Nature of magmatism and sedimentation at a Columbia active margin: Insights from combined U–Pb and Lu–Hf isotope data of detrital zircons from NW India     

Parampreet Kaur  Armin Zeh  Naveen Chaudhri  Axel Gerdes  Martin Okrusch 《Gondwana Research》2013,23(3):1040-1052

Detrital zircons from a Palaeoproterozoic quartzite, deposited between 1.85 and 1.82 Ga in the northern Aravalli orogen of NW India, show a distinctive age peak of ca. 1.85 Ga and variable, but largely subchondritic εHf_{1.85 Ga} between ? 1.3 and ? 21.0 corresponding to hafnium model ages of 2.5 to 3.6 Ga. These data indicate an important period of reworking of ancient (Eo- to Neoarchaean), strongly heterogeneous continental crust at this time. Prevalence of ca. 1.85 Ga subduction-related granitoids, almost identical U–Pb age spectra and εHf_t of detrital zircons in ca. 1.85 Ga metasedimentary rocks in the Aravalli orogen and the inner Lesser Himalaya indicate similar sediment provenances and thus a geological connection between these two terranes during late Palaeoproterozoic. All together, the data constrain a rapid succession of sedimentation, metamorphism and subduction-related magmatic activity and support the interpretation of an active geodynamic realm along the entire north Indian margin at ca. 1.85 Ga. Comparison of detrital zircon data in conjunction with published paleomagnetic data from north India and other crustal blocks of the Columbia supercontinent, additionally, suggest a close affinity of north India with Madagascar, the Cathaysia block of South China and South Korea during Columbia times.  相似文献   

Assessment of Seismically Induced Landslide Hazard for the State of Karnataka Using GIS Technique     

Naveen James  T. G. Sitharam 《Journal of the Indian Society of Remote Sensing》2014,42(1):73-89

Landslide hazards are a major natural disaster that affects most of the hilly regions around the world. In India, significant damages due to earthquake induced landslides have been reported in the Himalayan region and also in the Western Ghat region. Thus there is a requirement of a quantitative macro-level landslide hazard assessment within the Indian subcontinent in order to identify the regions with high hazard. In the present study, the seismic landslide hazard for the entire state of Karnataka, India was assessed using topographic slope map, derived from the Digital Elevation Model (DEM) data. The available ASTER DEM data, resampled to 50 m resolution, was used for deriving the slope map of the entire state. Considering linear source model, deterministic seismic hazard analysis was carried out to estimate peak horizontal acceleration (PHA) at bedrock, for each of the grid points having terrain angle 10° and above. The surface level PHA was estimated using nonlinear site amplification technique, considering B-type NEHRP site class. Based on the surface level PHA and slope angle, the seismic landslide hazard for each grid point was estimated in terms of the static factor of safety required to resist landslide, using Newmark’s analysis. The analysis was carried out at the district level and the landslide hazard map for all the districts in the Karnataka state was developed first. These were then merged together to obtain a quantitative seismic landslide hazard map of the entire state of Karnataka. Spatial variations in the landslide hazard for all districts as well as for the entire state Karnataka is presented in this paper. The present study shows that the Western Ghat region of the Karnataka state is found to have high landslide hazard where the static factor of safety required to resist landslide is very high.  相似文献   

Exact solutions: neutral and charged static perfect fluids with pressure     

Naveen Bijalwan 《Astrophysics and Space Science》2012,337(1):161-167

We show in this article that charged fluid with pressure derived by Bijalwan (Astrophys. Space. Sci. doi:, 2011a) can be used to model classical electron, quark, neutron stars and pulsar with charge matter, quasi black hole, white dwarf, super-dense star etc. Recent analysis by Bijalwan (Astrophys. Space. Sci., 2011d) that all charged fluid solutions in terms of pressure mimic the classical electron model are partially correct because solutions by Bijalwan (Astrophys. Space. Sci. doi:, 2011a) may possess a neutral counterpart. In this paper we characterized solutions in terms of pressure for charged fluids that have and do not have a well behaved neutral counter part considering same spatial component of metric e ^λ for neutral and charged fluids. We discussed solution by Gupta and Maurya (Astrophys. Space Sci. 331(1):135–144, 2010a) and solutions by Bijalwan (Astrophys. Space Sci. doi:, 2011b; Astrophys. Space Sci. doi:, 2011c; Astrophys. Space Sci., 2011d) such that charged fluids possess and do not possess a neutral counterpart as special cases, respectively. For brevity, we only present some analytical results in this paper.  相似文献   

Pollutant’s Horizontal Dispersion Along and Against Sinusoidally Varying Velocity from a Pulse Type Point Source   总被引：1，自引：0，他引：1  

Mritunjay K. Singh  Nav K. Mahato  Naveen Kumar 《Acta Geophysica》2015,63(1):214-231

An analytical solution of a two-dimensional advection diffusion equation with time dependent coefficients is obtained by using Laplace Integral Transformation Technique. The horizontal medium of solute transport is considered of semi-infinite extent along both the longitudinal and lateral directions. The input concentration is assumed at an intermediate position of the domain. It helps to evaluate concentration level along the flow as well as against the flow through one model only. The source of the input concentration is considered to be of pulse type. In the presence of the source, it is assumed to be decreasing very slowly with time, and just after the elimination of the source it is assumed to be zero. The dispersion coefficient and the advection parameter are considered directly proportional to each other. The analytical solution may be used to predict the solute concentration level with position and time in an open medium as well as in a porous medium. The effect of heterogeneity on the solute transport may also be predicted.  相似文献   

Origin of trondhjemite and albitite at the expense of A-type granite,Aravalli orogen,India:Evidence from new metasomatic replacement fronts     

