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Tapan Pal ¹, Biswajit Ghosh ², Sujit Chakraborty ³

Affiliations
1 Petrology Division, ER, Geological Survey of India, Kolkata, IN
2 Project: Andaman and Nicobar, Op: WSA, ER, Geological Survey of India, Kolkata, IN
3 Monitoring Division, CHQ, Geological Survey of India, Kolkata, IN

Abstract

The chromite bearing ultramafic rocks of Roro-Jojohatu areas in the Singhbhum Craton within the metasediments of the Iron Ore Group (IOG) is a part of Archaean greenstone terrain of Eastern India. In this area since all the primary silicates are altered, chromite has been used for host rock petrogenesis. Chromite occurs in different forms viz. (a) mainly cumulus phases in chromitite layers, (b) intercumulus phases forming banded/net textured chromite and (c) fine disseminations. Chemically all the chromites are aluminian chromite. The massive chromite and banded/net-textured chromites show high Cr-number (79-83) and intermediate Mg-number (51-60), but disseminated chromites have consistently low Cr-number (76-79) and low Mg-number (43-52). The plots of TiO₂ versus Cr-number, Al₂O₃ versus TiO₂, and Mg-number versus Cr-number reflect boninitic parental melt for the chromites. Al₂O₃ contents in liquid ranging from 9.67-11.03wt% and TiO₂ contents in liquid 0.42-0.75wt% also correspond for boninitic parentage. The FeO/MgO ratio in liquid ranging from 1.15 to 1.29 for massive chromites and 0.86-1.23 for banded/net-textured chromite, also suggest for boninitic source. Al₂O₃ versus TiO₂ plots indicate that chromites plot in the field of supra-subduction zone peridotites. Boninitic magma was produced from hydrous mantle melting in supra-subduction zone. At supra-subduction setting an oxidizing hydrous fluid derived from subducting slab facilitated the formation of chromitite layers at high fO₂ conditions.

Keywords

Chromites, Boninite, Supra-Subduction Zone, Roro-Jojohatu, Singhbhum Craton.

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M. N. Praveen ¹, Biswajit Ghosh ¹, H. S. Shrivastava ¹, M. L. Dora ², L. D. Gaikwad ¹

Affiliations
1 Geological Survey of India, E-5 Arera Colony, Bhopal - 462 016, IN
2 Geological Survey of India, Seminary Hills, Nagpur - 440 006, IN

Abstract

Sulphide mineralisation and syn-Volcanic hydrothermal alteration in the Betul Belt is associated with submarine bimodal volcanism. Felsic volcaniclastics form the favourable host rocks in most areas. Alteration zones have been metamorphosed to middle to upper-Amphibolite facies giving rise to various metamorphic mineral assemblages. Based on metal ratios, mineralisation can be classified into Zn-Cu and Zn-Pb-Cu types. The difference between the two types might be related to the composition of the footwall volcanics. Zn-Cu types are in close proximity to mafic volcanics towards their footwall side whereas, Zn-Pb-Cu types occur in areas dominated by felsic volcanics with little mafic volcanics towards the footwall. The sub-Parallel sheet like nature of the ore bodies and strata-Bound alteration might be related to the permeable nature of the host volcaniclastics.

Keywords

Sulphide Mineralisation, Classification, Hydrothermal Alteration, Subsea-Floor Replacement, Betul Belt, Central India.

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M. N. Praveen ¹, Biswajit Ghosh ¹

Affiliations
1 Geological Survey of India, E-5 Arera Colony, Bhopal-462 016, IN

Abstract

Multiple origin of gahnite of different generations and their relationship with other coexisting minerals like garnet, biotite, chlorite and sphalerite were studied in metamorphosed synvolcanic hydrothemally altered rock associated with base metal mineralisation from the Proterozoic Bhuyari prospect, Betul Belt, Central India. The present assemblages appear to be the result of overprinting of arnphibolite grade metamorphism on primary hydrothermal alteration products. Gahnite is found in a quartz + biotite + muscovite + pLagioclase + gahnite + garnet + chlorite assemblage. Petrographic evidence with supporting mineral composition data suggests the presence of two generations of gahnite. The first generation gahni te is found surrounding sphalerite grains and may be the product of desulphidation of primary sphalerite involving first generation garnet. Second generation gahnite show petrographic evidence of transformation from biotite and might be the result of overstepping of the zinc saturation limit of biotite during alteration to chlorite. The Bhuyari area was subjected to one prograde event followed by a retrograde metamorphic event and mineral paragenesis is in conformity with the metamorphic hlstory.

Keywords

Gahnite, Zn-Pb-Cu deposit, Hydrothermal alteration, Betul Belt, Madhya Pradesh.

