bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of Charnockite Formation and Breakdown in Southern Kerala: Implications for the Origin of the Southern Indian Granulite Terrain
Authors: Ravindra Kumar G. R. , Chacko Thomas
Published: November 2024

Field studies in southern Kerala have been successful in locating a Dumber of quarries in which charnockite has partially replaced garnet-biotite gneiss. Four types of charnockite formation have been recognised. Three of these involve the dehydration of gneisses by the influx of CO2 - rich fluids. Types I and II show charnockite concentrated along shear and foliation planes. In type III, high CO2 pressures are required by the presence of interlayered, scapolite-bearing calc-silicates. In type IV, charnockite is restricted to the margins of granitic dykes. and formed as a result of the decompression reaction gar + qtz + Na-plag = opx + Ca-plag, rather than a dehydration reaction. The widespread occurrence of arrested charnockitisation in southern Kerala suggests that the process of carbonic metamorphism invoked at Kabbaldurga, Karnataka, was not a local phenomenon, but extended over the entire southern Indian granulite terrain. In contrast to these examples of charnockite in the making, three types of charnockite breakdown have also been recognised. These involve the influx of water-rich solutions by means of granite pegmatites, leucocratic magmas, and pink granites. Present geochronologic data are not sufficient to determine whether the various types of charnockite formation and breakdown were different phases of a single metamorphic event or the result of several distinct metamorphic episodes.
Rb-Sr Age of the Belka Pahar Granite, Sirohi District, Rajasthan
Authors: Chakranarayan A. B. , Powar K. B. , Pande K. , Gopalan K.
Published: November 2024

At Belka Pahar, in the Sirohi district of Rajasthan, metasediments of the Delhi Super Group are associated with a medium-grained, leucocratic, alkali granite. Whole rock isotopic data for this granite define a Rb-Sr isochron corresponding to an age of 860±25 Ma and an initial 87Sr/86Sr ratio of 0.7059 ±0.0032.
Fluorite Mineralization in Garampani Thermal Spring Area, Palamau District, Bihar
Authors: Mukherjee A. L.
Published: November 2024

Fluorite mineralization in the form of salt (grains < 0.5mm diam, crystalline white) and veins (grains 1-6mm diam crystalline, in shades of blue and voilet) is a conspicuous associate of Garampani thermal spring, Palamau District, Bihar, that belongs to an ENE-WSW trending belt of thermal springs in the northeastern Peninsular India. The springs of the belt are chemivally similar, characteristicallt enriched in F-, and are associated with Post-Gondwana faulting.

The Gararnpani spring (67.5°C) which emerges along a silicified shear zone in Barakar sandstone (L. Gondwana), is of Na-Cl-HCO3 type with near neutral pH (7.52 at 25°C), moderate specific conductance (352 mmhos/cm at 25°C), and is relatively enriched in F- (9.1 ppm) and SiO2 (67.2 ppm). Shallow groundwaters of the region are Ca-Na-HCO3 (within Gondwanas) to Na-HCO3-Cl types (within Archaean crystallines) with near neutral pH (7.1-7.6 at 25°C), low specific conductance (132-207 mmhos/cm at 25°C) and have low F- (0.5-1.2 ppm) and SiO2(12.3-24.0 ppm) content. Minor variations in the physicochemical properties of the thermal spring water in different periods, indicate slight mixing of shallow water.

From the estimated activity products of [Ca++] [F-]2, it is apparent that the spring water and shallow non-thermal groundwaters are respectively oversaturated and undersaturated with respect to APFluorite values at respective on-site temperatures of the samples. Both are, however, undersaturated with respect to calcite solubility. Physically contrasted spring-salt fluorite and the adjoining vein fluorite are co-ceived as precipitates from spring water and mixed stream water respectively. In the latter case, however, precipitation appears as episodic in nature. It is further envisaged that near saturation values of the springs of the belt with respect to APFluorite could be related to subsurface fluorite mineralization.
Lower Carboniferous Conodonts from Spiti
Authors: Gupta V. J.
Published: November 2024

The present paper records Lower Carboniferous conodont fauna from the grey micritic limestone lying immediately above the Muth Formation exposed along the left bank of the Takche nala, between Kunzam La and Losar, Spiti valley, Himachal Pradesh.
Role of Microstructures in the Spontaneous Combustion of Raniganj Coals: A SEM Study
Authors: Singh Mahendra P. , Chandra D. , Prasad Y. V. S.
Published: November 2024

The Scanning Electron Micrography of bulk coal samples from Dishergarh, Sirpur and Kajora areas of Raniganj Coalfield has been attempted with a view to find out the role of microstructures in promoting the spontaneous combustion of these coals. Microanalysis of vitrain and c1arain has shown that these bands of R-VIII seam are highly porous as compared to the overlying and underlying seams. Further, finely dispersed pyrite has also been observed filling these micropores. It is concluded that the occurrence of ubiquitous micropores could be a prevalent factor responsible for the spontaneous combustion property of these coals in different ways.
Dynamic and Gravitational Groundwater Levels-A Two-Layered Groundwater Model
Authors: Morner Nils-Axel
Published: November 2024

The equipotential sulfate of the rotational and gravitational potentials corresponding to the density of water is known as 'geoid'. A continental geoid surface of water called the hydro-geoid separating two distinct masses of groundwater is proposed. The flow pattern, potential water outflow and water mass balance markedly differ between the groundwater above and below the hydro-geoid level. A two-layered groundwater model with clear distinction between the actual, 'dynamic', groundwater level and the 'gravitational' (hydro-geoid) groundwater level is advocated. The hydro-geoid level is deformed by the tides and, in the long-term range also, by all other factors affecting the gravitational and rotational potentials.
Remote Sensing and Isotope Techniques in Understanding the Hydrology of Volcanic Areas-A case study
Authors: Kayane Isamu , Shimano Yasuo , Sakura Yasuo , Kitaoka Goichi
Published: November 2024

