Gravity field over Singhbhum, its relationship to geology and tectonic history     

R.K. Verma  A.U.S. Sarma  M. Mukhopadhyay 《Tectonophysics》1984,106(1-2)

The gravity field over Singhbhum and adjoining areas lying between latitude 21° to 23°15′N and longitude 84° to 87°30′E has been analysed. The region has a very complex Precambrian history dating as far back as 3200 m.y. and extending up to 850 m.y., during which time it experienced a number of orogenic cycles. The activity has left an imprint on the gravity field which is marked by prominent gravity highs and lows. The highs are invariably surrounding the Singhbhum granite batholith, whereas the lows are conspicuous over the granites and their margins. The regional gravity field has been removed using a 4th order polynomial surface. The residual anomalies over prominent highs and lows have been interpreted using two-dimensional and three-dimensional models for underlying rock formations. It is inferred that the gravity highs are generally related to synclinal structures filled with sedimentary or metasedimentary formations and volcanics, such as the Iron Ore Group, the Singhbhum group, Dhanjori and Simlipal basins. The gravity lows can be attributed to a considerable thickness of granites of varying density, which could have been formed during different metamorphic/orogenic cycles by melting of a preexisting sialic crust.  相似文献   

Sr and Nd isotopic evidence for petrogenesis of mid-tertiary felsic volcanism in the mineral district of Zacatecas,Zac. (Sierra Madre Occidental), Mexico     

Surendra P. Verma 《Chemical Geology》1984,46(1):37-53

Twelve samples of mid-Tertiary felsic volcanic rocks from Zacatecas and San Luis Potosí (both belonging to the Sierra Madre Occidental) and one sample of Lower Tertiary porphyritic andesite from Zacatecas are analyzed for ${}^{87}\text{Sr}{}^{86}\text{Sr}$, K, Rb, and Sr. Eight selected samples are also analyzed for ${}^{143}\text{Nd}{}^{144}\text{Nd}$. A linear regression of the present-day ${}^{87}\text{Sr}{}^{86}\text{Sr}\text{and}{}^{87}\text{Rb}{}^{86}\text{Sr}$ of the felsic volcanic rocks in Zacatecas gives an approximate date of 30 ± 8 Ma. The initial ${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratios are high and widely distributed (from 0.705 to 0.712 or higher) whereas the initial ${}^{143}\text{Nd}{}^{144}\text{Nd}$ ratios are somewhat low and show a narrow range (0.5125–0.5127). The available isotopic and trace-element data are best explained in terms of a binary mixing model in which the magmas derived from a slightly depleted-mantle fractionate and mix with varying proportions of the overlying middle/upper continental crust and undergo further shallow-level fractional crystallization before eruption. This model is also compatible with the trace-element and Sr isotopic data published from other areas of the Sierra Madre Occidental for which a purely mantle origin has been proposed.  相似文献   

Relationship of gravity anomalies and tectonics in Assam, India     

R.K. Verma  R.P. Gupta 《Tectonophysics》1973,18(1-2)

Gravity data from Assam compiled on Bouguer, Hayford and Airy isostatic anomaly maps have been interpreted in terms of tectonics of the area. The gravity anomalies suggest that the Dauki fault is very deep-seated. A gravity high of about 60 mGal near Haflong is interpreted as being the expression of an intrusive body with a density contrast of about + 0.15 g/cm₃ with respect to the surroundings. From isostatic considerations, approximate crustal thicknesses over the Shillong Plateau, the Upper Assam valley and the Surma valley are estimated to be 40, 29 and 22 km respectively, suggesting a sharp change in crustal thickness from the Shillong Plateau to the Surma valley across the Dauki fault.  相似文献   

Magneto-radiative supersonic flow with variable specific heat     

B. G. Verma  S. K. Srivastava 《Pure and Applied Geophysics》1972,93(1):91-99

Summary Formulae for stagnation conditions and for the one dimensional flow through shock waves considering variable specific heat have been derived in the presence of magnetic field and radiation effects. These formulae have been compared with those for constant specific heat to obtain correction factors in order to make them valid for reasonably high Mach numbers.  相似文献   

Radiative magnetogasdynamic shocks in a viscous heat conducting gas     

B. G. Verma  S. K. Srivastava 《Pure and Applied Geophysics》1971,89(1):151-158

  相似文献   

Terrestrial heat flow in various parts of India     

R. K. Verma  R. U. M. Rao  M. L. Gupta  G. Venkateshwar Rao  V. M. Hamza 《Bulletin of Volcanology》1969,33(1):69-88

Results of heat flow studies made in different parts of India including Kolar Gold Field, Cuddapah basin, Singhbhum thrust zone, Aravalli mountain system of Precambrian age, Godavary valley of Mesozoic age and Cambay basin of Cenozoic age are discussed. Heat flow has been found to be low in the southern part of the Preambrian shield. Relatively higher values have been obtained along the northeastern (Singhbhum) and the northwestern parts of the shield (Aravallies). High heat flow has been found along the southeastern part of the Godavary valley and the Cambay basin. The correlation of heat flow with geology and tectonic history in the respective areas is discussed.  相似文献   

