bluuebunny/crossref_metadata_2025 huggingface dataset:
The Behaviour of Trace Elements in the Magmatic Members of the Singhbhum Granitic Complex
Authors: Sara A. K. , Sankaran A. V. , Bhattacharyya T. K.
Published: November 2024

Seventeen trace elements in 37 total rock samples belonging to six magmatic units of Singhbhum Granite, and nearly as many trace elements in II individual minerals separated from these rocks were estimated by quantitative and semi-quantitative spectrographic analysis respectively. Uranium was determined fluorimetrically in all the 37 samples. The trace element distributions in these samples have been studied in relation to those of the major elements as computed from the modal analyses on the basis of optical and chemical data on the constituent minerals.

The trends of variation of the trace elements and of the diadochic element ratios in these rocks conform broadly to those expected under conditions of fractional crystallisation of volatile-rich granitic melts. Distinctive trends of variation of several trace elements and diadochic element ratios with increasing differentiation were found for the three distinct but closely related phases into which these intrusive units may be classified on structural and petrologic grounds. Multivariate analyses and t-tests on 12 trace elements in samples belonging to the three phases indicate that the three phases of granites have significantly different trace element compositions.
Dharwar Conglomerates of Mysore - A Restudy
Authors: Sreenivas B. L. , Srinivasan R.
Published: November 2024

Compositional layering of pebbles has provided a positive structural criterion in distinguishing the tectogenic (autoclastic) conglomerates from the sedimentogenic ones in the Dharwars of Mysore. Making use of current bedding and graded bedding as markers of two different tectonic environments of arenite sedimentation, the stable areas of deposition in Dharwars of Shimoga, Chital drug and Bababudan schist belts are separated from the main geosynclinal regions. Stability in the depositional environment is found to be characteristic of the parageosynclinal stage; and the conglomerates deposited in stable regions are oligomictic as against the polymictic nature of the geosynclinal conglomerates.
A Reinterpretation of the Geological History of the Singhbhum Shear Zone, Bihar
Authors: Banerji A. K.
Published: November 2024

The Singhbhum shear zone represents a deep seated fracture that probably extended up to the upper mantle through which basic rocks poured out continuously and extensively together with some ultrabasic rocks. The northern block gradually subsided and received sediments interlayered with basic rocks and tuffs, with a conglomerate horizon at tbe base. Subsequently the movements were reversed along the line of fracture and it was transformed into a zone of shearing within which migma-magma activity and mineralisation took place. Residual stresses within the shear zone were released through wrench faulting after which the shearing movements resumed locally and continued even up to recent times at some places.
Studies on Some Granitic Rocks of Palni-Dindigul Area, Tamil Nadu
Authors: Narasimha Rao P.
Published: November 2024

The temperatures of formation of some granitic and charnockitic rocks from parts of Palni-Dindigul area have been determined by the felspar geologic thermometer. Two distinct ranges of temperatures are indicated among the rocks on the basis of which they are classified. Their petrogenesis is discussed on the evidences furnished by the temperatures, field relationships, twin laws of plagioclases and some significant petrographic characters. The older grey granitic rocks are of metasomatic origin and were probably products of synkinematic granitization while the pink perthite-quartz granites represent later magmatic intrusions. Among the charnockites also, two different types are recognized. One is formed by the charnockitization of the gneisses, while the other represents a magmatic type of charnockite.
Seasonal Variations in Foraminiferal Abundance and their Relation to the Substrate in Vellar Estuary, Madras
Authors: Ramanathan Rm.
Published: November 2024

Seasonal differences in the abundance of the benthic Foraminifera of the estuary are shown to be related to the standardized nomenclature of the sediment types relative to sand silt and clay.

The area with almost sandy substrate in November 1967 yields the lowest foraminiferal number due to the strongest currents caused by the floods observed in October 1967. The finest sediments and weaker currents are associated with the higher foraminiferal numbers in March and April 1968.

The most accommodative substrate for a higher foraminiferal number is found to be silty-clayey-sand, in which silt is dominating over clay.
Sedimentary Structures and Paleocurrent Analysis of the Barakar Sandstone in Chirimiri (Kurasja) Coalfield, Madhya Pradesh
Authors: Casshyap S. M. , Jain R. K.
Published: November 2024

The Barakar sandstone of Chirimiri (Kurasia) coalfield includes complete or truncated sedimentary cycles, some of which commence with pebbly gritty coarse sandstone and, fining upwards through coarse cross bedded sandstone, end up with carbonaceous siltstone or coal seam. Among the primary depositional structures, ripple drift, trough and tabular cross bedded sets and cosets are common. These structures have been described from the genetic and hydrodynamic viewpoints. Erosional structures occurring in the sandstone include channels, scour-and-fill, potholes and flute casts.

A paleocurrent analysis based on 88 cross bedding azimuths reveals the preponderance of two depositional current systems - the main current system which flowed from southeast, and a tributary system flowing from east-northeast. An increase in cross bedding variability at higher sampling levels reflects the meandering behaviour of depositing currents.

