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

S. S. Sarkar ¹

Affiliations
1 Department of Geology, Presidency College, Calcutta 700 001, IN

Abstract

The area around Sarat and Notopahar, Mayurbhanj District, Orissa, is characterised by a suite of Precambrian granitic rocks ranging in composition from quartz diorite through tonalite, granodiorite, granite to alkali feldspar granite. Field, petrological and petrochemical evidences indicate that the rocks of the Notopahar Granitic Complex (N.G.C.) are essentially comagmatic, representing a wide range of magmatic differentiates and can be correlated with the Mayurbhanj Granite (ca. 2084 Ma.). It is also noted that, the N.G.C. rocks are intrusive into the adjacent sheet-like body of gabbronorite.

Full Text

     

S. S. Sarkar ¹

Affiliations
1 Department of Geology, Durgapur Government College, Durgapur 713214, IN

Abstract

Two granite bodies, namely the Banresar and Manihari plutons, which are intrusive into the metasedimentary sequences of the Bihar Mica Belt, have been geochemically investigated.

The major trace and REE compositions of 21 granite samples indicate a crustal derivation of these granites from ∼23% partial fusion of a granodioriric-tonalitic component of the crystalline basement of Chhotanagpur gneissic terrain, (relics of which occur as enclaves within the plutons) followed by (a) ∼ 39% fractional crystallisation of quartz; two feldspars, and hornblende from this granitic melt and (b) emplacement of the differentiates within domical metasedimentary upwarps at about 17km depth (≡ 5 kb), during second phase of folding in this region. Mild activity of a residual alkali-rich vapour phase, mostly active through central portion of these plutons and gradually migrating towards periphery, gave rise to a spatial trace clement heterogeneity in these bodies.

he calc-alkaline character of these granites, along with their syntectonic emplacement into a sedimentary veneer having the polydeformational signature of Satpura orogeny, indicates a compressional tectonic regime. which might have caused a down buckling of the Chhotanagpur crystalline basement, leading to its partial fusion, to generate the parental granitic magma.

Full Text

     

P. K. Sikdari ¹, N. Dasgupta ¹, S. S. Sarkar ²

Affiliations
1 Center for Study of Man & Environment, CK-II, Sector-II, Salt Lake City, Calcutta-700091, IN
2 Presidency College, Calcutta-700073, IN

Abstract

Hydrogelogical investigation of the area around Saltora reveals the presence of groundwater under shallow water table condition within the Precambrain anorthositic country rock. VES study indicates that the water is stored within the weathered residuum and the underlying fractured rocks within a depth of 69 m. The groundwater flow is guided by the topography and the fracture system. Chemically the groundwater is suitable for drinking and irrigation purposes. The cardinal aquifer parameters such as permeability, transmissivity and specific yield are oflow order and hence water harvesting structures should be supplemented with groundwater abstraction structures to increase agricultural production and thus the economy of the area. Since the area is drought prone traditional methods of irrigation such as flooding must be ruled out and water should be transported from the source to the field by lined channels or pipes to minimise conveyance and evaporationallosses. Drip irrigation may also be adopted.

Keywords

Groundwater, Bankura District, West Bengal.

Full Text

     

Utpal Bose ¹, A. K. Mathur ¹, K. C. Sahoo ², S. Bhattacharya ¹, Krishan Dutt ¹, V. Aneel Kumar ³, S. S. Sarkar ¹, S. Chowdhury ¹, I. Chowdhury ¹

Affiliations
1 Geological Survey of India, Jhalana Dungri, Jaipur - 302 004, IN
2 Geological Survey of India, Bhubaneswar - 751 012, IN
3 Geological Survey of India, Hyderabad - 500 660, IN

Abstract

The oldest cratonic nucleus pf the Western Indian shield, familiarly known as the Banded Gneissic Complex (BGC), occupies a large tract in the Mcwar plains of South Rajasthan. It has essentially an old gneissic component (3.3 Ga) and a host of mafic bodies associated with detrital and chemogenic sediments which have been subjected to multiple phases of anatexis and granite intrusions (2.9 Ga and later events). The emplacement of Berach granite and succeeding dolerite dyke swarms mark the end-Archaean cratonization process. This also initiated intracratonic and cratonmarginal basin formation.

Later magmatism, especially along the basement-cover interface. is due to local remobilisation of the basement at the time of Proterozoic orogeny.

Keywords

Banded Gneissic Complex, Stratigraphy, Petrochemistry, Rajasthan.

Full Text