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1.
M. U. Shirazi M. Y. Ashraf M. A. Khan M. H. Naqvi 《International Journal of Environmental Science and Technology》2005,2(3):233-236
Water culture experiments were conducted to study the response of ten wheat genotypes to external K application (10 mmol KCI dm?3) at seedling stage under saline condition (0 and 100 mmol NaCl dm?3). The data showed that there was an increase in the shoot and root length with the application of external K. The increase was more pronounced under control than under saline conditions. The better performing genotypes under two treatments were Bhitai, NIAB-41, NIAB-I076 and Khirman. The enhanced growth of these genotypes under saline condition might be due to the quick response to external K application, resulting in high K/Na ratio. The results indicated that the genotypes, which have the ability of enhanced K/Na discrimination, might perform better under saline conditions when sufficient potassium is applied in the rooting medium. 相似文献
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3.
S. W. A. Naqvi 《Journal of Earth System Science》1994,103(2):279-300
Recent information on some consequences of the acute mid-water oxygen deficiency in the Arabian Sea, especially on carbon-nitrogen
cycling, is reviewed. An evaluation of published estimates of water column denitrification rate suggests an overall rate in
the vicinity of 30Tg Ny-1, but the extent of benthic contribution remains unknown. A decoupling of denitrification from primary production, unique
to the Arabian Sea, is revealed by nitrite, electron transport system (ETS) activity and bacterial production data. Results
of both enzymatic and microbiological investigations strongly point to a major role of organic carbon other than that sinking
from surface layers in supporting denitrification. Although denitrification is associated with an intermediate nepheloid layer,
it seems unlikely that the excess carbon comes with particles re-suspended along the continental margins and transported quasi-horizontally
into the ocean interior; instead, the particle maximum may directly reflect a higher bacterial abundance. It is proposed that
denitrification may be predominantly fuelled by the dissolved organic matter. 相似文献
4.
The chemical composition of the Dharwar metavolcanic suite from Chitaldrug is found to be similar to that of early Precambrian metabasalts from Canadian and Australian Shields. Its low K2O content and the similarities in the ferromagnesium trace elements with those of oceanic olivine normative tholeiites indicate a low K2O oceanic type of original magma. It is suggested that a protocontinent having a thin crust approaching basic composition existed during the pre-Dharwar era. 相似文献
5.
The protocontinental growth of the Indian Shield and the antiquity of its rift valleys 总被引：1，自引：0，他引：1
The evolution of the Indian Shield has been envisaged from the analysis of available tectono-lithostratigraphic, geochronological, geochemical and geophysical data. It appears that the Dharwar schist belts and their equivalents, except the Kolar schist belt, are not typical greenstone belts, but are representative of a transitional era of rapid transformation from simatic to sialic crust. In the Archaean—Proterozoic tract of India, relics of rocks older than 3.0 b.y. are identified in five widely separated regions of distinct tectono-litho-stratigraphic assemblages which probably represent the primordial continental nucleii. It is suggested that the growth of the Indian Shield has taken place through nucleation, accretion and merger into three protocontinents named Dharwar, Aravalli and Singhbhum. The cratonisation of the Indian unit seems to have been rapid and almost completed by the middle Proterozoic, as there is no significant variation in the composition of the clastic sediments and basalts from middle Proterozoic onwards. The continental nucleii appear to merge along the deep-seated lineaments, which are reflected on the tectonic map of India. Further, the Dharwar, Aravalli and Singhbhum protocontinents also seem to merge along a Y=shaped Narmada—Son—Godavari lineament which along with the Mahanadi lineament, between the two continental nucleii of the Singhbhum protocontinent have later developed into rift valleys. 相似文献
6.
S. N. Charan E. V. S. S. K. Babu S. M. Naqvi J. G. Rana Prathap M. Ram Mohan D. Srinivasa Sarma 《Journal of the Geological Society of India》2009,73(3):371-378
The major part of the Peninsular Gneiss in Dharwar craton is made up of Trondjhemite-Tonalite-Granodiorite (TTG) emplaced
at different periods ranging from 3.60 to 2.50 Ga. The sodic-silicic magma precursors of these rocks have geochemical features
characteristic of partial melting of hydrated basalt. In these TTGs, enclaves of amphibolites (± garnet) are abundant. These
restites are considered to be the residue of a basaltic crust after its partial melting. A detailed study of these (residue)
enclaves reveals textures formed due to the process of partial melting. Major, trace and REE analysis of these residue enclaves
and the melt TTGs and microprobe analysis of the coexisting minerals show partitioning of REE and HFSE between the precursor
melt of TTGs and the upper amphibolite facies residues. Formation of garnetiferous amphibolites with biotite, Cpx and plagioclase
consequent to melting, has squeezed the original MORB type of basaltic crust and given rise to the TTGs, depleted in Y, Yb,
K2O, MgO, FeO, TiO2 and enriched in La, Th, U, Zr and Hf. Coevally during the process of melting, the hydrated basalt was depleted in Na2O, Al2O3, LREE, Th, U and enriched in K2O, MgO, Nb, Ti, Yb, Y, Sc, Ni, Cr and Co. Mineral chemistry of co-existing garnet-biotite and amphibole-plagioclase in these
amphibolitic (restite) enclaves indicates an average temperature of 700 ± 50° C and pressure of 5 ± 1 Kbar. These data are
inferred to indicate that during the garnet stability field metamorphism, effective fractionation of HREE and HFSE has taken
place between the restites having Fe-Mg silicates, ilmenites and the extracted melt generated from the MORB type of hydrated
basalt. These results are strongly substantiated by the reported melting experiments on hydrated basalts. 相似文献
7.