A sedimentary analysis of the sandstone sequence suggests that the Barakar sedimentation in this coalfield was controlled, perhaps right from the beginning, by periodic tectonic uplifts of the granitoid landmass located to the east and southeast. It is suggested each tectonic uplift resulted in the deposition of a fining-upwards fluvial cycle.
Recognition, Correlation and Age of Erosion Surfaces in the Iron Ore Ranges of Bihar and Orissa
Authors: Ramana Rao K. L. V. , Vaidyanadhan R.
Published: November 2024

In the Iron Ore Ranges of Bihar and Orissa, three erosion surfaces have been recognised around 3000-2700 feet, 2300-2000 feet and 1600-1400 feet above M.S.L., based on model studies in the laboratory, and the relative positions in the field of the residual deposits of laterites and lateritic iron and manganese ores. These have been correlated with those in the neighbouring areas in the southeastern Chota Nagpur and the Simlipal massif in Bihar and Orissa respectively. Based on the study of sedimentary record in the adjoining Bengal Basin, the tentative ages assigned to them from the top are Upper Jurassic to Lower Cretaceous, Upper Eocene and Upper Miocene.
Algal Stromatolites from the Kaladgi (Precambrian) Formations, Near Alagundi, Bijapur District, Mysore State
Authors: Viswanathiah M. N. , Chandrasekhara Gowda M. J.
Published: November 2024

Occurrence of stromatolitic colonies has been observed in variegated limestones around Alagundi, and they are termed as 'algal stromatolites'. Depending upon the morphological similarities, four different forms have been recognised and their salient features described. Natural environmental factors that prevailed during their formation have been enumerated, and diminution of algal filaments into fine micrite is also discussed.
Evolution of the Drainage of Cauvery in South India
Authors: Vaidyanadhan R.
Published: November 2024

It is now realised that the course of the river Cauvery in South India as observed is different from what it was during its inception during late Cretaceous or early Tertiary times. The upper part of the course over the Mysore plateau might have had only slight modifications both headward as well as laterally; but the lower part from Sivasamudram appears to be quite different.

The vast flood plain of Palar, negligible flow even during flood times, the long and broad NE-SW trending dry valley from around Pennagaram in the south to Vaniyambadi in the north extending for about a distance of 65 miles in Tamil Nadu, southeast of Mysore plateau, require satisfactory explanation. It is suggested that the lower part of the Cauvery (Proto-Cauvery) flowed from Hogenakal, through the above valley on to the present course of the Palar river, and that the changes in the course of the rivers in this region were brought about during the Tertiary times, mainly aided by headwa(d erosion by tributaries along fracture zones and fault zones in the region.
Deep Main Faults in South India
Authors: Grady John C.
Published: November 2024

A system of deep, main faults containing carbonatite complexes and ultra basic to alkaline intrusions occurs in South India. The faults strike in a northeast-southwest direction across the Peninsula, and two main sets have been recognised at N 30°E and N 45° E. They occur in a block-faulted region in which some of the uplifted blocks form hills up to 2900 metres high and grabens have been downfaulted to as much as 1700 metres below sea level. Seismic records since the year 1800 show that the majority of earthquakes in the Precambrian Shield of South India are concentrated along one of the fault zones which is also the location of igneous intrusions, hydrothermal veins, pegmatiles and metasomatism. A positive gravity anomaly underlies this zone.

Minerals of economic importance occur in some of the intrusions. The most productive artesian wells drilled by the United Nations Groundwater Project in Tamil Nadu are located on one of the major faults of the system. It is thought that continued exploration with the aid of photogeology and geophysical surveys will reveal more of the deep, main faults, and possibly more ore bodies, in South India.
Reconnaissance Survey of the Quaternary Geology of the Cauvery Delta
Authors: Meijerink A. M. J.
Published: November 2024

The exposed Quaternary geology of the Cauvery delta has been mapped from aerial photographs. The study has been complemented by a series of augerings in the northern part-of the delta. The grain size distribution of Holocene deposits, consisting of natural. levee complexes, backswamps, coastal ridges and low lying areas under tidal and back-water influences have been studied. With the aid of subsurface data it has been attempted to reconstruct the Post-Tertiary development of the delta. The relative chronology of the formations could be established.

Eustatic curves are discussed briefly in the context of their applicability to the Indian subcontinent and they have been used for a provisional dating of various Holocene deposits. A late Pleistocene to early Holocene transgression was followed by delta formation in the south. Subsequently the main fluvial deposition shifted towards the north. Since the Atlantic period, a series of beach ridges were formed along the coast. Transportation of sands and finer material by long shore currents has resulted in the formation of a cuspate foreland on the southern part of the delta. Three marine stages in the cuspate foreland have been correlated with fluvio-marine stages in the north.
New Mammals from Murree (Kalakot Zone) of the Himalayan Foot Hills Near Kalakot, Jammu & Kashmir State, India
Authors: Ranga Rao A.
Published: November 2024

A new genus, including two species, of the Artiodactyl family (?) Choeropotamidae from the Murree group, is described. These are the first mammalian fossils known from the Murree outcropping within the present day limits of Indian territory.
Mineralogy, Chemical Characters and Genesis of the Chromite Deposits of Moulabhanja Area, Dhenkanal District, Orissa
Authors: Chakraborty K. L. , Mallik A. K.
Published: November 2024

Pockets of 'sack-form' chromite deposit occur at the intersection of dykes of olivine gabbro near Moulabhanja hills in the Dhenkanal district of Orissa. The dykes intruded the Precambrian granite-gneiss belonging to the Eastern Ghat orogenic belt. Chromite also occurs as minor accessory in olivine gabbro; and in this respect differs in its mode of occurrence from chromite deposits associated with the dunite-peridotite of the Iron ore orogenic cycle. The close association of chromite with olivine gabbro, the paragenetic sequence of the minerals in the rock, and the mineralogy, texture and chemical nature of the ore, suggest that the chromite melt was separated from the basic (olivine gabbro) magma as an immiscible liquid fraction and crystallized earlier than the silicate minerals.
Gondwanaland and the Growth of India
Authors: Crawford A. R.
Published: November 2024

New palaeomagnetic data clarify the manner of break-up of Gondwanaland and show that India was adjacent to Africa and Antarctica, but not Australia, during the Phanerozoic. This does not conflict with possible contiguity of parts of India and Australia before Gondwanaland came into existence.

