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Melluso L.,University of Naples Federico II | Srivastava R.K.,Banaras Hindu University | Petrone C.M.,University of Cambridge | Petrone C.M.,Natural History Museum in London | And 3 more authors.
Mineralogical Magazine

The rocks of the Jasra intrusive complex (Shillong Plateau, northeastern India) include phlogopite clinopyroxenites (with olivine or perovskite relics), alkali gabbros/monzodiorites, syenites and nepheline syenites. They have a potassic affinity (Na2O/K2O ∼1), and their mineralogy is dominated by clinopyroxene with which phlogopite, olivine, amphibole, feldspars, feldspathoids, oxides, orthopyroxenes, perovskite, titanite and other accessory phases are variably associated. The Jasra intrusive rocks are cumulates derived from at least two distinct magmatic liquids. The potassic affinity of the Jasra rocks differs from the nearby Sung Valley ijolitic-carbonatitic complex and from the ultrapotassic lamproitic rocks of the Damodar Valley, which are of approximately the same age. This suggests major variability in the mantle sources of small-volume alkaline volcanism in the Early Cretaceous of northeastern India. © 2012 Mineralogical Society. Source

Chakarvorty M.,Allahabad University | Pati J.K.,Allahabad University | Patil S.K.,Dr Ks Krishnan Geomagnetic Research Laboratory | Shukla S.,Allahabad University | And 2 more authors.
Environmental Monitoring and Assessment

The winter fog in India is a recurrent phenomenon for more than a decade now affecting the entire Himalayan and sub-Himalayan regions covering an area of nearly 500,000 km2. Every winter (December-January), the air and surface transports in cities of northern India (Amritsar, New Delhi, Agra, Gwalior, Kanpur, Lucknow, and Allahabad) are severely disrupted with visibility reduced to <50 m at times. Since dust particles are known to act as nuclei for the fog formation, this study is aimed to carry out physicochemical characterization of the dust particulates accumulated during a protracted fog period from one of the severely fog affected cities of north India (Allahabad; 25°27′33.40″N-81°52′45.47″E). The dust-loaded tree leaves belonging to Ficus bengalensis and Ficus religiosa from 50 different locations between January 24 and 31, 2010 are sampled and characterized. The mass of dust, color, grain shape, size, phase constituents, and mineral magnetic parameters, such as magnetic susceptibility, SIRM, χ fd%, and S-ratio, show minor variation and the regional influence outweighs local anthropogenic contributions. The dust compositions show fractionated rare earth element pattern with a pronounced negative Eu anomaly similar to upper continental crust and further suggesting their derivation from sources located in parts of north and central India. © 2014 Springer Science+Business Media Dordrecht. Source

Agarwal K.K.,University of Lucknow | Bali R.,University of Lucknow | Patil S.K.,Dr Ks Krishnan Geomagnetic Research Laboratory | Nawaz All S.,University of Lucknow
Asian Journal of Earth Sciences

The Almora Crystalline Zone (ACZ) in the Kumaun Lesser Himalaya is disposed in the form of a large thrust sheet over the unfossiliferous Precambrian-Palaeozoic sedimentary sequences and have tectonic contacts, known as North Almora Thrust (NAT) and South Almora Thrust (SAT). The rocks are metamorphosed under greenschist and amphibolite facies and contain mainly diamagnetic and paramagnetic minerals. The structural and fabric data collected from the field has been found to be matching with the newly generated magnetic data of crystalline rocks from the vicinity of the NAT and SAT. Anisotropy of Magnetic Susceptibility (AMS) measurements has become an important tool for fabric study based tectonic evolution of metamorphic terrains. These rocks show a very strong preferred orientation of lineation (k max) and the mean shape of the strain ellipsoid is prolate due to the late stage thrust sheet movements. However, in places, a few samples show high mean susceptibility due to the presence of ferromagnetic minerals. © 2010 Academic Journals Inc. Source

Srivastava P.R.,Banaras Hindu University | Gokani S.A.,Dr Ks Krishnan Geomagnetic Research Laboratory | Maurya A.K.,Dr Ks Krishnan Geomagnetic Research Laboratory | Singh R.,Dr Ks Krishnan Geomagnetic Research Laboratory | And 6 more authors.
Advances in Space Research

One-to-one relation with its causative lightning discharges and propagation features of night-time whistlers recorded at low-latitude station, Allahabad (geomag. lat. 16.05 N, L = 1.08), India, from continuous observations made during 1-7 April, 2011 have been studied. The whistler observations were made using the Automatic Whistler Detector (AWD) system and AWESOME VLF receiver. The causative lightning strikes of whistlers were checked in data provided by World-Wide Lightning Location Network (WWLLN). A total of 32 whistlers were observed out of which 23 were correlated with their causative lightnings in and around the conjugate location (geom. lat. 9.87 S) of Allahabad. A multi-flash whistler is also observed on 1 April with dispersions 15.3, 17.5 and 13.6 s 1/2. About 70% (23 out of 32) whistlers were correlated with the WWLLN detected causative lightnings in the conjugate region which supports the ducted mode of propagation at low latitude. The multi-flash and short whistlers also propagated most likely in the ducted mode to this station. © 2013 COSPAR. Published by Elsevier Ltd. All rights reserved. Source

Niyogi A.,Allahabad University | Pati J.K.,Allahabad University | Patel S.C.,Indian Institute of Technology Bombay | Panda D.,Physical Research Laboratory | Patil S.K.,Dr Ks Krishnan Geomagnetic Research Laboratory
Journal of Earth System Science

This paper provides first report of silica-rich anthropogenic spherules of varying colour, shape, size, surface texture and chemical composition found in road-deposited sediments (RDS) of Allahabad city, Uttar Pradesh, India. Morphological details and lithophile elemental composition of the silica-rich spherules are compared to microtektites and impact spherules from India to demonstrate their striking morphological similarities and chemical variability. This study suggests the need to use spherule data carefully while assigning an impact origin to spherule-finds or spherule-bearing lithological horizons. © Indian Academy of Sciences. Source

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