bluuebunny/crossref_metadata_2025 huggingface dataset:
Petrology and Geochemistry of Hornblendic Rocks from Kanigiri-Gogulapalle Area, Andhra Pradesh
Authors: Rama Rao P. , Narasinga Rao A.
Published: November 2024

Hornblendic rocks (hornblende schists, amphibolites, and hornblendites) occur in intimate association with metasedimentary schists and granitic rocks in the Kanigiri Gogulapalle area of Andhra Pradesh, India. Field studies indicate that a majority of these rocks are possibly concordant intrusives, some of them being metasedimentary. Petrographic study shows that most of them consist of hornblende and plagioclase as essential minerals, whereas some are characterized by tremolite and plagioclase with accessory calcic minerals. Absence of detrital minerals and pyroxenic cores in the amphiboles characterize all the rocks.

Geochemical studies reveal that the rocks are most probably magmatic intrusives judged from the low Niggli k and high TiO2 values and the presence of high Sr, Cr, V, and Ni amongst the trace elements.
Tectonic Uplift of the Nellore Mica Belt, India, as Revealed by Fission Track Dating Technique
Authors: Parshad Rajinder , Lal Nand , Nagpaul K. K.
Published: November 2024

Fission track ages of two cogenetic minerals viz., garnet and apatite collected from the pegmatites of Nellore Mica. Belt of India, emplaced during the closing stages of the Eastern Ghats Orogeny (1500-1600 Ma) are found to be 1065 Ma and 440 Ma respectively. The data has been interpreted in terms of tectonic uplift of the pegmatites. The average rate of uplift for this region has been calculated as 0.04 mm/year.
Geochronological and Geological Studies on a Granite of Higher Himalaya, Northeast of Manikaran, Himachal Pradesh
Authors: Bhanot V. B. , Bhandari A. K. , Singh V. P. , Kansal Ashok K.
Published: November 2024

Rb-Sr whole-rock data is presented for a biotite-granite of Central Crystallines. The whole-rock isochron age is found to be 467±45 m.y. This should represent the time of intrusion of the granite. A brief account of the geology and petrography is also presented. The age of the biotite is found to be 8.8±2.0 m.y., which is the youngest Rb-Sr age reported so far for a mineral from the Himalaya. This fixes the period when the rocks of this area, after being heated and uplifted, cooled to a temperature of about 300°C.
Geology and Geochronology of Early Precambrian of the Ukrainian Shield
Authors: Shcherbak N. P.
Published: November 2024

The Early Precambrian of the Ukrainian shield is represented by geological formations older than 2.6 b.y. The Archean formations are established in three big regions of the Ukrainian shield. These regions are tectonic blocks. Each block is characterized by specific petrological and geological features. In each block the grade of metamorphism of the rock is different.

The metamorphic rocks are represented by three series and the granites are represented by three complexes.

In the lower parts of the section of the series, effusive rocks predominate and in its upper parts metamorphosed sedimentary rocks are predominant. The effusive rocks of acidic and medium composition are characterized by dominating quantities of sodium. Genetically acidic and medium rocks are the products of differentiation of tholeiite-basalt magma.

Geochronologically the complexes of granites are characterized in detail. These data were obtained on accessory minerals and correspond to 2.8 b.y. ± 100 m.y. Dates of about 3.0 b.y. were obtained on zircon from metamorphosed effusive rocks by means of U-Th-Pb isotope methods. The data obtained on micas of metamorphosed rocks reflect superimposed processes.
Study of Lead Isotopes for Investigating the Origin of Endogenic Deposits with Special Reference to Some Ore Deposits from India
Authors: Chernyshev I. V. , Safonov Yu. G. , Radhakrishna B. P. , Krishna Rao B. , Vasudev V. N. , Deb M.
Published: November 2024

The isotope composition of leads from ore deposits in general reflects the age of ore mineralisation and its genetical features. Two examples have been given to illustrate a direct connection of ore lead isotope composition with the source ore. Calculations of the model age from lead isotope data form the basis for genetic reconstructions of Precambrian deposits. Radical improvement in the accuracy of mass spectrometric isotope lead analysis has made possible the employment of two-stage and in some cases more complicated models for genetic reconstructions. The Penehanga Bay lead-zinc deposit and gold-silver deposits of South Dakota have been studied using high accuracy mass spectrometer. Both the deposits show that ore formation took place one to two billion years after craton formation, and lead present in ores originated at least from two different Sources.

Keeping this background of experience, fifteen galena samples from five sulphide and gold-sulphide deposits of the Indian Shield have been selected and determination of lead isotope composition has been carried out by the Soviet authors in the USSR using recently developed M.I.1320 Mass Spectrometer. The isotopic ratios of galena from Ingaldhal copper deposit are the most primitive among the analysed ores of the Indian Shield. The results of lead isotopic determination have been interpreted in terms of the general theory of 'plumbotectonics '.
Gravity Field, Structure and Tectonics of the Raniganj Coalfield - Three Dimensional Model
Authors: Verma R. K. , Bandyopadhyay T. K. , Mukhopadhyay Manol
Published: November 2024