Relative movement of the pole and a Gondwanaland which is known to have existed at least from the Cambrian to the time of break-up in the late Mesozoic implies non-synchroneity of glaciations geographically distant from one another, the products of which have also been scattered by drift. Precambrian tillites are unlikely to be synchronous; glaciations merely follow the poles.

A difference is established between the Indian peninsula. the Indian shield and Gondwanic India. The development of India has been in five stages; before Gondwanaland existed, during its life-span, during association with Madagascar while separate from Africa, during movement as Gondwanic India, and since collision and fusion with Asia.
Late Pleistocene Gastropods from Nalagarh Tehsil, Himachal Pradesh
Authors: Bhatia S. B. , Mathur Anil K.
Published: November 2024

Six gastropod taxa from a late Pleistocene terrace of the river Sirsa are described. These include three new species belonging to the family Pupillidae. The palaeoecological implications of the fauna are also discussed.
Petrography and Origin of the Krol Sandstone around Solon, Himachal Pradesh
Authors: Bhattacharyya Ajit , Chanda S. K.
Published: November 2024

Earlier studies on the geology of the Krol Belt in general have included little detailed information pertaining to the petrology and mineralogy of the Krol Group. The work reported herein represents a part of a comprehensive petrological study of the Krol Formations and provides information mainly about the petrology and probable environment of deposition of the basal unit of the Krol Group, namely the Krol sandstone, that overlies the Infra-Krols.
The Deformation of the Bar Conglomerate
Authors: Murty T. V. V. G. R. K. , Bhargava L. R.
Published: November 2024

The basal Delhi conglomerates seen at Bar are reputed for the intense deformation seen in them. Heron's memoir on central Rajputana contains a brief description of these conglomerates.

The pebbles in the conglomerate are mostly made up of quartzites. They vary in size from small pebbles to large cobbles. The percentage deformation in the long axes of the pebbles is around 175, and in some extreme cases about 700. The pebbles lie in the cleavage/bedding surface with their long axes almost parallel to each other. The long axes are coincident with the true dip of cleavage surface.

The overall matrix of the conglomerate is psammo-pelitic and consists of sharply alternating psammite and pelite layers. A strong cleavage is seen in the matrix which is parallel to the bedding.

The pebbles are in all cases flattened and elongated. A two stage deformation model in which an early phase of flattening followed by flow is suggested for the pebbles in the conglomerate.
Job Charnock and Charnockite
Authors: Pichamuthu C. S.
Published: November 2024

Job Charnock was an officer of the East India Company in Bengal due to whose initiative the British were able to acquire Calcutta. He died in 1692 and his tombstone is found in a mausoleum in the compound of St. John's Church. Holland discovered that this tombstone was made of the hypersthene-bearing rock occurring rear Madras and whose petrology he was investigating at that time. As this was a new type of rock, Holland suggested for it the name Charnockite in honour of Charnock, the Founder of Calcutta.

In this paper, a description is given of the mausoleum, the tombstone and the epitaphs on it. The life, career and character of Job Charnock are briefly outlined.
Palaeomagnetism and Geological Correlation of Certain Precambrian Formations of Andhra Pradesh
Authors: Prasad C. V. R. K. , Damodara Reddy V.
Published: November 2024

The magnetic studies on the ferruginous sandstone samples from the Kaverisamudram area and the metamorphosed shales from Beduduru area of Cuddapah basin are presented here along with the results from the dykes near Tirupati. From a comparison of these results with those obtained from other Precambrian formations of India, it is found that the Bijawars are equivalent to Cuddapahs. The results from the metamorphosed shales have indicated that the igneous activity in Cuddapah basin was contemporaneous with sedimentation. This igneous activity is also found to be contemporaneous with one of the intrusive phases of the Tirupati area.
Differentiated Hypersthene-Olivine Dolerite Dyke near Harohalli, Mysore State
Authors: Sadashivaiah M. S. , Ikramuddin M.
Published: November 2024

Textural, mineralogical and petrochemical variations observed across the width of the differentiated hypersthene-olivine dolerite dyke situated near Harohalli have been described and discussed. The salient features of the dyke are (i) the occurrence of mafic minerals rich in iron, and plagioclase less rich in anorthite content at the borders, with a progressive decrease of iron content in the mafic minerals and increase in anorthite content of the plagioclase towards the central zone and (ii) the textural variation from the flow and hyalopilitic at the margins, intersertal, intergranular, ophitic and subophitic at the intermediate zones and poikilitic at the centre. The chilled margins show a higher content of iron, alkalies and silica and a lower content of MgO, CaO and Al2O3. than the central portion. These characters indicate that the differentiation is due to thermodiffusion as described by Wahl as the observed features cannot be explained by any other known mechanisms of differentiation.
Overthrusting and Emplacement of Basic Rocks in Lesser Himalaya, Garhwal, U. P.
Authors: Jain A. K.
Published: November 2024

The metamorphosed basic rocks, probably emplaced along dislocation zones during overthrusting and facilitating such movements, are persistent at the base of Uttarkashi thrust sheet in the Precambrian-Lower Palaeozoic rocks of innermost Lesser Himalayan region of Uttarkashi, Garhwal. Marked absence of such basic rocks in Tertiary rocks, and along thrusts of Sub-Himalaya and outermost Lesser Himalaya in Garhwal, may be taken as indicating a probable Upper Cretaceous age for these intrusives related to the initial phase of Himalayan orogeny.
Petrology of Picrodolerites from the Dedan Cluster, Gujarat
Authors: Krishnamacharlu T.
Published: November 2024