Parampreet Kaur  Naveen Chaudhri  Nusrat Eliyas 《地学前缘(英文版)》2019,10(5):1891-1913

The A-type Harsora-Dadikar granites in the Alwar complex of northern Aravalli orogen,NW India provide evidence for subsolidus-requilibration of feldspars.They record three new discrete stages of albitisation,producing trondhjemite and albitite sequentially at the expense of original granite.Stage-Ⅰ metasomatism deanorthised the magmatic oligoclase and transformed the grey least-albitised granite to pinkish grey microcline-oligoclase granite.Stage-II converted the latter to trondhjemite by replacement of microcline to oligoclase.Stage-Ⅲ metasomatism led to the formation of albitite/albite granite from trondhjemite,where the metasomatically formed oligoclase was replaced by albite.This stage of metasomatism resulted in nearly complete disappearance of amphibole and biotite,producing a monomineralic rock(albitite),which is consistent with Korzhinskii theory of infiltration metasomatism.The reaction fronts delineating the Stage-Ⅱ and Stage-Ⅲ are sharp and easily discernible by their prominent color differences in Harsora on the outcrop scale.Chemically,the mineral transformations during three stages are manifested by the differential gains/losses in Na,K,Ca,Rb,Ba,Sr,Fe and Mg.The formation of albite,Cl-rich marialitic scapolite and Cl-rich amphibole in the albitised granites are suggestive of Naand Cl-brines as the metasomatising fluids.The fluid-rock interactions,which can significantly transform the pristine mineralogy of granitoids,should be carefully considered to avoid any misinterpretations about their petrological history.  相似文献   

Radio AGNs among Luminous Infrared Galaxies     

M. S. Yun  J. E. Hibbard  J. J. Condon  Naveen Reddy 《Astrophysics and Space Science》1999,266(1-2):29-34

An analysis of radio and FIR emission in over 1500IRAS selected galaxies produces a good linear correlationbetween radio and FIR luminosity, indicating that star formationin normal field galaxies dominates the infrared luminosityin the local volume. Galaxies with clear radio-excess (definedas having at least5 times larger radio flux over expected from FIR) are identified as hosting a radio AGN, and they account for onlyabout 1% of the whole sample. This fraction increases to 10% among themore luminous galaxies with L _1.4GHz 10²³ W Hz^-1 (equivalently L _60m 10¹¹ L), however. The characteristic mid-IR excess of a Seyfert nucleus is ubiquitously present amongthe radio-excess objects, suggesting that mid-IR excess isa robust tracer of an AGN despite the high mid-IR opacity.We conclude that about 30% of the luminous infrared galaxies(L _60m 10¹¹ L) host an AGN based on themid-IR excess, and about 40% of the mid-IR excess AGNs alsohost a radio AGN. A VLA imaging survey of a distance limited sample of IR luminousgalaxies has revealed the presence of 100 kpc scale giant radioplumes in 3 out of 9 cases (Mrk 231, Mrk 273, NGC 6240). Theirlarge spatial extent, energetics, and presence of a powerful AGN in each case suggests that an AGN is the power source. Such plumesare not detected in other ultraluminous infrared galaxies which lack clear evidence for an AGN, such as Arp 220.  相似文献   

Coastal boulders as evidences of high-energy marine events from Diu Island,west coast of India: storm or palaeotsunami?     

Prizomwala  S. P.  Gandhi  Drasti  Ukey  Vishal M.  Bhatt  Nilesh  Rastogi  B. K. 《Natural Hazards》2015,75(2):1187-1203

Natural Hazards - The coastal segment of Diu Island from west coast of India has been studied for its boulder deposits. The dimensions, morphology and characteristics of these boulders were studied...  相似文献   

A cognitive framework for road detection from high-resolution satellite images     

Naveen Chandra  Jayanta Kumar Ghosh  Ashu Sharma 《国际地球制图》2019,34(8):909-924

Road network extraction from high-resolution satellite (HRS) imagery is a complex task. It is an important field of research and is widely used in various cartographic applications such as updating and generating maps. The objective of this research work is to develop a novel framework, emulating human cognition, for detection of roads from HRS images. Roads network from HRS images are detected using support vector machines within the different stages of cognitive task analysis. In the first stage, basic information about the cognitive parameters which are required for image interpretation is collected. In the second stage, the rule-based method is used for knowledge representation. Lastly, during knowledge elicitation, the developed rules are used to extract roads from HRS images. The proposed method is validated using 16 HRS images of developed suburban, developed urban, emerging suburban and emerging urban region.  相似文献   

Petrogenesis and Tectonic Significance of the Neoproterozoic Magmatism of the Tusham Ring Complex (NW Indian Shield): Insight into Tectonic Evolution of the Malani Igneous Suite and Rodinia Supercontinent     

Naveen Kumar  Kumar  Naresh  Sharma  Radhika  Singh  A. Krishnakanta 《Geotectonics》2020,54(3):428-453

Geotectonics - The present study is carried out to probe geodynamic evolution and tectonic history of A-type granitoids from the Riwasa and Nigana areas in the Tusham Ring Complex (TRC), western...  相似文献   

Interacting binaries: Science cases where simultaneous multicolor medium‐resolution spectroscopy makes a difference     

E. Mason  P. Gandhi 《Astronomische Nachrichten》2011,332(3):260-261

This contribution to “The 1st year of science with X‐shooter” conference illustrates 2 different applications of the new ESO multi‐waveband spectrograph to the study of interacting binaries. In particular we present spectra collected during the late decline of U Sco 2010 outburst and during a low/hard X‐ray phase of the black hole candidate GX339‐4. In both cases the unprecedented spectral coverage and resolution offered by X‐shooter have unveiled unexpected features (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献