A residual Bouguer gravity anomaly map of the Raniganj Coalfield, West Bengal, India, has been prepared using graphical method of regional and residual separation. The gravity anomaly map reveals a minimum residual gravity of the order of -27 mgal in the central part of the coalfield. The residual gravity field over the basin has been interpreted in terms of the Gondwana sediments overlying the crystalline metamorphic rocks, using a three dimensional model with the help of computer programme given by Strange and Woollard (1969). A density contrast of -0.37 gm/cm3 between Gondwana sediments and metamorphic rocks has been used for calculations. The maximum thickness of sediments filling the basin is estimated to be 2.9 km in the central part of the basin. The basement depths obtained by three dimensional analysis are correlated with available borehole data in the coalfield and are found to give a good indication of the reliability of the model constructed.
Alluvial Fan Model for the Himalayan Piedmont Deposits
Authors: Roy Subimal Sinha
Published: November 2024

The Ganga-Brahmaputra fluvial plains are separated from the Himalayan foothills by the extensive piedmont belt. Four longitudinal large-scale terraces that have sequentially developed are recognised ill the interfluvial region of the Tista and the Jaldhaka rivers. These terraces are composed primarily of Boulder Beds and Gravel Beds, and of subordinate Sand Beds, and show rapid facies variations. These deposits are dissected by streams into cut and fill type transverse small-scale terraces. The evolution of the Himalayan piedmont tJelt is consistent with a dynamic alluvial fan model in which the sediments are considered to have been derived through upliftdependent episodic debris-flows and rrtass emplacement. The vertical and lateral accretion of the fans is in consequence to shifting of the mountain front, and to flattening of the stream gradient in the mountains. The hinge-lines of the fans migrated toward south with time, while the transitional zones between the fanglomeratic and the floodplain facies, toward north. Several empirical relationships in the magnitude-frequency matrix between uplifting, terracing and fan-formation are suggested.
Development of Flexural Slip Folds, Overlapping Boudins and Extension Faults in Multilayered Materials: Field Evidence and Experimental Model
Authors: Dubey A. K. , Behzadi H.
Published: November 2024

Structural features of natural chevron folds were studied in north Cornwall, England and an experiment was performed to simulate these structures. The study reveals that the amount of interstitial flow (Biot, 1965) varies along the fold limb and this variation is attributed to the formation of, (1) limb thinning and hinge thickening, (2) variation in the intensity of development of extension faults along the fold limb, and (3) development of overlapping boudins.
Structures in the Tethys Himalayas and their Tectonic Significance
Authors: Kanungo D. N. , Murthy D. S. N.
Published: November 2024

Structural studies of Tethys sediments between Malari and Lapthal show development of many minor structures e.g. - 'cleavages, tension and shear fractures' - which have been utilised to deduce the stress fields responsible for the deformation of these rocks. The primary sedimentary structures such as bedding, current bedding suggest shallow deposition conditions. The shape of folds, the fracture cleavages, quartz and calcite filled tension gashes and other fractures, and the thrusts are all taken as evidence for 'shallow-level' deformation of these rocks in which 'brittle deformation' was dominant.

The study suggests that major compressive stress responsible for the deformation of these rocks was always directed northeast-southwest and was lying sub-parallel to the earth's surface, the P-intermediate was directed NW-SE and was also horizontal, while the P-minimum was always invariably perpendic:ular to the earth's surface. Hence, it is concluded that these rocks have been deformed by horizontal compression and it appears that the major push was from the SW in this part of the ranges.
Sulphur Isotope Abundance Variations in Sulphides of the Dharwar Craton-Part I: Kalyadi
Authors: Menon A. G. , Venkatasubramanian V. S. , Ananta Iyer G. V.
Published: November 2024

Sulphur isotope abundance variations in chalcopyrite, pyrite and pyrrhotite samples from the sulphide deposits of Kalyadi have been measured with a double-collector mass spectrometer provided with digital ratio recording. The results fall into two groups - one with a near-zero per-mil value and another with a small positive value ~5‰. Data on coexisting sulphide minerals enable temperatures of deposition to be calculated, these being low ~250° C. The Ohmoto-procedure is adopted, and the range of d34S values of the minerals explained by assuming an initial total sulphur d34STS value and a range of pH and fO2 values that are plotted on an fS2 - fO2 diagram consistent with the stability fields of the minerals.
Hogbomite from Fe-Ti Deposits of Madangere, Ankola Taluk, Karnataka
Authors: Devaraju T. C. , Uttangi V. H. , Coolen J. J. M. M. M.
Published: November 2024

Hogbomite analysing 59.94% Al2O3, 6.01% TiO2, 0.21% V2O3, 21.02%, FeO, 0.14%, MnO, 9.66%, MgO and 1.06% ZnO occurs as a widely distributed mineral phase in the vanadiferrous Fe-Ti ore deposits of Madangere area. It occurs in well developed prismatic crystals, and small scales/rods/patches enclosed in magnetite ore grains, and locally as rims to spinel. While the coarse prisms of hogbomite bear characters of primary mineral phase, the small scales/rods/patches appear to represent exsolved phase and that forming rims to spinel is derived by the alteration of spinel. The mineral is reported for the first time from India.
Petrogenesis of Amphibolites in the Kolar Schist Belt, India-A Preliminary Report
Authors: Rajamani V. , Shivkumar K. , Hanson G. N. , Granath J. W.
Published: November 2024

The amphibolites in the Kolar schist belt include four textural types, schistoic, granular, massive and fibrous and occur in abundance in that order. The fibrous variety consists of two coexisting calcic amphiboles (A1 rich hornblende and A1 poor actinolite). The other three varieties contain hornblende and plagioclase (An40 to An85). The texture, mineralogy and mineral chemistry suggest metamorphism in the middle to upper amphibolite facies.

