare earth element (REE) pattern with relative enrichment of LREE over HREE and absence of a significant negative Eu anomaly typifies both enclaves and granite. Geochemical similarities of enclaves and granite are attributed to the involvement of enriched mantle sources in their genesis. However, dominant crustal components were involved in the formation of high Ba–Sr granites. A granite crystallization age of 233 ± 2 Ma was obtained from SHRIMP U–Pb zircon dating. This age is slightly younger than the Triassic collision event in the Hongseong Belt. Geochemical data, U–Pb zircon age, and regional tectonics indicate that the Haemi high Ba–Sr granite formed in a post-collisional tectonic environment. A Mesozoic post-collisional lithospheric delamination model can account for the genesis of high Ba–Sr granite in the Haemi area.  相似文献   

Estimation of Coda Wave Attenuation for the National Capital Region, Delhi, India Using Local Earthquakes   总被引：1，自引：0，他引：1  

William K. Mohanty  Rajesh Prakash  G. Suresh  A. K. Shukla  M. Yanger Walling  J. P. Srivastava 《Pure and Applied Geophysics》2009,166(3):429-449

Attenuation of seismic waves is very essential for the study of earthquake source parameters and also for ground-motion simulations, and this is important for the seismic hazard estimation of a region. The digital data acquired by 16 short-period seismic stations of the Delhi Telemetric Network for 55 earthquakes of magnitude 1.5 to 4.2, which occurred within an epicentral distance of 100 km in an area around Delhi, have been used to estimate the coda attenuation Q_c. Using the Single Backscattering Model, the seismograms have been analyzed at 10 central frequencies. The frequency dependence average attenuation relationship Q_c = 142f ^1.04 has been attained. Four Lapse-Time windows from 20 to 50 seconds duration with a difference of 10 seconds have been analyzed to study the lapse time dependence of Q_c. The Q_c values show that frequency dependence (exponent n) remains similar at all the lapse time window lengths. While the change in Q₀ values is significant, change in Q₀ with larger lapsetime reflects the rate of homogeneity at the depth. The variation of Q_c indicates a definitive trend from west to east in accordance with the geology of the region.  相似文献   

Effect of geojute technique on density,diversity and carbon stock of plant species in landslide site of North West Himalaya     

Harsh Mehta  Raj Kumar  M. Ayub Dar  G. P. Juyal  Sridhar Patra  Sneha Dobhal  A. C. Rathore  Rajesh Kaushal  P. K. Mishra 《山地科学学报》2018,15(9):1961-1971

Mountainous regions of the globe experience landslides due to heavy rainfall and unplanned construction on slopes. Geojute is adopted globally as a landslide rehabilitation measure, but its impact on natural vegetation development is poorly understood. The present study was conducted to examine the impact of geojute application on vegetation restoration, ecology and carbon stock in a recently occurred landslide, during 2012. The results revealed that the geojute application improved the richness, diversity, density and basal area of plant species at the landslide site. Likewise, biomass production, carbon stock and carbon sequestration of plant species was observed significantly higher in geojute treatments compared to control (without geojute treatment). Moreover, significant improvement in soil moisture was recorded beneath the geojute treatments. Further, results showed that the geojute is highly effective in controlling soil erosion at the landslide site. The findings of this study revealed ecological and environmental benefits of geojute application in term of improvement in vegetation recovery processes, species diversity and carbon sequestration at the landslide site. The scientific outcome of this study can be helpful for planning the rehabilitation measures in landslide affected regions of the globe.  相似文献   

Parameterization of rain induced surface roughness and its validation study using a third generation wave model     

R. Rajesh Kumar  B. Prasad Kumar  D. Bala Subrahamanyam 《Ocean Science Journal》2009,44(3):125-143

The effect of raindrops striking water surface and their role in modifying the prevailing sea-surface roughness is investigated. The work presents a new theoretical formulation developed to study rain-induced stress on sea-surface based on dimensional analysis. Rain parameters include drop size, rain intensity and rain duration. The influences of these rain parameters on young and mature waves were studied separately under varying wind speeds, rain intensity and rain duration. Contrary to popular belief that rain only attenuates surface waves, this study also points out rain duration under certain condition can contribute to wave growth at high wind speeds. Strong winds in conjunction with high rain intensity enhance the horizontal stress component on the sea-surface, leading to wave growth. Previous studies based on laboratory experiments and dimensional analysis do not account for rain duration when attempting to parameterize sea-surface roughness. This study signifies the importance of rain duration as an important parameter modifying sea-surface roughness. Qualitative as well quantitative support for the developed formulation is established through critical validation with reports of several researchers and satellite measurements for an extreme cyclonic event in the Indian Ocean. Based on skill assessment, it is suggested that the present formulation is superior to prior studies. Numerical experiments and validation performed by incorporating in state-of-art WAM wave model show the importance of treating rain-induced surface roughness as an essential pre-requisite for ocean wave modeling studies.  相似文献   

Ultrahigh-temperature metamorphism from an unusual corundum+orthopyroxene intergrowth bearing Al–Mg granulite from the Southern Marginal Zone,Limpopo Complex,South Africa     

