Occurrence and Emplacement of Chromite Ores in Sindhudurg District,Maharashtra, India     

Sridhar D. IYER  Elapavalooru V.S.S.K. BABU  Premchand G. MISLANKAR  Anup R. GUJAR  Navso V. AMBRE  Victor J. LOVESON 《《地质学报》英文版》2010,84(3):515-527

<正>In the present study,we present the occurrence and emplacement of chromite ore deposits from two abandoned mines(Kankavali[Janoli]and Wagda) in the Sindhudurg district of Maharashtra,India.These ores,that occurred as lenses and are associated with metamorphic and ultrabasic rocks,consist of octahedral grains of chromite,while clinochlore is present between the interstices of these grains.The Kankavali(Janoli) and Wagda ores revealed a dominance of Cr_2O_3 followed by FeO and variable proportions of A1_2O_3,MgO,and SiO_2.The former deposits have a slightly higher Cr_2O_3(average 52 wt%) and FeO(～18 wt%) than those from Wagda(Cr_2O_3～50 wt%,FeO～25 wt%).The similar Cr~# values(0.73 for Kankavali[Janoli],0.74 for Wagda) correspond to those reported for typical podiform-type chromite deposits.We suggest that the ores were emplaced as phacoliths in folded outcrops with a steep easterly dip and a northwest-southeast trend.We postulate the continuation of the fold structure from Janoli to Wagda(～4.5 km apart) and the probable (sporadic) occurrence of chromite along this stretch.The possibility of the contribution of chromite grains from these areas to the coastal placer deposits cannot be ruled out.  相似文献   

District-wide drought climatology of the southwest monsoon season over India based on standardized precipitation index (SPI)   总被引：5，自引：1，他引：4  

D. S. Pai  Latha Sridhar  Pulak Guhathakurta  H. R. Hatwar 《Natural Hazards》2011,59(3):1797-1813

District-wide drought climatology over India for the southwest monsoon season (June–September) has been examined using two simple drought indices; Percent of Normal Precipitation (PNP) and Standardized Precipitation Index (SPI). The season drought indices were computed using long times series (1901–2003) of southwest monsoon season rainfall data of 458 districts over the country. Identification of all India (nation-wide) drought incidences using both PNP and SPI yielded nearly similar results. However, the district-wide climatology based on PNP was biased by the aridity of the region. Whereas district-wide drought climatology based on SPI was not biased by aridity. This study shows that SPI is a better drought index than PNP for the district-wide drought monitoring over the country. SPI is also suitable for examining break and active events in the southwest monsoon rainfall over the country. The trend analysis of district-wide season (June–September) SPI series showed significant negative trends over several districts from Chattisgarh, Bihar, Kerala, Jharkhand, Assam and Meghalaya, Uttaranchal, east Madhya Pradesh, Vidarbha etc., Whereas significant positive trends in the SPI series were observed over several districts from west Uttar Pradesh, west Madhya Pradesh, South & north Interior Karnataka, Konkan and Goa, Madhya Maharashtra, Tamil Nadu, East Uttar Pradesh, Punjab, Gujarat etc.  相似文献   

Aquatic hyphomycetes in hyporheic freshwater habitats of southwest India     

Naga Mangala SudheepKandikere Ramaiah Sridhar 《Limnologica》2012,42(2):87-94

The hyporheic zones constitute a major site of storage of organic matter and energy flow in freshwater ecosystems. To complement the studies carried out in North America and Europe, we evaluated the sediment quality and occurrence of aquatic hyphomycetes in coarse particulate organic matter (CPOM; ≥5 mm) and fine particulate matter (FPM; ≤1 mm) in three locations of Kaiga stream and eight locations of Kadra dam of the River Kali in Western Ghats. The pH of sediments of stream and dam was acidic (5.8-6.6) and the average organic carbon of stream sediments was higher than dam sediments (8.6% vs. 3.9%). Among the eight minerals monitored, Fe was highest in all sediments and Ni was below detectable limit in four dam sediments. Spores of aquatic hyphomycetes were directly released from the CPOM fractions of sediments upon bubble chamber incubation, while the FPM fractions produced spores indirectly by colonization of sterile leaf baits followed by bubble chamber incubation. The species richness and diversity in CPOM was higher than FPM in stream as well as dam sediments. The Sorensen's similarity indices between the fungal flora of CPOM in stream (66.7-81.8%) and dam (69.2-88%) locations were generally higher than FPM. The spore output per mg CPOM was between 1215 (dam) and 3384 (stream). The species richness was negatively correlated with Cr (P < 0.01; r = −1.000) of stream sediments, while it was negatively correlated with organic carbon (P < 0.05; r = −0.740) and positively correlated with K (P < 0.05; r = 0.750) of dam sediments. Occurrence and survival of aquatic hyphomycetes in hyporheic habitats of freshwater bodies indicate the importance of such zones as reservoir of fungal inoculum necessary in fundamental functions such as organic matter processing and energy flow. The present study provides baseline data on the sediment quality and fungal composition of stream and dam locations of River Kali of Kaiga region, which will develop as center of industrial activities in future.  相似文献   

