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21.
N. V. Chalapathi Rao Anup K. Sinha Suresh Kumar Rajesh K. Srivastava 《Journal of the Geological Society of India》2013,81(6):733-736
We report a rare accessory groundmass mineral of K-rich titanate, having a composition close to that of potassium triskaidecatitanate (K2Ti13O27), from an underground drill-core sample of ultrapotassic rock from southwestern part of the Jharia coal field in the Damodar valley, at the northern margin of the Singhbhum craton, Eastern India. Potassium triskaidecatitanate is regarded as a typomorphic mineral of orangeites (Group II kimberlites) of Kaapvaal craton, southern Africa, and its occurrence in the Jharia ultrapotassic rock is significant since ultrapotassic suite of rocks elsewhere from the Damodar valley have been recently suggested to be peralkaline lamproites based on mineral-genetic classification. The important role played by a unique geodynamic setting (involving a thinned metasomatised lithospheric mantle and inheritance of an Archaean subduction component) at the northern margin of the Singhbhum craton in deciding the petrological diversity of the early Cretaceous ultrapotassic intrusives from the Damodar valley is highlighted in this study. 相似文献
22.
Horizontal surface visibility range, one of the simplest measures of local atmospheric pollution, is critical for aviation, surface transport besides long-term impact on human health and climate. Long-term observations from multiple stations (including airports) across the world show statistically significant decline in visibility. We have studied climatology and trends of morning poor visibility days (PVD, visibility <4 km) and afternoon good visibility days (GVD, visibility >10 km) based on 279 surface meteorological stations well distributed over India for the period 1961–2008. During last 5 decades, all India averaged range of annual morning PVD has increased from 6.7 to 27.3 % days, while the range of afternoon GVD has decreased from 76.1 to 30.6 % days. Annually, the morning PVD increased significantly at 3.3 % days per decade, and the afternoon GVD declined significantly at ?8.6 % days per decade. Seasonally, the highest increase in morning PVD has occurred in winter (+4.3 % days per decade), while post-monsoon has the highest decrease in afternoon GVD (?9.2 % days per decade). In spatial distribution, visibility has decreased nationwide especially over Indo-Gangetic (IG) plains, central, east and northeast India which is due to increased wintertime fog, water vapor and aerosol loading. The IG plains suffer from increased fog or smog and aerosol loading during wintertime. Long-term visibility impairment over India is visible through increasing morning PVD (decreasing GVD) and decreasing afternoon GVD (increasing PVD) which are spatially well correlated with increasing relative humidity and decreasing wind speed (seasonal). 相似文献
23.
In recent years, biological toxicity tests have been conducted for soil assessment of environmental pollutants to evaluate the environmental risk due to heavy metals. In this study, batch tests were conducted with soils contaminated with hexavalent chromium (Cr6+) using sulfur-oxidizing bacteria (SOB). For control soils (without Cr6+), the electrical conductivity (EC) increased linearly over time in all samples, indicating that no toxic substances were present in the soil. The initial EC varied between 6 and 7.8 mS/cm, and the final EC varied between 22 and 27 mS/cm after incubation for 65 h. For batch tests performed using Cr6+-contaminated soil, the EC increased slightly or remained stable in all the test samples after a few hours. Thus, the presence of toxic substance Cr6+ inhibited the SOB, which leads to no sulfuric acid formation and therefore, no change in EC. These results indicated that SOB can be employed as a test microorganism to assess the quality of heavy metal-contaminated soils. 相似文献
24.