Volcatlic area has special hydrological characteristics such as scanty overland runoff, abundant springs, large storage capacity and long residence time of groundwater. A methodology of groundwater field survey is discussed taking Aso volcanoes in Japan as an example. Utility of stream network analysis, remote sensing techniques, numerical simulation and isotope techniques are shown with examples.
Landuse and Land Protection in Mining Areas- A Case Study in Jharia Coalfield
Authors: Ghosh Rekha
Published: November 2024

Some countries have enacted specifiic legislations for landuse management in mining areas. The position in India is causing serious concern and the Government has taken active interest to control land degradation. One among various protective measures taken in India is aforestation, because, green-belts, other than agriculture, have enviornmental utility. Landuse management in mining areas is concerned mainly with environmental degradation due to mining, the focal subject being waste disposal and quarry and goaf filling.

Landuse management schemes taken up by some mining areas in India have been discussed. As a specific case, the Jharia Coalfield has been studied in detail. A landuse map of the area has been prepared based on study of aerial photographs and maps. The landuse management scheme suggested in India has not yet been properly implemented. Some steps to help the rapid development of the scheme has been suggested.
Iron-Titanium Oxide Geothermometry for some Deccan Trap Tholeiitic Basalts, India
Authors: Sethna S. F. , Czygan W. , Sethna B. S.
Published: November 2024

The oxygen fugacity and temperature of equilibration of the iron-titanium oxides for thirty samples of basaltic rocks, taken from different parts of the Tholeiitic Flood Basalt Province of Deccan Trap (Tertiary); are given. Temperatures range from 950° to 1200°C and oxygen fugacity from 9 to 12 (as -log10). Picritic basalts from Igatpuri along the Western Ghats, that form compound lava fiows, give lower temperatures of equilibration of the iron-titanium oxides (considered to represent the liquidus of the host rock) as compared to the simple thin lava flows of normal tholeiitic basalt from the eastern parts of the Deccan trap outcrop.
Distribution of Dinocysts in the Jurassic Rocks of Kachchh, India
Authors: Kumar Arun
Published: November 2024

A list of dinocysts is provided for the Jhura Dome Section (Jhurio Formation of Upper Bathonian to Callovian age) and Khari Nadi Section (Middle Member of the Jhuran Formation of Lower Kimmerdgian to Tithonian age) of Kachchh. These dinocyst assemblages are compared with the assemblages of dinocysts of equivalent age described from different parts of the world. A new dinocyst Forma-A is described from the Jhura Dome section.
Contrasting Volcanic Suites in Naga Hills and Their Bearing on the Tectonic Evolution of the Naga Hills Ophiolite Belt, N.E. India
Authors: Venkataramana P. , Datta A. K.
Published: November 2024

The 200 km long Naga Hills opiliolite belt which forms the northern part of the Indo-Burman ophiolites is made up of two contrasting volcanic suites. viz.; (1) high-Mg basalts (Mg-number 52 to 71) comparable to mid-oceanic ridge basalts and (2) low-Mg (Mg-number 23 to 49) akin to seamount type volcanism.

Based on geological and geochemica 1 evidences, a three stage model comprising (1) marginal basin spreading event, (2) seamount event and (3) collision event, is presented to explain the origin and evolution of the Naga Hills ophiolites.
Biostratigraphy of Jurassic Chari Formation: A Study in Keera Dome, Kutch, Gujarat
Authors: Bardan Subhendu , Datta Kalyanbrata
Published: November 2024

A biostratigraphic subdivision has been proposed in 210 metres-thick Jurassic Chari Pormation exposed around Keera, Kutch. Evaluation of the relevant pieces of earlier works and new findings emerged in course of present study allow establishment of six distinctive assemblage-zones especially on the basis of rich cephatopod biota. These biozones are largely facies transgressive and hence are often not correlatable with lithofacies distribution. A possible correlation between these biozones at Keera and those established in the type section at Jumara, Kutch from the earlier work has also been attempted.
Otoceras and the Permian-Triassic Boundary
Authors: Guptai V. J. , Hongfu Yin
Published: November 2024

The present paper aims at re-evaluation of Otoceras as the criterion of basal Triassic and its bearing on the Permian-Triassic boundary.
Geochemistry and Environmental Significance of Banded Garnet Amphibole rock (BGA) Around Naurhiya, Bijawar Group in Sidhi District, Madhya Pradesh
Authors: Bandyopadhyay B. K. , Roy Abhinaba
Published: November 2024

Occurrence of thin but persistent horizons of banded garnet-amphibole-rock (BGA) is reported from the Proterozoic Bijawar or Mahakoshal Group in Sidhi district, Madhya Pradesh. The physical appearance, mineralogy and chemistry of the rock are closely comparable to some metamorphosed manganiferous iron-formations. The rock occurs in association with a sequence of low-grade metasediments, mainly comprising wacke and argillites together with subordinate quartz arenite, banded magnetite quartzite, limestone, tuffs and basic volcanics, which bear similarity with the sediment-hosted Algoma type iron formation. Although there is a broad similarity in the composition of the Bijawar BGA rocks with the known B1F of the world, the former showsan appreciable enrichment in A12O3, MnO, MgO, CaO, Ba, Zn, Co, Ti, Y and V compared to the latter.
Are Patna and Bisanattam Granites (Adjoining the Kolar Schist Belt) cogenetic?
Authors: Rajamani V. , Krogstad E. J. , Hanson G. N. , Balakrishnan S.
Published: November 2024

