bluuebunny/crossref_metadata_2025 huggingface dataset:
Nepheline Syenite from Rairakhol, Sambalpur District, Orissa
Authors: Panda P. K. , Patra P. C. , Patra R. N. , Nanda J. K.
Published: November 2024

A newly identified body of nepheline syenite with associated non-feldspathoidal syenites from the Rairakhol area of Sambalpur district in the Eastern Ghat belt of Orissa sector adds to the present population of such complexes in this segment of Precambrian crust of Indian Peninsula. Recent researches have emphasized the significance of these bodies as a major Late-Proterozoic tectonothermal marker event in this belt.

The Rairakhol syenitc complex consists mainly of nepheline syenite, syenite and minor quartz syenite. Biotite and hornblende are the chief mafic constituents which occur as accessories in varying proportions. This body is emplaced within an interbanded sequence of quartzite, khondalite and charnockite. Syenitic rocks have a flow banding/foliation well-developed at many localities. A pink pegmatitic K-feldspar sycnite possibly represents a late-magmatic product. Occurrences of a few relatively smaller bodies of similar composition are also recorded.
Solubility of Gold and Silver in Oxygen-Saturated Fluids and the Formation of High Fineness Gold Grains in the Lateritic Profile
Authors: Jaireth Subhash
Published: November 2024

This short note reports calculated solubilities of gold and silver in low-temperature, moderately saline, oxygen-saturated fluids. Based on the solubilities of goId and silver it is argued that the quantity of gold transported by the fluids depends on the concentration of silver in the primary ores. In ores, where silver/gold ratio is high (>1 to 10) the fluids become saturated in silver and cannot dissolve geologically significant concentrations of gold. In ores where the silverlgold ratio is low (< 1), the fluids remain undersaturated with respect to silver and can dissolve geologically realistic concentrations of gold and silver. The oxidised fluids will start depositing gold and silver as they move downwards and are reduced by the Fe+2 bearing minerals of the primary ores. The formation of gold in the lateritic profiles can be explained by a prolonged process of interaction between the fluid and the primary ores.
Metamorphism and Structural Interpretation of the Zanskar Shear Zone, PJW Himalaya, India
Authors: Routh Joyanto
Published: November 2024

Herren in 1987, reported normal faults resulted in the telescoping of metamorphic isograds within a 200 meter zone between Sumche Topko to Mulung Topko in the Zanskar Shear Zone NW Himalaya. However petrographic study-of sections obtained from Mulung Topko and surrounding areas (pensila-padarn section) indicate that the rocks belong to the kyanite-sillimanite-starurolite grade only. Extension crenulation cleavage and other shear criteria show an initial NESW movement after which a layer parallel extension occurred and the shear zone developed. Minieralogical assemblage and mapping indicate that the isograds run paralleI to each other before they possibly truncate against the shear zone along the Pensila-Padam section. A probable model has been proposed to explain the features.
Geochemical Constraints on the Genesis Phosphorites of Chhattisgarh Basin, Durg District, M.P., India
Authors: Khan M. W. Y. , Mukherjee A.
Published: November 2024

This paper documents the geochemical and mineralogical characters of the phosphorite of Charmuria Formation (Chhattisgarh Basin). X-ray diffraction studies have revealed presence of carbonate fluorapatite as the only apatite mineral in this phosphorite, along with quartz as major gangue, and kaolinite-illite, calcite and pyrite in subordinate amounts. Structural formula of this apatite closely resembles carbonate fluorapatite. Further, CaO/P2O5 ratio (1.37 - 1.99) suggests that this phosphorite has not been affected by weathering. Quartz dominance over clay minerals and low CIA (24.79 - 46.87) is attributed to the tuffaceous nature of siliceous clays (lithofacies-A). The depletion of Sr, and trace elements of organic association in siliceous clays, phosphorite and phosphatic siliceous clays point to a common provenance.
Geodynamic Evolution of Indian Shield During Proterozoic: Geochemical Evidence from Mafic Volcanic Rocks
Authors: Raza M. , Jafri S. H. , Alvi S. H. , Shamim Khan M.
Published: November 2024

Geochemical data on Proterozoic volcanic rocks of Indian shield overwhelmingly suggest that tlhey were generated in two different tectonic settings. The mafic volcanic suites of Aravalli (Aravalli craton) and Bijawar (Rundelkhand craton) belts and those of lesser Himalayan region appear to be lift related continentat type. On the other hand Delhi volcanics (Aravalli craton), Dongargarh volcanics (Bhandara craton) and Dbanjori-Jagannathpur volcanics (Singhbhum craton) exliibit the characteristic signature of subduction zone magmatism implying the destruction of oceanic lithosphere by processes akin to those of modern plate tectonics. Geochemical and geological evidences suggest the occurrence of a nearly Proterozoic ocean in Central India located between Dharwar-Singbhum-Malwar rotocontinent in the south and Bundelkhand protocontinent in the north. During middle Proterozoic, the oceanic lithosphere subducted towards south along the northern margin of southern protocontinent. The lack of complete calc-alkaline series in the subduction - generated volcanic suites suggests that are volcanism along this margin could not acquire maturity and that the period of subduction was short lived. The collision of the two protocontinents led to the closure of ocean and induced the Satpura - Delhi orogeny at about 1500 m.y. ago-The ophiolitic seqeunce of Phulad (Delhi belt), Dalma (Singhbhum belt) and probably Tal (Bijawar belt) are the possible evidences of closure.
High-Alumina Hypersthene in a Basalt Flow from Mt. Sundook, Siberian Traps, Russia
Authors: Murari R. , Krishnamurthy P. , Gopalan K. S. , Nesterekno G. V. , Tihonenko P. I.
Published: November 2024