Picritic dykes of oceanite and ankaramite composition occur around Dedan in the Kathiawar peninsula of Gujarat State. They have been studied across their width, with reference to the distribution and crystallisation of olivine and pyroxene. Olivine and pyroxene occur both as large phenocrysts and as small crystals in the groundmass. Considerable variation in the concentration of olivine and pyroxene is observed from the central portion of the dykes to the margins. A gradual decrease in the grain size and content of these minerals is seen from the centre to the margin of the dykes It is also observed that the grain size of these two minerals shows a direct relationship with the percentage of these minerals. This is explained by flow differentiation proposed by Bhattacharji and Smith for the Muskox feeder dyke.
Geology of the Jensurigudda Iron Ore Deposit of Chickmagalur District, Mysore
Authors: Mishra R. N.
Published: November 2024

The Jensurisudda Iron ore deposit is one of the prominent iron ore occurrences in the Bababudan hills of Mysore State belonging to the 'Bababudan Series' of Dharwarian age.

The formation consists of bedded hematite and limonite resting over ferruginous shale with lenses of quartzites. The structure is a major fold with axis trending NNWSSE. The harder rocks viz. the quartzites and the ores display innumerable irregular folds. Structural control or localisation is present in a broad sense. Harder or lumpy ore overlies softer ore and blue dust. The ore body extends to a depth of 20 metres. It is inferred that the ferruginous shales are the source rocks for ore formation and that the concentration has been achieved through 'lateritic weathering'.
Petrogenetic Significance of Zn Distribution, and of Zn/Fe, Zn/Pb Ratios in Granitic Biotites
Authors: Viswanathan S.
Published: November 2024

The zinc content of biotite is a potentially useful petrogenetic tracer to determine if a granitic pluton formed by magmatism (crystallization-differentiation), metasomatism, or anatexis. This conclusion stems from a geochemical study of Zn distribution, and of Zn/Fe, Zn/Pb ratios in granitic biotites from the 2.7 billion year old Giants Range batholith of northeastern Minnesota, U.S.A. Results show that the zinc contents of biotites from metasomatic granitoids (477 ppm), anatectic tonalites (498 ppm) and their parent metasedimentary rocks (498 ppm) are significantly lower than those characterizing magmatic granites (754 ppm) and magmatic leucogranites (943 ppm). Also, in a magmatically fractionated series of granit c rocks, the Zn contents and Zn/Fe ratios of biotires increase progressively in the sequence tonalite-granodiorite-adamellite-graniteleucogranite, whereas the Zn/Pb ratios decrease.
Gondwana Pebble-Slate in the Rangit Valley Tectonic Window, Darjeeling Himalayas and its Significance
Authors: Roy Subimal Sinha
Published: November 2024

To the south of the Central crystalline zone of the Darjeeling Himalayas, in the interior parts of the frontal zone of the nappes, a sequence of the Lower Gondwana rocks occurs in a window, overlain by the tectonic cover of the Daling-Darjeeling group of metamorphites. A prominent marine fauna bearing pebble-slate horizon is developed at the base of this sequence. The stratigraphy and lithologic characters of this horizon are described in detail, and are considered significant in the context of the palaeogeography and tectonic evolution of this part of Himalaya.
Skull Characters of Crocodylus biporcatus, Cuvier
Authors: Badam C. L.
Published: November 2024

The paper gives a detailed morphological account of the skull of Crocodylus biporcatus Cuvier, collected from the Pinjor Stage of the Upper Siwaliks and housed in the museum of the Centre of Advanced Study in Geology, Panjab University, Chandigarh. The species is a synonym of the salt water crocodile, C. porosus Schneider inhabiting India and Malaysia. The present attempt to study this species in India would be the second one after Falconer and Cautley gave the first account of the form in 1836.
Stratigraphy and Microfauna of the Eocene Beds of Rajasthan
Authors: Khosla S. C.
Published: November 2024

Stratigraphic successions of the Eocene beds of Rajasthan are described from four localities, three in district Bikaner and one in district Jaisalrner. A total of one hundred twelve species of microfauna, comprising thirteen larger foraminifers, forty-four smaller foraminifers and fifty-five ostracodes are recorded. The Eocene beds are divided into two formations, the lower Khuiala and the upper Bandah. On the basis of the larger foraminifers and pelecypods which occur dominantly, the Khuiala Formation is subdivided into six assemblage zones: Zone 1-Assilina granulosa zone, Zone 2-A. daviesi zone, Zone 3-A. lacunata zone, Zone 4-Venericardia mutabilis zone, Zone 5-Assilina sp. zone, Zone 6-Barren zone, and the Bandah Formation into two assemblage zones: Zone 7-Discocyclina sella zone, Zone 8-Nummulities maculatus/Discocyclina dispansa zone. While a more or less complete and comprehensive succession of the Eocene beds, represented by zones 1-8, occurs at locality I , only zones 1 and 2 occur at localities II and III, and zones 3-5, 7 and 8 occur at locality IV. The Khuiala and the Bandah Formations are assigned to Lower Eocene (Ypresian) and Middle Eocene (Lutetian) respectively on the basis of microfauna contained in them.
Foraminiferal Biostratigraphy and Geological Evolution of the Thanjavur Sub-Basin, South India
Authors: Banerji Ranjit K.
Published: November 2024

