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Nair, N. G. K.
- The Spiti Ordovician-Silurian Succession
Abstract Views :196 |
PDF Views:176
Authors
R. K. Goel
1,
N. G. K. Nair
1
Affiliations
1 Dept. of Geology & Geophysics, University of Roorkee, IN
1 Dept. of Geology & Geophysics, University of Roorkee, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 18, No 1 (1977), Pagination: 47-48Abstract
Classic pin valley section in Spiti (Himachal Pradesh) India, has been re-examined and formal stratigraphic nomenclature in terms of the Lower Paleozoic succession of Spiti is proposed.- Minor Element Geochemistry of Pyrite and Sphalerite in the Polymetallic Sulphide Deposit of Deri, Sirohi District, Rajasthan - A Preliminary Study
Abstract Views :177 |
PDF Views:2
Authors
Affiliations
1 Department of Earth Sciences, University of Roorkee, Roorkee 247672, IN
1 Department of Earth Sciences, University of Roorkee, Roorkee 247672, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 22, No 3 (1981), Pagination: 143-146Abstract
Data on the distribution of Cd, Mn, Cu, Ag, Ni and Co in four monomineralic fractions each of sphalerite and pyrite from five ore samples of the Precambrian stratiform zinc-lead-copper deposit of Deri, Rajasthan are presented. The minor element geochemistry of the sulphides suggests possible volcanic exhalative origin.- Age Data on Pegmatites Of South Kerala and their Tectonic Significance
Abstract Views :216 |
PDF Views:2
Authors
Affiliations
1 Department of Geology, Friendship University, Moscow, RU
2 Centre for Earth Science Studies, Trivandrum 695010, IN
3 IGEM, Academy of Sciences, Moscow, USSR, RU
1 Department of Geology, Friendship University, Moscow, RU
2 Centre for Earth Science Studies, Trivandrum 695010, IN
3 IGEM, Academy of Sciences, Moscow, USSR, RU
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 23, No 9 (1982), Pagination: 458-462Abstract
K/Ar mica age of chrysoberyl-bearing pegmatites from four localities of Trivandrum district, Kerala ranges from 445 to 474 m.y., with a mean around 460 m.y. There is a close agreement between the ages of the concordant and cross-cutting pegmatites, between muscovite and biotite ages, as also between various size fractions. Chrysoberyl occurs within feldspars in association with quartz and muscovite. Since the formation of chrysoberyl-quartz association requires a higher pressure or temperature, the reported age would indicate the time of emplacement of the chrysoberyl-bearing pegmatites at the closing phase of a major tectonomagmatic event. It is interesting to note that these pegmatites of south-western India are younger compared to those of other localities viz., Rajasthan, Bihar. Nellore and Mysore.- Petrochemistry of the Chengannoor Granite, Alleppey District, Kerala
Abstract Views :183 |
PDF Views:2
Authors
M. Santosh
1,
N. G. K. Nair
1
Affiliations
1 Centre for Earth Science Studies, P. B. No. 2235, Trivandrum 695010, IN
1 Centre for Earth Science Studies, P. B. No. 2235, Trivandrum 695010, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 24, No 6 (1983), Pagination: 291-298Abstract
The granite of Chengannoor, Alleppey district, Kerala, having an intrusive relationship with Precambrian charnockite-cordierite gneiss sequence is inferred to be a post-kinematic granite of magmatic origin. The major mineral constituents are mesoperthitic K-feldspar with quartz and two generations of plagioclase. A late/post intrusive potash metasomatism caused changes in the mineralogy and chemical composition of the granite.
Recent K-Ar dating of hornblende from the Chengannoor granite assigns an age of 550 m.y. for the granite (Soman, Golubyev and Santosh. Ind. Jour, Earth Science) (in press).
