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

D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi, IN

Abstract

At least five types of stromatolites have been reported from the Aravalli succession near Udaipur. Excepting Collenia columnaris all other forms are phosphatic. Association of these stromatolites with phosphorite deposits of economic importance has been clearly demonstrated. Age significance of these stromatolitic forms has also been discussed in detail.

Full Text

     

D. M. Banerjee ¹, Ursula Klemm ²

Affiliations
1 Department of Geology, University of Delhi, Delhi, IN
2 Max-Planck-Institut fuer Chemie, Air Chemistry Department, Palaeoatmos. Res. Group, Postfach 3060, D-6500 Mainz, West Germany, DE

Abstract

Stromatolitic phosphorites and carbonates from the Proterozoic Aravalli sediments of Western India, have been subjected to organo-geochemical studies, involving a modified gc-ms technique. The stromatolitic phosphorites have an average value of 0.22% TOC which is significantly different from the average TOC value (0.64%) for all types of phosphorite from the Indian subcontinent. With only a few exceptions, the isoprenoids-pristane and phytane and the n-alkanes, account for about 30% of the total amount of volatiles (1-20 ppm). Normal alkanes occur in the range of n-c₁₂ to n-c₃₁ with maxima between n-c₁₇ and n-c₂₁ . No odd/even predominance has been observed. Besides pristane and phytane, other isoprenoids identified in these rocks are iSO·C₁₆ and iSO-C₁₈. The low pristane to phytane ratio of 1.14 suggests a reducing micro-environment within the laminae of shallow-water cyanobacterial/algal stromatolites. The phosphate is assumed to be precipitated within the pore-waters under anoxic conditions through the activities of biological agents, which is supported by geological and geochemical data. The overall basinal environment, however, remained oxidizing, as is evident from the associated sedimentary structures.

Full Text

     

D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi 110 007, IN

Abstract

No Abstract.

Full Text

   

D. M. Banerjee ¹

Affiliations
1 University of Delhi, Delhi, IN

Abstract

No Abstract.

Full Text

   

Viqar Husain ¹, D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi 110 007, IN

Abstract

The lower Palaeozoic (possibly Cambrian) phosphorites of Birmania in Western Rajasthan are pelletal as well as microcrystalline. Carbonate fluorapatite is the only mineral phase in these phosphorites. Petrodiagenetic and mineralogical studies indicate primary precipitation of apatite directly from the basinal waters. Suggestions have been made for an extensive Cambrian sea encompassing the phosphogenic provinces of Western Rajasthan, Hazara in Pakistan and Mussoorie hills of Kumaun Himalayas.

Full Text

     

D. M. Banerjee ¹

Affiliations
1 Geology Department, University of Delhi, Delhi 110 007, IN

Abstract

No Abstract.

Full Text

   

P. Bhattacharya ¹, D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi 110 007, IN

Abstract

Dunnet's matching curve technique has been applied for evaluating the finite strain of basal conglomerate clasts occurring at the base of Delhi as well as Aravalli rock formations. The study revealed that deformation shown by the enclosing clasts are close to the theoretical values.

Full Text

     

K. Bheemalingeswara ¹, M. Deb ¹, D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi-110 007, IN

Abstract

The Tiranga Hill is located in the southernmost part of the 25 km long Pur-Banera mineralized belt in the Bhilwara District of Rajasthan. Exploration by Government agencies has revealed low grade Pb-Zn-Cu sulfide mineralization along this Early to Middle Proterozoic metasediments and meta-volcanics, regionally metamorphosed to amphibolite facies. At Tiranga, the mineralization occurs within a metamorphosed banded iron-formation spatially associated with spectacularly-folded banded magnetite quartzite (BMQ) bands.