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Biswajit Ghosh ¹, John Mahoney ², Jyotisankar Ray ³

Affiliations
1 Geological Survey of India, Op WB-SK-AN, ER, Kolkata - 462 016, IN
2 Department of Geology and Geophysics, University of Hawaii, SOEST, 1680 East-West Road, Honolulu, HI96822, US
3 Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata - 700 019, IN

Abstract

The ophiolite assemblage around Mayodia, Dibang Valley, Arunachal Pradesh falls in the eastern extension of the Indus suture belt and is represented by peridotite tectonite hornblendite (dyke) and amphibolite. The entire succession is overlain by metabasalt carapace interlayered with metapelitic pelagic sedimentary rocks. The basal peridotite may be classified as wehrlite. The hornblendite typically occurs as intrusive within the peridotite tectonite and is represented by cumulus primary amphibole. The amphibolite is characterized by well developed gneissose banding. The pillow lava is represented by actinolite-Chlorite-Albite-Epidote schist. The evolutionary trend of the ophiolite suite has been assessed based on major, trace and rare earth element data which favours partial melting of a depleted mantle source. Tectonic discrimination diagrams for the amphibolite and metabasalt clearly indicate their MORB affinity. Such ophiolite assemblage has developed as a result of collision of India and Asia that started with the closing of Tethyan ocean during Mesozoic and Early Tertiary.

Keywords

Mayodia Ophiolite, Petrology, Geochemistry, Tectonic Setting, Northeastern Himalaya, Arunachal Pradesh.

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Biswajit Ghosh ¹, M. N. Praveen ², H. S. Shrivastava ²

Affiliations
1 Geological Survey of India, E-5 Arera Colony, Bhopal - 462 016
2 Geological Survey of India, E-5 Arera Colony, Bhopal - 462 016, IN

Abstract

Gahnite Chemistry from metamorphosed Zn-Pb-Cu sulphide occurrences of Betul Belt, Central India has been presented here. Gahnites of this Belt are suggested to be a product of desulphidation of sphalerite during metamorphism. Although the very presence of zincian spinels in rocks may appear to constitute an exploration guide for metamorphosed massive sulphide (MMS) deposits, spinels that are likely to be spatially associated with sulphides appear to have characteristic Zn-rich, Mg-poor compositions.

Keywords

Gahnite Chemistry, Zn-Pb-Cu-Deposits, Genetic Implications, Betul Belt, Central India.

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Biswajit Ghosh ¹, Namita Chakma ²

Affiliations
1 Khorad Amena High School, Satgachia, Barddhaman 713 422, IN
2 Department of Geography, The University of Burdwan, Barddhaman 713 104, IN

Abstract

Rice is an important cereal crop of West Bengal and in many of the Indian states. There is a compelling need to increase rice productivity vertically in West Bengal due to less availability of land and greater dependency of the population on the productivity of the land. For this reason, the economic and ecological potentiality of the system of rice intensification (SRI) has been evaluated by several researchers. In the present study, Monteswar and Memari-II C. D. blocks of Barddhaman district, West Bengal have been selected to analyse the impacts of SRI on economic and ecological aspects of rice-growing. Results show that benefit-cost (B : C) ratio in SRI practice is significantly higher than the conventional method of rice cultivation. Under SRI B : C ratio varies from 5.06 : 1 to 3 : 1, but in the conventional method it varies from 2.18 : 1 to 1.78 : 1. Therefore, SRI farmers are experiencing multiple benefits in terms of both economics and ecology.

Keywords

Agro-Ecology, Benefit–Cost Ratio, Economic and Ecological Potentiality, System of Rice Intensification.

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Sarmistha Mukhopadhyay ¹, Jyotisankar Ray ¹, Basab Chattopadhyay ², Shyamal Sengupta ², Biswajit Ghosh ¹, Subrata Mukhopadhyay ¹

Affiliations
1 Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata - 700 019, IN
2 Geological Survey of India, Central Petrological Laboratories, 15 A&B Kyd Street, Kolkata - 700 016, IN

Abstract

The Elagiri complex (12°31' N: 78°35' E) represents one of the important silica - oversaturated syenite plutons of the Southern Granulite Terrane of the Indian shield. This article for the first time reports the mineral chemistry of the Elagiri complex and brings out important petrogenetic significance. The litho-members of Elagiri complex are intrusive into high grade country rocks viz. granite gneiss, amphibolite and pyroxene granulite. The country rocks are foliated bearing evidences of multiple folding and deformation. On the other hand, the constituent litho members of the Elagiri complex (syenites, gabbro and later intrusives marked by lamprophyre and carbonatite) show preservation of igneous layering in terms of discernible parallelism of the constituent minerals. The Elagiri complex shows presence of sharp contacts among litho members and marked absence of chilled facies peripheral to the margin. Electron microprobe data have been critically used to systematize the constituent mineral-phases of the different lithomembers of the complex. Geothermobarometric data indicate a temperature of equilibration in the range of ∼700° to 500° C at ∼2.0 to 5.2 kb which corresponds to shallow level (cf. 18.2 km) equilibration-depth of the complex. Field observations and mineral chemistry data suggest that liquid immiscibility plays an important role during the evolution of the Elagiri complex.

