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

V. Divakara Rao ¹, S. M. Naqvi ¹, K. Satyanarayana ¹, S. M. Hussain ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad, IN

Abstract

Major and trace element analyses of gneisses from parts of the Karnataka State, reveal heterogeneity in their chemical, modal and normative compositions. On the basis of chemical differences it is suggested that the parent material for these gneisses was pelitic/arkosic in nature. Heterogeneity in their composition is attributed to their age difference, degree of granitisation and migmatisation to which the pelitic/arkosic parent material was subjected.

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S. M. Hussain ¹, S. M. Naqvi ¹, T. Gnaneshwar Rao ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad-500 007, IN

Abstract

The ultramafic rocks of Holenarasipur schist belt show micro-spinifex texture, deformed pillow lava-like structures and contain interbedded fuchsite-quartzite. Compositionally the mafic-ultramafic rocks are similar to peridotitic, pyroxenitic and basaltic komatiites. Available data exhibit a gap between 20 and 30% MgO content, which suggests discontinuity in their composition. A two stage melting model is projected to explain this compositional gap. The abundance of komatiitic mafic-ultramafic rocks supports the view that the Holenarasipur schist belt is a true greenstone belt.

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S. M. Hussain ¹, S. M. Ahmad ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad 500 007, IN

Abstract

Two occurrences of anorthosite enclaves in the 3.4 b.y. old gneisses surrounding the Holenarasipur schist belt are reported. The Mandagere enclave has An₉₂ whereas, Arkalgud enclave has An₈₃. Both the bodies are metamorphosed to higher amphibolite facies and exhibit granoblastic texture. They are associated with ultramafic enclaves. These occurrences along with the lunar type anorthosites of Holenarasipur Group greenstone belts are significant in early crustal evolution models.

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S. M. Hussain ¹, S. M. Naqvi ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad 500 007, IN

Abstract

Two types of conglomerates occur in the Holenarasipur schist belt. The Tattekere conglomerate occurring in the older horizon (>3.4 b.y.) ofthe belt is oligomictic and is tectogenic (autoclastic), devoid of pebbles of detrital sedimentary origin. The Gopalapura conglomerate occurring in the younger horizon (3.2 to 3.0 b.y.) of the belt is, on the other hand, polymictic and sedimentogenic. Occurrence of gneiss pebbles in this conglomerate indicates presence of gneissic terrain in the source area and strongly supports the view that considerable sialic crust had evolved before the younger greenschist sequences were deposited in this region. This extensive crust is formed by widespread emplacement of acidic plutons during the time gap between the older and younger sequences of Holenarasipur. It is proposed that older Holenarasipur schists and gneisses which intruded it supplied the debris to the younger belt.

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S. M. Hussain ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad 500007, IN

Abstract

During the 6^th Indian Scientific Expedition to Antarctica, geological and geochemical studies were carried out in the Schirmacher oasis and the Petermann I areas of Wohlthat ranges in Antarctica. The greasy-looklng porphyroblastic bedrock of Petermann I area described in this report ranges in composition from 'quartz-alkali feldspar syenite' to ' alkali-feldspar granite'.

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R. H. Sawkar ¹, S. M. Hussain ², S. M. Naqvi ²

Affiliations
1 Hutii Gold Mines, Bangalore, IN
2 National Geophysical Research Institute, Hyderabad, IN

Abstract

No Abstract.

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S. M. Hussain ¹, V. Divakara Rao ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

Gamet-biotite gneisses (GBG), augen gneisses (AG) and quartzo-feldspathic gneisses (QFG) constitute the main litho-units in the granulite terrain of Schirmacher Oasis, East Antarctica. The GBG and AG show chemical and mineralogical similarities. The QFG differs from GBG and AG both in major and trace elements. Overall composition of these different polyphase gneisses indicate increase in silica and alkalies from GBG to QFG and decrease in CaO, FeO and MgO. In trace elements Rb increases from GBG to QFG, while Sr and Ba increase in AG and decrease in QFG. The REE distribution patterns in GBG. AG and QFG differ in that, the total REE in GBG is 160.70, in AG 148.32 and the QFG 119.30. The LREE/HREE and Ce_n/Tb_n ratios of GBG and QFG are similar while in AG these differ slightly (GBG = 5.16 and 3.18; AG = 6.93 and 5.10; QFG = 5.62 and 3.90 respectively). Majority of the gneisses exhibit negative Eu anomaly (GBG = 0.55; AG = 0.35; QFG = 0.43) except two from AG having no anomaly. Overall major, trace and REE abundances in the garnet-biotite and augen gneisses suggest their origin by progressive metamorphism of a pelitic source. Partial melting of GBG locally appears to have formed quartzo-feldspathic gneisses. These gneisses resemble the metapelites of the Eastern Ghat granulite terrain and Kerala khondalite belt of India in their overall compositions.