Application of sedimentological, geochemical and discriminant analysis techniques to the engineering geological investigation of damsites assists in understanding the variation of rock types, stratal correlation, porosity, folding and faulting, through studying the history of depositional and diagenetic environments. Factor analysis (Rao & Naqvi, 1977) resulted in the proposal of a tidal depositional model consisting of subtidal, shoal, bar, intertidal and supratidal carbonate environments, and channels and dune‐and‐flat terrigenous environments. Discriminant analysis has now been employed to extend the paleo‐environmental model laterally. Samples (142) from four new drill holes were examined, and the data compared with the earlier data by a discriminant analysis technique. The results confirm our pre‐existing model of a prograding tidal complex. Regional correlation of depositional environments of strata shows an anticlinal structure. Faulting in the sequence is indicated by secondary dolomitisation, breccia‐tion and stfatal discontinuities. The secondary dolomites replaced both limestones and sandstones in the sequence. The amount of porosity is related to depositional facies and dolomitisation. It is possible to understand the hydrologic regime with the aid of regional structure, depositional and diagenetic facies, and porosity. Because this factor and discriminant analysis technique intensively uses information from each length of drill core, the possibility exists of more confident interpretation of new data from less extensive drilling, with consequent saving in cost. 相似文献
8.
The Kalyadi polymetallic copper deposit occurs within the Middle Archaean (≥3.0 Ga), medium-grade Kalyadi schist belt which
consists predominantly of ultramafic-mafic schists interbedded with chemogenic chert, detrital high Al-Mg schists and siliceous
schists. This sedimentary exhalative type (SEDEX type) ore-body is the only copper deposit hosted in cherts in the western
Dharwar craton. The Kalyadi supracrustal rocks are intruded by tonalite-trondhjemitic gneisses (ca. 3.0 Ga) and granite (ca.
2.6 Ga). The Kalyadi copper deposit is polygenetic in nature. The primary ores represented by disseminations of pyrite ± linneite
and chalcopyrite ± magnetite essentially along the bedding lamination of the metachert are referred to as the metamorphosed
chert-sulphide rhythmites of a primary stratiform type. The ore is of low-grade and records imprints of at least two events
of deformation. Pyrite is characterised by high-Co values (262–4524 ppm) and high–Co/Ni ratios (3.0–19.7). Rare earth element
patterns of the primary ores and the host metacherts are identical, characterised by La enrichment, absence of Eu anomalies
and flat to depleted HREE patterns with δ
34 S = −0.8‰. The secondary (remobilised) ores are structurally controlled occurring as veins and stringers discordant to the
bedding lamination or schistosity. The constituent ores are chalcopyrite-pyrite-pyrrhotite with minor pentlandite. These sulphides
with low-Co/Ni ratios (0.87–1.80), have either a strong positive or negative Eu anomaly and show slight HREE enrichment. The
δ
34 S value ranges from +2.64 to −4.29‰. It is interpreted that the primary stratiform ores and the cherts were derived from
volcanogenic hydrothermal fluids as syngenetic/chemical deposits in a deep sea environment. The secondary epigenetic mineralisation
is related to subsequent migmatisation, deformational events and granitic activity.
Received: 8 September 1995 / Accepted: 18 November 1996 相似文献
9.
Ortho- and para-amphibolites occur throughout the Dharwar schists, gneisses and ultramafics in Karnataka State, India. From the chemical data alone, these ortho- and para-amphibolites cannot be very clearly differentiated. While the ortho-amphibolites follow the Karroo trend, the para-amphibolites appear to have been evolved from the metamorphism of low-Si and -K graywackes. The amphibolitic xenoliths occurring in Peninsular gneisses follow both the igneous and graywacke field, indicating that probably both para and ortho types constitute these enclaves. Their trace element concentrations, like those of Ni, Co and Cr, are not related to the Mg and Fe contents of the amphibolites. Probably these amphibolites have been derived from basic rocks, which were predominant over the Archaean crust, either directly or after having gone through a sedimentary cycle. The higher concentration of Ni, Co, Cr and other elements, such as Mg, in these amphibolites, as compared with younger oceanic basalts, thus indicates the higher concentration of these elements in Archaean basalts and the proto-mantle. 相似文献
10.
S. M. Naqvi 《Bulletin of Volcanology》1971,35(4):1069-1093
Forty-two samples of the Jogimardi trap from Chitaldrug schist belt, Mysore, were analysed for their major elements. It is inferred that the Jogimardi trap is a submarine lava flow of eugeosynclinal environment. The composition of the suite varies from tholeiitic basalt to andesite and spilite. The original magma, which was probably tholeiitic in nature, might have given rise to this association due to varying and incomplete degree of spilitisation, which in turn seems to be related to the short period of contact between metasomatic liquid and the tholeiitic flows. The suite bears the imprint of low grade metamorphism of green schist facies. This resulted in the development of mineral assemblage comprising chlorite, epidote and plagioclase but without bringing about any change in the original basaltic texture. At and near the contact with granite, the tholeiitic lava was converted into orthoamphibolite, most probably due to granitie intrusion. 相似文献