Structural and geochemical evidence including major and trace elements, and Pb-isotopic data on K-feldspars, froin the granitoid rocks adjoining the Kolar Schist Belt are presented to show (1) that the Patna Granite an the NW of the belt is dissimilar to any granitoid rock E of the belt and (2) that the main granitoid gneiss immediately E of the belt, the Karnbha Gneiss, is nearly identical to the Bisanattam Granite of Narayanaswamy er al (1960).
Environmental Geology of the Ganga River Basin
Authors: Subramanian V. , Sitasawad R. , Abbas N. , Jha P. K.
Published: November 2024

The lithology of the Ganga basin especially the carbonates of the recent alluvium, controls the river water chemistry. Illites and kaolinite are the dominant clay minerals in the suspended sediments. The average TOS is 171 ppm and essentially reflects the Indian river-water average.

Considering the sediment transport at Farakka (744 million tonnes/yr) as a measure, the Ganga is placed as the third largest sediment transporting river of the world after the Yellow and Amazon rivers. Basin area and discharge, rather than the basin elevation, control the erosion rate. The total erosion rate (549 t/km2/yr) of the basin at Calcutta is almost three times that of Amazon and three and half times that of the world average (150 t/km2/yr).

The high sedimentation fate (42 mm/yr) in the Yamuna around Delhi is mainly due to the solid waste supply from urban areas. For selective heavy metals, the total drain anthropogenic contribution to the river Yamuna is Mn (42%), Fe (76%), Cu (62%), Zn (90%) and Pb (50%) of the metal increase in the sediments from Wazirabad to Okhla. Excellent correlation among Cu, Zn and Pb in the core and in surface sediments indicates their common source. The additional metals carried into the surface and core sediments of the Yamuna due to increased human utilization of the river basin are in relatively mobile fractions of the sediments and hence pose clear environmental hazards.
Geothermobarometry of the Central Crystallines from the Garhwal Himalaya
Authors: Gairola V. K. , Ackermand D.
Published: November 2024

Pelitic schists, gneisses and amphibolites from the Central Crystallines of the Garhwal Himalaya display evidence of multiple deformation (D1, D2 and D3) and polymetamorphism (M1, M2 and M3)' During the M1 episode of regional metamorphism which represents a thermal peak, the pelitic schists and gneisses developed the assemblage: sillimanite-kyanite-garnet- biotite-plagioclase-K-feldspar-quartz±garnet. Widespread development of garnet and sillimanite (locally kyanite) in muscovite-bearing schists and gneisses, hornblende in amphibolites, and diopside in calcschists indicate prograde metamorphism in the sillimanite-muscovite zone of the amphibolite facies. During the M2 and M3 episodes the higher grade rocks of the M1episode retrograded under PT conditions of greenschist facies.

The electron microprobe analyses of coexisting minerals from the schists. gneisses and amphibolites have been used to estimate the PT conditions of metamorphism during the Ml episode through the pertinent models of geothermobarometry. These models of geothermobarometry suggest temperatures of 645°C±50°C and pressures of 7.5±0.5 kb during the thermal peak of metamorphism (M1 episode).
Geology and Tectonic Setting of Central Crystalline Rocks of Southern Part of Higher Himachal Himalaya
Authors: Kakar Ramesh K.
Published: November 2024

The granitic, gneissic and schistose metamorphic rocks of Central Crystalline Zone in the southern part of Higher Himachal Himalaya exposed at Wangtu, Karcham, Sangla, Kalpa, Spilu and adjoining areas of Satluj and Baspa valleys have been investigated and classified into Wangtu Gneissic Complex, Karcham Group and Haimanta Group on the basis of lithology, rock association and tectonic setting. The Wangtu Gneissic Complex represents the oldest basement exposed in this part of the Himalaya and is of deep crustal origin. The klippen of Jutogh rocks in the Lesser Himalaya, especially that of the Chor area, is comparable with the Karcham Group.
Nature and Behaviour of Fractured Hard-Rock Aquifers of the Kandy District, Sri Lanka
Authors: Wilbert Kehelpannala K. V.
Published: November 2024

This paper deals with the hydrogeological properties of the groundwater resources of the Kandy District of Sri Lanka. The main groundwater resources of the district are fractured crystalline hard-rock aquifers. These crystalline hard-rocks comprise quartzites, charnockites, granites, granitic gneisses, khondalites, quartzo-feldspathic rocks, gneisses, migmatites, calc-silicate rocks, and marbles of Precambrian age. The behaviour of these rocks as fractured aquifers is completely different from rock to rock, and is, to a great extent, controlled by the tectonic lineaments (fracture zones, joint zones and fault zones) of the area. It would appear that a considerable amount of groundwater, the yield ranging from 50 l/min. to over 1500 l/min., can be exploited along the lineaments.
Asyrnmetry in Two Rhynchonellid Species from the Jurassic Formations of Kutch, Western India
Authors: Ghosh Diptendu N.
Published: November 2024