Keywords

Geochemistry, Gneisses, East Antarctica.

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A. M. Dayal ¹, S. M. Hussain ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

Lamprophyre dykes intrude the late Proterozoic metamorphic terrain of Schimucher Oasis, Queen Maud Land, East Antarctica. Rb-Sr whole-rock/mineral isochron ages of two lamprophyre dykes are 455 ± 12 Ma (Sr₁ = 0.70886 ± 5) and 458 ± 6 Ma (Sr₁ = 0.71388 ± 98). This lamprophyre dyke activity of Schirmacher Oasis, may be interprete4 as a manifestation of post orogenic alkaline magmatism related to the Ross orogeny of the Transantarctic mountains.

Keywords

Geochronology, Alkaline Igneous Activity, Lamprophyre, East Antarctica.

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S. G. D. Sridhar ¹, S. M. Hussain ², P. Periakali ¹, V. Kumar ³

Affiliations
1 Department of Applied Geology, University of Madras, Guindy Campus, Chennai - 600 025, IN
2 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai - 600 025, IN
3 Department of Geology, National College, Tiruchirappali - 620 001, IN

Abstract

The shallow marine and tropical ostracod taxon Kotoracythere inconspicua(Brady) is encountered from the surface sediments of Indian waters Fifty-Two sediment and bottom water samples were collected over an year, representing the four seasons, in a transect (depth 0-13 m) off Rameswaram, southeast coast of India. Living specimens of this species are found in all the seasons. Systematics and ecology of the species are presented Biogeographically, this taxon has an extremely wide distribution in tropical, littoral zones of all oceans, excepting east Pacific. Its wide geographic distribution is explained through currents and by passive dispersal by ships.

Keywords

Ostracoda, Ecology, Biogeography, Palk Bay, Indian Ocean.

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J. Madhavaraju ¹, S. M. Hussain ², M. Guruvappan ², S. Ramaswamy ², S. P. Mohan ²

Affiliations
1 Estacion Regional del Noroeste, Institute de Geologia, Universidad Nacional Autonoma de Mexrco, Hermosillo, Sonora - 83000, MX
2 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai - 600 025, IN

Abstract

The lower Niriyur Formation of Cauvery Basin is well exposed in the Periyakurichi area. The lower Niriyur Formation exhibits three carbonate petrographic types viz wackestone, packstone and boundstone whereas clastic rocks are represented by arenite and wacke types. The clastic rocks of Niriyur Formation exhibit microgranular calcite cement and fossils namely algae, bryozoa and molluses which suggest that these sediments were deposited under shallow marine environment. The carbonate rocks of Niriyur Formation contain the rich fossil assemblages composing algae, forarmnifera, ostracodes and mollusks. An attempt has been made to study the carapace-valve ratio of ostracod fauna which suggests the slow rate of sedimentation in the basin. The occurrence of Sporolithon-Rich flora together with forarmnifera has been found to be characteristic of depth range 20-40 m. The outcrop sequence stratigraphic study of the lower Niriyur Formation shows two sequence boundaries, Transgressive Systems Tract (eight shallowing upward parasequences), Maximum Flooding Surface and Highstand Systems Tract. The lower Niriyur Formation of Ariyalur area is represented by mixed clastic and carbonate rocks showing shallowing upward metre scale parasequences, which represent the subtidal cycles.

Keywords

Petrography, Sequence Stratigraphy, Parasequences, Depositional Environments, Niriyur Formation, Cauvery Basin, Tamil Nadu.

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S. M. Hussain ¹, P. V. Sunder Raju ¹

Affiliations
1 National Geophysical Research Institute. Hyderabad - 500 007, IN

Abstract

No Abstract.

