The review of study site have revealed the change in vegetation cover of Sal Dense to Sal Medium and Sal Open in 6 forest
Mosaics owing to biotic and abiotic conditions prevailing in the specific areas. Analysis carried out using thematic map derived
from aerial photograph of 1976 and satellite data of IRS 1C LISS III False Colour Composite (FCC) of March 1999 revealed the
cause for change in forest density classes. Deforestation, encroachment and agriculture have been identified as the underlying
causes, which have affected some specific locations to a marked extent. There has been a progressive and remarkable change
among vegetation classes from 1976 to 1999. It is evident from forest type and density map that Sal density has significantly
reduced from Sal Dense 65.61 % in 1976 to Sal Dense 11.12% in the year 1999 followed by Sal Open 11.18 % and Sal Medium 18.24
%. The overall change has been estimated to be 42.11% of the total forested area. 相似文献
Summary ?A newly developed ocean general circulation model has been tested and verified with some idealized experiments. Generally
two types of idealized experiments have been done here. First types are called as “symmetric experiments” and second types
are called as “transport experiments”. The first types of experiment help to correct the model core and any deficiency from
boundary conditions. The second types of experiment are the type of validation experiment. In both the experiments there are
no continents, so in the first type of experiments where symmetric forcings are provided one can expect that model should
maintain the symmetric nature. In the second type of experiments one can expect that model should respond correctly to the
wind forcings, if no wind curl is present in the wind forcing there will be no circulation in the extratropics and if there
is no wind the equator there will be no circulation. The model reproduces the possible envisaged results of these experiments
and gives the confidence for performing the realistic integration.
Received February 20, 2002; accepted July 7, 2002
Published online: February 20, 2003 相似文献
Level-II urban land use information available in this Town and Country Planning maps, Survey of India toposteets for Phillaur and Phagwara towns and the land use information generated through visual interpretation of satellite data was digitized, integrated and analysed using PAMAP GIS. The land use map of the two towns suggest that the wastelands located near the point of present disposal can be utilised for siting sewage treatment plants in both the towns. The STP sites suggested were away from the thickly habttared area. It was observed that some of the areas earmarked for locating STP’s, were partially brought under habitation before the execution of the preject. Hence, it is necessary that planning and execution of such projects should be done on a real time basis so that the sites identified for locating STP’s are not brought under other land uses. 相似文献
Large charnockite massifs cover a substantial portion of the southern Indian granulite terrain. The older (late Archaean to
early Proterozoic) charnockites occur in the northern part and the younger (late Proterozoic) charnockites occur in the southern
part of this high-grade terrain. Among these, the older Biligirirangan hill, Shevroy hill and Nilgiri hill massifs are intermediate
charnockites, with Pallavaram massif consisting dominantly of felsic charnockites. The charnockite massifs from northern Kerala
and Cardamom hill show spatial association of intermediate and felsic charnockites, with the youngest Nagercoil massif consisting
of felsic charnockites. Their igneous parentage is evident from a combination of features including field relations, mineralogy,
petrography, thermobarometry, as well as distinct chemical features. The southern Indian charnockite massifs show similarity
with high-Ba-Sr granitoids, with the tonalitic intermediate charnockites showing similarity with high-Ba-Sr granitoids with
low K2O/Na2O ratios, and the felsic charnockites showing similarity with high-Ba-Sr granitoids with high K2O/Na2O ratios. A two-stage model is suggested for the formation of these charnockites. During the first stage there was a period
of basalt underplating, with the ponding of alkaline mafic magmas. Partial melting of this mafic lower crust formed the charnockitic
magmas. Here emplacement of basalt with low water content would lead to dehydration melting of the lower crust forming intermediate
charnockites. Conversely, emplacement of hydrous basalt would result in melting at higher {ie565-01} favoring production of
more siliceous felsic charnockites. This model is correlated with two crustal thickening phases in southern India, one related
to the accretion of the older crustal blocks on to the Archaean craton to the north and the other probably related to the
collision between crustal fragments of East and West Gondwana in a supercontinent framework. 相似文献
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
Major and trace element geochemistry of Proterozoic granitoids from the Dirang and Galensiniak Formations, of Lesser and Higher Himalayas, respectively, emplaced in and around Dirang and Tawang regions of the western Arunachal Himalaya, is discussed. In general, these granitoids are massive as well as foliated in nature and are characterized by granitic mineralogical compositions. Porphyritic and hypidiomorphic textures are common in massive type, whereas others show porphyroblastic and foliated textures. Augen structure is also observed in a number of samples. Geochemical and normative compositions together with petrographic features classify them as peraluminous granitoids. Major and trace element geochemistry of most of these granitoids shows granitic nature, while few samples also show monzonitic characteristics. Observed geochemical characters, such as their peraluminous and alkali-calcic/calcic-alkalic nature, crudely defined geochemical patterns, different multi-element and rare-earth element patterns, together with low Mg# (Mg number) of these granitoids suggest their derivation from lower crustal material rather than a mantle source. Multi-element and rare-earth element patterns corroborate their genesis from different crustal melts. It is difficult to explain variations observed in granitoid rocks by partial melting alone; definitely different other processes like migration of melts, magma mixing, assimilation and fractional crystallization also played important role in the genesis of these granitoids. These melts were likely generated at low temperature (730–760 °C) and low pressure (2–5 GPa). The chemical compositions suggest that most of these Paleoproterozoic granitoids are emplaced within the syn-collisional tectonic setting, while few granitoid samples also indicate their volcanic-arc nature. Probably, later group of granitoids are slightly younger to the syn-collisional type. 相似文献
This study presents the chemical composition (carbonaceous and nitrogenous components) of aerosols (PM2.5 and PM10) along with stable isotopic composition (δ13C and δ15N) collected during winter and the summer months of 2015–16 to explore the possible sources of aerosols in megacity Delhi, India. The mean concentrations (mean?±?standard deviation at 1σ) of PM2.5 and PM10 were 223?±?69 µg m?3 and 328?±?65 µg m?3, respectively during winter season whereas the mean concentrations of PM2.5 and PM10 were 147?±?22 µg m?3 and 236?±?61 µg m?3, respectively during summer season. The mean value of δ13C (range: ??26.4 to ??23.4‰) and δ15N (range: 3.3 to 14.4‰) of PM2.5 were ??25.3?±?0.5‰ and 8.9?±?2.1‰, respectively during winter season whereas the mean value of δ13C (range: ??26.7 to ??25.3‰) and δ15N (range: 2.8 to 11.5‰) of PM2.5 were ??26.1?±?0.4‰ and 6.4?±?2.5‰, respectively during the summer season. Comparison of stable C and N isotopic fingerprints of major identical sources suggested that major portion of PM2.5 and PM10 at Delhi were mainly from fossil fuel combustion (FFC), biomass burning (BB) (C-3 and C-4 type vegitation), secondary aerosols (SAs) and road dust (SD). The correlation analysis of δ13C with other C (OC, TC, OC/EC and OC/WSOC) components and δ15N with other N components (TN, NH4+ and NO3?) are also support the source identification of isotopic signatures.
The proper usage of modal composition and geochemical classification of granitoids is discussed for assigning a proper nomenclature
for the Angadimogar pluton, Kerala, southwestern India. This discussion is mainly aimed at addressing questions concerning
the nomenclature of Angadimogar pluton (syenitevs. granite). Modal composition and whole-rock XRD data clearly show that the pluton exposed near Angadimogar is a quartz-syenite
and its geochemistry is typical of a ferroan, metaluminous, alkali (A-type) granitoid 相似文献