Babita Sharma Sumer Chopra Anup Kumar Sutar B. K. Bansal 《Pure and Applied Geophysics》2013,170(12):2127-2138
In the present study ground motions for a Mw 8.5 scenario earthquake are estimated at 13 sites in Kumaun-Garhwal region using the empirical Green’s function technique. The recordings of 1991 Uttarkashi earthquake of Mw 6.8 at these sites are used as an element earthquake. A heterogeneous source model consisting of two asperities is considered for simulating the ground motions. The entire central seismic gap (CSG) can expect acceleration in excess of 100 cm/s2 with NW portion in excess of 400 cm/s2 and SE between 100 and 200 cm/s2. The central portion can expect peak ground acceleration (PGA) between 200 and 400 cm/s2. It has been observed from simulation of strong ground motion that sites located near the rupture initiation point can expect accelerations in excess of 1g. In the present analysis, Bhatwari and Uttarkashi can expect ground accelerations in excess of 1g. The estimates of the PGA are compared with earlier studies in the same region using different methodologies and it was found that the results are comparable. This has put constrains on the expected PGAs in this region. The obtained PGA values can be used in identifying the vulnerable areas in the central Himalaya, thereby facilitating the planning, design and construction of new structures and strengthening of the existing structures in the region. 相似文献
25.
The early Cretaceous (Albian–Aptian) Sung Valley ultramafic–alkaline–carbonatite complex is one of several alkaline intrusions that occur in the Shillong Plateau, India. This complex comprises calcite carbonatite and closely associated ultramafic (serpentinized peridotite, pyroxenite and melilitolite) and alkaline rocks (ijolite and nepheline syenite). Field relationship and geochemical characteristics of these rocks do not support a genetic link between carbonatite and associated silicate rocks. There is geochemical evidence that pyroxenite, melilitolite and ijolite of the complex are genetically related. Stable (C and O) and radiogenic (Nd and Sr) isotope data clearly indicate a mantle origin for the carbonatite samples. The carbonatite Nd (+0.7 to +1.8) and Sr (+4.7 to +7.0) compositions overlap the field for Kerguelen ocean island basalts. One sample of ijolite has Nd and Sr isotopic compositions that also plot within the field for Kerguelen ocean island basalts, whereas the other silicate–carbonatite samples indicate involvement with an enriched component. These geochemical and isotopic data indicate that the rocks of the Sung Valley complex were derived from and interacted with an isotopically heterogeneous subcontinental mantle and is consistent with interaction of a mantle plume (e.g. Kerguelen plume) with lithosphere. A U–Pb perovskite age of 115.1±5.1 Ma obtained for a sample of Sung Valley ijolite also supports a temporal link to the Kerguelen plume. The observed geochemical characteristics of the carbonatite rocks indicate derivation by low-degree partial melting (0.1%) of carbonated mantle peridotite. This melt, containing a substantial amount of alkali elements, interacted with peridotite to form metasomatic clinopyroxene and olivine. This process could progressively metasomatize lherzolite to form alkaline wehrlite. 相似文献
26.
Numerous early Cretaceous mafic and alkaline dykes, mostly trending in N-S direction, are emplaced in the Archaean gneissic
complex of the Shillong plateau, northeastern India. These dykes are spatially associated with the N-S trending deep-seated
Nongchram fault and well exposed around the Swangkre-Rongmil region. The petrological and geochemical characteristics of mafic
dykes from this area are presented. These mafic dykes show very sharp contact with the host rocks and do not show any signature
of assimilation with them. Petrographically these mafic dykes vary from fine-grained basalt (samples from the dyke margin)
to medium-grained dolerite (samples from the middle of the dyke) having very similar chemical compositions, which may be classified
as basaltic-andesite/andesite. The geochemical characteristics of these mafic dykes suggest that these are genetically related
to each other and probably derived from the same parental magma. Although, the high-field strength element (+rare-earth elements)
compositions disallow the possibility of any crustal involvement in the genesis of these rocks, but Nb/La, La/Ta, and Ba/Ta
ratios, and similarities of geochemical characteristics of present samples with the Elan Bank basalts and Rajmahal (Group
II) mafic dyke samples, suggest minor contamination by assimilation with a small amount of upper crustal material. Chemistry,
particularly REE, hints at an alkaline basaltic nature of melt. Trace element modelling suggests that the melt responsible
for these mafic dykes had undergone extreme differentiation (∼ 50%) before its emplacement. The basaltic-andesite nature of
these rocks may be attributed to this differentiation. Chemistry of these rocks also indicates ∼ 10–15% melting of the mantle
source. The mafic dyke samples of the present investigation show very close geochemical similarities with the mafic rocks
derived from the Kerguelen mantle plume. Perhaps the Swangkre-Rongmil mafic dykes are also derived from the Kerguelen mantle
plume. 相似文献
27.
