Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

S. K. Acharyya ¹, J. R. Kayal ¹, A. Roy ¹, R. K. Chaturvedi ¹

Affiliations
1 Geological Survey of India, 27, J. L. Nehru Road, Calcutta - 700 016, IN

Abstract

Macroseismic and microseismic (aftershock) investigations were carried out by the Geological Survey of India immediately after the Jabal pur earthquake (M 6.0) of May 22, 1997. The meizoseismal area of an intensity VIII (MSK) is 35 km long and 15 km wide, trending ENE-WSW. The aftershock investigation was earned out by a five-station temporary microearthquake (MEQ) network. Five felt aftershocks (M≥3.0) and 23 aftershocks in the magnitude range 1.5 to < 3.0 were recorded by the network. These are mostly clustered in an elongated area, 15 ×10 krn, near the main shock epicentre. and occurred at a depth range 35-40 k.m which is compatible with that of the main shock. The fault-plane solution of the main shock and the aftershocks revealed reverse faulting with left-lateral strike-slip component The hypocentral section and the fault-plane solutions indicate that the pre-existing ENE-WSW trending Nannada South Fault is deep-ischolar_mained to mantIe depth, and has been activated at the crust-mantle boundary to produce the main shock and the aftershocks. The failure appears to be caused in response to the northward post collisional movement of the Indian plate.

Keywords

Earthquake, Aftershocks. Microseismicity, Fault-Plane Solution, Jabajpur, Madhya Pradesh.

Full Text

     

A. K. Chaudhuri ¹, A. B. Pal ¹, A. Roy ¹

Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur-721302, IN

Abstract

Three phases of folding have been detected in a large exposure along the Sapai lladi near Amaidegri (22°01': 84°08') in the Ghoriajhor manganese belt in the western part of the Gangpur Group. Reclined to inclined folds (F₁) plunging SSE have been coaxially refolded by open upright F₂ folds, and finally, upright folds with ENE-trending axial planes (F₃) cause culmination and depression of axes of open-folded reclined folds. The multiple deformations cause characteristic outcrop patterns and they are reflected in two distinct S-pole girdles around a plane of symmetry which is the axial trend of F₃ folds.

Full Text

     

A. Roy ¹

Affiliations
1 Geological Survey of India, 28 B, Theatre Road, Calcutta 700017, IN

Abstract

Computer-aided trend surface mapping of the Pb values from the Sargipalli Pb-Zn mineralized belt (Orissa) revealed that the fourth-degree surface (trends and residuals) is of utmost significance for prediction of further promising pay zones of the unexplored extension areas.

Full Text

     

A. Roy ¹

Affiliations
1 Geological Survey of India, 28 B, Theatre Road, Calcutta 700 017, IN

Abstract

The paper examines the results of computer based factor analysis performed on multi-element data from detailed soil geochemical survey over the lead-zinc mine at Sargipalli. Eleven elements (Pb. Cu, Zn, Ni, Co, So, Zr, Ag, Sr, Bi and Ga), measured on each of 216 soil samples by spectrographic and atomic absorption spectrophotometric methods were considered. The results from the factor analysis (R-mode) indicated that the multi-element soil geochemical distribution patterns around the Sargipalli deposit could be explained by a six-factor model. The proper evaluation of this model in relation to sound geological/geomorphological facts known from the area of study, would provide a significant insight into the probable nature of dominant underlying factors influencing the areal distribution of trace elements in soils around the ore body, and hence may serve as an indirect aid in locating further potential prospecting targets in the area.

Full Text

     

A. Roy ¹

Affiliations
1 Geological Survey of India, Nagpur 440022, IN

Abstract

Mesoscopic and microscopic studies on the K-feldspar augens of Thimphu augengneiss of Bhutan suggests microshearing followed by a rotational mechanism. Megacrysts of K-feldspar are often broken into smaller segments by ductile shear faulting, followed by a combination of simple shear and flattening deformation giving rise to the augens.

Full Text

     

A. Roy ¹, A. K. Saha ², S. N. Sarkar ³

Affiliations
1 Geological Survey of India, ER, 12 Russel St., Calcutta-700071, IN
2 Department of Geology, Presidency College, Calcutta-700073, IN
3 95A, Ballygunge Gardens, Calcutta-700019, IN

Abstract

Correspondence analysis, using the concept of joint probability distribution of two random variables, individual samples and chemical variables, was applied to two sets of multi-metallic data from Mosaboni copper mines (18th, 21st & 25th revels) and Sargipalli lead-zinc mine falling within the Gangpur-Singhbhum metallo-tectonic belt. The analysis results factor loadings for individual samples and variables, which when plotted as points on two-dimensional coordinate (factorial) axes with the same origin recognize distinct geochemical domains characterised by natural groupings or clusters of samples and variables. The simultaneous variation of trace elements in these two data sets with sample locations (background/anomalous) seems to reflect overall trends of geochemical evolution of base metal mineralisation in the region.

Keywords

Statistical Studies, Economic Geology, Copper, Lead-Zinc, Sargipalli, Mosaboni, Bihar, Orissa.

Full Text

     

A. Roy ¹

Affiliations
1 Department of Geology, Presidency College, Calcutta, IN

Abstract

No Abstract.

Full Text

   

A. Roy ¹, A. Sarkar ¹, S. K. Bhattacharya ², H. Ozaki ³, M. Ebihara ⁴

Affiliations
1 Department of Applied Geology, Indian School of Mines, Dhanbad, IN
2 Physical Research Laboratory, Ahmedabad, IN
3 Tokyo Metropolitan University, JP
4 Tokyo Metropolitan University, IN

Abstract

Modelling ofREE data indicates that while mafic rocks of Dhanjori Group are partial melting products of a spinel Iherzolite source, Dalma ultrabasics are the residue after the melt-extraction from an original garnet lherzolite rock. Ultramafics of Newer dolerite dykes indicate either derivation by mantle meta somatism or effect of post magmatic serpentinisation. REE data in conjunction with the available geochronological data suggest that significant mantle heterogeneity existed over relatively smaller distances (∼100 km) even during Proterozoic and that the mantle evolved in a non-uniform manner with distinct localised processes.

Keywords

REE Geochemistry, Singhbhum Craton, Mantle Heterogeneity.

Full Text