Electron probe microanalysis (EPMA) and preliminary x- ray diffraction studies on a basalt flow from Mt.Sundook have revealed the presence of rare high-alumina hypersthene in the groundmass. The basalt occurs at the base of a 800 m flow sequence (Ivakinsky and Syverminsky suite) that unconformably overlies a Permo-Carboniferous sedimentary sequences. It is postulated that besides normal processes of fractionation, assimilation-fractional Crystallization (AFC) processes involving the parental magma and crustal components (pelitic sedinientary rocks) were responsible for the formation of hypersthene in the basalt. The presence of a complex feldspar and pyroxene assemblage may also be an additional evidence for the operation of such an AFC process.
Tectonic Setting, Petrochemistry and Tungsten Metallogeny of the Sewariya Granite in the South Delhi Fold Belt, Rajasthan
Authors: Bhattacharjer J. , Fareeduddin  , Jain S. S.
Published: November 2024

The Scwariya granite, 'largest of the Erinpura granite intrusions' occurs along the western margin of the Middle-Late Proterozoic Soulh Delhi Fold Bell. Synkincmalic with the Delhi orogeny, the granite body intrudes a rifled back arc type basin (Barotiya Formation) and hosts W ± Sn ± Li mincralization in pneumatolytic quartz veins. Innumcrable metasedimentary enclaves occur which are traversed by syn-to post-tectonic ductile shear zones. Geochemistry of Ihe granite suggests it to be a well differntiated, calc-alkliline, S-typc metallogcnetically specialised orogenic massif. The nature of the granite and the host supracrustals and Ihe tectonic discriminant diagrams indicate that it may have evoled in an arc-related environment. W ± Sn ± Li mineralization in this granite, Pb-Zn-Cu and Zn-Cu mineralization in the contiguous units of Barotiya and Sendra formations respectively suggests a conspicuous metallogenic zoning.

The Sewariya granite forms a central link to the major Sn-W hosted granite rocks in Rajasthan Haryana sector that lie along a 500 km long NNE-SSW trending lineament. Although associated with felsic plutonic suites of contrasting geotectonic environments, W -Sn mineralizalion along this belt defines a single metallogenic province, a large part of which is unexplored.
Uranium Mineralisation in the South-Western Part of Cuddapah Basin: A Petromineralogical and Geochemical Study
Authors: Dhana Raju R. , Roy Minati , Roy Madhuparna , Vasudeva S. G.
Published: November 2024

Two types of uranium mineralisation occur in the south-western part of Cuddapah basin, viz., stratabound type hosted by impure dolostone of the Vempalle Formation of the Papaghni Group and structuralIy-controlled type hosted by deformed basement grani toid. The carbonate-hosted type occurs over a 140 km-long belt from Reddipalle in the west to Maddimadugu in the east with promising mineralisation at Tummalapalle, Rachakuntapalle and Gadankipalle. It is sandwiched between a Iower massive limestone and upper shale and cherty limestone. The rnineralised carbonate rock is a stromatolite-bearing 'siliceous, calcitic doIostone ' (SCD+phosphate) associated with other impure dolostones, quartzite, chert, phyllite, conglomerate, and intrusive dolerite a nd basalt. Uranium mineralisation occurs along the bedding plane, carbonate-phosphate conlact, micro-stylolites, grain boundaries of clasts and within pelioids, mainly in the form ultrafine pitchblende, in intimate association with pyrite and as disseminations in cellophane-rich parts, besides as minor phases ot'coffi~itea nd U-Ti compIex. The associated ore minerats include pyrite, molybdenite, chalcopyrite, bornite, digenite and covellite. The fertile basement granite fs.1.) is the source of uranium and the mineralisation, which appears to be polygenetic(syn-, dia- and epi-genetic), is controIled by impure nature of dotostone and organic activity. The mineralisation in the southern part of the belt in Cuddapa h district is typically molybdenum-rich, whereas the northern portion, in parts of Anantapur district, is characterised by high content of copper. The rnineralised SCD in the S/SE parts is also marked by high content of P, V and Pb, in addition to Mo. There is a good positive correlation of U with Pand V (r : 0.98 and more).