The soils, neglecting the effects of ancient workings, are highly anomalous in Pb and Zn and also to certain extent in Cu. The major anomalies coincide spatially with the cores of synformal folds in BMQ bands, suggesting structural control of the richer parts of the mineralization. The Tiranga soils display strong interelemental correlations between Cu, Pb, Zn, Ag, Fe and Mn, The base metals display similar dispersal behaviour in soils and stream sediments. Their relative mobility in the weathering zones of Tiranga Hill is : Zn >Cu >Pb. Somewhat surprising, however, is the lower concentration of Fe and Mn as well as Ni and Cr in the soils compared to the bedrock.

Full Text

     

D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi 110 007, IN

Abstract

Phosphorus plays an important role in terrestrial environmental management. Mining of phosphate ore without observing necessary safeguards can cause enormous damage to the general ecosystem and in particular to the aquatic bodies which receive excess P influx. A careful enumeration of the actual mining situations observed in five phosphate mining centres brings out the fact that while some damage to the surrounding environment has already been caused due to mining operations in the area, more serious hazards are forthcoming, if suitable legislations are not enacted to contain them. Case studies include mines at Jhamarkotra, Matoon-Kanpur, Jhabua, Maldeota-Durmala and Purulia.

Full Text

     

D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi, IN

Abstract

No Abstract.

Full Text

   

D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi, IN

Abstract

No Abstract.

Full Text

   

D. M. Banerjee ¹, Neeta Saigal ²

Affiliations
1 Department of Geology, University of Delhi, Delhi 110 007, IN
2 Wadia Institute of Himalayan Geology 33, General Mahadeo Singh Road, Debra Dun, U.P., IN

Abstract

Stromatolitic and pelletal phosphorite deposits, belonging to Cumbum Subgroup of Nallamalai Group have recently been reported from Chelima-Pachcherla areas of Kurnool district in Andhra Pradesh. Most phosphorites of these areas are linked to the carbonate stromatolites like other Proterozoic phosphorite deposits of India. However, there are many variants which occur amidst quartzose rocks, assuming pel1etal forms, showing well marked neomorphic grain-growths and marked enrichment of elements like F, K₂O, Ba, Co, Mn, V, Y and Pb. Based on mineralogy, petrology, and geochemistry of these phosphorites, a protected-isolated supratidal lagoon type of environment has been visualised for the precipitation and diagenetic alteration of the Cumbum phosphorite.

Full Text

     

D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi - 110 007, IN

Abstract

A metamorphosed palaeosol surface separates the upper part of the Archaean Banded Gneissic complex from the basal Proterozoic Debari Formation of the Aravalli Supergroup. Mineralogical and petrological studies reflect presence of two mineralogical assemblages namely, quartz-feldspar-white mica-sericite-biotite-chlorite-calcite and quartz-kyanite-white mica-garnet. Geochemistry of the rocks collected along vertical profiles through the palaeosol units show high CIA indices in comparison to low CIA values of less altered basement gneisses. From bottom to the top, in the basement rocks as well as the palaeosol unit, a perceptible increase in Al₂O₃, SiO₂, and TiO₂, contents could be seen. Iron shows gradual upward increment in the assemblage-I while assemblage-2 contains very little iron. Na₂O shows upward decrease while K₂O shows quantum jump in abundance. K-Al correlation is strong and significant. Another iron-rich palaeosol unit is described between the basement gneisses and the Matoon dolomites. Based on the identification and characterization of the palaeosol units, the geological conditions prevailing before the onset of Aravalli sedimentation has been discussed. Diagenetic and metamorphic imprints on the palaeosols, now occuring as metamorphosed rock units have been defined and interpreted. This study has been utilised for reflecting the atmospheric conditions dominating during the early Proterozoic time.

Keywords

Metamorphic Petrology, Geochemistry, Palaeosol, Banded Gneissic Complex, Rajasthan.

Full Text

     

D. M. Banerjee ¹

Affiliations
1 Department of Geology, University of Delhi, Delhi-11007, IN

Abstract

No Abstract.

Full Text