Browsing by Author "R. Chandra"

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Fe-Ti-enriched mafic rocks from south Andaman ophiolite suite: Implication of late stage liquid immiscibility
(2001) Anant Shastry; Rajesh K. Srivastava; R. Chandra; George A. Jenner
Andaman ophiolite suite (AOS) is amongst one of the ophiolite complexes of the world, which comprises complete dismembered ophiolitic sequence. It consists of ultra-mafic and mafic cumulates, sheeted dykes, pillow lavas, felsic rocks (mainly plagiogranites), and sedimentaries, including ribbon chert. In the present communication, a mafic rock that is highly enriched in FeO-TiO2 and encountered in the ophiolites of south Andaman is presented. Fe-Ti-enriched mafic rock is not yet reported from the south AOS. Genetically this rock may be associated with leucocratic rocks of AOS because it is experimentally proved that Fe-enriched basaltic melt and plagiogranite melt can be generated by late stage liquid immiscibility. Similar to most of the other plagiogranite occurrences of the world, Andaman plagiogranites are also supposed to be end-products of magmatic differentiation of a mafic magma. But the discovery of Fe-Ti-enriched mafic rocks supports liquid immiscibility process.
Geochemical characteristics and genesis of oceanic plagiogranites associated with South Andaman ophiolite suite, India: A late stage silicate liquid immiscible product
(2002) Anant Shastry; Rajesh K. Srivastava; R. Chandra; George A. Jenner
Plagiogranite is a leucocratic low-K member of the Andaman Ophiolite Suite (AOS) that occurs as bands (dykes?) of irregular shapes and sizes, particularly in the cumulate sequence of the suite. It is medium-to coarse-grained and commonly shows hypidiomorphic granular texture. At places granophyric texture (intergrowth between feldspar and quartz) is also seen. The main mineral constituents are plagioclase (mainly albite), quartz and minor mafic minerals. Mineralogically and chemically these rocks are classified as low-K dacite (trondhjemite/tonalite type). Low Rb concentrations (< 5) and low Rb/Sr ratios (< 0.015), observed in studied plagiogranites and associated Fe-Ti enriched rock, are characteristic of oceanic derivatives. All elements, plotted on the primordial mantle normalized multi-element spidergrams show enriched patterns. Variations in the concentrations of Nb, Sr, Zr, and Y are limited but other elements show wide variations. Strong negative anomalies for Nb are also observed. These rocks show characters analogous to those of orogenic granites, emplaced in volcanic are settings. On the basis of observed petrological and geochemical characteristics and their spatial association with Fe-Ti enriched mafic rocks, it is concluded that the Andaman plagiogranites are the integral part of AOS having crystallized from late stage immiscible silicate liquid.
High-Ti type N-MORB parentage of basalts from the south Andaman ophiolite suite, India
(Indian Academy of Sciences, 2004) Rajesh K. Srivastava; R. Chandra; Anant Shastry
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, trachybasalt, or basanitic chemical composition. High-field strength element (HFSE) geochemistry suggests that studied basalt samples are probably derived from similar parental magmas. Al2O3/TiO 2 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. © Printed in India.
Influence of pre-harvest application of calcium and alar on post-harvest changes in cv. 'Sardar' guava fruits
(1999) R. Chandra; P.N. Gupta; C.B.S. Rajput
Three consecutive sprays of calcium chloride (1 or 2%) or calcium nitrate (1 or 2%) were applied 18, 12, and 6 days before harvest and one spray of alar (500 or 1000 ppm) was applied 18 days before harvest on cv. 'Sardar' guava (Psidium guajava L.) trees. The fruits were stored under ambient conditions [12 ± 3°C and 74-87% relative humidity (RH)]. Calcium and alar treatments delayed ripening and had a favourable effect on the quality of the fruits during storage. In general, the treated fruits exhibited a higher calcium level in the fruit pulp, a lower cumulative physiological loss in weight, and had lower invertase and pectinase activities. Calcium nitrate was better than calcium chloride in prolonging the storability and quality of guava fruits. Alar (1000 ppm) or calcium nitrate (2%) was most efficient in maintaining the edible quality and marketability of guava fruits up to eight days of storage.
Recent Prospects of Medical Imaging and Sensing Technologies Based on Electrical Impedance Data Acquisition System
(Institute of Physics, 2023) R. Kumar; R.K. Ratnesh; Jay Singh; R. Chandra; G. Singh; V. Vishnoi
Highlights Attractions of submitted works are as following: Develop a portable, low-cost GUI-based electrical impedance tomography (EIT) system. Developed EIT is highly accurate and sensitive The Developed EIT monitor accurately, stomach, heart, pulmonary, cancer and fetal activity The proposed EIT is a low-cost noninvasive imaging method © 2023 The Electrochemical Society (“ECS”). Published on behalf of ECS by IOP Publishing Limited.