The foraminiferal biostratigraphy of the marine Meso-Cenozoic sequence of Thanjavur sub-basin, situated in the south-western part of the Cauvery basin, is worked out in detail. On the basis of the distribution of well known planktonic and associated benthonic foraminifera, fifteen biostratigraphic zones ranging in age from Albian to Lutetian, are recognised. It is suggested that the Cretaceous-Tertiary boundary should be placed between Globotruncana gansseri - G. contusa assemblage Zone and Globorotalia velascoensis Zone in this sub-basin. The foraminiferal fauna of these zones are compared with those of the exposed marine sequence in the northern parts of the Cauvery basin. Certain aspects of inter-regional stratigraphic correlation and palaeoecology are discussed.
On The Age of the Pondicherry Formation of Madras South India
Authors: Samanta Bimal K.
Published: November 2024

A sequence of three planktonic foraminiferal zones, the Globorotalia angulata Zone, Globorotalia velascoensis Zone and Globorotalia aequa Zone, is recognised in the Pondicherry Formation of South India. The G. angulata Zone includes the lower marlstone, the G. velascoensis Zone includes the algal limestone and the G. aequa Zone corresponds to the discocyclinid limestone and the upper marlstone. The lower zone is dated as Middle Palaeocene and the upper two as Upper Palaeocene. Thus, on planktonic foraminiferal evidence, the Pondicherry Formation is Middle to Upper Palaeocene in age.
A New Mammalian Fossil from the Lower Murree of Kalakkot, Jammu And Kashmir State, India
Authors: Khan Aijaz
Published: November 2024

The problem of age and environment of deposition of Murree rocks in the Tertiary stratigraphy of north-western Himalaya is under debate for more than fifty years. The age of Murree Series was regarded as Lower Miocene by celebrated geologists viz. Pilgrim (1912), Wadia (1928 & 1966), Gansser (1964) and others on the basis of Fatehjang fauna (Lower Burdigalian) occurring at the base of these rocks in Potwar Basin, Pakistan.

During the course of geological mapping in Kalakot area, the present author found a new species of Upper Eocene (?) rhinoceratoid. This is the first rhinoceratoid fossil recorded from the lower Murree of Jammu foot hills, and its identification has revealed that it has a close affinity with the Russian and American rhinoceratoids of Palaeogene age. This means that the well established unconformity representing a big gap between the Subathu and Murree sediments in Potwar Basin has certainly narrowed down east of Jhelum Syntaxis.
Distribution Coefficient (KDFe2+-Mg) of Orthopyroxene-Biotite and Garnet-Biotite Mineral Phases in Relanon to Equilibrium
Authors: Dhana Raju R.
Published: November 2024

Petrographic study of the granitic rocks of Chipurupalle-Razam area in Srikakulam district of Andhra Pradesh showed that biotite was formed either from orthopyroxene or garnet in reaction with potassium feldspar, under textural disequilibrium conditions. To test whether chemical equilibrium was attained during the formation of biotite, iron distribution coefficient (KDFe2+-Mg) in orthopyroxene-biotite and garnet-biotite mineral phases was considered. KD of orthopyroxene-biotite pair varies from 1.1 to 2.0, while that of garnet-biotite pair varies from 2.6 to 6.5. After considering the effects of temperature difference and of other elements on the distribution coefficient, the large variation in KD values in the area was mainly related to the chemical disequilibrium conditions which operated during the biotite formation. An examination of KD values from different areas showed that in a majority of orthopyroxene-biotite phases and in all garnet-biotite phases, biotite is Mg-rich while the coexisting orthopyroxene or garnet is Fe-rich; and this was explained by the principles of crystal chemistry.
Calc-Silicate Skarns from Chinnabantupalli, Srikakulam District, Andhra Pradesh
Authors: Bhattacharyya C.
Published: November 2024

Calc-granulites of Chinnabantupalli area, Srikakulam district were subjected to contact metasomatism by the injection of K-feldspar-forming fluid. This paper describes the mineralogy of the calc-silicate skarns, mineral chemistry of clinopyroxene and garnet, and emphasizes the textural aspects which have a bearing on the genesis of skarn minerals. The minerals like wollastonite, hornblende, biotite, epidote-clinozoisite-zoisite, a part of the scapolites, garnets and calcites were secondarily formed as a result of contact metasomatism. Most of the scapolites are suggested to be of regional metamorphic origin. The formation of wollastonite, other conditions remaining same, is shown to have been favoured by higher CaO/(FeO+MgO) ratio of these rocks.
Genesis of Lead-Copper Ores in Agnigundala Area Andhra Pradesh
Authors: Krishna Rao J. S. R. , Dhana Raju R.
Published: November 2024

Lead-Copper deposits in dolomites, cherty dolomites, quartzites, and calcareous quartzites occur at Bandalamottu, Dhukonda, and Nallakonda of Agnigundala area. The mineralization is mainly controlled by stratigraphic and lithologic features. Galena, sphalerite and pyrite are the dominant ore minerals in dolomites, while chalcopyrite and bornite are dominant in quartzites. Linnaeite, covellite, chalcocite, and bravoite are accessories. In addition to these, X-ray patterns show the presence of violarite, cobaltite, niccolite, stibnite, meneghinite, sternbergite, penroseite, and cuprobismutite. Malachite and azurite are the liberation products of chalcopyrite and bornite during oxidation.