The structurally-controlled uranium mineralisation occurs around Rayachoti (outside the SW margin of Cuddapah basin) along a number of fracture zones within the basement granitoid, and is hosted by mylonites and cataclasites indicative of intense dislocation metamorphism. Of many such zones, the one between T. Sundupalle and Sanipaya is promising and has a strike extension of about 16 km. This mineralisation is epigenetic hydrothermal vein-type, mainly represented by coffinite, pitchblende, U-Ti. complex and secondary uranium minerals.
Some Geo-Technical Aspects of Meander Cutoff in Alluvial Environment
Authors: Chakraborty K.
Published: November 2024

The non-tidal Bhagirathi river, one of the most important waterways of West Bengal, India, displays picturesque meanders the behaviour of which appears to be random because of urpredictable bank-erosion. Thus an investigation has been made on some geo-technical aspects of the soil of the banks of the river. The results show that the nature of thc erosion of the banks which possess very closely similar soils, is difficult to explain only on the basis of the soil properties. It appears that the existing hydro-dynamic environment, its mega-or micro-Ievel changes and the soils of the banks are the key factors behind this bank-erosion.
Gold Mineralisation in the Precambrians (Bhukia Area) of Southeastern Rajasthan-A New Discovery
Authors: Grover A. K. , Verma R. G.
Published: November 2024

Several; ancient mines or old working exist in the vicinity of Bhukia village near Ghatol in Banswara district, Rajasthan, within Precambrian metamorphosed volcano-sedimentary rocks. These old workings/mines were earlier explored for base metals, specially for copper. Recent work carried out in this part indicated prcsence of native gold in visible form in some of the grab samples taken from two mine dumps. The maximum size of gold flake noticed is 4x2 mm. Higher gold values are generally associafed with high copper and arsenic values. This suggests re- examination of the ancient mines and certain lithounits present between Salumbar and Banswara, southeastern Rajasthan for gold.
Early Proterozoic Aravalli Metasediments and Their Relation with the Ahar River Granite Around Udaipur, Rajasthan
Authors: Guha D. B. , Garkhal R. S.
Published: November 2024

The Aravalli Supergroup around udaipur area, comprising volcano-sedimentary assemblage, is classified into three Groups, viz., the Delwara, the Debari and the Jharol Groups, based on two prominent horizons of conglomerate. The Lower Aravalli Delwara Group is separated from the Middle Aravalli Dcbari Group by a pronounced unconformity marked by a thick horizon of conglomerate exposed at Kabita which has heen correlated with the Debari conglomerate of the type locality. The Bari Lake volcanics are correlated with the Delwara volcanics and the quartzite-conglomerate occurring within the former are intertrappean in nature. The Ahar River Granite is identified as the post-Middle Aravalli intrusive granite, which intruded the Delwara volcanics and the Debari phyllite in comagmatic pulses of the same granitic magma.
LANDSAT Thematic Mapper Data Applied to Structural Studies of the Eastern Ghat Granulite Terrane in Part of Andhra Pradesh
Authors: Chetty T. R. K. , Murthy D. S. N.
Published: November 2024

LANDSAT TM data have been used as an aid to studying the regional geology of the granulite terrane in the southern part of Eastern Ghats. The technique in conjunction with regional traverses proved to be useful in identifying regional structural elements, such as shear zones, fold patterns of different scales and other lineament patterns, in poorly exposed and inaccessible areas. A major crustal scale ductile shear zone, designated as Sileru shear zone, with a dextral sense is highlighted and lies at the western margin of the high grade terrane. The other shear zones within the granulite terrane, characterised by migmatitic gneisses and typical L-S mylonitic fabrics, are associated with transpressional tectonics. Fold patterns varying from tight upright isoclinal folds to refolded large scale recumbent folds, along with complex fold interference structures on mesoscopic to regional scale are described. The interpretation of LANDSAT data, followed by limited ground based traverses from Sileru to Visakhapatnam in Visakhapatnam district and from Chinturu to Eleswaram in East Godavari district are the constraints in precisely defining the regional structures and understanding the tectonic processes that fashioned shear zones and fold patterns in granulite terranes. A fold thrust thin-skinned tectonic model involving two tectonothermal events for the study area is envisaged.
Occurrence of the Coral Reefs on the Bhandarpule Coast, District Ratnagiri, Maharashtra
Authors: Sukhtankar R. K. , Pandit S. J. , Shirke A. J. , Kulkarni S. A.
Published: November 2024

Development of living corals in the form of patch reefs has been recorded in the intertidal zone at Bhandarpule beach, District Ratnagiri, Mabarashtra. These are pink and reddish in colour and are composed of corals of the order of Stolonifera. These occur as a thin blanket on the hard substrate of volcanic breccia. Their occurrence in association with oyster bed and sea cave but at different elevations represents minor fluctuations of the sea level during the Holocene, associated with the Flandrian transgression.
Archaean Meta Lamprophyres from Nuggihalli Schist Belt, Hassan District - Karnataka
Authors: Sugavanam E. B. , Mallikarjuna C. , Vidyadharan K. T.
Published: November 2024

The Archaean Dharwar greenstone belts of Karnataka predominantly consist of iron enriched tholeiitic Metabasalts, basaltic komatiites, sulphidic chert bands and argillite-graywacke sequence. In Nuggihalli schist belt, in association with mafic-ultramafic rocks, calc-alkaline lamprophyres (Spessartite-Kersantite suite), comparable with Kamblada-Yilgam of Western Australia, have been recorded for the first time. Gold mineralisation is associated with these meta-lamprophyres.

The lamprophyres, in Nuggihalli belt, is a highly banded hornblende-biotite rich quartzo-felspathic rock, forming sill like bodies at the contact of mafic-ultramafic rocks, intensely co-folded along with the enclosing rocks, recording three phases of deformation.