The relationship of heat flow with age of basement rocks     

V. M. Hamza  R. K. Verma 《Bulletin of Volcanology》1969,33(1):123-152

The relationship of heat flow to age of the basement rocks has been studied for USA and Canada, Australia and India. In areas of sedimentary basins the ages of the cores obtained from the metamorphic or igneous basement were used for such correlation. It is found that heat flow values for all continents studied show a definite correlation with age the relatively high heat flow being associated with younger basements. Such correlation when fully established will enable us to correlate heat flow values with geology and ages of tectonic events which have occurred in the earth’s crust.  相似文献   

Eddy correlation measurements of CO2, latent heat,and sensible heat fluxes over a crop surface   总被引：14，自引：0，他引：14  

Dean E. Anderson  Shashi B. Verma  Norman J. Rosenberg 《Boundary-Layer Meteorology》1984,29(3):263-272

Eddy correlation equipment was used to measure mass and energy fluxes over a soybean crop. A rapid response CO₂ sensor, a drag anemometer, a Lyman-alpha hygrometer and a fine wire thermocouple were used to sense the fluctuating quantities.Diurnal fluxes of sensible heat, latent heat and CO₂ were calculated from these data. Energy budget closure was obtained by summing the sensible and latent heat fluxes determined by eddy correlation which balanced the sum of net radiation and soil heat flux. Peak daytime CO₂ fluxes were near 1.0 mg m^–2 (ground area) s^–1.The eddy correlation technique was also employed in this study to measure nocturnal CO₂ fluxes caused by respiration from plants, soil, and roots. These CO₂ fluxes ranged from - 0.1 to - 0.25 mg m^–2s^–1.From the data collected over mature soybeans, a relationship between CO₂ flux and photosynthetically active radiation (PAR) was developed. The crop did not appear to be light-saturated at PAR flux densities < 1800 Ei m^–2 s^–1. The light compensation point was found to be about 160 Ei m^–2 s^–1.Published as Paper No. 7402, Journal Series, Nebraska Agricultural Experiment Station. The work reported here was conducted under Nebraska Agricultural Experiment Station Project 27-003 and Regional Research Project 11–33.Post-doctoral Research Associate, Professor and Professor, respectively. Center for Agricultural Meteorology and Climatology, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, NE 68583-0728.  相似文献   

Correlation of magnetic properties with Δ(Sr) of igneous rocks from the northeast Pacific and Gulf of California     

Surendra P. Verma  Subir K. Banerjee 《Physics of the Earth and Planetary Interiors》1982,30(4):291-299

The magnetic properties of basalts and diabases recovered under Legs 63 and 64 of the Deep Sea Drilling Project are summarized. They are first correlated with the measured grain sizes of the opaque minerals and the overall alteration states of the rocks, the latter measured by conventional chemical parameters such as water content, total volatiles content, and Fe₂O₃/FeO ratio. It is shown, however, that the decrease in ⁸⁷Sr/⁸⁶Sr upon leaching (Δ(^87/86Sr)) is perhaps the best quantifier of the overall alteration state of the whole rocks as well as of the degree of low-temperature oxidation suffered by the titanomagnetites. It is well correlated with Curie-point variations caused by changes in the Fe³⁺/Fe²⁺ ratio.  相似文献   

Geomorphic control on the formation of mixed layer clays by progressive degradation of biotite: A case study from Jutulsessen Gjelsvikfjella,East Antarctica     

Kamlesh Verma  Sanjeeb Bhattacharya  A. M. Asim Ansari  Prakash K. Srivastava  Amit Dharwadkar 《Journal of the Geological Society of India》2014,83(5):532-534

Eleven glacial sediment samples collected from different elevation of Jutulsessen Nunatak, Gjelsvikfjella of East Antarctica were studied for the clay mineralogical analysis using X-ray diffraction technique. The result shows prominent peak at 10, and 3.34 Å suggesting the presence of biotite possibly derived from the catchment where biotite rich granite gneisses are exposed. The detailed investigation on the shape of biotite peak of certain samples shows the signs of alteration of biotite in to a mixed layer containing tri-octahedral smectite (low charge vermiculite). The presence of mixed layer along with the biotite is found to be associated with the samples of lower geomorphic level. The progressive alteration of clay sized biotite to form a mixed layer in the lower horizons of Jutulsessen Nunatak is probably due to the periodic accumulation of melt-water during the austral summer.  相似文献