Major and Rare earth elements (REE) data indicate that (a) the fibrous amphibolite is somewhat similar to high-Mg basalts of Archean greenstone belts but with a strongly, heavy REE depleted pattern, (b) the other three varieties are similar to low-K oceanic tholeiites with slightly light REE depleted patterns and with strong positive Eu anomalies, and (c) the two groups do not represent primary melt compositions generated by the partial melting of a pyrolite mantle. It is concluded that the Kolar amphibolites must have been evolved from at least two separate parent magmas generated from different temperature and pressure (depth) conditions.
Geomorphic Evolution and its Significance in Exploration Planning of the East Coast Bauxite Deposits of India
Authors: Ramam P. K.
Published: November 2024

The East Coast Bauxite deposits top either the Khondalite or Charnockite Group of Archaean rocks that constitute the bulk of the Eastern Ghat physiographic province. Subsequent to the Eastern Ghat orogeny (1400-1600 m.y.), faulting in Mesozoic was the major tectonic event recorded in the Indian Peninsula.

The Eastern Ghat terrain was subjected to uninterrupted planation in the intervening period. The attainment of a clear macro-relief instead of a featureless plain (peneplain) is visualised as a consequence. This macro-relief, possibly modified to some extent due to Mesozoic faulting, after attaining stability and with the onset of monsoonal climate in upper Cretaceous promoted the process of residual chemical weathering. Chemical leaching was accentuated and optimised during Upper Tertiary-Quaternary period when there was copious rainfall with less of evapo-transpiration, resulting in thick bauxitic duricrusts. This view is at variance with the concept of an once extensive residuum formed at lower levels and what are now seen at high altitudes are their erosional relics, owing their elevation and discontinuous nature to post-residuum uplift followed by denudation. As the gibbsitic duricrusts formed insitu have not been disturbed later, an in-depth study of their geomorphic characteristics, especially the slope morphology, assumes added relevance as it aids geological prognosis of the behaviour of the pay zone in terms of grade and thickness fluctuations. Once the geomorphic evolution of the duricrusts has been logically reconstructed, a conceptual approach instead of a regular grid for exploration planning is considered more pragmatic not only for acquiring a geologic grip but also in minimising exploration costs.
Geochemistry and Significance of Mafic-Ultramafic Rocks from the Southern Part of the Holenarasipur Schist Belt, Karnataka
Authors: Hussain S. M. , Naqvi S. M. , Gnaneshwar Rao T.
Published: November 2024

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.
Geophysical Investigations for Barite at Gopalpur, Khammam District, Andhra Pradesh (India)
Authors: Varaprasada Rao S. M. , Bhimasankaram V. L. S.
Published: November 2024

Barite deposits are known to occur in the Shernavala outlier near Khammam Town and are found associated with Pakhal sediments of Upper Proterozoic age. The results of electrical resistivity profiling were significant in tracing a shear zone consisting of vein quartz. The gravity method was useful in demarcating the barite body from the associated quartz, and the ore reserves were estimated to be 86,000 tonnes.
Angular Unconformity Between Sargur and Dharwar Supracrustals in Sigegudda, Karnataka Craton, South India
Authors: Viswanatha M. N. , Ramakrishnan M. , Swami Nath J.
Published: November 2024

The major angular unconformity between the Peninsular Gneiss and Dharwar Supergroup in Sigegudda belt, Karnataka, is now 'discovered' to separate the Sargur from Dharwar Supracrustals. It is the most critical area known so far in the craton to exemplify the Sargur-Dharwar relationship. In conformity with modern stratigraphic practice, the unconformity marked by supermature conglomerates incontrovertibly separates two major rock sequences in early Precambrian geological record of Karnataka Craton.
Borings on Belemnoid Rostra from Utatur Group of Upper Cretaceous Rocks of Trichinopoly District, Tamil Nadu
Authors: Ghare M. A.
Published: November 2024

The activity of algae, fungi, sponges, bryozoa and barnacles on the belemnoid rostra from clays of the Utatur Group in the form of micro borings are described. The sponge and bryozoan borings are represented by Clionoides Fenton & Fenton and Talpina Hagenow respectively; while, barnacle borings are represented by ichnogenus Brachyzapfes Codez and De Saint-Seine. The algal borings are assigned to ichnogenus Calcideletrix Haentzschel. Ichnogenera Nygmites Haentzschel and Radiarites ichnogen. nov. are the borings of fungi. Ichnogenus Cylindrocavites Ichnogen nov. is erected to accommodate circular borings of unknown affinities.