Sphenorhynchia asymmetrica (Kitchin) from the upper and upper middle Macrocephalus Beds of Middle Callovian age and Rhactochynchia pseudoinconstans (Kitchin) from the Lower Patcham Beds of Upper Bathonian age of Kutch, Western India, show typical asymmetry in their shell development. This is particularly noticeable at the anterior commissure. This is compared with similar asymmetric features exhibited by other brachiopod species from different parts of the world. On the basis of the nature of asymmetry in the two Kutch species, the strength of numerical observation in them and on a consideration of the reproductive mechanisms in brachiopods, it is suggested that the asymmetric developments in these two species has led to an easily recognisable dimorphism which possibly is reminiscent of sexual dimorphism.
Petrology of the Elchuru Alkaline Pluton, Prakasam District, Andhra Pradesh, India
Authors: Madhavan V. , Leelanandam C.
Published: November 2024

The oblong alkaline pluton at Elchuru is constituted of shonkinite, malignite, nepheline syenite (foyaite and pulaskitic foyaite) and nepheline gneiss (including litchfieldite and mariupolite); the bulk of the pluton is, however, made up of nepheline syenite and nepheline gneiss. These alkaline rocks are emplaced conformably and permissively by a simple mechanism of dilation of the surrounding country rocks under tensional stress. During emplacement, the pluton deformed its own nearly solid periphery producing an outer ring of nepheline gneiss with subsolvus assemblage which surrounds the central core of nepheline syenite with hypersolvus assemblage.

The field, petrographic and geochemical studies, when viewed together, suggest that all the rocks of the pluron arc comagmatic and that nepheline syenites (and nepheline gneisses) are the differentiated products of a basic alkaline magma. The present study has shown that the alkaline magma remained strongly undersaturated throughout the differentia tion process.

The agpaitic coefficient of these rocks is very near to, but invariably less than unity. In tune with their miaskitic chemistry, these rocks show low Na2O/K2O and Fe2O3/FeO ratios and a generally lower content of MgO, TiO2 and MnO. The contents of Sr and Ba are very high and with differentiation the ratios Ba/Sr and Sr/Ca fall whereas K/Ba ratio rises. The uniformly higher KJRb ratios of these rocks suggest a deep seated source for the magma.
Tectonometamorphic Evolution of the Great Himalayan Thrust Sheets in Garhwal Region, Kumaun Himalaya
Authors: Roy A. B. , Valdiya K. S.
Published: November 2024

The so-called 'Central Crystallines' building the bulk of the Great Himalaya (=Himadri) comprise two major tectonic units. The upper unit is constituted of highgrade psammitic metamorphics associated with anatectic granites of the Vaikrita Group, and the lower unit is made up of Precambrian granites, gneisses, amphibolites, meta-sediments and their mylonitic equivalents recognized as the Munsiari Formation. The Vaikrita Group makes a huge lithotectonic slab bounded by moderately inclined Main Central (Vaikrita) Thrust in the south and the steeply dipping Trans-Himadri (Malari) Thrust in the north. Sandwiched between the Munsiari and the Main Central (Vaikrita) Thrusts, the Munsiari is a severely tectonized and drastically condensed lithotectonic sheet representing the root zone of the Lesser Himalayan crystalline nappes.

In small-scale, the Vaikrita shows extremely intricate internal deformation resulting from polyphasal folding and repeated transposition of foliation planes. The bulk non-coaxial strain in the rocks is attributable to the variation in the case of slip on the shear planes during thrust propagation. The period of thrusting is coeval with the main phase of progressive metamorphism, anatexis and attendant granite emplacement during the late Eocene to Lower Miocene period. Later deformation and retrogressive metamorphism are related to the uplift during the Middle and Upper Miocene, culminating in the Middle Pleistocene, when the Vaikrita rocks were brought to a brittle field of deformation from the earlier ductile and brittle-ductile fields.

The Vaikrita exhibits an abrupt rise in the grade of metamorphism to sillimanite zone of progressive (Barrovian type) metamorphism from a very low to medium grade of (Himalayan) metamorphism in the Munsiari. In the deeper level (~30 km), the Vaikrita rocks underwent progressive regional metamorphism and anatexis that gave rise to granites, which extensively invaded the metamorphics. The episodic uplift of the Vaikrita Group was due to the shifting of thrust movements by relay from the Main Central (Vaikrita) Thrust, to the Munsiari Thrust and the other minor thrusts of the schuppen zone in the south. A part of the uplift can be attributed to the diapiric rise of the anatectic granites.
Geology and Structure of the Area Around Naswadi With Special Reference to Bagh Bed Exposures, Baroda District, Gujarat
Authors: Karanth R. V. , Sant D. A. , Shah N. C.
Published: November 2024

Geologically the area around Naswadi comprises Precambrian metamorphics and granite, Bagh Beds and Deccan Traps. The various formations have been dislocated at several places owing to tectonic movements along the Narmada Rift Zone. Most of the fau1ts lie parallel to the main Narmada lineament, e.g., ENE-WSW, and they have been further dislocated by NW-SE fractures.
Influence of Basement Tectonics on the Delhi Sedimentation in the Bayana Graben, Northeastern Rajasthan
Authors: Singh S. P.
Published: November 2024

The Bayana graben contains over 3000m thick volcano-sedimentary sequence classified into the Raialo, the Alwar, and the Ajabgarh Groups of the Delhi Supergroup. The sedimentary pile consists of several sedimentary facies of fluvial to marginal marine environments. The volcanics show alkaline to high-K-tholeiitic affinity indicating continental magmatic environment.

