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1.
A complete dismembered sequence of ophiolite is well exposed in the south Andaman region that mainly comprises ultramafic
cumulates, serpentinite mafic plutonic and dyke rocks, pillow lava, radiolarian chert, and plagiogranite. Pillow lavas of
basaltic composition occupy a major part of the Andaman ophiolite suite (AOS). These basalts are well exposed all along the
east coast of southern part of the south AOS. Although these basalts are altered due to low-grade metamorphism and late hydrothermal
processes, their igneous textures are still preserved. These basalts are mostly either aphyric or phyric in nature. Aphyric
type exhibits intersertal or variolitic textures, whereas phyric variety shows porphyritic or sub-ophitic textures. The content
of alkalies and silica classify these basalts as sub-alkaline basalts and alkaline basalts. A few samples show basaltic andesite,
trachy-basalt, or basanitic chemical composition. High-field strength element (HFSE) geochemistry suggests that studied basalt
samples are probably derived from similar parental magmas. Al2O3/TiO2 and CaO/TiO2 ratios classify these basalts as high-Ti type basalt. On the basis of these ratios and many discriminant functions and diagrams,
it is suggested that the studied basalts, associated with Andaman ophiolite suite, were derived from magma similar to N-MORB
and emplaced in the mid-oceanic ridge tectonic setting. 相似文献
2.
Doklady Earth Sciences - Kaladgi rocks are very well exposed in Belgaum district of Karnatak state, with adjacent to Maharashtra state. The rocks exposed in the study area comprises mainly of... 相似文献
3.
Dubey Anant Aishwarya Borthakur Annesh Ravi K. 《Geotechnical and Geological Engineering》2022,40(4):2371-2378
Geotechnical and Geological Engineering - Total soil suction is considered to be the accumulative influence of matric and osmotic suction, assuming that the soil is biologically inert. However,... 相似文献
4.
Petrographic investigations on the light yellow marble outcrops in the Griesscharte, Tyrol, Austria/Italy revealed them to be dolomite. The white to blue-grey veins in these marbles were those of calcite. Inside these calcites and along the calcite-dolomite phase boundaries minute and microscopically unidentifiable crystallites (? 10 μ) were observed. These crystallites were recognised by X-ray diffractometry as dolomite and their form and distribution were established by scanning electron microscopy. Trace-element distributions on the calcite-dolomite neighbours were studied by neutron-activation method to elucidate the formation mechanism of these calcites in the marble.Genetic relationships of the dolomite crystallites, the calcite host and the surrounding dolomite marble have been discussed in the light of the petrographic and chemical studies. These findings substantiate a deposition of a new formed vein of calcite from the solution circulating in the fissures of the dolomite marble during prograde metamorphism rather than a simple deposition of mobilized sedimentary calcite. The dolomite crystallites in the calcite seem to have been formed post-tectonically, partly by the nucleation in the calcite cleavage planes during Mg-metasomatism and partly from the exsolutions during retrograde metamorphism. 相似文献
5.
Jatin Srivastava Dinesh Shukla Vishal Chand Ram Naraian Harish Chandra Anant R. Nautiyal 《洁净——土壤、空气、水》2010,38(8):771-774
The presence of arsenic (As) in water is of great public concern. Arsenic exists in three common valence states viz., As(0) metalloid arsenic, As(III) (arsenite) and As(V) (arsenate). Arsenite [As(III)] is the most toxic form among arsenicals which, predominates in anaerobic conditions, generally in flooded soils and in the water with high BOD. Experiments were conducted to investigate the effect of As(III) on the mycorrhization in vetiver (Vetiveria zizanioides (L.) Nash) grass in hydroponics. Studies showed significant alteration in the mycorrhizal colonization in the roots of vetiver exposed to higher concentrations of As(III) starting from 1.0, 2.0, 3.0, 4.0 to 5.0 mg/L prepared in 5% Hoagland nutrient solution without addition of phosphate ions. Considerable reduction in the mycorrhizal intensity (M) was observed in all the treatment sets as compared to the control suggesting a negative impact of the As(III) on the mycorrhizal association. Simultaneously, the study also showed that, As(III) is toxic to the vetiver plants having mycorrhizal association however plants with non‐mycorrhizal (cleansed) roots were found to be able to survive for a longer period exposed to As(III). 相似文献
6.
Spatial and depth-wise distribution of sediment components, organic carbon and selected metals (Fe, Mn, Al, Ni, Cr, Co, Zn and Pb) is studied across upper and middle tidal flats from lower and middle estuarine regions of Kundalika Estuary, central west coast of India. Silt and clay form the major components in lower and middle estuary, respectively. Sand, silt, clay and organic carbon showed band-type distribution along the estuary. The sediment deposition over the years took place in varying hydrodynamic conditions in lower and middle estuarine regions. Upper flats of the lower estuary represent mud while middle flats of the lower estuary facilitated the deposition of sandy mud. Correlation results indicated the importance of clay and organic carbon in removal and trapping of metals at lower and middle estuary, respectively. Factor analysis indicated that the distribution of metals is largely controlled by Fe–Mn oxyhydroxides and organic carbon. The middle flats of the lower estuary showed an anthropogenic source for Ni, Cr and Co while middle flats of the middle estuary showed a mainly lithogenic source. 相似文献
7.
Kakatkar Rashmi Gnanaseelan C. Chowdary J. S. Parekh Anant Deepa J. S. 《Theoretical and Applied Climatology》2018,131(3-4):1235-1247
Theoretical and Applied Climatology - In this study, factors responsible for the deficit Indian Summer Monsoon (ISM) rainfall in 2014 and 2015 and the ability of Indian Institute of Tropical... 相似文献
8.
Bijoy Thompson C. Gnanaseelan Anant Parekh P. S. Salvekar 《Journal of Earth System Science》2008,117(2):169-178
The variability in the long-term temperature and sea level over the north Indian Ocean during the period 1958–2000 has been
investigated using an Ocean General Circulation Model, Modular Ocean Model version 4. The model simulated fields are compared
with the sea level observations from tide-gauges, Topex/Poseidon (T/P) satellite, in situ temperature profile observations from WHOI moored buoy and sea surface temperature (SST) observations from DS1, DS3 and DS4
moored buoys. It is seen that the long (6–8 years) warming episodes in the SST over the north Indian Ocean are followed by
short episodes (2–3 years) of cooling. The model temperature and sea level anomaly over the north Indian Ocean show an increasing
trend in the study period. The model thermocline heat content per unit area shows a linear increasing trend (from 1958–2000)
at the rate of 0.0018 × 1011 J/m2 per year for north Indian Ocean. North Indian Ocean sea level anomaly (thermosteric component) also shows a linear increasing
trend of 0.31 mm/year during 1958–2000. 相似文献
9.
10.
The influence of Mg2+ ions on the ion-activity product of calcium and carbonate dissolved in seawater has been investigated. The present approach is based mainly on: (1) the preponderance of this element in the marine system; (2) the observations by Weyl (1965), Jansen and Kitano (1963), and more recently by Plummer and Mackenzie (1974) on the higher solubility of magnesian calcite relative to pure calcite; and (3) the inferences drawn from our laboratory studies on the Ca2+—Mg2+ ion-exchange behaviour on surfaces of pure calcite. From these considerations, the pK value corresponding to a calcite containing 12 mole% of MgCO, has been estimated to be 7.7± 0.1 at 20°C. This value has serious reflections on the extent of saturation of seawater with respect to calcium-carbonate polymorphs. The reassessed degree of carbonate saturation for an average warm-surface ocean turns out to be only between 1.0 and 2.2. 相似文献