The present study shows that the borers and the belemnoids belonged to the same biocoenose and indicate littoral to shallow sublittoral depths of well aerated, slightly turbulent but clear marine waters.
Glacial and Periglacial Morphology of the Jorya and Adjoining Glaciers, Kinnaur District, Himachal Pradesh
Authors: Ameta S. S. , Swain P. K.
Published: November 2024

The glacial and periglacial region of the Jorya, Janapa, Naradu and Tumur glaciers shows Alpine sculptures like horn, cirques, 'U' troughs, serrated ridges, hanging glaciers, moraines, crevasses and glacial tables. 1 to 3km recession and 150m to 120m vertical shrinkage are noticed in these glaciers. Floor of cirques lies between 4800 and 4900m height a.s.1. suggesting active orographic firn line at a height of 5000m a.s.1. at the time of formation of the cirques. Evolution of the landforms took place in three stages: i) advent of the glacial climate, ii) advancement of the glaciers and iii) active deglaciation period.
Alteration of Beach Sand Ilmenite from Manavalakurichi, Tamil Nadu, India
Authors: Subrahmanyam N. P. , Rao N. K. , Narasimhan D. , Rao G. V. U. , Jaggi N. K. , Rao K. R. P. M.
Published: November 2024

The study shows that the alteration of ilmenite has taken place according to the two stage model proposed by Grey and Reid (1975). Identification of the intermediate altered compound, pseudorutile, was found difficult in earlier studies by optical and X-ray diffraction methods, because of the occurrence of this phase in altered ilmenite in very fine grain size (30 Å), its poor crystallinity and coincidence of many of the diffraction lines with those of other phases. The present study has shown that the Mossbauer technique is more suitable in the identification and estimation of this phase.

The relative amount of pseudorutile increases progressively in the magnetic fractions in the following order: 0.30 - 0.35 amps (5%), 0.25 - 0.30 amps (40%), 0-0.25 amps (75%) and 0.35 - 0.50amps (95%), indicating that the magnetic susceptibility of the grains is increasing initially with progressive pseudorutile formation, and decreasing in the later stages of alteration. Reflectivity and hardness are also increasing up to the stage of pseudorutile formation and decreasing in the later stages.
Radiometric Geochronology of the Himalaya
Authors: Saini Hari S.
Published: November 2024

The radiometric age data obtained by different dating methods have been interpreted in terms of possible orogenic activities prevailing in the Himalaya. In general, the age data confirm four main events, the Precambrian, the Late Precambrian-Cambrian Assyntian (Caledonian), the Late Palaeozoic-Hercynian and the Late Cretaceous-Tertiary Himalayan Orogeny. The mineral dates are particularly significant in delineating different phases of the last i.e. the Himalayan orogeny which indicates main activity of the young Himalayan metamorphism around 70 to 50 Ma and followed by a momentous phase of major uplift during 25 to 10 Ma, which was responsible for the rise of the deeper part of the Himalaya into great folds and thrust slices and the formation of nappe structures.
Petrology of a Scapolite-Bearing Rock From Karera, District Bhilwara, Rajasthan
Authors: Sharma Ram S.
Published: November 2024

The scapolite-garnet-epidote-hornblende-pyroxene-calcite ± plagioclase rock of the Aravalli Group (Early Precambrian) is found as thin bands within the high-grade paragneisses of the underlying Banded Gneissic Complex around Karera in northwest peninsular India. The mineralogy and chemical composition of the rock imply that it is derived from impure calcareous sediments. Significant amounts of chlorine are present in both scapolite and hornblende. In epidote and garnet ferric iron is an important component and its presence together with hematite indicates high fo2 during recrystallization of the rock. The partitioning data of Na/(Na+Ca) between scapolite (Me71.3) and the coexisting plagioclase (An85-90) and its reference to the experimentally based diagram yield recrystallization temperature of 650°-700° C, conforming to those computed from other mineral equilibria of the enclosing paragneisses. The scapolite is considered to develop as a result of extreme diminution of PH20, presumably by incoming of chlorine from an evaporite component.
Sivaganga Formation, its Sedimentology, Micropalaeontology and Sedimentation History
Authors: Banerji Ranjit K.
Published: November 2024

The textural study of the sand grains of Sivaganga Formation indicates that sedimentation commenced in a fluvial environment passing through the lacustrine-marsh conditions and ending with the influence of tidal estuary. The clayey sediments in the upper part have yielded an arenaceous foraminiferal assemblage having a low dominance and diversity value belonging to the Neocomian-Aptian (Early Cretaceous) age. The sedimentary basin was formed as a result of downwarping of the crystalline basement along the prominent Eastern Ghat trend during Late Jurassic and Early Cretaceous. The basin established its fragmentary connections with the open sea situated at some distance towards the east and southeast.
Living and Dead Foraminiferida in the Araniar River Estuary, Chingleput District, Tamil Nadu State
Authors: Reddy A. N. , Reddy K. R. , Jagadiswara Rao R.
Published: November 2024

The living and dead foraminiferida in the substrate samples collected from 14 Stations in the Araniar River estuary along the east coast of India from June 1978 to May 1979 have been studied quantitatively. The average salinity ranges from 23.5 to 38.5% and it is considered to be the principal controlling ecologic factor that limits the distribution and abundance of foraminiferida. The pattern of distribution of foraminiferida is also explained in terms of deposition of fluviatile sediments in the estuary. The abundance and living/dead ratios of foraminiferida tests have been compared with those recorded in the nearby Dugarazupatnam and Pennar estuaries.
Compaction in Limestones: A Reappraisal
Authors: Chanda S. K. , Bhattacharyya Ajit , Sarkar Soumen
Published: November 2024

An important outcome of recent research on carbonate diagenesis has been the increasing realization that compaction may be as important as cementation in the lithification of carbonate sediments. Absence of compaction-deformation features should no longer be relied upon as unique evidence against compaction in limestones. The paucity of such features arises from the fact that the load-bearing capacity of allochems (grains) is hardly exceeded in the normal course of lithification of carbonate sediments. Their load-bearing capacity seems to have been exceeded only in the presence of rigid bodies (nodules) or surfaces (hardgrounds or ernersion surfaces). Wherever this prerequisite is met, compaction-deformation may be set into motion in the adjacent sediments, irrespective of their environments of deposition.