The field and mineralogical associations, textural, petrographic and petrochemical features show that Pb, Zn, and Fe sulphides represent a primary sedimentary genesis, subsequently metamorphosed and recrystallized, while copper mineralization is due to later hydrothermal activity. The presence of linnaeite and bravoite indicates low temperature of the order of 300°C and below, low pressure, and low oxidation for the ore formation.
Geochemistry of Granite-Greenstone Terrain of South India
Authors: Sreenivas B. L. , Srinivasan R.
Published: November 2024

A critical evaluation of the available major and trace element data on rocks of the granite-greenstone belts or South India leads to the following inferences: Barrovian and Abukuma facies series of metamorphism are recognizable in the terrain. Rocks of peridotitic and basaltic komatiite affinities occur in the pre-Dharwar and early Dharwar ultramafic-mafic sequence. The bulk of the greenstones are island arc tholeiites with a strong calc-alkaline affinity. The presence of detrital pyrites in the oldest conglomerates, and the occurrence of red beds in the topmost Dharwar sequence, indicate that an oxygenic atmosphere evolved through the Dharwar times. The pre-Dharwar granitoids were probably tonalitic, and through time, alkali fractionation gave rise to the Champion gneisses, Peninsular gneisses and Closepet granites. The available data are inadequate to elucidate the fractionation pattern of the granitic crust of Peninsular India.

Pyrolite and eclogite mantle are invoked for tectonomagmatic events during the pre-Dharwar and Dharwar times, respectively. Convection, and eclogite sinkers, are proposed as alternative geodynamic models.

From the geochemical evolution, it is contended that the granite-greenstone belts of Peninsular India represent a more evolved crustal condition as compared to the Archaean granite greenstone belts of South Africa and Western Australia. Obviously, the granite-greenstone belts of all the shield areas, did not evolve simultaneously.
Some New Approaches to Geochemistry of Precambrian Hydrothermal Ore Deposits in India
Authors: Raymahashay B. C.
Published: November 2024

Recent field data on hydrothermal ore deposits and experimental data on solution chemistry of minerals and dissolved species have been applied to certain Precambrian ore deposits of India. Parameters of the environment of ore deposition like temperature, fugacity of gases and concentration of dissolved species have been calculated from selected mineral assemblages. Possible lines of future research have been suggested and gaps in the present knowledge pointed out .
Geochemistry of Precambrian Carbonatite Complexes of India: Present Status of, and Gaps in our Knowledge
Authors: Udas G. R.
Published: November 2024

Carbonatites of Precambrian age occur at Newania and Mundwara in Rajasthan, Sevathur and Hogenakal in Tamil Nadu, Kunavaram in Andhra Pradesh, and KolJegal in Karnataka. The Newania carbonatite is 959±24 m.y. old (K-Ar age of an alkali amphibole), and the Sevathur carbonatite is 720±30 m.y. old (K-Ar age of a biotite). Although comprehensive geochemical studies involving major, minor, and trace elements and carbon, oxygen and strontium isotopes have been undertaken on the 37.5±2.5 m.y. old Eocene carbonatite complex at Amba Dongar, Gujarat, geochemical studies on the Precambrian carbonatites of India have been confined only to routine determinations of selected elements like Sr, Ba, Y, Ce, La, Nb, Zr, Th, Mn, Ti, F and P to demonstrate their carbonatitic affinites. Except for two K-Ar ages, and for some limited trace element data, no attempts have been made to elucidate the chronologie and petrogenetic evolution of these Precambrian carbonatites by the application of Rb-Sr, K-Ar, and U-Pb geochronometry, critical element ratios, stable and radiogenic isotope abundances, and geothermometry. Basic researches aimed at formulating geochemical criteria for locating commercially exploitable economic Precambrian carbonatite complexes are yet to be initiated in India.
The Mayurbhanj Granite - A Precambrian Batholith in Eastern Inola
Authors: Saha A. K.
Published: November 2024

The term 'Mayurbhanj Granite' is proposed here for a batholithic body of biotite-amphibole-(stilpnomelane) granite grading to alkali-feldspar granite which covers nearly 1000 sq. km area in the northern part of Mayurbhanj district, Orissa. The batholith shows intrusive relationship with the adjoining Singhbhum Granite, Dhanjori Group gabbro-anorthosite and the Singhbhum Group metamorphites, and is made up of three units which were successively emplaced within the same magmatic cycle: (a) fine-grained, homophanous biotite-ferrohastingsite (-stilpnomelane) microgranite, in part granophyric, (b) coarse-grained, homophanous to well-foliated ferrohastingsite-biotite granite, which is porphyroblastic and gneissos in the east, and (c) 'biotite aprogranite injections within the porphyroblastic gneisses in the east. The second unit is by far the largest and was intruded synkinematically with respect to the second-generation folding in the Singhbhum Group metamorphites, probably about 1.1 × 109 years ago.
Mineralogy of an Unusual Alteration Product of Kyanite from Karnataka, India
Authors: Ramakrishnan M. , Narayanan Kutty T. R. , Anantha Iyer G. V.
Published: November 2024

An alteration product of kyanite from Kudinirkatte near Holalkere, Karnataka State, is found to be a hydrous alumino-silicate with a chemical composition corresponding to that of muscovite. Thermal, X-ray diffraction, and infrared spectral data show distinct variation from the known polymorphs of muscovite. On hydrothermal reactions with potassium-rich solution, the alteration product converts to 1M muscovite, and in sodium-rich solution, it converts to a mixture of muscovite and paragonite. When seeded, it converts to 2M muscovite at a higher temperature and pressure. The alteration product of kyanite has a 1M muscovite structure with randomly distributed montmorillonite domains.
Inference of Granitic Batholiths by Gravity Studies in South India
Authors: Krishna Brahmam N. , Kanungo D. N.
Published: November 2024

Three well-defined gravity 'lows' in Kodaikanal, Gudalur and Erode regions are explained as due to granitic batholiths at depth. The scattered outcrops of granitic bodies exposed in these regions are suggested to be interconnected at depth, and, therefore, are merely the surface expressions of the three concealed batholiths. Although the exposures of the individual granitic bodies in the Kodaikanal-Coimbatore region are elongated in an east-west direction, it is surmised, from structural evidences, that the main batholith is elongated in a roughly NNW-SSE direction.