The basin is characterised by a set of synsedimentary dislocations which have controlled basin evolution, magmatism, and sedimentation. Based on the distribution patterns of various stratigraphic units and their sedimentological framework, a five-stage evolutionary sequence of the basin and associated sedimentation patterns have been discussed.
Carbon Stable Isotopes of Fluid Inclusions in the Granulites of Southern Kerala: Implications for the Source of CO2
Authors: Santosh M. , Jackson D. H. , Mattey D. P. , Harris N. B. W.
Published: November 2024

Carbon dioxide-rich inclusions commonly occur in banded charnockites and khondalites of southern Kerala as well as in incipient charnockites formed along oriented zones by desiccation of gneisses. Combined pressure-temperature data from solid phases and CO2 equation of state barometry from fluid inclusion isochores depict that high density carbon dioxide was the dominant ambient fluid species in all the three rocks. Carbon stable isotope analysis of the fluids using a stepped heating technique in samples collected from Ponmudi, Kottavattom, Manali and Kadakamon show that the banded charnockites and gneisses contain ca. 50-60ppm carbon with d13C values in the range of -8 to -12.3‰. The incipient charnockites are characterised by abundant CO2 (upto 200 ppm) with d13C in the range, -7.5 to -10.3‰. The carbon stable isotope value of + 1.2‰ obtained for calc-silicate is in ccntrast to the value for the intercalated banded charnockite from Kadakamon (-10‰) depicting that decarbonation was not the source of CO2, Whereas the heavier carbon-enriched nature of incipient charnockite from Manali may suggest a juvenile source, the carbon isotope values in Ponmudi and Kottavattom suggest a mixed source, possibly due to the interaction of externally derived CO2 with graphite in the rocks.
A Jurassic-Cretaceous Dolerite Dike from Sri Lanka
Authors: Yoshida M. , Funaki M. , Vitanage P. W.
Published: November 2024

A dolerite dike from southwestern Sri Lanka gave whole-rock K-Ar ages of 152.6 ± 7.6 Ma and 143.3 ± 7.2 Ma. Many of the other dolerite dikes of Sri Lanka are considered to be of Mesozoic ages judging from the present age data and tectonometamorphic history of Sri Lanka. Petrographic similarities should not be used for age correlations, because dolerites of different age may have the same petrography.

Preliminary natural remanent magnetization (NRM) after AF and thermal demagnetization gave a mean inclination of 24.6° and declination of 67.5° with a95=21.7°. A virtual geomagnetic pole position calculated from the mean NRM was rotated relative to Antarctica so as to fit with that obtained from the Jurassic Ferrar dolerite of Antarctica. This rotation results in the location and attitude of Sri Lanka to attach with Antarctica at Lutzow-Holm Bay as suggested by Barron et al. (1978).
Strain Analysis in a Part of the Chamba Syncline using Deformed Quartz Pebbles in Chamba Region of Northwestern Himalaya
Authors: Singh Keser , Thakur V. C.
Published: November 2024

Samples of deformed pebbles in the slates from the Manjir Formation were collected from normal and inverted limbs of the Chamba Syncline. The axial ratios and orientation on two dimensional sections were determined from deformed quartz pebbles. The finite strain was calculated using Rf/f technique. The two dimensional data were combined to give three dimensional finite strain and type of strain experienced by the pebbles at each locality. Regional variation in the strain distribution is represented by finite distortional strain (es) for both normal and inverted limbs of the syncline. The results show that the deformation is of flattening type and the amount of strain increases from inner arc to outer arc of the Chamba Syncline. A total of about 28 per cent shortening has been noticed in the Manjir Formation.
Geochemistry and Genesis of Two Late Precambrian Granite Plutons of Bihar Mica Belt, Eastern India
Authors: Sarkar S. S.
Published: November 2024

Two granite bodies, namely the Banresar and Manihari plutons, which are intrusive into the metasedimentary sequences of the Bihar Mica Belt, have been geochemically investigated.

The major trace and REE compositions of 21 granite samples indicate a crustal derivation of these granites from ~23% partial fusion of a granodioriric-tonalitic component of the crystalline basement of Chhotanagpur gneissic terrain, (relics of which occur as enclaves within the plutons) followed by (a) ~ 39% fractional crystallisation of quartz; two feldspars, and hornblende from this granitic melt and (b) emplacement of the differentiates within domical metasedimentary upwarps at about 17km depth (= 5 kb), during second phase of folding in this region. Mild activity of a residual alkali-rich vapour phase, mostly active through central portion of these plutons and gradually migrating towards periphery, gave rise to a spatial trace clement heterogeneity in these bodies.

he calc-alkaline character of these granites, along with their syntectonic emplacement into a sedimentary veneer having the polydeformational signature of Satpura orogeny, indicates a compressional tectonic regime. which might have caused a down buckling of the Chhotanagpur crystalline basement, leading to its partial fusion, to generate the parental granitic magma.
Fe-Chlerite, Grunerite, Stilpnomelane, Ankerite and Siderite Occurrence in the Iron-Formation of Chiknayakanhalli Schist Belt, Karnataka
Authors: Laajoki Kauko , Devaraju T. C.
Published: November 2024

Electron probe microanalytical data is given for Fe-chlorite (31% FeO) and grunerite (31.4% FeO) occurring in the mixed oxide-silicate facies iron-formation and for ankerite (av. 17.5% FeO), siderite (av. 44,2% FeO) and stilpnomelane (31.6% FeO, 5.9% Al2O3, 2% K2O) in the carbonate iron-formation of Chiknayakanhalli Schist belt. While Fe-rich chlorite, ankerite and siderite appear to represent recrystallized diagenetic and primary sedimentary phases of the same minerals, grunerite has formed from metamorphic alteration of minnesotaite and stilpnomelane from a montmorillonite (nontronite?)-like precursor. The minerals identified in the iron-formation fit into the overall greenschist to low amphibolite facies metamorphism witnessed by the schists.
A Note on the Establishment of Gravity Base at Marmagoa
Authors: Ramadass G. , Varaprasada Rao S. M.
Published: November 2024