REE values, plotted against MORB values confirm lamprophyric affinity with increased values for Sr, K, Rb, Zr and Y. In Rock/Chondrite values plot, very pronounced increase in values of Ba, Rb, K, P, Zr and Ti is indicated while a pronounced depletion in Nb is brought out, characteristic of Calc-alkaline lamprophyres.

Search for similar rocks in many ultramafic belts in Southern Peninsular Shield will be of great Significance in working out the tectonic evolution ofthese greenstone belts and also serve as favourable target areas for gold exploration.
Gravity and Magnetic Studies Over Parts of Khairagarh Basin, Central India
Authors: Rao R. L. N. , Srinivas R. , Sethuram S. , Subba Rao J. R.
Published: November 2024

Interpretation of gravity and magnetic data in a strip of 250 sq.km. over Lanji-Darekasa tract of Khairagarh basin has been attempted in order to delineate regional structures and controls of uranium mineralisation in the province. Magnetic map indicates three parallel east-west trending lineaments representing basic dykes cutting across the geologic fonnations. The orthogonally intersecting gravity and magnetic trends around Saheki (80° 31' : 21° 27' 30") reveal a tectonised zone favourable for uranium minelisation. Gravity low of the order of five milligals near Nimbanaka (21° 19' : 80° 31' ) suggests a sharp increase in the thickness of Bijli rhyolites.

Based on observed gravity, magnetic data and the available surface geological information, the paper proposes a model for configuration of Khairagarh basin along Lat. 21° 25' between Parsori and Khairagarh. Maximum thickness for volcano-sedimentary pile filling the basin along this section is estimated to be around 2300m. The model also indicates possibility for the presence of a concealed high density formation (Pitepani Volcanics?) below Bortalao sandstones.
Carbonic Metasomatism and Charnockitic Alteration
Authors: Santosh M. , Radhika U. P.
Published: November 2024

Field relations in an orthogneiss quarry within the Palghat Gap region illustrate the development of charnockite alteration halos surrounding alkaline pegmatite dykes. Altered orthopyroxenes in the charnockitic zones are artifacts from concordant melt pockets within the gneisses, where orthopyroxene has developed prior to the charnockitie alteration during regional metamorphic, in a process equivalent to dehydration melting. The charnockitic halos represent metasomatic alteration zones developed through the infiltration of CO2-H2O fluids expelled from the dykes at shallow crustal levels. Such examples of greasy green charnockitie alterations could be a widespread phenomenon in different crustal blocks of varying metamorphic grades, and are unrelated to regional prograde granulite processes.
Orbicular Rocks from Closepet Granite Near Hoskote, Tumkur Dt., Karnataka
Authors: Srikantia S. V. , Bhat P. G. K. , Subramani N.
Published: November 2024

The paper records the first occurrence of Orbicular rocks from the Closepet Granitoid belt near Hoskote, Tumkur district, Karnataka. The orbicules occur in a dioritic country rock enclosed within grey Closepet Granitoid. These are multishelled orbicules with shells of plagioclase and hornblende with a core of the same minerals. There are also proto-orbicules. The chemical analyses of orbicules fall in mafic tonalite field on K2O - CaO plots. Individual shells reflect a basic rock parentage. The orbicules are derived from a metabasic enclave due to granitic action by melting, diffusion and concretionary process in hydrous stage.
High-Temperature Reactions of Alkali and Plagioclase Feldspars With Alkali and Alkaline Earth Chlorides: Formation of Celsian
Authors: Swamy V. , Menon A. G. , Anantha Iyer G. V.
Published: November 2024

High-temperature reactions (Ca 900°C) involving albite, K-feldspar or plagioclase and K, Ba-or K, Sr chlorides were experimentally studied. These experiments reveal that the reaction between K-exchanged albite, potash feldspar, or plagioclase and Ba-chloride/Ba-K chloride results in the formation of celsian by the breakdown of the starting feldspar structure above 800°C. Sr-feldspar does not form under similar conditions. A size-effect of the large M-site cation appears to be responsible for the formation of celsian. The reaction between K-feldspar and barium chloride may be used as a method for synthesizing celsian.
The Crystalline Thrust Sheets in the Himachal Himalaya and the Age of Amphibolite Facies Metamorphism
Authors: Bhargava O. N. , Bassi U. K.
Published: November 2024

Three distinct crystalline thrust sheets exist in the Himachal Himalaya. These in ascending tectonic order of superposition are: (i) Kulu Thrust Sheet, (ii) Jutogh Thrust Sheet and (iii) Vaikrita Thrust Sheet. The crystalline thrust sheets show five deformations and polyphase metamorphism. The analysis of existing data suggests that there have been Precambrian deformations and attendant metamorphism. The Kulu and Vaikrita Thrust Sheets extend throughout the length of the Himalaya and the latter's equivalents consistently form the floor for the Tethyan sequences.
Roles of Relief and Climate on Composition of Detrital Sediments of Bharathapuzha Basin, Kerala
Authors: Anirudhan S. , Thiuvikramji K. P. , Roy Chacko P. T.
Published: November 2024

Channel sediments of Bharathapuzha (BP) basin provide an unique opportunity to examine the relative roles of climate and relief on the character of first cycle detritus derived from a source area of high grade metamorphic rocks, as the major tributaries of the river are set in diverse climatic domains. For e.g., Gayathripuzha (GP) and Thuthapuzha (TP) are in a tropical setting, while Kalpathipuzha (KP) enjoys a semi-arid climate. Sediments of a tropical-, low relief stream, the Tirur river (TR) lying adjacent to Bharathapuzha (BP) in the north, have also been examined.