A striking correspondence between the isoseismals for the Coimbatore earthquake of February 8, 1900 and the gravity contours is noticed. It is suggested that the Coimbatore earthquake (and the reported seismicity near Kottayam and 'Palghat Gap') could be the result of some minor readjustments of the boundaries of the batholith along fault planes.
Petrographic Characters of Coals from Makum Coalfield, Assam
Authors: Mukherjee B. C.
Published: November 2024

High sulphur coals from Makum Coalfield, Assam, give an interesting petrographic assemblage, the maceral vitrinite forming around 90 per cent of the constituent macerals. Separation of the macerals Vitrinite, Fusinite, Exinite and Micrinite is attempted by gravity separation technique and concentration of these macerals; of good petrographic purity, is obtained. Chemical analyses of the macerals thus separated, reveal among other things (regarding rank etc.) the presence of sulphur dominantly in the Exinite group. From this observation, the removal of sulphur of these coals is visualised.
Evolution of Peninsular Gneiss Restraints, Reasons and Reflections
Authors: Srinivasan R. , Sreenivas B. L. , Krishna Rao B.
Published: November 2024

Peninsular Gneiss' is a product of syntectonic remobilization of some sialic basement (Fundamental gneiss?) with reference to Dharwar folding. The preservation or obliteration of the basement relation with respect to Dharwars is a function of varying degrees of remobilization characteristic of low pressure and high pressure metamorphic belt regions of Karnataka. By remobilization the basement highs within the schist belts were transformed to mantled gneiss domes, and tonalites were made over to granodiorites and adamellites. With a common source of heat, accompanying the remobilization, retrogression of high grade metamorphic rocks of older' Sargur Supergroup' and prograde metamorphism of volcanics and sediments of 'Dharwar Supergroup' were accomplished.
Source and Fixation of Nickel in the Nickeliferous Limonite Profile of Sukinda Valley, Orissa
Authors: Chakraborty K. L. , Chakraborty Tapan Lal
Published: November 2024

Nickeliferous limonite occurs over a wide area above tbe serpentinized ultramafic rocks of Sukinda Valley (85°45'E: 21°4'N - 85°52'E: 21°4'N), Orissa, India. It is overlain by a thin mantle of laterite, and is itself underlain successively by silicified ultramafics and serpentinites with layers of chrornitite, followed by unaltered or partly altered dunite-peridotite. Nickeliferous limonite profile extends from 1.22 metres up to 7.0 metres on an average below the laterite cover. NiO content in limonite varies from 0.32 to 1.17 per cent; in the primary ultramafic rocks (e.g., dunite-peridotite) from 0.44 to 0.75 per cent, and in the chromitite from 0.13 to 0.40 per cent. Thin laminations of the chromite layers are preserved in the limonite on the hanging and foot-wall sides, indicating its formation in situ. No separate nickel mineral was identified.

It is concluded that nickel was fixed in the lattice positions of olivine and chromite in dunite-peridotite and chromitite respectively. The element was released during breakdown of these minerals by residual weathering, and was precipitated in the limonite profile at the base of the laterite mantle in an acid environment.
The Living Foraminifera of Dummulapeta Creek East Coast of India
Authors: Venkata Rao T. , Subba Rao M.
Published: November 2024

Dummulapeta Creek is a marginal marine environment near Kakinada, east coast of India. The foraminifera as well as seasonal variations in their abundance and distribution in the creek have been investigated in relation to different ecological factors like salinity, temperature, pH, and dissolved oxygen of waters in contact with the sediment, and texture and organic matter content of the sediments.

Fifty-six species of foraminifera have been identified from the creek. Of these, 33 species were never found in living condition in the creek. Of the remaining 23 species represented by living individuals, only QuinquelOculina seminulum, Ammonia beccarii, A. tepida, A. dentatus, and Miliammina fusca var. occur abundantly in the creek. These species seem to reproduce in the creek in December under relatively low temperature and salinity conditions.
The Bauxite Deposits of Anantagiri, Visakhapatnam District, Andhra Pradesh
Authors: Ramam P. K.
Published: November 2024

Bauxite forms cappings at altitudes varying from 1090 to 1445 m above mean sea level, over the garnet-sillimanite gneisses near Anantagiri in Visakhapatnam district, Andhra Pradesh. Major cappings occur on Galikonda, Raktakonda, Katuki and Chittamgondi hills while those near Kottavalasa are relatively small. Bauxite is either light to dark brown or pink in colour and moderately hard with crystalline gibbsite occuring in varying proportions. The average thickness of bauxite in the various cappings may range between 3 and 15 m, while the maximum thickness encountered is about 50 m on Galikonda. A typical profile of the bauxite residuum in the area consists of a lateritic bauxite underlain by partially lateritised khondalitic gneiss or lithomarge followed by kaolinised and unaltered khondalitic gneiss. These bauxites are low in silica and titania and relatively high in iron oxide when compared to those derived from the Deccan basalts. The development of bauxite over the sillimanite rich gneisses, relict foliation, pseudomorphs of gibbsite after sillimanite, garnet and felspar, and the unaltered partings of the bed rock within the bauxite residuum, reveal that these bauxites' are formed from tbe in situ transformation of the subjacent garnet-sillimanite gneiss (khondalite). While the lithology and physical properties of these gneisses are congenial for lateritisation/bauxitisation on a regional scale, the preservation of some of the cappings with remarkable thickness may be attributed to a favourable structural setting. It is surmised that these bauxites are of post Mio-Pliocene age.
Geochemistry of Subsurface Hornblendic Rocks from Kolar and the Archaean Crustal Composition of the Peninsular Shield
Authors: Divakara Rao V. , Venkatnarayana B. , Ramana Y. V.
Published: November 2024