Keywords

Mineral Chemistry, Pyroxene Thermometry, Equilibration Depth, Liquid Immiscibility, Elagiri Complex, Indian Shield.

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Mrinal Mandal ¹, Debasis Ghosh ², Biswajit Ghosh ³

Affiliations
1 Department of Geography, Sidho-Kanho-Birsha University, Purulia, West Bengal, IN
2 Department of Geography, University of Calcutta, West Bengal, IN
3 Department of Geography, Barabazar Bikram Tudu Memorial College, Purulia, West Bengal, IN

Abstract

Indiscriminate and unscientific sand mining has become a serious environmental threat to the river systems and its surrounding environment. The rapid rate of urbanization has increased the demand for sand, which is supplied from river bed through sand mining. Sand mining from river bed results in channel degradation and erosion, change in local gradient, head cutting, increased turbidity, bank erosion and sedimentation of riffle areas and ruins its flow regimes and total sedimentary environment. In lower reaches of Ajay river, unscientific sand mining is a serious issue from Illambajar (Birbhum) to Mongalkot (Burdwan) fluvial environment of Ajay river basin, which is highly affected by in-stream sand mining. Natural morphological characteristics of Ajay river are changed and damaged due to over mining of sand. Excessive in-stream sand mining is a threat to Illambajar bridge and Nutanhut bridge. River embankments are also affected by river bed mining. Sand mining also affects the adjoining groundwater system. In Mongalkot and Ketugram Blocks (Burdwan), ground water level becomes lower than the past. Sand mining also generates extra vehicle traffic, which negatively impairs the environment and pollution level continuously gets higher. Total station survey was carried out to detect the changes in river bed. Topographical sheets and satellite images were geocoded to extract past status of river health and tried to correlate with the present situation. GPS (Handheld-Germin etrexH-20) was used as necessary tool in the present study. The main objective of the present study is to evaluate the impact of sand mining on riparian environment.

Keywords

Sand Mining, Sedimentation, Head Cutting, Embankments, Organism.

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Biswajit Ghosh ¹, Sandip Some ¹, Animesh Thakur ¹

Affiliations
1 Department of Geology, University of Calcutta, 35, Ballygunge Circular Road, Kolkata – 700 019, IN

Abstract

Zincian spinels (gahnites) from the Mamandur Zn-Pb-Cu prospect of the Southern Granulite Terrain have been studied. Gahnites in the quartzofeldspathic gneiss occur either as (a) porphyroblastic grains closely in association with cordierite and sphalerite or as (b) inclusions in poikiloblastic quartz grains, restricted within quartz veinlets. Compositionally these gahnites belong to two different clusters corresponding to two modes of occurrences. The origin of the porphyroblastic gahnites is linked with the process of desulphidation of sphalerite whereas those occurring as inclusions within poikiloblastic quartz are direct crystallisation products from silica rich hydrothermal solution. A new compositional field for this latter group of gahnites is proposed here.

Keywords

Gahnite, Cordierite, Desulphidation, Mamandur, Base Metal.

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Debasis Ghosh , Mrinal Mandal , Biswajit Ghosh

Abstract

The study basically deals with five basic indicators namely: Healthcare Institution Population Ratio (HCIPR), Doctor Bed Ratio (DBR), Bed Population Ratio (BPR), Doctor Healthcare Institution Ratio (DHCIR) and Bed Healthcare Institution Ratio (BHCIR) to explore the status of healthcare facility (HCF) of the Purulia district. We have collected secondary database from District Statistical Handbook, Purulia, 2012.The Healthcare Facility Index (HCFI) has been computed to understand the status of HCF of the district. The study reveals that Purulia-I block enjoys the best HCF among the all blocks. The majority of the blocks have lagged behind from the Purulia-I on the basis of HCF.