Ten new gravity base stations have been established by the Centre of Exploration Geophysics in the gap between Londa Railway Station and Marmagoa Port. Details about the descriptions of bases and their values arc presented
Quaternary Geology of Kerala : Evidence from Radiocarbon Dates
Authors: Rajendran C. P. , Rajagopalan G. , Narayanaswamy
Published: November 2024

An event of transgression (8000-6000 Y.B.P.) and another event of regression (30Q0..5000 Y.B.P.) which gave rise to extensive peat and shell deposits during Holocene in Kcrala is recorded. The initiation of the backwater system in Kerala is linked to these events.
Significance of Small-Scale Structures in the Kolar Schist Belt, South India
Authors: Mukhopadhyay Dilip K.
Published: November 2024

Well-preserved small-scale deformational structures in the banded ferruginous quartzite in the Kolar Schist Belt indicate four phases of folding (F1- F4 ) , and a shearing movement at low angle to the foliation planes. Both the F 1 and F 2 folds are very tight to isoclinal with attenuated limbs and sharp hinges. They are nearly (but not strictly) coaxial, resulting in type-3 interference pattern. The F3 folds are open and recumbent or gently plunging reclined with axial trend towards NNE-SSW. The folds of the fourth generation (F4) are of the nature of warps with vertical axial planes striking NE through E to SE. It is suggested that the F1 folds were originally isoclinal and recumbent/gently plunging reclined with northerly axial trend, coaxially refolded by upright and isoclinal F1 folds. As the F2 folds became isoclines further squeezing in the same direction was accommodated by a subhorizontal shearing movement at low angle to the foliation planes. resulting in wide variation in plunge of F1-F2 fold axes. The F1-F2 folds and mesoscopic shear zones developed due to an E-W subhorizontal compression acting over a protracted period of time. The F3 folds developed due to gravity induced vertical compression on subvertical foliations. whereas the F4 folds indicate a longitudinal shortening during the relaxation period at the waning phase offolding episodes.
Genus Anisomyon (Gastropoda) from the Cretaceous of Southern India
Authors: Ayyasami K.
Published: November 2024

A new species of the patelliform gastropod genus Anisomyon is reported for the first time from the Indian Cretaceous sediments. Its occurrence, palaeoecology and stratigraphic importance are discussed. A stereopair photograph of this important fossil is given for better resolution.
Hot Vents and Massive Sulphide Bodies on the Southern Parts of the East Pacific Rise (EPR) Seafloor Spreading Centres: Geometep-4
Authors: Roonwal G. S.
Published: November 2024

New ore bodies of sulphide on the diverging plate boundaries on the East Pacific Rise were discovered during the German Expedition Geometep-4 in the South Pacific. The marine sulphides occurring along the rift system are attributed to large-scale hydrothermal circulation through the fractured volcanic rocks on the seafloor. Such hydrothermal plumes in contact with basalt, result in leaching of metals and their subsequent reconcentration and deposition. Certain transition metals such as Cu Zn Fe get concentrated in the form of disseminated, stockwork particulate deposits that may hold commercial value. The occurrence of these deposits on the seafloor can be traced by certain geological, geophysical and biological tools.
Avian Egg Shells from Pleistocene of Kutch
Authors: Mohabey D. M.
Published: November 2024

Fossil avian egg shell fragments are described from the Kothara Formation of Pleistocene age, south of Naliya in Kutch District, Gujarat. This is the first record of avian egg shells from western India.
Morphometric Studies on a part of Central Indian Ocean
Authors: Kodagali V. N.
Published: November 2024

Morphometric and slope angle studies carried out on a part of Indian Ocean Basin have shown that gentle slope angle ranges dominate, 92% of the area represented by 0-3° slopes. Young's hypothesis of log-normal distribution of slope angle frequencies is found to be valid for deep sea topographic data also. Elevation-relief ratios and ruggedness values are relatively high for the southern portion of the study area whereas these values are less in the northern portion. Some of the features like abyssal hills and the seamount recorded in the region might have been formed due to volcanism. Some secondary topographic features could have resulted due to post-depositional processes. Slope angle, elevation-relief and ruggedness can be used in inferring certain features in the oceanic surface.
Undaturbidite in the Talchir Group, Talchir Gondwana Basin, Orissa
Authors: Pandya K.L.
Published: November 2024

A sedimentary sequence constituted of interbedded sheet sandstones and shales and lenticular channel sandstones exhibits a number of sedimentary structures common in turbidites. These are various types of sole marks, graded bedding, ripple-drift cross laminations, parallel laminations and asymmetric current ripples. The sheet sandstones. show characteristic internal vertical arrangement of structures identical to turbidite sequences while the shales are laminated. Besides, a few rolled boulders and cobbles are found within the sequence.

The combination of sedimentary structures suggests origin by a turbidity current mechanism. The association of lenticular channel sandstones, rolled boulders and cobbles and the grain-size characteristics, on the other hand, suggest it to be undaturbidite, having the characteristics intermediate between tractive and turbidity current deposits. The probable depositional environment of the sequence is discussed.
Some New Data on the Genesis of Granitic Pegmatites
Authors: Shmakin B. M.
Published: November 2024

The correlation between the type of mineralization in granitic pegmatites and the depth of their formation is supported with new data. The fluid pressure in pegmatites is 2-3 times greater than that of the calculated lithostatic pressure due to the over-pressure of volatiles in the closed pegmatite system. Experimental work shows that during cooling the pegmatite melt saturated with volatile components divides into two or three fluids. Such a 'liquation' provides an explanation for many of the complex structures and peculiarities of the mineral composition obsei ved in pegmatites.