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J. Madhavaraju ¹, S. Ramasamy ¹, S. P. Mohan ¹, S. M. Hussain ¹, N. Gladwin Gnana Asir ¹, V. Stephen Pitchaimani ¹

Affiliations
1 Department of Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennai- 600 025, IN

Abstract

Petrography, fluid inclusions and surface texture studies have been carried out on the Nimar Sandstone, which have provided fruittful results on pravenance and depositional environment The detrital omposition of sandstones plotted in the Q-F-L diagram suggests cratonic orrgin The modal percentages of different types of quartz plotted in the diamond diagram Indicate that these sediments were derived from the low-grade metamorphic rocks Quartz grains show randomly distributed primary inclusions, small trails of pseudosecondary inclusions and needle-shaped solid phases also support that the source rocks are mainly low-grade metamorphc rocks The surface textures on quartz grains reveal the presence of twenty-two distinct surface textures Based on their origin, these textures are grouped into three types viz I) thirteen features that show mechanical origin, II) five features that exhibit mechanical and/or chemical origin and III) four features that reveal chemical (precipitational)origin The quartz grans exhibit conchoidal fractures, arcuate steps, and fractured plates/planes, which resulted during the liberation of these grains from the crystalline formations They also exhibipt petransportational features such as pedological overgrowths, silica globules, flower and pellicles, which are indicative of short transportation and rapid deposition of these sediments Vs, straight and curved scratches are more common on the quartz grains from the upper Nimar Sandstone (whtch are characteristic features of marine environment), whereas the lower frequency of these features on the quartz grains from the lower Nimar Sandstone suggest fluvia depositional environments.

Keywords

Petrography, Quartz grains, Fluid inclusion, Surface textures, Nimar Sandstone, Provenance, Depositional environment, Bagh Beds, Madhya Pradesh.

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G. Parthasarathy ¹, S. R. Sharma ¹, T. R. Ravindran ², A. K. Arora ², S. M. Hussain ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN
2 Indira Gandhi Centre for Atomic Research, Kalpakkam - 603 102, IN

Abstract

We report here powder X-ray diffraction, differential thermal analysis and Laser-Raman spectroscopic data on the graphite from Schirmacher Oasis (70°45' S, 11°40' E), East Antarctica. The sample was collected from Precambrian garnet-biotite gneiss. The present X-ray studies show that the structural parameters like inter-planar spacing, d₀₀₂ (3.3500 A), and crystallite size, L_c (552 A) of this sample. These values are found to be very close to that of well-crystallized graphite. All the five observed X-ray diffraction peaks have been indexed to the hexagonal phase of graphite, indicating the metamorphic origin of graphite. The observed full width at half maxima (FWHM) of the (002) peak is 0.148 A and the estimated graphitizing degree (GD=13lA) showed the high-grade metamorphism of the host rock. The estimated peak metamorphic temperature is found to be ∼973 K (700°C). DTA studies on the same graphite sample show a strong exothermic peak at 1023 K, which corresponds, to the combustion of carbonaceous matter under atmospheric condition. The absence of extra weak peak in the range 1090-1110 K, indicates the absence of any noticeable detntal graphite in the sample. The first order Laser - Raman spectra of the sample shows a strong well-ordered Raman peak (O) at 1581cm"¹ and a weak broad peak due to disorder (D) at 1354cm"¹. The intensity ratio disordered-to-ordered Raman peak (D/O) area has been used to estimate the in-plan crystallite size (La) of the graphite. The experimental values of D/O = 0.143 and D/D+O = 0.125 indicate that the sample is well crystallized graphite, thereby indicating the high metamorphic grade of the host rocks. The structural parameters obtained by Raman spectroscopic method and the estimated in-plane crystallite size (La = 298 A) indicate that the metamorphic grade of the host rock of the studied sample falls in the sillimanite zone. The present study suggests that the peak metamorphic temperature of the host rock could be in the temperature range of about 973 K (700°C).

Keywords

East Antarctica, Graphite, X-Ray Diffraction, Schirmacher Oasis, High-Temperature Dta, East Antarctica.

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V. Divakara Rao ¹, S. M. Naqvi ¹, K. Satyanarayana ¹, S. M. Hussain ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad, IN

Abstract

Geochemical prospecting for copper in the Nuggihalli schist belt, Karnataka has indicated that the serpentinised dunites are moderately enriched in copper. The copper appears to have no structural control and the enrichment is not uniform in the dunite.

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S. M. Naqvi ¹, V. Divakara Rao ¹, K. Satyanarayana ¹, S. M. Hussain ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad, IN

Abstract

An area of about 115 Sq km was sampled on a 0.4 km spacing grid. The samples, collected from the bed rock, after removing the thin soil cover, were analysed for Cu, Zn, Pb and Co by the emission spectrograph using indium as internal standard. The Cu concentration map of the area shows nine zones of anomalous Cu content, the highest giving a value of 4000ppm. Of these, four zones of highly anomalous Cu content (2000 ppm-4000 ppm) are very promising and are recommended for detailed geochemical exploration.

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