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T. M. Ganesan ¹, K. Gopalakrishnan ¹, R. Renganathan ¹, S. S. Sivasankaran ¹

Affiliations
1 Geological Survey of India, Inner Ring Road, Guindy Industrial Estate, Chennai 600032, IN

Abstract

A sheath fold with inverted hinge is recorded within the charnockite exposed around Nekkanamalai in the Southern Granulite Terrain. The area lies within the NNE-trending Gudiyatham-Bhavani Straight Belt (GBSB) bounded on either side by two distinctly different tectono-stratigraphic terranes brought into juxtaposition along major tectonic contacts. Such folds are known in regions of re-folding, with later folding events of high intensity at high angles to the earlier folds, as well as in shear zones, where the direction of shear is subparallel to the sheath axes. The sheath fold in the area is interpreted to be due to superposed folding resulting from the complicated pattern of deformation produced during the welding of different terranes along the GBSB, which had brought about not only plunge reversals but also plunge inversion of the earlier folds.

Keywords

Structural Geology, Sheath Fold, Granulite Belt, Tamil Nadu.

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R. P. Nagar ¹, Jayalal ¹, Fareeduddin ², S. S. Sivasankaran ¹, C. L. Harpavat ¹

Affiliations
1 Geological Survey of India, Project-Gold, Jaipur - 302 004, IN
2 Geological Survey of India, PPOD, Bangalore - 560 078, IN

Abstract

Exploration work during 1993-97 in 1000 km2 area extending from Salumbar to Parsola has led to recognition of several gold bearing zones in almost all horizons of lower Aravalli sequence starting right from basal quartzite to pebbly schist/conglomerate except perhaps in schistose rocks. In general, gold content of lowermost rocks like basal quartzite and meta-basalts is lower (mean gold:90 ppb and 106 ppb respectively) than the gold contents of rocks of upper horizons like dolomitic marble-I, dolomitic marble-I1 and composite-gneiss (mean gold:452 ppb, 361 ppb, 191 ppb respectively). In addition to locating gold mineralisation in Rajpura, Padwa, Kukra, Dhaulimagri, Bhungabhat, Amalva-Dagocha-Rathri, Barasarpatia and Mokpura areas in dolomite marble, potential gold zones in sheared quartzite and gneiss are identified in Bhabrana, Navagaon, Dhuntarnagra and Jaitana-Mandii areas. Gold mineralisation is shear controlled and is associated with structural elements of both the first and second deformations. Vast gold potential of Aravalli fold belt (AFB) has been indicated by the presence of deep-ischolar_mained faults, boron bearing rocks/minerals, silicification/jasperization and highly anomalous gold contents in stream sediment (up to 910 ppb) and lithogeocll&nical samples (mean: 301 ppb, maximum: 6500 ppb).

Keywords

Gold, Exploration, Genetic controls, Aravalli fold belt, Proterozoic, Salumbar, Parsola, Rajasthan.

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R. Gopalakrishnan ¹, S. S. Sivasankaran ²

Affiliations
1 PPOD Division, AMSE Wing, Geological Survey of India 40th Cross Eshwar Nagar, Bangalore - 560 082, IN
2 Geological Survey of India, Western Region, Jaipur, IN

Abstract

No Abstract.

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