The average mineralogical maturity of sands expressed as Q:F:R ratio, for the mainstream of BP varies from 72:19:9 for coarse to 53:38:9 for medium sand and to 49:44:7 for fine sand, implying an arkosic composition. The Q:F:R ratios of GP and TP, the two high relief tributaries on the one hand and of KP, the low relief trib utai) on the other are similar to that of mainstream of BP basin. However, quartz arenite (Q:F:R = 93:5:2) is under transport in the tropical-low relief, Tirur river (TR).

The chemical maturity index (CMI), i.e. the ratio of SiO2/Al2O3, for the sediments of main stream (7.27) and for the tributaries, amply demonstrates the immaturity of the channel sediments. Nevertheless a value 120, for Tirur river sands indicates their super maturity.
Effect of River Discharge on the Morphology of Benthic Foraminiferal Test
Authors: Nigam Rajiv , Khare Neloy
Published: November 2024

Twenty one surface sediment samples collected from the inner shelf region off Karwar at 22-52 m water depth range have been studied for foraminiferal content. Based on the external test morphology the entire foraminiferal population (148 species) can be placed into two broad morpho-groups namely angular-asymmetrical and rounded-symmetrical morpho-groups. The surficial distribution of these groups revealed that angular-asymmetrical morpho-group gets adversely affected by high turbulence associated with increased fresh water river disCharge, whereas, rounded-symmetrical morpho-group responded in a reverse manner. Since areal extent of river induced turbulence depends upon fresh water discharge due to monsoonal rains, the results show high potential in generating proxy data for the reconstruction of paleomonsoonal history through the study of morpho-groups in sub surface sediments of coastal regions.
Magma Fractionation and Mixing in Nephelinite Plug Associated with Deccan Magmatism at Murud-Janjira, South of Bombay, India
Authors: Dessai A. G.
Published: November 2024

The nephelinite occurs as a N-S trending plug (500 × 200 m.) intrusive into basalts. The rock is porphyritic and principally composed of complexly zoned phenocrysts of clinopyroxene, Fe-Ti oxide and olivine <5%) in a fine grained groundmass dominated by clinopyroxene, nepheline and Fe-Ti oxides. Mineralogically and chemically the rocks vary between pyroxene melanephelinites and nephelinites.

The mineral chemistry implies that the magma has undergone varying degrees of polybaric crystallisation in a subcrustal magma chamber with mixing of more fractionated magma with primitive pulses in which are incorporated disaggregated mantle xenolith phases.
Ore Mineralogy of Western Auriferous Zone of Gadag Greenstone Belt, Karnataka
Authors: Ugarkar A. G. , Devaraju T. C.
Published: November 2024

Gadag greenstone belt, which has a history of ancient gold mining, hosts three distinct auriferous zones viz., Western Zone, Middle Zone and Eastern Zone distributed both in metavolcanic and metasedimentary suites. The paper presents ore mineralogy of the Western Auriferous Zone which is hosted by pillowed and sheared metavolcanic rocks. Based on the relative abundance of quartz veins and sulphide minerals this zone could be classified into Type-A ore and Type-B ore.

Type-A ore comprises white quartz veins (30-90 cms thick) displaying evidence of early deformations. They contain chloritic/micaceous leafy aggregates and traces of arsenopyrite, pyrite, chalcopyrite and sphalerite ± scheelite; gold occurs in native form in vein quartz.

Type-B ore comprises mainly chlorite-muscovite/sericite-ankerite-monazite sulphide schist with subordinate vein quartz. Associated sulphides are arsenopyrite, pyrite, pyrrhotite, chalcopyrite, sphalerite and galena in the orderof decreasing abundance. Scheelite is seen occasionally. Gold occurs as: (i) native gold in silicate and quartz gangue, (ii) native gold inclusions and microfracture fillings in arsenopyrite and (iii) in combined state in arsenopyrite. Arsenopyrite could serve as a main pathfinder mineral for exploration, mining as well as processing of Type-B ore.

Mineralogical characteristics, wall-rock alterations and structural features related to Type-A ore, Type-B ore and host rocks characterise the gold mineralisation in the Western Auriferous Zone as structure controlled hydrothermal epigenetic lode.
Gold Mineralisation in Kappil Prospect, Malappuram District, Kerala
Authors: Nair R. S. , Suresh Chandran M.
Published: November 2024

A preliminary appraisal of gold mineralisation at Kappil indicates its association with quartz veins traversing the Archaean metamorphic complex comprising biotite-hornblende gneiss, quartz-magnetite granulite (QMG) and amphibolite. Gold mineralisation is confined to the highly sheared and fractured quartz veins/QMG carrying stringers and rich disseminations of pyrrhotite, pyrite, chalcopyrite and arsenopyrite. The visible native gold is distributed along fracture planes in quartzose portion and also as fine disseminations in pyrrhotite, pyrite and arsenopyrite indicating its introduction along with sulphide mineralisation.