- Author's Reply
Abstract Views :214 |
PDF Views:130
Authors
Affiliations
1 Centre for Earth Science Studies, Trivandrum 695010, IN
1 Centre for Earth Science Studies, Trivandrum 695010, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 25, No 7 (1984), Pagination: 474-474Abstract
No Abstract.- Petrogenesis of the Angadimogar Syenite, Kerala and its Taphrogenic Affiliation
Abstract Views :229 |
PDF Views:2
Authors
M. Santosh
1,
N. G. K. Nair
1
Affiliations
1 Centre for Earth Science Studies, P. B. No. 2235, Sasthamangalam. Trivandrum 695010, IN
1 Centre for Earth Science Studies, P. B. No. 2235, Sasthamangalam. Trivandrum 695010, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 6 (1986), Pagination: 494-507Abstract
A syenite pluton occurring ncar Angadimogar in Cannanore district. northern Kerala and emplaced close to the continental margin and along a NW-SE trending faultlineament is reported. Alkali feldspar constitutes the dominant mineral with subordinate albitic plagioclase and quartz. corresponding to nordmarkitic composition. The syenite shows unique assemblage of accessory minerals. namely hornblende, riebeckite. crocidolite and acmite with diopside, bi.otite. zircon, sphene and calcite. High alkali content, with dominance of Na20 over K20, moderate transition dement contents and low Rb values are characteristic. Petrochemical features suggest melt equilibration from a K-rich, Rb-depleted mantle source, with subsequent amphibole and alkali feldspar fractionation. Significant increase in fO2, fH2O and peralkalinity towards the residual stage is deduced. The syenite belongs to the group of Late Precambrian-Early Palaeozoic alkaline intrusives of the region, with its generation and emplacement correlatable with the taphrogenesis of the western continental margin of lndia.- Chrysoberyl Pegmatites of South Kerala and their Metallogenic Implications
Abstract Views :210 |
PDF Views:2
Authors
Affiliations
1 Centre for Earth Science Studies, Trivandrum 695 010, IN
2 Peoples Friendship University, Moscow, RU
1 Centre for Earth Science Studies, Trivandrum 695 010, IN
2 Peoples Friendship University, Moscow, RU
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 5 (1986), Pagination: 411-418Abstract
Recent investigations prove that the southern part of Kerala and the adjoining areas further to the south in Tamil Nadu constitute a chrysoberyl-pegmatite field in the granulite terrain of southwestern India. Gem stones like chrysoberyl and its varieties, sapphire, topaz and zircon are mostly derived from pegmatites, though some come from the alluvial beds also. Chrysoberyl-pegmatites occur in a predominantly garnet-sillimanite ± graphite gneissic terrain with intermittent bands of garnet-biotite gneiss and enderbites. Geochronological data reveal that the pegmatites were emplaced 445-474 m.y. ago. Fluid inclusion studies show that the pegmatite minerals contain liquid carbon dioxide and give an entrapment temperature of 500-570°C. CO2 densities permit a pressure estimate of 250 Mpa and more, which is also consistent with the sillimanite-andalusite and quartz-chrysoberyl associations in the pegmatites. The similarities in geology, the ages of pegmatites and granites and also the mineral composition of pegmatites of southwestern India and the alluvial gem gravels of Sri Lanka suggest that the al1uvial gem beds of Sri Lanka may also be of pegmatitic origin.- Rb-Sr Geochronology of the Ambalavayal Granite, Kerala
Abstract Views :207 |
PDF Views:150
Authors
Affiliations
1 Centre for Earth Science Studies, P. B. 2235, Sasthamangalam, Trivandrum 695 010, IN
2 Physical Research Laboratory, Navarangpura, Ahmedabad 380 009, IN
1 Centre for Earth Science Studies, P. B. 2235, Sasthamangalam, Trivandrum 695 010, IN
2 Physical Research Laboratory, Navarangpura, Ahmedabad 380 009, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 27, No 3 (1986), Pagination: 309-312Abstract
Rubidium and strontium determinations are reported for seven whole-rock samples of the Ambalavayal granite of northern Kerala. The data yield a well defined Rb-Sr isochron, corresponding to an age of 595 ± 20 Ma and initial 87Sr/86Sr ratio of 0.7171 ± 0.0022. The age marks a regime of Late Precambrian-Early Palaeozoic granite magmatism in the southwestern Indian shield. The agreement of the Rb/Sr age with the previously measured K/Ar age of 560± 30 Ma indicates no significant secondary thermal event in the region. The evolved initial Sr ratio suggests either an exclusive origin or significant crustal contamination of magma derived from a deeper source.- Petrochemistry and Tectonic Significance of the Peralimala Alkali Granite, Cannanore District, Kerala
Abstract Views :206 |
PDF Views:8
Authors
N. G. K. Nair
1,
M. Santosh
1
Affiliations
1 Centre for Earth Science Studies, P. B. No. 2235, Trivandrum 695010, IN
1 Centre for Earth Science Studies, P. B. No. 2235, Trivandrum 695010, IN