In many regions heterogeneous pegmatites (primarily magmatic or metamorphic) may converge through the processes of albitization and muscovitization. A specific group of post-magmatic pegmatite-like bodies can be formed as well.
The Prakasam Alkaline Province in Andbra Pradesh, India
Authors: Leelanandam C.
Published: November 2024

The Prakasam alkaline province is essentially composed of three major nepheline syenite plutons at Elchuru, Purimetla and Uppalapadu, and one silica-oversaturated (syenite and quartz syenite) pluton at Settupalle. These four post-orogenic plutons, all occurring in the Prakasam District of Andhra Pradesh, display dissimilar internal structures and variable rock associations; they are almost exclusively salic and generally show evidence of passive emplacement.

The gross petrographic characteristics of the individual plutons are presented, and a generalised discussion on the petrogenetic aspects is included. The undersaturated and oversaturated syenites of the province are supposed to have formed from a critically undersaturated hornblende syenite magma by branching differentiation mechanism. The gabbros represent tholeiitic magmatism preceding the emplacement of alkaline rocks, and the ferrosyenites represent the final product of a closed system fractionation (with Jow fO2) of magma that gave rise to gabbro-anorthosite complexes.

The geological setting of the plutons is portrayed and the tectonic significance of the province, especially in its regional context, is highlighted. The feldspathoidal plutons of the province are conspicuously confined to an extremely narrow linear belt which is close to the known basement fracture zone, with which the major Bouguer gravity axis runs in close paralJelism ; this belt lies at the junction between two (granitegreenstone and gneiss-granulite) terrains.

The localisation of feldspathoidaI plutons at the western margin of the middle Proterozoic mobile belt and their absence in the cratonic region is significant. The over-all development of the mobile belt is speculated in the light of currently fashionable tectonic models. Crustal shortening and thickening of the mobile belt due to collision tectonics, predate the emplacement of the alkaline plutons; the lithosphere controls the character of the magmatism, and pre-existing abyssal faults determine the location of alkaline magmatism.
Angular Unconformity Between Manikaran Quartzite and Chlorite Phyllite, Rampur Window, Kulu District, Himachal Pradesh
Authors: Sen D. B.
Published: November 2024

An angular unconformity between Manikaran quartzite and overlying chlorite phyllite is observed near Dharmoar, Parvati valley section of the Rampur window. The chlorite phyllites were deposited over the deformed and eroded surface of the quartzites. It is suggested that this unconformity has influenced the control of uranium mineralisation in the rocks of Rampur Group of the area.
Least Squares Modelling of Crystal Fractionation in Pavagarh Lava Flows of Gujarat
Authors: Mukherjee Pulok Kr. , Gupta Praveen Kumar
Published: November 2024

The Pavagarh Hill is made up of a lava suite comprising seventeen horizontal flows. Its geochemical variation provides compelling evidence that there exists genetic relationship among the various flows and hence it offers an interesting case study for crystal fractionation process. In this paper, least squares modelling, using the massbalance relation has been carried out, to determine the most probable phases and their amounts that must be extracted from or added to a flow to obtain the composition of the next younger flow. The stability of the model was tested by performing singular value analysis. The outcome of this modelling supports the hypothesis that the whole series is a result of crystal fractionation in two episodes with first and eleventh flow serving as the parent magma for the two sub-series. However, minor amount of magma mixing was needed to explain the evolution of lower series. Further, on the basis of the estimated phase proportions, that need be subtracted or added, the trace element abundances in derivative magma are computed, using Rayleigh fractionation law, and are found to be comparable with the observed values.
Stratigraphy of the Penganga Group Around Adilabad, Andhra Pradesh
Authors: Chaudhuri Asru K. , Dasgupta Somnath , Bandyopadhyay Goutam , Sarkar Subir , Bandyopadhyay P. C. , Gopalan K.
Published: November 2024

The Proterozoic sequence around Adilabad, Andhra Pradesh comprises a distinct lithostratigraphic unit of 'Group' status and has been given the name Penganga Group. The Penganga Group has been classified into three Formations which are, in order of younging, Pranhita Sandstone, Chanda Limestone and Sat Nala Shale. The sequence is dominated by limestones and shales which were deposited in relatively deep water environment and, thus, contrast sharply with the conglomerate, sandstone and shallow water limestones of the Pakhal Group. Radiometric dating of fresh glauconites from middle part of the Penganga Group gives an age of 770 ± 30 Ma. Thus, the Penganga Group is the youngest of all other Proterozoic sequences in Pranhita-Godavari Valley.
Basalt Microlapilli in Deep Sea Sediments of Indian Ocean in the Vicinity of Vityaz Fracture Zone
Authors: Nagender Nath B. , Iyer S. D.
Published: November 2024

Two cores recovered from the flanks of Mid-India oceanic ridge in the vicinity of Vityaz fracture zone consist of discrete pyroclastic layers at various depths. These layers are composed of coarse-grained, angular basaltic microlapilli in which labradorite is the major mineral set in a glassy mesostasis. Chemically the microlapilli are similar to Mid-Indian oceanic ridge basalts. The microlapilli are suggested to have been formed by the process of granulation, transportation and deposition, during Late Quaternary when lava of low viscosity erupted from small vents on a segment of Vityaz fracture zone.
On the Validity of the foraminiferal Species Globotruncana Renzi Gandolfi
Authors: El-Nakhal Hamed A. , El-Naggar Zaghloul R.
Published: November 2024