So far as the mud-supported carbonate sediments are concerned, they may undergo autolithification entirely through solution-reprecipitation without the benefit of subaerial exposure. In the case of grain-supported carbonates too, there are indications that an appreciable amount of their cement may be derived from elsewhere in adjacent rocks undergoing deeper burial diagenesis within the same basin. While burial diagenesis seems normal, subaerial diagenesis is exceptional for carbonate sediments, other than those of the nearshore areas.
Evolution of Pre-Siwalik Tertiary Basin of Himachal Himalaya
Authors: Srivastava V. K. , Casshyap S. M.
Published: November 2024

The Subathu, Dagshai and Kasauli rocks of Himachal sub Himalaya have been classically interpreted as of marine brackish or lagoonal origin. In this study, the pre-Siwalik Tertiary rocks of southern Himachal Pradesh are grouped into five distinct lithofacies, which collectively represent a consanguineous association of sediments deposited in related geomorphic environments: 1. Fossiliferous green shale, locally red, with lenses of limestone interpreted as tidally influenced shelf deposits; 2. Clean white sandstone interpreted as coastal barrier bars; 3. Red mudstone locally green, and lenses of grey sandstone with channel lag interpreted as lagoonal and tidal flat deposits; 4. Grey sandstone with channel lag and red mudstone and siltstone inferred to have accumulated in distributary channel and inter-distributary plains of fluvio-delta complex; 5. Grey, white sandstone and mudstone interpreted as a mixed assemblage of fluvio-delta and coastal barrier facies.

Two systems of currents operated during the deposition of these rocks: one, across the delta plain complex was directed towards south and southwest following the prevailing regional paleoslope; and the other representing longshore currents in adjacent coastal areas operating parallel to shoreline, was directed towards west-northwest.
Distribution of Alkali and Alkaline Earth Elements in Bauxites-Laterites of Paduvari Plateau (South Kanara District, Karnataka State)
Authors: Devaraju T. C. , Khanadali S. D.
Published: November 2024

Analysis of 34 bauxite-laterite and 11 precursor granitic gneiss samples, from Paduvari plateau, fer alkali and alkaline earth elements has revealed: (1) the strong depletion of laterites/bauxites in Ca, Na, K, Sr, Li and Rb, with a reduction in Ca by 124 times, Na and K by 55 times, Sr by 38 times, Li and Rb by 7½-8 times, (2) low mobility of Mg and Be to result in a depletion of only 2½ times, (3) the lack of significant or systematic variation in the content of these elements in the laterite-bauxite profile and (4) the retention of Na: K and Li : Rb ratios of the precursor gneiss in the laterite/ bauxite. The study substantiates the general observation that alkali and alkaline earth elements with their low ionic potential (except Be) are thoroughly leached during lateritization.
Superposed Deformation in Delhi Rocks near Patan, Sikar District, Rajasthan
Authors: Ray J. N.
Published: November 2024

The Delhi Supergroup of rocks exposed around Patan (27°48'N, 75°58'E), Sikar district, Rajasthan, was subjected to three successive phases of deformation. First phase folds have variably oriented axial planes with moderate to steep plunge towards ssw while second phase folds have, in general, N-S to NNE-SSW trending sub-vertical axial planes and steep south-southwesterly plunging fold axes. Most of the major folds and associated flexures of the area were produced during this phase of folding. The first and second phase folds are generally co-axial. Expression of last phase of folding is mild and extremely localised.
Trace Fossils from the Ordo-Silurian Rocks of Kinnaur, Himachal Himalaya
Authors: Bhargava O. N. , Bassi U. K. , Chopra Suresh
Published: November 2024

Ichnofossils Teichichnus, Phycodes aff. palmatum, Planolites, Ichnogenus indet. A and B, and Phycodes circinatum, P. aff. palmatum, Skolithos, Rouaultia and Planolites are being reported respectively from the basal and middle parts of the Yamrang La Formation of Ordovician age. Arthrophycus, Chondrites, Planolites, Rusophycus, Skolithos and Ichnogenus indet, C occur in the basal part of the Manchap Formation of silurian age. Phycodes circinatum Magdefrau 1934 mainly know from Lower Ordovician probably represents an Upper Ordovician age in this area.
2900 M. Y. Old Stromatolite from Sandur Greenstone Belt of Karnataka Craton, India
Authors: Murthy P. S. N. , Krishna Reddy K.
Published: November 2024

Confirmed stromatolites from a limestone band from Sandur greenstone belt of Karnataka Craton are reported for the first time. The stromatolites are oval to elliptical in shape in gently dipping bedding plane and conical in cross section. Indirect radiometric age data indicates the rocks in which the structures occur are 2900 m.y. old. The discovery of stromatolites demonstrates that biological processes were operative in the early Archaean basins of the Karnataka Craton.
Petrology of the Precambrian Banded Iron Formation of Gandhamardan Hill, West of Keonjhargarh, Orissa
Authors: Pandey N. , Chatterjee B. K.
Published: November 2024

