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Chattopadhyay, A.
- Petrology of Post -Archaean Magmatic Rocks in the Eastern Indian Craton
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Authors
Affiliations
1 Geological Survey of India, 15, KYD Street, Calcutta 700 016, IN
1 Geological Survey of India, 15, KYD Street, Calcutta 700 016, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 51, No 1 (1998), Pagination: 31-42Abstract
Minor rhyolite intrusives spatially associated with granophyric granites occur along the eastern and southwestern fringe of the Archaean Singhbhum Granite batholith in the eastern Indian Craton. Some minor trachyte dykes occur within the batholith and both are of post-Archaean age. On the basis of major and trace element studies it has been inferred that a process more complex than simple fractional crystallisation has controlled the observed chemical variation in both the rocks. However, the two are genetically unrelated and have been generated from different sources. All the rhyolites, which are scattered as small bodies over an extensive area, are produced from similar source compositions. The chemical variation among the rhyolites is the result of a difference in degree of melting and the samples enriched in LREE and other incompatible elements represent a lower degree of partial melt. Composition of the rhyolites suggests that neither muscovite nor aluminosilicates were present in the source. The likely source is therefore the trondhjemites and mafic-ultramafic rocks constituting the Archaean crust of the region. Similar source for rhyolites distributed over a large area indicates a homogeneous composition for the Archaean crust.Keywords
Rhyolite, Trachyte, Eastern Indian Craton, Geochemistry, Partial Melting.
- Recording and Analyzing Geospatially Accurate Structural Data Through 'Digital Mapping' Technique: A Case Study from the Canisp Shear Zone, NW Scotland
Abstract Views :210 |
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Authors
Affiliations
1 Department of Geology, University of Delhi, Delhi-110 007, IN
2 Department of Earth Science, Durham University, Durham DH1 3LE, GB
1 Department of Geology, University of Delhi, Delhi-110 007, IN
2 Department of Earth Science, Durham University, Durham DH1 3LE, GB
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 75, No Spl Iss 1 (2010), Pagination: 43-59Abstract
Spatial accuracy of structural data is an important factor for construction of a properly scaled model of crustal structures. Digital Geological Mapping methods can add the required spatial accuracy to the data, and also can improve the versatility of the geological/structural map in many ways, which are difficult to achieve through conventional mapping techniques. The present paper describes the methodology of digital mapping and discusses its applicability in structural analyses in the Canisp Shear Zone (CSZ) - a reactivated continental basement structure in the Precambrian Lewisian Gneiss complex of NW Scottish Highland. The CSZ is reinterpreted as a major dextral transpressional shear zone developed during Laxfordian deformation. It overprinted an earlier Inverian shear zone fabric, and was later reactivated and/or overprinted by brittle shearing of different phases and different scales. Spatial analyses within the ArcGISTM environment has helped bring out the geological relationships between different types of structural data in the shear zone, highlighting the partitioning of deformation into zones of high and low strain. A kinematic interpretation based on the geospatial data analysis, combined with conventional stereographic projection technique, is presented.Keywords
Digital Mapping, Geospatial Accuracy, Geographical Information System (GIS), Shear Zones, Northwest Scotland.References
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- Certain Generalizations of Enestrom-Kakeya Theorem
Abstract Views :191 |
Authors
Affiliations
1 Mathematics Department, I.I.T., Kharagpur-721 302, IN
1 Mathematics Department, I.I.T., Kharagpur-721 302, IN
Source
The Journal of the Indian Mathematical Society, Vol 72, No 1-4 (2005), Pagination: 147-156Abstract
According to well known Enestrom-Kakeya theorem, the polynomial p(z) = ∑= o ajZj has all its zeros in |z| ≤ 1, provided
an≥an-1≥...≥a1≥a0>0.