The major element geochemistry on drill core samples has indicated a tholeiitic affinity for the amphibolite and a mixed pelitic and arkosic parentage for the biotite-hornblende gneiss. Trace element studies have shown sympathetic relationship of Au with Cu.

Five lensoid gold-bearing lode zones a re distributed along shear zones trending in a N-S direction. In the initial stages gold was syngenetically deposited with sulphide-bearing magnetite quartzite (now QMG), later, remobilisation and redistribution have caused enrichment and deposition of gold along shear zones. Post-magmatic processes are considered responsible for the localisation of gold and metal sulphides.
Petrochemistry and Tectonic Setting of the Champawat Granite Suite of Lesser Himalaya, Pithoragarh District Uttar Pradesh
Authors: Hussain Shabbir , Raju S. , Dayal B. , Fareeduddin
Published: November 2024

The concordantly emplaced polyphase granite suite exposed in the Champawat area of Pithoragarh district of Uttar Pradesh represents a part of the southernmost granitoid belt of Himalayan region. In the field it can be divided into four successive mappable phases, viz. biotite granite, grey granite, leucogranite and microgranite. Mineralogically the biotite granite and grey granite are classified as "granodiorite" while the leucogranite and microgranite are classified as "granite". All these varieties of granite show xenoliths of country rocks. Champawat granite suite is a well differentiated, polyphase, calc-alkaline, peraluminous, S-type granitoid batholith that ranges in composition from granite to granodiorite- adamellite and trondhjemite. It is interpreted to be the product of anatexis of supracrustals at middle to lower crustal levels. The geochemical discriminant diagrams of the Champawat granite suite suggest that it is an orogenic granite showing characters of continental collision environment.
Influence of Geology on the Localization of Ancient Caves
Authors: Deshmukh Megha
Published: November 2024

Of the 1545 caves in India, more than 1200 caves are located in the region of Deccan Trap in Maharashtra State. The reconnaissance survey of these caves demonstrated that more than 1000 caves are concentrated in the area made up of amygdaloidal basalts, as they provide suitable medium for carving. In contrast to this, in the region of compact basalts, which do not provide homogeneous medium for carving due to their jointed nature, the cave centres are few and far between. This clearly indicates that the carving activity in the Deccan Trap region was influenced by the geological factors and not by trade routes as is commonly believed.
North Gujarat Rivers: Remnants of a Super Fluvial System
Authors: Sridhar V. , Merh S. S.
Published: November 2024

A thickness of over 300 m of dominantly alluvial sediments in the north Gujarat plains suggest that the sedimentation took place during the late Quaternary period in a huge graben bounded by faults that are related to the Cambay basin. An ancient super fluvial system was responsible for this vast accumulation. Most of the present day rivers are the remnants of that former system and have exposed the sediments in cliff sections. The present course of the Sabarmati appears to be unrelated to the former system for much of its length. Its course is controlled by a major lineament that developed subsequent to the deposition of the entire sequence. The earlier course of the river is now represented by the river Rupen. The uplift of the Aravallis during the Mid-Late Quaternary and the eustatic sea level changes might have disrupted the older system.
Spinifex-Textured Peridotitic Komatiite from Honnabetta Area, Nagamangala schist Belt, Karnataka
Authors: Devapriyan G. V . , Ananthar T. R. , Vidyadhar K. T. , Raghu Nandan K. R.
Published: November 2024

Metaultramafite exposure in the newly cut Hemavathi canal section in Honnnbetta area in the Nagamangala belt exhibits excellent spinifex texture with komaliitic chemistry implying their volcanic origin. Though, several such localities of spinifex textured peridotitic komaliitcs (STPKs) have already been recorded from Ghattihosahalli, Kummanghatta, Banasandra, Mayasandra and Karighatta areas, this new find of plate and random spinifex textured ultmmafic variant from Honnabetta is the first report from the Nagamangala belt. They show yellowish green colour with skeletal forms of olivine blades, which are totally altered to talc-tremolite-chlorite, anthophyllite, iddingsite and antigorite. Parallel sheafs and aggregates of bladed olivine pseudomorphs form plate spinifex with criss crossing random orientation pattern. The primary igneous mineralogy consists of altered relict olivine and clinopyroxene phenocrysts. A few samples exhibit micro-spinifex texture with randomly oriented, elongated platy, pseudomorphs of olivine separated by tremolite in the groundmass. Gradational change from fine to coarse-grained spinifex with long crystals (rare) of clinopyroxene in a fine-gained groundmass of tremolite and chloriteis also observed. Medium-grained spinifex rockshow crystals upto 5 to 2 mm thick and 10 to 50 mm long in sheafs with parallel grouping and abut against each other randomly at angles varying from 40 to 60° enclosing triangular to rectangular interstitial talc, chforitc, pale green finegrained chlorite and glassy material. Ilmenite-magnetite and chrornite are the important accessory opaque minerals, with ilrnenite at places showing oriented picotite inclusions. Normative plots indicate that the STPKs of Honnabetta are hurzburgitic peridotites.