The Precambrian Banded Iron Formation of Gandhamardan hill, Keonjhar district, Orissa, belongs to Noamundi Group. It is restricted largely to oxide facies of Lake Superior type. The sulphide facies in association with black chert is present in small amount. It is almost unmetamorphosed and exhibits many depositional and penecontemporaneous deformation sedimentary structures. A preliminary field and petrographic examination reveals that iron formation was initially deposited at least in major part as hematite-magnetite-chert rock in a near-shore epicontinental environment partially restricted from free-circulation of sea water. Iron and silica were precipitated almost contemporaneously largely due to physico-chemical changes in sea water. The presence of siliceous stromatolitic laminations and alga-like spheroid Archaeospheroides barbertonis similar to that of Fig Tree cherts, however, suggests biogenic activity during the deposition of the Banded Iron Formation.
The Study of Dinosaurian Eggs from Infratrappean Limestone in Kheda District, Gujarat
Authors: Mohabey D. M.
Published: November 2024

Well-preserved dinosaurian eggs from the infratrappean limestone of Kheda district, Gujarat are described. The mode of occurrence of these eggs and their distribution pattern suggest them to be autochthonous egg clutches. The distribution of these egg clutches indicates that dinosaurs probably nested in colonies.
Ostracoda from Vestfold Hill Lake Terraces, Antarctica
Authors: Anantha Padmanabha Setty M. G.
Published: November 2024

Six species of ostracodes are recorded from two transects of terraces of Deep Lake, Vestfold Hills, Antarctica. Two species (Xesteleberis sp. and Bradleya dictyon) range from Cretaceous to Recent, Poseidonamicus aff. P. major ranges from Oligocene to Recent, while Krithe tunnida ranges from Pliocene to Pleistocene to Recent. Paradoxostoma antarcticum and Loxoreticulatum fallax are reported from Antarctica and range from Pleistocene to Recent. Bradleya and Krithe were typical deep water (psychrospheric) forms during Paleocene to Oligocene as today but they were found in shallow (-45 to -37 m) depths here. Ostracodes are extremely rare as compared to the associated foraminiferal assemblage. Dissolution effect, loss of ornamentation, thinning and fragmentation of the fauna are considered to be mainly due to gradational external stress, and large scale physical environmental shifts such as high salinity, low temperature and high dissolved carbon dioxide content of the Deep Lake waters. Disparity in abundance is attributed to wind erosion, differential deposition after ablation of ice from ice sheets, physiographic variation of the region and high rate of dissolution of calcareous forms including foraminifera.
Geophysical Exploration for Uranium in Suryamalai Batholith, Salem District, Tamil Nadu, India
Authors: Anantharaman K. B. , Sethuram S.
Published: November 2024

Abnormally radioactive granitoids are targets of uranium exploration because they can be the source for uranium deposits as well as the hosts. Significant uranium mineralization is known to occur northwest of Suryamalai granite batholith at Kullampatti situated 40 km southwest of Salem. This paper embodies the geophysical exploration for uranium, using results of magnetic and radiometric methods. The investigations revealed that uranium mineralization is structurally controlled and such structures have magnetic expression. Incidentally, correlation of anomalous content of W with U is also brought to light.
Petrology of the Area East of Daltonganj, Palamau District, Bihar
Authors: Lahiri Gopal , Das Somnath
Published: November 2024

The Precambrian terrain to the east and south east of Daltonganj (84°04' : 24°02'), shows considerable variation in composition and mineral assemblage within the metamorphites comprising: paragneisses with local migmatitic variants, metapelites, calcgranolites and amphibolites. There are evidences of polyphase deformation in the metamorphics. Within the metamorphics is emplaced a post-kinematic leucogranite body forming an oval outcrop in the central part of the area. The present investigation reveals a calcalkaline suite post-dating metamorphism and comprising diorite, granodiorite and tonalite. The leucogranite appears to be the culminating phase of this calcalkaline magmatism.
Contemporaneous Intrabasinal Faulting in Gondawana Basin - The Jurabaga Fault of IB River Coalfield, a Type Example
Authors: Mukhopadhyay Abhijit , Chaudhuri P. N. , Banerji A. L.
Published: November 2024

An example of contemporaneous intrabasinal faulting in a Gondwana basin is described. The intrabasinal Jurabaga fault of Ib River Coalfield has been identified as contemporaneous fault on parameters followed in the Gulf Coast Province of U.S.A. namely, (a) abrupt increase in thickness of strata, and (b) increase of throw with depth on the downthrown side with respect to the upthrown side of the fault. The developmental history of Jurabaga fault in space and in time is reconstructed.
Geochemistry and Petrogenesis of the Peninsular Gneisses, Dharwar Craton, India
Authors: Jayaram S. , Venkatasubramanian V. S. , Rajagopalan P. T.
Published: November 2024

Systematic measurement of the abundances of major, trace and rare earth elements has been carried out on a number of samples of the Peninsular gneisses. The data suggests that the Peninsular gneisses could be broadly differentiated into Western tonalitic group and an Eastern granodioritic group. The dividing line roughly corresponds to the western margin of the Chitradurga greenstone belt. The Geochemical data also suggests that bulk of the Peninsular gneisses are magmatic. Critical differences in trace and rare earth element abundances are observed between the western tonalites and the eastern granodiorites.
Crustal Evolution and Metallogeny-Evidence from the Indian Shield: A Review
Authors: Radhakrishna B. P.
Published: November 2024