Keywords

HCIPR, DPR, BPR, DHCIR and BHCIR

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Thungyani N. Ovung ¹, Jyotisankar Ray ¹, Xueming Teng ², Biswajit Ghosh ¹, Madhuparna Paul ¹, Proloy Ganguly ¹, Saradee Sengupta ¹, Supriyo Das ¹

Affiliations
1 Department of Geology, Calcutta University, 35 B.C. Road, Kolkata 700 019, IN
2 School of Earth Sciences and Resources, China University of Geosciences Beijing, 29 Xueyuan Road, Beijing 100083, CN

Abstract

Mineralogical studies on the mantle and crustal sections of the Manipur Ophiolite Belt (MOB) lead to important findings pertaining to its genesis and controlling tectonic milieu. The wide compositional gap in the Cr# and Mg# content of spinel in the mantle peridotites of MOB implies upper mantle melting in two different tectonic settings. The tectonic discrimination diagrams based on spinel chemistry indicate a midoceanic ridge (MOR) origin for the high-Al spinel peridotites and a supra-subduction zone origin for the high-Cr spinel peridotites. The pyroxenite mantle dyke, ultramafic cumulate and pillow-basalt record temperature in the range of 600-1030°C, 600-800°C and 700-1005°C respectively. Plotting of clinopyroxene composition of pillow-basalt in the TiO₂-Na₂O-SiO₂/100 (wt%) tectonic discrimination diagram, implies a subduction-related origin of the basalts. Experimental studies on the serpentine stability indicate that it was dominantly affected by high temperature-low deformation setting.

Keywords

Mineralogical Study, Ophiolite Belt, Pyroxenite Mantle Dyke, Pyroxene Thermometry.

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Arindam Guha ¹, Biswajit Ghosh ², Sukanya Chaudhury ², Komal Rani ¹, K. Vinod Kumar ¹

Affiliations
1 Geosciences Group, National Remote Sensing Centre, Indian Space Research Organization, Balanagar, Hyderabad 500 625, IN
2 Department of Geology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, IN

Abstract

We have collected, processed and analysed the reflectance spectra of representative chromitite samples of spot type, clot type and disseminated type textural variants to understand the diagnostic spectral features of each of these samples. We have found that the reflectance spectrum of each textural variant is distinct from the spectra of other variants despite having few common absorption features. Spectral features of chromitite samples are governed by the spectra of two dominant minerals, chromite and chlorite. Spectral features of chromitite at 550 nm and 1100 nm are governed by electronic transition process in Fe³⁺ and crystal field effect in Fe²⁺ ions present in chromite structure respectively. On the other hand, spectral features at 1400 nm, 1900 nm and 2300 nm are related to the vibration of O–H, H–OH and metal hydroxide bonds in chlorite. Amongst these features, the spectral feature at 1100 nm (due to Fe²⁺ in chromite grains) is common to all three major textural varieties of chromitite samples studied here. Electron probe micro analysis (EPMA) data of chromite and chlorite grains of each texture are used to relate the presence and abundance of Fe₂₊ (in chromite grains) with absorption feature. Width of the 1100 nm feature has a correlation value 0.95, while depth of the same feature has a correlation value 0.94 with the abundance of chromite mineral estimated using modal analysis of chromite samples. Therefore, spectrometric parameter of 1100 nm spectral feature of chromitite can be used as proxy for estimating modal abundance of chromite in chromitite samples after estimating deposit specific correlation coefficient.

Keywords

Chromitite, Electronic Processes, Modal Analysis, Spectral Feature, Texture, Vibrational Processes.

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Biswajit Ghosh ¹, Namita Chakma ²

Affiliations
1 Khorad Amena High School, Satgachia, Purba Barddhaman 713 422, IN
2 Department of Geography, The University of Burdwan, Purba Barddhaman 713 104, IN

Abstract

In the present study we used the ecological footprint method to numerically measure the sustainability of agricultural production at the micro level. For this, two community development blocks of Barddhaman district, West Bengal, India were selected. As a consumption- based method, it is most suitable for measuring cropland footprint, biocapacity of croplands, and their ecological surplus and deficit status of an environmental indicator. The integrated result represents higher sustainability of agricultural system, but crop-wise assessment explores some negative aspects with respect to self-sufficiency of the study area that demand necessary transformation of existing cropping pattern.

Keywords

Agricultural Land Use, Biocapacity, Ecological Footprint, Sustainability.

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Tuhin Chatterjee ¹, Biswajit Ghosh ¹

Affiliations
1 Plant Bio-technology Laboratory, Post Graduate Department of Botany, Ramakrishna Mission Vivekananda Centenary College, Rahara, Kolkata-700 118, West Bengal, IN

Abstract

Micropropagation of medicinal plants is used to produce active compounds for herbal and pharmaceutical industries. This procedure is considered to provide optimal levels of carbohydrates, organic compounds, mineral nutrients. Environmental factors and growth regulators influence high regeneration rates of many in vitro grown plant species, and thus assisting in micropropagation. Micropropagation protocols have been developed for a wide range of medicinal plants, including endangered and vulnerable ones. In this communication the role of in vitro propagation of medicinal plants is briefly reviewed.

Keywords

Medicinal Plants, Micropropagation, Importance, Genetic Evaluation.

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