Geochemistry of Mesoproterozoic Deonar Pyroclastics from Vindhyan Supergroup of Central India: Evidences of felsic magmatism in the Son valley     

Meenal Mishra  Vaibhava Srivastava  P. K. Sinha  Hari B. Srivastava 《Journal of the Geological Society of India》2017,89(4):375-385

Deonar Pyroclastics of Semri Group in the Vindhyan Supergroup originated as a result of violent and explosive intrabasinal submarine volcanism during the Mesoproterozoic period. These pyroclastics are rhyolitic to rhyodacitic in composition, comprised of banded, massive, pumiceous flow, breccia, vitric tuff, lapilli and volcanic bomb. The pyroclastic deposits represent welded and non-welded ignimbrites, exhibit typical eutaxitic texture. Mantle normalized multi-element patterns show enrichment in LILs and depletion in HFSFs. Ti, Nb and REE contents show close correlation with Zr, indicating their immobile character. HFSEs and Th/Nb, La/Nb and Zr/Nb values indicate contamination and these signatures represent mixing between mantle-derived rocks and the average continental crust. Deonar Pyroclastics reflect continental rift environment. Felsic magma plausibly generated by underplating of the mature Proterozoic crust of the Indian craton (which acted like a ‘heating lens’) resulted in extensive melting of metabasalt in the lower crustal levels. The high heat flow beneath the Indian shield accentuated heat generation which led to extensive partial melting of metabasalts. Thus, generation of rhyolitic magma occurred along the reactivated deep seated fractures and rifting of the craton, resulting in the explosive intra-basinal felsic vulcanicity in the Vindhyan basin.  相似文献   

Modeling of turbulent dissipation and its validation in periodically stratified region in the Liverpool Bay and in the North Sea     

Kaushik Sasmal  Subhendu Maity  Hari V. Warrior 《Ocean Dynamics》2015,65(7):969-988

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Short-Term Periodicities in the Time Series of Solar Radio Emissions at Different Solar Altitudes   总被引：1，自引：0，他引：1  

R.P. Kane  Hari Om Vats  H.S. Sawant 《Solar physics》2001,201(1):181-190

A spectral analysis of the time series of daily values of 12 parameters, namely, ten solar radio emissions in the range 275–1755 MHz, 2800 MHz solar radio flux, and sunspot numbers for six continuous intervals of 132 values each during June 1997–July 1999 showed considerable differences from one interval to the next, indicating a nonstationary nature. A 27-day periodicity was noticed in Interval 2 (26.8 days), 3 (27.0 days), 5 (25.5 days), 6 (27.0 days). Other periodicities were near 11.4, 12.3, 13.3, 14.5, 15.5, 16.5, 35, 40, 50–70 days. Periodicities were very similar in a large vertical span of the coronal region corresponding to 670–1755 MHz. Above this region, the homogeneity disappeared. Below this region, there were complications and distortions due to localized solar surface phenomena.  相似文献   

Lightning-generated waves escaping out through plasma holes in the nightside Venus ionosphere     

R. N. Singh  Hari Om Upadhyay 《Journal of Earth System Science》1991,100(4):321-330

The plasma waves in the Venus ionosphere measured by OEFD aboard PVO are analysed. It is shown that these waves are generated by lightning like cloud-to-cloud discharges anywhere in the Venus ionosphere-surface waveguide. The theoretical minimum attenuation for waveguide mode propagation at 5.4 kHz is consistent with the maximum occurrence rate at this frequency. The lightning-generated and globally-propagating signals when encountered with plasma holes or ion-trough structures escape out partially and are detected by the OEFD aboard PVO. The 100 Hz signals can propagate upwards in whistler mode. Even the localized electrostatic mode waves would be converted into electromagnetic waves in the plasma holes and ion-trough regions.  相似文献   

Analyses of fission track etching and annealing phenomena in muscovite     

Hari S. Saini  O. P. Sharma  K. K. Nagpaul 《Pure and Applied Geophysics》1977,115(4):951-959

Variation of fission track density with etching time has been analysed to standardize the etching conditions. The relations between the etching parameters (i.e., temperature, concentration and time) have been established. The differences in unheated samples and samples heated for different times at a constant temperature have been studied Graphs of thermal annealing vs. optimum etching time and of density reduction vs. length shrinkage have been constructed for applications in fission track geochronology.  相似文献   