Compared to the Ghattihosahalli-Kummanghatta and Banasandra STPKs, tlonnabella STPKs show characteristic plate and random spinifex texture. In texture they are similar to Karighatta STPKs and in composition they compare well with Mayasandra STPKs with their low CaO:Al2O3 ratios. lnspite of alteration (hydration), deformation and metamorphism, preservation of primary igneous structures and textures is almost perfect in Honnabetta. Such a zone with a possible thermal erosion model for the Komatiitic types imply some sulphide bodies at depth, as incidence of sulphide associated with gold minerrrlisation arc observed in Honnabetta area.
P-T Conditions of Metamorphism and Fluid Inclusion Characteristics of the Coorg Granulites, Karnataka
Authors: Srikantappa C. , Venugopal L. , Devaraju J. , Basavalingu B.
Published: November 2024

Charnockites and basic granulites occur extensively around Coorg in Western Ghats. Minor metasedimentary rocks like kyanite/sillimanite bearing gneisses and ironstone also occur. A set of late dolerite dykes cross cut all the lithologies.

The Coorg granulites record a near-peak metamorphic conditions of 720 to 760° C at pressures of 7 lo 8.6 kb. Charnockites and basic granulites contain high-density ( 1.07 to 1.09 g/cc) carbonic inclusions. Micro-textures, mineral P-T and fluid inclusion data indicate "clockwise" P-T trajectory, pointing to a relatively rapid uplift/erosion of the Coorg granulites.
Garnet-Kyanite Bearing Pelitic and Associated Mafic Granulites along Jalsoor-Mercara Shear Zone: Evidence for Deep Burial and Later Uplift
Authors: Krishnaraj N. S. , Janardhan A. S. , Basavalingu B.
Published: November 2024

Garnet-kyanite-sillimanite bearing pelitic and garnetiferous mafic granulites exposed at several places along the Jalsoor-Mercara and Bavali shear zones preserve evidences of deep burial of atleast 30 km. Estimation of P-T conditions of metamorphism of these granulites gives T of 725-800°C and P of 7 to 8.6 kb. Increase of pressure form core to rim in the garnet-kyanite assemblages and kyanite mantling garnet are the most significant aspects of these lithologies, suggesting long residence in the deep crust and possible thrust tectonics.

Moreover, fibrolitic sillimanite overgrowing kyanite in pelites and the developement of opx-calcic plag symplectites around garnet in the mafic rocks indicate decompression/uplift, subsequent to crustal thickening. This uplift could be part of a later event unrelated to the burial episode.

Significantly, syenite and anorthosite bodies of late Proterozoic age occur along these shear zones indicating that these lineaments were reactivated again in late Proterozoic times.
Grain Growth Parameters and Mineral Zoning: A Comparative Study from the Humboldt Mountains, East Antarctica
Authors: Pant N. C. , Verma P. K.
Published: November 2024

Certain aspects of regional metamorphism of East Antarctica granulite terrain in the Humboldt Mountains are revealed through a study of the grain size of garnets and chemical zoning present in them. The Ferry and Cashman approach to grain size (Crystal size Distribution-CSD) development and Walther and Wood approach of grain growth are utilised to draw intersting conclusions. The growth of garnets was slower in the deeper levels but produced large, chemically unzoned grains.
Palynology of Carbonaceous Clays of Nimar Formation, Jhabua District, Madhya Pradesh, India
Authors: Kumar Pramod
Published: November 2024

Carbonaceous clays of Nimar Formation, exposed near Umrali village in Jhabua District, Madhya Pradesh have been palynologically analysed. The palynoflora dominated by the pollen of conifers compares favourably with Jabalpur, Rajmahal, Vemavaram/Raghavapuram and Bhuj palynoassemblages. Due to nonavailability of Early Cretaceous palynofossils, the assemblage is dated as Late Jurassic.

The palynoflora points towards prevalence of fresh water, warm humid, swampy conditions during the deposition of the Carbonaceous clays of Nimar Formation.
A Study of Hogbomite in the V-Ti-Fe Deposits of Karnataka
Authors: Jayaraj K. R. , Khanadali S. D. , Devaraju T. C. , Spiering B.
Published: November 2024

Hogbomite is of widespread occurrence as an accessory and minor mineral in the V-Ti-Fe ore deposits of Ubrani, Tavarekere, Masanikere, Magyatahalli and Devaranarsipur in Shimoga district and Mulemane in Uttar Kannada district. Both primary and secondary hogbomite are found. The mineral shows considerable variation in chemistry. The analytical data indicate that hogbomite structure is relatively more open than that of coexisting magnetite/ilmenite and can admit a variety of substitutions.
Hummocky Cross-Stratification in Barakar Formation, Ramgarh Coalfield, Bihar
Authors: Gupta Abir
Published: November 2024