A survey of the important metalliferous deposits of India has been attempted in the light of developing ideas about crustal evolution and metallogeny. Mantle dominated volcanic regime of the Archaean is indicated to be characterized by simple ores of gold, chromium, nickel and copper. A marked change is apparent at the end of the Archaean with the emergence of large areas of land and oxygenated atmosphere and hydrosphere. Near surface processes begin to play the dominant role. Proterozoic is thus marked by the first appearance of uranium-gold-bearing conglomerate, spectacular development of banded iron formations and sediment-hosted Pb-Zn-Cu deposits. High temperature albitization phenomena connected with younger plutons has led to concentration of beryllium, tantalum, niobium, zirconium and tin in granite pegmatites. A special type of barium-rich volcanism has given rise to a unique type of barite deposit within the Proterozoic Cuddapah Basin. Tensional tectonic regime of the Proterozoic has given place to plate tectonic regimes in the Phanerozoic, thereby enabling further recycling of crustal material and concentration of metals. The full metal potential of the Himalayan folded mountain belt is yet to be ascertained. Alluvium and palaeo-channels of major rivers, off-shore extensions of beach placers, and metals on the sea bed are promising fields where exploration effort has to be concentrated in the coming years.
Petrology of Sillimanite Gneisses from Garividi, Andhra Pradesh
Authors: Sivaprakash C.
Published: November 2024

Sillimanite+K feldspar+quartz±garnet±Fe-Ti oxide-beartng rocks occur associated wIth calc-silicate locks and manganese formations near Ganvidi in Vijayanagaram district of Andhra Pradesh The whole-rock chemistry shows varying rock oxidation ratios which are reflected in the mineralogical assemblages Almandine garnet is oxidized to mixtures of hematite, quartz and hydrous alummosilicates in oxidized rocks and is absent in highly oxidized rocks in the latter, ilmenite is oxidized to mixtures of rutile and hematite Such relatively high temperature alteration/oxidation effects could have occurred with the influx of water Garnet compositions, and the presence of sillimanite + K-feldspar associiation rather than muscovite+quartz, suggest minimum pressures of 6 Kb, temperatures around 700° and XH2O around 0 6 during metamorphism.
Cleavage in the Lesser Himalaya of Bhutan
Authors: Sengupta Subhasish
Published: November 2024

In the low grade rocks of Bhutan, a situation of multilayer anisotropy is preserved in the form of alternate argillaceous and arenaceous layers. Planar fabric parallel to the axial plane of F2 folds, varies in morphology from crenulation cleavage to slaty cleavage and one type grades into the other. The variation is controlled by the difference of the material in which the cleavage occurs and also by the position where it occurs with reference to F2 mesoscopic fold. In the short limb these are discrete laminae separating microlithons with crenulated S1 fabric (Type I). In the long limb it is a coarser slaty cleavage, defined by parallel alignment of phyllosilicate sheafs (Type II).

Mechanical rotation of grains plays an important role in producing both the cleavage types. It is suggested that deformation in the layered material starts as a crenulation process. Further, inhomogeneity is introduced in the material in the form of asymmetrical folds of competent bands. The long and short limbs of the asymmetrical buckles are differently oriented with respect to the principal axes of strain and respond differently during further deformation. In the short limb lying at small angle to the direction of compression, mechanical rotation ceases to be operative after a certain stage and chemical processes become dominant. The result is a discrete crenulation cleavage developed due to solution transfer. In the long limb lying in the zone of extension. mechanical rotation continues and produces a phyllosilicate preferred orientation defining the slaty cleavage fabric. Grain growth produces the coarsening of the fabric in this limb.
Nature of Aquifers and their Inter-Relationship in a Part of Sutlej Basin, Punjab
Authors: Jagannathan V. , Pandey D. S.
Published: November 2024

Results of a detailed hydrological test conducted with arrays of observation wells have been utilized in deciphering inter-relationship between aquifers in the SutIej basin. Drawdown values obtained at various distances from the pumped well are interpreted, and it is shown that the aquifers below the first clay layer are under leaky confined condition.
Seismicity of the North-East India Region
Authors: Gupta Harsh K. , Rajendran Kusala , Singh H. N.
Published: November 2024

The north-east India region is seismically one of the most active regions In the world. An earthquake data base for the region from the earliest time to 1984 is presented here. These data would be utilized for investigating the earthquake phenomenon in the region.
Banded Iron-Formation of Huliyar-Kudurekanve Area, Tumkur District, Karnataka State
Authors: Nadagouda D. B. , Hanagodimath R. S. , Devaraju T. C.
Published: November 2024

The banded Iron-formation, corresponding mostly to oxide facies, exposed in the south-western parts of Chitradurga belt has been studied with respect to their field, petrographic, mineralogical and petrochemical aspects. It is concluded that, these iron-formations are essentially the results of chemical precipitation of iron and silica derived from continental weathering of basic rocks under anaerobic, quiet, below-wave base marine conditions. The banding is attributed to cyclic changes in climatic conditions.
Syngenetic and Epigenetic Features and Genesis of tbe Bauxite-Bearing Laterite of Boknur-Navge Plateau, Belgaum District, Karnataka
Authors: Krishna Rao B. , Satish P. N. , Sethumadhav M. S.
Published: November 2024

Bauxite-bearing laterite of Boknur-Navge plateau, Belgaum district, Karnataka, exhibits textural, mineralogical and geochemical features of both syngenetic and epigenetic origin. While the syngenetic features of the lateritic residuum developed during a major episode of residual weatheringof'the source rock (Deccan basalt), the epigenetic features originated during an episode of secondary alteration of the pre-existing lateritic material.