The validity of the Late Cretaceous planktonic foraminiferal species Globotruncana renzi Gandolfi, and the relationship between this species and Globotruncana angusti-carinata Gandolfi, are discussed. It is suggested that G. renzi be dropped since it is a junior synonym of G. angusticarinata.
Malanjkhand: Proterozoic Porphyry Copper Deposit, M.P. India
Authors: Sikka Deshbandhu
Published: November 2024

The Malanjkhand porphyry copper deposit is estimated to contain 789 million tonnes averaging 0.83% Cu @ cut-off-grade of 0.20% Cu, 0.004wt% Mo, 0.2 gm/T Au, 6 gm/T Ag. 448 million tonnes 0.84% Cu (millhead grade) are available for open pit mining to a depth of 100 MRL. The deposit can support a mine, mill, smelter and refinery complex to produce 100,000 TPY of cathode copper at an installed cost of US$557.126 millions.

The deposit is arcuate in shape, 2,600 meter long, 142 meter wide, 900 meter deep and open for exploration at depth across and along strike. The deposit consists of a large body of primary copper ore in granitic rocks and is overlain by a cap of oxidized ore (7.532 million tonnes 0.8 wt % Cu). The granitic rocks are biotite granite, quartz diorite, granodiorite and adamellite (quartz monzonite). The granitic rocks are 1684±67m.y. and 1816±73m.y., (Middle Proterozoic age). Hypogene alteration includes sericitization, saussuritization, chloritization, propylitization, silicification, potassic and sodic alterations. The main primary copper mineral is chalcopyrite. The secondary copper minerals are a number of copper sulfides, sulfates, carbonates, oxides, native copper and chlorides.
Probable Causes of the Failure of Kantalai Dam- Sri Lanka
Authors: de S. Jayawardena U
Published: November 2024

The Kantalai reservoir dam collapsed in April, 1986. National and international investigators have observed that the failure could have occurred mainly due to three reasons.

Firstly, failure of mortar joints in the sluice barrel, secondly, vibration effect that may have affected while installing a pump house by driving piles. Finally, dewatering of seepage water from the intake well during the stage of excavation for the same construction.

A brief geological investigation in the area around the dam-site of the oldest reservoir in Sri Lanka was carried out within the first 48 hours of the disaster. Geological structure, rock types and weathering conditions of the foundation rocks were visually observed with special attention to the locations where the failure occurred.

The block material, charnockite. is an excellent rock but showed signs of extensive spheroidal weathering. The author wishes to point cut that the failure to remove these weak residual materials prior to construction of the dam could have been a major contributing factor that led to reservoir leakage through these materials. Continuation of further weathering and erosion of finer particles due to leakage could have been another factor to accelerate the process of collapse of the dam. Observations evidenced that the joint orientation, rock foliation and its structure do not comply with the ideal geological requirements for a dam-site.
A Study of the Rare Illite Deposits Around Mujjur, Near Gadag, Karnataka State
Authors: Khoshroo Ali , Devaraju T. C.
Published: November 2024

Clays are localized in their occurrence to the sheared and deeply weathered rhyolite-rhyodacite). These contain illite in association with minor proportion of neoforrned chlorite and a large proportion of relic quartz. XRD, IR and thermal properties of Mujjur illite correspond to pure illite. The clays are characterized by higher alkalies (K20 4.7%), with correspondingly low PCE value of 1420°C, absence of swelling minerals and very low CEC and dye adsorption.
Archaean Shelf-Facies and Stromatolite Proliferation in Dharwar Supergroup, North Kanara District, Karnataka
Authors: Srinivasan R. , NAQVI S. M. , Vasantha Kumar B.
Published: November 2024

The stromatolitic cherty dolomite of KaIche is a lithostratigraphic equivalent of the carbonate rocks of the Joldhal Formation of Archaean age. Morphotypes suggest development in subtidal to lower intertidal zone of the Dharwar seas. Some of the forms observed near Kalche are comparable to the domical forms observed near Kumsi in the Shimoga schist belt and Vanivilaspura in the Chitradurga schist belt. The morphotypes observed in these regions contrast with the actively and passively branched columnar stromatolites observed near Dodguni and Bhimasamudra in the Chitradurga schist belt where the stromatolites evolved in an intertidal environment. Diversity of morphotypes of stromatolites appears to have occurred in the Archaean itself, although such diversity appears to have attained stratigraphic significance by the middle Proterozoic.
Terrace Evolution in the Jakh-Bargal Area, District Nainital, Kumaun Lesser Himalaya, Uttar Pradesh
Authors: Kumar Anjani
Published: November 2024

Three levels of depositional terraces are well developed along the Ghat Gad and Khairna valley suggesting three phases of uplift. The rate of deposition in the Ghat Gad valley might have been greater than the rate of uplift, while in the Khairna valley the rate of deposition perhaps lagged behind the rate of uplift. Waterfalls, debris. Fans and triangular fault facets also suggest uplift. Landslide debris have contributed towards the formation of terraces ( = T2 terrace) in Garjauli and Barga) areas. Drop IQ the river profiles of Khairna and Ghat Gad being of the order of 40 m/km and 100 m/km respectively, indicating that the Ghat Gad has a very high down-cutting capacity. The formation of new terraces in the area can thus be attributed to the continuing slow rise of the terrain and high down-cutting capacity of the rivers, west of Garampani fault.