Informatics Publishing Limited

Piyali Sengupta ¹, Jyotisankar Ray ¹

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

Abstract

Deccan volcanism with a tremendous burst of volcanic activity marks a unique episode in Indian geological history and covers nearly two third of Peninsular India. Occurrences of mafic sill in the continental basalts are rather rare throughout the flood basalt provinces and only few sporadic reports have been described from different Continental Flood Basalts of the world. In the present article, petrology of mafic sill from the Narshingpur-Lakhnadon section of Eastern Deccan province of India has been presented. The mafic sill in the field is found to occur in a relatively deep valley amidst Gondwana rocks, which occur as the basement of the extrusion. The sill is spatially associated with three initial flows viz. flow I, II and III of adjacent Narshingpur-Harrai-Amarwara section. The sill in its central part is a medium grained rock and petrographically corresponds to dolerite containing augite, plagioclase and rare olivine grains; the chilled facies of the sill is characterized by phenocrysts of olivine, plagioclase and augite that are set in groundmass consisting predominantly of plagioclase, olivine and glass. Mineral chemistry indicates that olivine phenocrystal phase is magnesian (Fo₆₁). Plagioclase phenocrystal composition ranges from An ₅₁ to An ₇₁ whereas the same variation of the groundmass plagioclase composition corresponds to An ₃₁ to An ₆₂. The overlap in the compositions for groundmass and phenocrystal plagioclase may be explained due to fluctuating PH₂O condition. The pyroxene compositions (both groundmass and phenocryst) in majority of the cases are clubbed well within the augite field, however, in a few cases, groundmass compositions are found to fall in the sub-calcic augite and pigeonite field. Some zoned pyroxene phenocrysts, characteristically display different types of zoning patterns. Opaque minerals in the mafic sill are found to be magnetite and ilmenite and this coexisting iron-oxide composition helps to constrain the prevalent fO₂ condition in the parent magma. The geochemistry of the mafic sill and associated basaltic lava flows indicates close genetic link amongst them. Critical consideration of trace elements indicates a distinct enriched mantle source (EM-I/EM-II/HIMU) for the parental magma. Trace element modeling indicates that equilibrium batch- melting of plume source followed by fractionation of olivine, clinopyroxene and plagioclase and subsequent heterogeneous mixing of melt and settled crystals can very well explain the genesis of the mafic sill and the associated basaltic flows.

Keywords

Mafic Sill, Pyroxene Zoning, Thermometry, Ree Geochemistry, Eastern Deccan Province.

Full Text

     

Piyali Sengupta ¹

Affiliations
1 Hidayatullah National Law University, Raipur, IN

Abstract

This paper deals with quite debated topic i.e. Indian Debt Management. Management of debts has always been a troublesome job for the economists since Independence. The first part of the paper deals with meaning and types of Public debt in India. Subsequently the paper talks about the sources of both external debts and internal debts. The third part of the paper analyses the debt position of India and debt trap.

Subsequently, the trend in debts and liabilities has been focused upon. Finally, the methods of redemption of debt have been discussed in detail.

Full Text

     

Pranab Kumar Das ¹, Sekhar Chandra Dutta ¹, Piyali Sengupta ¹

Affiliations
1 Department of Civil Engineering, Indian Institute of Technology, Dhanbad 826 004, IN

Abstract

To comprehend the seismic vulnerability of a particular region, seismic damage assessment of a large number of buildings needs to be conducted. However, a realistic representation of structural damage can only be obtained through post-earthquake field observations and reconnaissance survey reports. Post-earthquake damage survey reports for Nepal (Gorkha) earthquake (2015) and Imphal (India) earthquake (2016) presented in this study are utilized to give an overall idea about the nature of seismic damage prevalent for the widespread civil engineering infrastructural developments in the particular geographical regions. Further, the study applies the existing rapid visual screening (RVS) schemes for predicting seismic vulnerability of the structures to judge the sanctity of the schemes. An extensive state-of-the-art review of the existing RVS schemes reported in the literature is presented. A comparative study exhibiting the efficacy of the existing RVS schemes is conducted on the basis of damage survey reports obtained from the Nepal and Imphal earthquakes. Finally, a modified RVS scheme is proposed here for seismic damage assessment of masonry and low-rise reinforced concrete buildings located in hilly regions of the Indian subcontinent and other developing countries. Excerpts from the study can be useful for researchers and practising engineers to perform seismic damage assessment of buildings using the proposed RVS scheme.

Keywords

Buildings, Damage Assessment, Rapid Visual Screening, Reconnaissance, Seismic Vulnerability.

Full Text