G. A. Belyanin  H. M. Rajesh  K. Sajeev  D. D. Van Reenen 《Contributions to Mineralogy and Petrology》2012,164(3):457-475

The Southern Marginal Zone of the Limpopo Complex is composed of granite-greenstone cratonic rocks reworked by a Neoarchean high-grade tectono-metamorphic event. Petrographic and mineral chemical characterization of an Al–Mg granulite from this zone is presented here. The granulite has a gneissic fabric with distinct Al-rich and Si-rich layers, with the former preserving the unusual lamellar (random and regular subparallel) intergrowths of corundum and symplectic intergrowth of spinel with orthopyroxene. The Al-rich layer preserves mineral assemblages such as rutile with orthopyroxene + sillimanite ± quartz, Al-rich orthopyroxene (~11 wt%), spinel + quartz, and corundum in possible equilibrium with quartz, while the Si-rich layer preserves antiperthites and orthopyroxene + sillimanite ± quartz, all considered diagnostic of ultrahigh-temperature metamorphism. Application of Al-in-opx thermometry, ternary feldspar thermometry and construction of suitable pressure–temperature phase diagrams, compositional and model proportion isopleth results indicate P–T conditions as high as ~1,050–1,100 °C, and ~10–12 kbars for the Al–Mg granulite. Our report of ultrahigh-temperature conditions is significant considering that the very high temperature was reached during decompression of an otherwise high-pressure granulite complex (clockwise P–T path), whereas most other ultrahigh-temperature granulites are linked to magma underplating at the base of the crust (counterclockwise P–T path).  相似文献   

Genetic Algorithm Based Feature Subset Selection for Land Cover/ Land Use Mapping Using Wavelet Packet Transform     

S. Rajesh  S. Arivazhagan  K. Pratheep Moses  R. Abisekaraj 《Journal of the Indian Society of Remote Sensing》2013,41(2):237-248

A genetic algorithm based approach is used in this paper for the selection of a subset from the combination of Wavelet Packet Statistical and Wavelet Packet Co-occurrence textural feature sets to classify the LISS IV satellite images using neural networks. Generally, adding a new feature increases the complexity of training and classification. Hence there is a need to differentiate between those features that contribute ample information and others. Many current feature reduction techniques such as Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) involve linear transformations of the original pattern vectors to new vectors of lower dimensions. Hence a multi-objective Genetic Algorithm has been employed to reduce the complexity and increase the accuracy of classification. Four indices - user’s accuracy, producer’s accuracy, overall accuracy and kappa co-efficient are used to assess the accuracy of the classified data. Experimental results show that the proposed Genetic Algorithm approach with lesser number of optimal features produces comparable results with that of our earlier approach using more features.  相似文献   

Biogenic uraninite precipitation and its reoxidation by iron(III) (hydr)oxides: A reaction modeling approach     

Nicolas F. Spycher  Montarat Issarangkun  S. Sevinç ?engör  Tim R. Ginn  Rajesh K. Sani 《Geochimica et cosmochimica acta》2011,75(16):4426-4440

One option for immobilizing uranium present in subsurface contaminated groundwater is in situ bioremediation, whereby dissimilatory metal-reducing bacteria and/or sulfate-reducing bacteria are stimulated to catalyze the reduction of soluble U(VI) and precipitate it as uraninite (UO₂). This is typically accomplished by amending groundwater with an organic electron donor. It has been shown, however, that once the electron donor is entirely consumed, Fe(III) (hydr)oxides can reoxidize biogenically produced UO₂, thus potentially impeding cleanup efforts. On the basis of published experiments showing that such reoxidation takes place even under highly reducing conditions (e.g., sulfate-reducing conditions), thermodynamic and kinetic constraints affecting this reoxidation are examined using multicomponent biogeochemical simulations, with particular focus on the role of sulfide and Fe(II) in solution. The solubility of UO₂ and Fe(III) (hydr)oxides are presented, and the effect of nanoscale particle size on stability is discussed. Thermodynamically, sulfide is preferentially oxidized by Fe(III) (hydr)oxides, compared to biogenic UO₂, and for this reason the relative rates of sulfide and UO₂ oxidation play a key role on whether or not UO₂ reoxidizes. The amount of Fe(II) in solution is another important factor, with the precipitation of Fe(II) minerals lowering the Fe⁺² activity in solution and increasing the potential for both sulfide and UO₂ reoxidation. The greater (and unintuitive) UO₂ reoxidation by hematite compared to ferrihydrite previously reported in some experiments can be explained by the exhaustion of this mineral from reaction with sulfide. Simulations also confirm previous studies suggesting that carbonate produced by the degradation of organic electron donors used for bioreduction may significantly increase the potential for UO₂ reoxidation through formation of uranyl carbonate aqueous complexes.  相似文献   

A Comparative Study of Built-up Index Approaches for Automated Extraction of Built-up Regions From Remote Sensing Data     

Avnish Varshney  Edida Rajesh 《Journal of the Indian Society of Remote Sensing》2014,42(3):659-663

Accurate built-up information is imperative for loss estimation and disaster management after the occurrence of catastrophic events such as earthquake, tornado, tsunami and flood. These catastrophic events leave behind a trail of mass destruction with property and human losses amounting to millions. Once a natural disaster hits a region, built-up information is required within a short span of time for disaster management. Nowadays, earth observation satellite imagery serves as a promising source to extract the land use / land cover classes. However, the automatic extraction of urban built-up from remote sensing data is a known challenge in the remote sensing community. The normalized difference built-up index (NDBI) algorithm has been recognized as an effective algorithm for automatic built-up identification from medium spatial and spectral resolution satellite images. Few researchers have modified this algorithm and proposed new quantitative expressions for the built-up index. In this paper, three built-up index based, unsupervised built-up extraction algorithms have been reviewed and compared. An automated kernel-based probabilistic thresholding algorithm is used to assort the built-up index values, obtained from modified built-up index algorithms, into built-up and non built-up regions for enhancing the efficiency of the built-up detection process. Qualitative assessment of these algorithms involves computation of several parameters including recently developed parameters like allocation disagreement and quantity disagreement, and classical parameters such as error of omission, error of commission and overall accuracy. This paper presents a case study where the algorithms have been implemented on Landsat-5 Thematic Mapper (TM) image of the city of Delhi and its surrounding areas for detection of built-up regions automatically.  相似文献