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

D. Padmalali ¹, S. Santhosh ², D. S. Suresh Babu ¹

Affiliations
1 Centre for Earth Science Studies, Trivandrum - 695 031, IN
2 Department of Geology, University of Kerala. Kariavattom P.O., Trivandrum - 695 581, IN

Abstract

The Tertiary carbonaceous clay deposits of Kerala abound in iron sulfide minerals such as pyrite and marcasite. Pyrite is confined mainly to the Quilon beds and marcasite to the Warkalli beds. Manganese, Zn, Pb, Ni, Co, Cd and Cu are substantially high in marcasite than in pyrite. Trace metals (except Zn) are markedly high in the carbonaceous clays of the Warkalli section than in those of the Pozhikkara section. The observed variation in the trace metal contents of sulfide minerals as well as carbonaceous clays of the two sections might have resulted from differences in depositional environments.

Keywords

Geochemistry, Iron Sulfide Miperals, Tertiary Deposits, Kerala.

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Ajith G. Nair ¹, K. T. Damodaran ², D. S. Suresh Babu ¹

Affiliations
1 Centre for Earth Science Studies, P.B. No.7250, Akkulam, Thiruvananthapuram-695031., IN
2 Marine Geology Division, School of Marine Sciences, Cochin University of Science and Technology, Kochi-682016, IN

Abstract

Characterisation of ilmenite collected from the source to the mouth of the River Valliyar shows progressive alteration with the exception of a junction. where a major tributary joins the main stream. Mineralogical and compositional comparison between alluvial ilmenites and those collected from the beach sediments of adjoining area indicates that the River Valliyar partly contributes to the enrichment of the Manavalakurichi deposit. FeO/Fe₂O₃ and Ti/(Ti+Fe) ratios along with ore microscopic and XRD studies confirm the degree of alteration in the ilmenites of the study area.

Keywords

Weathering, Ilmenite, Placer, Manavalakurichi, Tamil Nadu.

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V. Nandakumar ¹, D. S. Suresh Babu ¹

Affiliations
1 Centre for Earth Science Studies, P.B. No. 7250 Akkulam, Thiruvananthapurarn 695 031, IN

Abstract

The patterns developed on detrital garn.ets exemplify the hierarchy and intensity of processes suffered by the grains. Different features noticed over the grain surfaces denote chemical, mechanical and mixed origin. Sequential formation of microrelief patterns are observed in a variety of cases.

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D. S. Suresh Babu ¹, D. Padmalal ¹, P. R. Arun ¹

Affiliations
1 Centre for Earth Science Studies, Akkulam, Thiruvananthapuram - 695 03 1, IN

Abstract

Estimation of water balance and sediment yield pertaining to two forest watersheds of southern India was carried out as part of the forest conservation program in Kerala State. The tropical watersheds namely Upper Peppara (-80km²) and Upper Neyyar (-140km²) of southern Kerala region host two important wildlife sanctuaries maintained in the Western Ghats of Indian subcontinent, which have high biodiversity values. The watershed evaluation conducted during the period 1995-2000 reveals that Peppara reservoir catchment yields an average of 1600 tons of suspended sediment and 126Mm³ of run off water every year. On the other hand, Neyyar reservoir at Full Reservoir Level (FRL) carries a suspended sediment load of 1400 tons during the peak monsoon month of June and it receives 207Mm³ of run off from its catchment annually. Unit plot measurements for soil loss indicate that grassland yields substantially high sand-Silt material, of the order of one ton per hectare annually. A management plan map for the Upper Neyyar watershed has been prepared taking into consideration of landscape features. One micro watershed, Panampara (6.73km²) falling within Peppara sanctuary was closely monitored to check its physical health. A number of locally feasible conservation strategies have been proposed to improve the water holding capacity as well as to minimise soil erosion in this subwatershed area. Periodic and manual silt removal from reservoirs during summer periods is recommended to maintain the storage capacity rather than constructing an upper dam or increasing the height of existing dam, as actively being considered.

Keywords

Forest Watershed, Water Balance, Sediment Yield, Conservation Structures, Siltation, Western Ghats, Kerala.

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Sabu Joseph ¹, K. P. Thrivikramaji ², D. S. Suresh Babu ³

Affiliations
1 Department of Environmental Sciences, University of Kerala, Kariavattom, Thiruvananthapuram - 695 581, IN
2 Department of Geology, University of Kerala, Kariavattom, Thiruvananthapuram - 695 581, IN
3 Centre for Earth Science Studies, P.B. No.7250, Akkulam, Thiruvananthapuram - 695 03 1, IN

Abstract

The early-modern red dune sands (teris) in the erstwhile Tirunelveli District of southern Tamil Nadu are typified by the large content of heavy minerals (HM), particularly ilmenite. Size-specific studies show that HMs dominate the -80 to +100 mesh, and magnetic susceptibility (X) studies demonstrate the presence of three fractions of ilmenite, viz., a (X= 286×10^-6), b(127×10^-6) and c (72×10^-6),which the fraction b is most abundant (range = 52-85%). Optical studies show a variety of exsolution features between ilmenite and haematite dominantly in fraction a, less in b and almost absent in fraction c. Chemical and XRD data of ilmenite fractions, indicate that a and b are relatively unaltered and belong to the ferrian ilmenite state, whereas c is altered and reaches the hydrated ilmenite state with notable development of pseudorutile and rutile phases. Further, the b fraction is composed of relatively pure ilmenite compared to a and c. Based on this investigation, the boundary between altered and unaltered ilmenite has been drawn at a magnetic susceptibility of 127×10^-6 cgs units. Hence, a physical separation of bulk ilmenite in terms of grain size and magnetic susceptibility can provide commercial ilmenite concentrates of relatively homogeneous nature in respect of composition and crystallinity.

Keywords

Ilmenite, Teri Sands, Magnetic Susceptibility, Alteration, Tamil Nadu.

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