中印度洋初始热液事件的证据     

Sridhar D.IYER 《地质学报》2005,79(1):143

中印度洋发育有海山、深海山丘、断裂、线形构造等地貌构造单元及来源不同的基性和硅铝质火山岩。有证据表明这一带出现了初始热液事件 :1由低温热液作用于早期玄武岩而形成的细碧岩 ;2玄武质玻璃产生的沸石岩片 ;3铁锰壳的化学变化 ;4大量的含有赭石沉积物和磁铁矿球粒的火山-  相似文献   

The economics of mining seabed manganese nodules: A case study of the Indian Ocean nodule field     

Ranadhir Mukhopadhyay  Sankalp Naik  Shawn De Souza  Ozinta Dias  Sridhar D Iyer  Anil K Ghosh 《Marine Georesources & Geotechnology》2013,31(7):845-851

Abstract

Because of ever-growing demand for strategic metals, the focus of the international community has fallen on deep sea manganese nodules occurring at a water depth of more than 4500?m. We present an economic appraisal and strategy for mining of nodules from the Indian Ocean Nodule Field- one of the four economically potential areas in the world oceans. In contrast to the prevailing perception of non-viability of nodule mining, our analysis indicates a fair degree of economic feasibility and commercial sustainability to mine the deep-sea manganese nodules.  相似文献   

Application of In-situ Lysimetric Studies for Determining Soil Hydraulic Conductivity     

B. Hanumantha Rao  V. Sridhar  R. R. Rakesh  D. N. Singh  P. K. Narayan  P. K. Wattal 《Geotechnical and Geological Engineering》2009,27(5):595-606

Several techniques such as laboratory column studies, under normal and accelerated gravity environments, numerical modeling and pedo-transfer functions have been employed by previous researchers to determine hydraulic conductivity of soils. However, these methods suffer with several limitations, particularly, as far as regeneration of in-situ soil conditions and boundary conditions, in an exceptionally small model, are concerned. Under these circumstances, in-situ lysimeters are found to be quite useful for conducting the investigations to obtain hydraulic conductivity of fully saturated or partially saturated soils. These lysimeters can easily be installed in the soil mass, without disturbing its state, and are large enough to exhibit representative soil mass that exist at the site. With this in view, an attempt was made in this study to determine hydraulic conductivity of the soil mass beneath a waste disposal site in India by installing a lysimeter. Details of the instrumentation are presented in this paper along with the methodology to determine hydraulic conductivity of the soil mass.  相似文献   

Comparison of vegetation indices for practicable homology     

R. Jaishanker  T. Senthivel  V. N. Sridhar 《Journal of the Indian Society of Remote Sensing》2005,33(3):395-404

Vegetation indices are widely used to assess quantitatively the biophysical characteristics of vegetation from remote sensing measurements. Different indices have their own advantages in retrieving vegetation information. It is very difficult to precisely attribute any vegetation index to any particular vegetation biophysical parameter. This study examines the correlations among different vegetation indices derived from a set of mustard, gram and wheat fields at three different phenological growth stages. The results are presented as correlation matrices along with correlation scatter plots. Homologous (equi-magnitude) vegetation information is represented by NDVI, PVI and AtRVI for wheat crop with leaf area index less than 1.  相似文献   

Investigation of natural background radiation of sediments in Rameswaram Island,Tamil Nadu,India     

I. Inigo Valan  I. Vijayalakshmi  R. Mathiyarasu  S. G. D. Sridhar  V. Narayanan  A. Stephen 《Arabian Journal of Geosciences》2018,11(23):762

The aim of the study is to assess the natural background radiation in and around Rameswaram Island. In this context, samples were collected to measure the gamma radiations of ²³⁸U, ²³²Th, and ⁴⁰K using NaI(Tl) detector-based gamma ray spectrometer. The average activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K are noted to be well below the world average values. The calculated absorbed dose rate, radium equivalent activity, and hazard index values were below the prescribed limit. The grain size of the sediment was analyzed following Trefethen’s nomenclature, and its correlation with the natural background radioactivity was studied. The sample that contained clay show elevated activity of ⁴⁰K. The percentage of heavy minerals shows concomitant variation in natural radioactivity, especially in the activity of ²³⁸U and ²³²Th.  相似文献   

Impact of sea level rise and shoreline changes in the tropical island ecosystem of Andaman and Nicobar region,India     

Mageswaran  T.  Sachithanandam  V.  Sridhar  R.  Mahapatra  Manik  Purvaja  R.  Ramesh  R. 《Natural Hazards》2021,109(2):1717-1741

Natural Hazards - We report here a four decades of shoreline changes and possible sea level rise (SLR) impact on land use/land cover (LULC) in Little Andaman Island by using remote sensing (RS) and...  相似文献   

Real time wave forecasting using neural networks     

M.C. Deo  C. Sridhar Naidu 《Ocean Engineering》1998,26(3):191-203

Forecasting of ocean wave heights, with warning time of a few hours or days, is necessary in planning many operation-related activities in the ocean. Such information is currently derived by numerically solving the differential equation representing wave energy balance. The solution procedure involved is extremely complex and calls for very large amounts of meteorological and oceanographic data. This paper presents a complementary and simple method to make a point forecast of waves in real time sense based on the current observation of waves at a site. It incorporates the technique of neural networks. The network involved is first trained by different algorithms and then used to forecast waves with lead times varying from 3 to 24 h. The results of different training algorithms are compared with each other. The neural output is further compared with the statistical AR models.  相似文献