Residual weathering of basalt took place in three stages and culminated in the formation of a well-differentiated lateritic residuum consisting of vermicular laterite and massive (textureless and pisolitic) bauxite. Lateritic weathering, under the activity of slightly acidic meteoric waters, involved leaching of ∼90% SiO2, ∼60% Fe2O3 and almost all the K, Na, Ca and Mg from the weathered zone leading to the relative enrichment of Al. Part of the dissolved Si, Fe and AI of the circulating waters were subjected to local migration and reprecipitation, resulting in the segregation of AI-rich (bauxite) and Fe-Si-rich (laterite) units within the laterite profile.

Secondary products derived from the alteration of the bauxite and laterite show zonat variation in their mode of occurrence, textures, mineralogy and chemical composition. During the secondary alteration, the bauxite and laterite of the ∼10 m thick bauxite-bearing laterite zone were subjected to 1) silication and ferrification at the upper horizon, 2) silication at the intermediate horizon, and 3) minordesilication at the lower horizon. Among the three types of alterations, silication is widespread. The 'late-or post-bauxite' episode of alteration of the lateritic residuum was probably brought about by the action of highly acidic meteoric waters charged with Si.
SHRIMP U-Pb Geochronology of the Closepet Granite and Peninsular Gneiss, Karnataka, South India
Authors: Friend C. R. L. , Nutman A. P.
Published: November 2024

Zircons separated from a sample of Peninsular gneiss (82-KD 14) from Kabbaldurga quarry, and a homogeneous Closepet granite (KO84-13) from near Ramnagaram have been dated with the ion microprobe SHRIMP. The Peninsular gneiss sample, a metatexite, contains an arrested charnockite transition and constitutes an amphibolite-granulite close pair. It was split into amphibolite facies, transitional and granulite facies (charnockite) domains prior to zircon separation.

Zircon populations separated from each domain are morphologically similar and have the same U-Pb isotopic systematics suggesting that they record events common to both the amphibolite facies and granulite facies domains. The pooled data yield a U-Pb age of 2963 ± 4 Ma (20s) for the gneiss protolith at Kabbaldurga, with a few older inherited zircons found as cores in magmatic zircon. A concordant U-Pb age of 2528 ± 5 Ma was obtained for newly grown zircon and overgrowths, interpreted to have formed during a migmatisation event which led to the formation of the Closepet granite.

Zircons separated from the Closepet granite sample gave a concordant age of 2513 ± 5 Ma, interpreted as the time of crystallisation of the granite. This age was obtained from both zircon cores and overgrowths which are indistinguishable in age and arc both interpreted to have formed during the melting event. In preserved cores no indication of any inherited grains with a significantly older history was found.

This is the first precise age on the Closepet granite. The slight age difference between the metatexite event (2528 ± 5 Ma) and the granite age 2513 ±5 Ma) may indicate the length of time of the event during which the Closepet granite formed. The data provide a minimum constraint on the age of the charnockite event in the region.
Mechanism Solution of Burma-India Border Earthquake of August 6, 1988
Authors: Banghar A. R.
Published: November 2024

This paper presents the focal mechanism solution for the Burma-India border earthquake of August 6, 1988. Use was made of the first motions of P waves and polarization (or first motions) of S waves. The mechanism solution is characterised by a predominant component of thrust faulting. The deduced orientation of the axis of compression is northeasterly. This orientation of the axis of compression is nearly parallel to the trend of tectonic features in the epicentral region of this event.
Orbulina universa d' Orbigny in Late Pleistocene Sediments of Northern Indian Ocean
Authors: Jaiprakash B. C.
Published: November 2024

The genus Orbulina d' Orbigny 1839 in the Late Pleistocene sediments of the Northern Indian Ocean is represented by abundant population of O. universa d' Orbigny 1839 and rare O. bilobara d' Orbigny 1846. Temporal variation in the abundance and test size or O. universa has been analysed for their inter-relationship and paleoclimatological implications. The results suggest an inverse relationship between abundance and test growth which corroborates Allan Be's (1973) observations on Recent O. universa from Indian Ocean.
Exploration of Metallic Minerals and their Discrimination Using Partial Extraction of Metals by Electrolysis (PEXMEL) Method
Authors: Banerjee Buddhadeb , De S. S. , Das L. K.
Published: November 2024

Partial electrolytic extraction of metals can be effectively utilised for direct detection of polymetallic minerals in addition to their discrimination which is a difficult task by other geophysical exploration techniques. The principle lies in trapping the metallic cations from the electrolyte formed by leaching of the ore body at depth by a direct current supply impressed on ground surface and analysing the electrolyte chemically for determination of different metallic contents diagonising the target.

Field tests have been successfully carried out with this approach over known and unknown mineralised bodies at Kendadih, Seraikella areas in Singhbhum district, India.