Equatorial night-time F-region zonal electric fields     

S. S. Hari  B. V. Krishna Murthy 《Annales Geophysicae》1995,13(8):871-878

Night-time F-region vertical electrodynamic drifts at the magnetic equatorial station, Trivandrum are obtained for a period of 2 years, 1989 and 1990 (corresponding to solar cycle maximum epoch), using ionosonde h^‘F data. The seasonal variation of the vertical drift is found to be associated with the longitudinal gradients of the thermospheric zonal wind. Further, the seasonal variation of the prereversal enhancement of the vertical drift is associated with the time difference between the sunset times of the conjugate E-regions (magnetic field line linked to F-region) which is indicative of the longitudinal gradients of the conductivity (of the E-region). The vertical drifts and the causative zonal electric fields at Trivandrum are compared with those at Jicamarca and F-region zonal electric field models. It is seen that the night-time downward drift (as also the causative westward electric field) at Jicamarca is greater than that at Trivandrum. The prereversal enhancement of the drift is greater at Jicamarca than at Trivandrum during the summer and the equinoxes, whereas during the winter the opposite is the case.  相似文献   

Extreme water levels along the central Red Sea coast of Saudi Arabia: processes and frequency analysis     

Antony  Charls  Langodan  Sabique  Dasari  Hari Prasad  Knio  Omar  Hoteit  Ibrahim 《Natural Hazards》2021,105(2):1797-1814

Natural Hazards - Knowledge about extreme water levels is essential for efficient planning and design of coastal infrastructure. This study uses a high-resolution (~?60 m) coupled...  相似文献   

Multivariate statistical analysis for characterization of sedimentary facies of Tarakan sub-basin,North Kalimantan     

Septriono Hari Nugroho  Purna Sulastya Putra  Eko Yulianto  Dardji Noeradi 《Marine Georesources & Geotechnology》2018,36(8):907-917

A study of sediment dynamics has been conducted on the Tarakan sub-basin, North Kalimantan, Indonesia using multivariate analysis. Multivariate statistical techniques can be used to determine sediment with similar characteristics and be a good proxy to recognize sedimentary facies and depositional environment. These methods have been applied to characterize the sedimentary facies at Tarakan sub-basin. A total of 23 samples were taken from several locations on the different depths of 56–2554?m that represent varieties of environment. The study is interpreted using compositional data analysis associated with a grain size trend analysis (GSTA), principal component analysis (PCA), and cluster analysis (CA). The GSTA value showed the dominance of poorly sorted silt indicating that the sediment is mostly deposited in low-energy depositional. The CA and the PCA determined three distinct sedimentary facies: shelf facies, upper bathyal facies, and lower bathyal facies. The facies were grouped as similar sediment and depositional environment. Sedimentological variables applied in the characterization were described to be an important tool for the interpretation of depositional environments – indirectly showing hydrodynamic energy.  相似文献   

A possible detection of radio pulses from Geminga at 103 MHz     

Hari Om Vats  Ashok K. Singal  M. R. Deshpande  K. N. Iyer  Rupal Oza  Chhaya R. Shah  S. Doshi 《Monthly notices of the Royal Astronomical Society》1999,302(4):L65-L67

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Strain and Crystallographic Fabric in Mesoscopic Ductile Shear Zones of Garhwal Himalaya     

Hari B. Srivastava  Atul Sahai  Surya N. Lal 《Gondwana Research》2000,3(3)

The MCT Zone of Bhagirathi valley of Garhwal Himalaya is characterized by numerous mesoscopic ductile shear zones. These shear zones are developed in response to nearly NNE-SSW maximum horizontal compression and provide an opportunity to study the variation in strain and crystallographic fabrics within the ductile shear zones.The grain shape and orientation of quartz under microscope reflect that strain is higher in the center and it progressively decreases towards the shear zone boundary. The preferred orientation of quartz c-axes across the shear zone suggests that the single girdle of the quartz c-axes are probably first developed at the shear zone boundary and become prominent in the center of shear zone with increase in the intensity of deformation. The strong crystallographic preferred orientation normal to foliation suggests that the internal deformation of the quartz might have taken place by dislocation creep mechanism exhibiting a non-coaxial deformation history.  相似文献