Major and minor elemental analyses of the subsurface hornblendic schists, granulites and basalts from the Kolar schist belt, India (a Precambrian schist belt), suggest that the crust was mostly basic in the Archaean times and similar to tholeiitic basalt.
Implication of the Mobile Belt of the Indies Archipelago on the Concept of Continental Drift Between India and Australia
Authors: Karunakaran C. , Ray K. K. , Saha S. S.
Published: November 2024

The Indies mobile belt stretching from northern Burma through the Indonesian to the Australasian archipelagoes is essentially Upper Mesozoic-Cainozoic in age. It is intercontinental in a sense that it is situated between the continents of India and Australia on one side and Sino-Sunda continent on the other, but essentially intracontinental because subsurface continuity of the continental mass and pre-geosynclinal sedimentary formations can be envisaged between the two sectors of continental mass below the geosyncline.

Studies of the geology of the various parts of the Indonesian mobile belt especially the transverse vertical gelogical cross sections of various segments of the belt in Assam-Burma, Andaman-Nicobar, Mentawal-Sumatra and Australasian sectors, suggest spatial continuity of the continental crust and pre-geosynclinal geological formations below the Upper-Mesozoic-Cainozoic geosynclinal formations of the mobile belt.

Absence of any imprint on the Indonesian mobile belt expected due to continental drift between India and Australia corroborates the view of the non-existence of such continental drift.
Occurrence of Fossil Lion and Spotted Hyena from Pleistocene Deposits of Susunia, Bankura District West Bengal
Authors: Dutta Arun Kumar
Published: November 2024

The note records the occurrence of fossil lion, Panthera cf. leo, and spotted hyena, Crocuta cf. sivalensis, in the Pleistocene alluvial deposits near Susunia in Bankura district West Bengal. This is the first definite record of fossil lion from India, and that of C. cf. sivalensis from any Pleistocene deposit in Peninsular India. The fossils are described and their distribution is briefly discussed,
A Contribution to the Geology of Lansdowne Area, Garhwal Himalayas, India
Authors: Gupta L. N.
Published: November 2024

Lansdowne granite gneiss shows a tectonic contact with the underlying Lansdowne metamorphites. The metamorphites show repeated and superposed progressive regional metamorphism. Three phases of deformation and folding are noticed. The rare assemblage, chloritoid, staurolite, kyanite, andalusite and quartz is present in the area.

Granite is metamorphosed into augen gneiss, mylonites and phyllonites. Muscovitisation, tourmalinisation and greisening indicate chemical alteration in the granitic rocks. Textural features are correlated with deformation and folding.
Diagenesis of the Dark Grey Limestone of Nagod Formation, Madhya Pradesh
Authors: Srinivasa Rao K. , Ghosh D. B. , Chamanlal
Published: November 2024

The rocks of the Vindhyan supergroup show evidences of deposition in a shallow marine environment, the depositional basin being similar to 'epeiric sea'. The dark grey limestone unit of the Nagod Limestone Formation is a low magnesian limestone and is invariably an intrasparite or oosparite with variable amounts of authigenic cement spar, neomorphic spar and micrite occupying intra- and inter-allochemical pore spaces. Fibrous nonferroan calcite, dog tooth fringe of nonferroan calcite, drusy mosaic of ferroan calcite and syntaxial rim cement, constitute the different types of cements noticed. Authigenic minerals like dolomite, quartz, plagioclase and pyrite are present in small quantities. Based on the precipitational and recrystallisation fabrics of the calcite and the presence of different authigenic minerals, the diagenetic history of the limestone is worked out.
A Comparative Study of the Geochemistry of Zinc and Cadmium in the Skaergaard Intrusion
Authors: Dissanayake C. B.
Published: November 2024

Being group lIb elements, both Zn and Cd show similar chemical properties. The chemical analysis of a suite of rocks and separated minerals from the Skaergaard intrusion, East Greenland has enabled a detailed comparison to be made of the geochemistry of Zn with that of Cd.

Both Zn and Cd show an affinity for ferromagnesian minerals, A study of their mode of entry into structural sites however, points to the fact that while Zn shows a definite preference for Fe2+ sites in all the minerals studied, Cd shows a lesser tendency to substitute for the Fe2+ sites, except in the case of pyroxene. While Zn shows a very weak tendency to substitute for Ca2+ sites, Cd displays a much stronger affinity for the Ca2+ sites.
Regional Magnetic Investigations in the Coastal Tract East of North Cuddapah Basin
Authors: Bhaskara Rao V. , Narasimha Swamy G.
Published: November 2024

Three magnetic profiles were laid across the coast, east of North Cuddapah basin. Three subsurface ridge systems were inferred and related to the rejuvenation of the Eastern Ghats and the great east to west compressional forces during the Cuddapah orogeny. The extension of the Gondwana basins belween the ridges in the coastal tract is examined and discussed.