Effect of dust storm on ocean color and snow parameters 总被引：1，自引：0，他引：1
Vinay K. Kayetha Senthil Kumar J. Anup K. Prasad Guido Cervone Ramesh P. Singh 《Journal of the Indian Society of Remote Sensing》2007,35(1):1-9
The present study clearly shows the influence of dust storms on chlorophyll bloom in the offshore region of the Arabian Sea,
with a time lag of few days, during the pre-monsoon season. Various satellite derived parameters over the Arabian Sea, Himalayan
and Tibet snow covered regions show large changes due to the influence of dust storms. The MODIS snow albedo gives unreliable
values under the influence of dust storms due to increase in the aerosol loading over these regions and snow albedo product
must be used in combination with snow pixel counts during the dust storm season. A detailed study is required for the quantitative
evaluation of dust storms on the chlorophyll blooms in the Arabian Sea region and on the snow parameters in the Himalayan
region. 相似文献
28.
SARAL carried onboard a radar altimeter that provides very precise measurements of the sea surface height (SSH). Like other altimetric missions, SARAL carries a passive microwave radiometer (PMR) for wet tropospheric correction to SSH. In the present study, new algorithms are developed for the retrieval of cloud liquid water (CLW) and total precipitable water vapor (TPW) over the global oceans from PMR measurements of the brightness temperatures. A radiative transfer and genetic algorithm based retrieval scheme is proposed for the estimation of CLW and TPW from SARAL PMR. The comparisons of CLW from PMR with independent measurements from GPM-GMI and SSMIS within and outside ±40° latitudes show correlation (R) of 0.86 and 0.83, bias of 0.7 and ?3.61?mg/cm2, and root mean square error (RMSE) of 8.42 and 8.07?mg/cm2, respectively. Similarly, TPW from PMR with GPM-GMI and SSMIS show R of 0.99 and 0.98, bias of ?0.04 and ?0.03?g/cm2 and RMSE of 0.17 and 0.17?g/cm2, respectively. The retrieval accuracy of CLW and TPW from the new algorithms is compared with these parameters provided in the SARAL geophysical data records as finished products, which showed substantial improvement in the quality of the parameters from the new algorithm. 相似文献
29.
In this paper, we have considered a model for FRW space-time in the presence of coupled scalar field φ and potential V(φ) with causal viscous fluid and polytropic fluid. We have shown that irrespective of fluid the causality theory provides late
time acceleration of the universe. In all cases, the potential always decreases due to evolution of the universe. 相似文献
30.
Topographic corrections of synthetic aperture radar (SAR) images over hilly regions are vital for retrieval of correct backscatter values associated with natural targets. The coarse resolution external digital elevation models (DEM) available for topographic corrections of high resolution SAR images often result into degradation of spatial resolution or improper estimation of backscatter values in SAR images. Also, many a times the external DEMs do not spatially co-register well with the SAR data. The present study showcases the methodology and results of topographic correction of ALOS-PALSAR image using high resolution DEM generated from the same data. High resolution DEMs of Jaipur region, India were generated using multiple pair SAR images acquired from ALOS-PALSAR using interferometric (InSAR) techniques. The DEMs were validated using differential global positioning system measured elevation values as ground control points and were compared with photogrammetric DEM (advanced spaceborne thermal emission and reflection radiometer – ASTER) and SRTM (Shuttle Radar Topography Mission) DEM. It was observed that ALOS-PALSAR images with optimum baseline parameters produced high resolution DEM with better height accuracy. Finally, the validated DEM was used for topographic correction of ALOS-PALSAR images of the same region and were found to produce better result as compared with ASTER and SRTM-DEM. 相似文献