Sequence of moderately sorted siltstone to coarse grained sandstone containing abundant hummocky cross-stratified and swaley cross-stratified bedding has been described from five stratigraphic levels in a part of Barakar Formation, along the Damodar river, Ramgarh coalfield, Bihar. Scour and drape type and non-erosional based growing bed-forms, both types of hummocky crossstratification have been observed. The large dimension of hummocks, upsweeping of laminae, sigmoidal nature, broadly undulating erosive and flat base, draping and also the presence of tide influenced associated sedimentary structures, high sulphur and phosphorous content in the coal seams, high vitrinite content in the coal, absence of fining upward sequence, clay mineralogy, high concentration of chromium, similarities in trace element content with that of Assam coalfieds and presence of marine microfossils probably indicate that the observed part of Barakar Formation were deposited in an estuarine to marginal marine environment, Water depth was probably of the order of 1-30 m.
Precambrian Bimodal Volcanism in Weddell Sea, West Antarctica
Authors: Divakara Rao V.
Published: November 2024

Rhyolites and basalts constitute bulk of the bimodal volcanism in the Bertrab and Littlewood nunataks of Weddell Sea area, western Antarctica. Rhyolites with occasional granophyres from the two nunataks are compositionally similar except for high Ba in Littlewood. Basalts, of tholeiitic to calc-alkaline nature are mainly from the Bertrab nunatak and show compositional variation (basalt to basaltic-trachy-andesite) both in major (SiO2, 45.82 to 53.81%, MgO, 4.67% to 11.20% Na2O, 1.58 to 4.26%) and trace elements (V, Cr, Rb, Sr and Ba). The rare earth elemental abundances and their distribution patterns in the rhyolites from the two nunataks are broadly similar with comparable total REE (Bertrab 80.33; Littlewood 86.82), moderate LREE/HREE fractionation (CeN/YbN= 4.36 in Bertrab and 4.33 in Littlewood) and negative europium anomdies.

Overall major and trace elemental chemistry of the acid volcanics coupled with the systematic compositional variation from the basic to the acid end suggests a common source of origin for this bimodal volcanism. The source magma, a melt of the upper mantle appears to have evolved in a compressional tectonic regime and has intruded (extruded) in an extensional rift tectonic setting.
Marine Magnetic Studies Over a Lost Wellhead in Palk Bay, Cauvery Basin, India
Authors: Ramana M. V. , Subrahmanyam V. , Sarma K. V. L. N. S. , Seshavataram B. T. V.
Published: November 2024

Close grid masine magnetic surveys in the vicinity of a drill well site PH 9-1 in Palk Ray revealed that the area is characterized by smooth magnetic field except for a local anomaly caused by a lost wellhead. The smooth magnetic field is attributed to the deep burial of Precambrian granitic basement devoid of any charnockite intrusions. The seismic reflection records of the study area show >3200 m thick sediments over the basement.
Petrography, Geochemistry and Petrogenesis of Alkali Lamprophyres of Jungel Suite, Central India
Authors: Kumar Vinod
Published: November 2024

A systematic petrographic and geochemical study of three, previously unreported carnptonite dykes from Bijawar of Son valley is presented with a brief discussion on their petrogenesis. These larnprophyres show transition from alkali basalt and owe their origin through fractionation combined with local enrichment of volatiles, largely derived from mantle instead either by hybridization or assimiIation of basic magma with granite/late stage granitic fluids or mixing with an andesitic magrna as proposed by some earlier workers.
Retrieval of the trace of the true axial surface on an oblique section through a fold
Authors: Choudhuri Anjan Rai
Published: November 2024

On an oblique section, the line connecting the points of maximum curvature of the bounding surfaces of folded layers may not coincide with the trace of the actual axial surface. Methods have been suggested for construction of the true axial trace on an oblique section.
Cretaceous and Middle Eocene Radiolaria from Ejected Sediments of mud Volcanoes of Baratang Island in Andaman Sea of the Northeastern Indian Ocean
Authors: Ling Hsin Yi , Sharma V. , Singh Surender , Mazumdar D. , Mahapatra A. K.
Published: November 2024

Radiolarians from seven samples of ejected sediments of mud volcanoes of Baratang Island in the Andaman Sea provide additional evidence for the presence of Cretaceousand MiddIe Eocene strata beneath the island. A general NNE-SSW alignment of the mud volcanoes suggests the structural control for their occurrence due to regional tectonics.
Mineralogy and Geochemistry Of Detrital Magnetites from the Beach Sands of Cox's Bazar, Bangladesh and their Petrogenetic Implications
Authors: Mitra Sachinath , Ahmed Syed Samsuddin
Published: November 2024

Ti-poor magnetites from Cox's Bazar beach are seen to be remarkably homogeneous, chemically and optically, containingless than 2% uIvospinel. Mg, Ti, Cr, A1 and V, though in insignificant amounts, are found to be responsible in contributing to the reduction in hyperfine field of the Mossbauer spectrum, which showed linewidths of 0.18 mm/s at B-site and 0.26mm/s at A-site. Certain fraction of these magnetites manifests authigenic growth, presumably in a locally reduced condition. Intergrowth of ilmenite with titanomagnetites possibly resulted from oxidation of ulvospinel-magnetite and a regular partitioning of Cr, V, AI, Mg and Mn observed between coexisting titanomagnetite and ilmenite suggests a chemical equilibrium. The temperature and oxygen fugacity of coexisting titanomagnetite-ilmenite phases as calculated ranged from 625-850°C and 10-15 to 10-21 respectively. These temperatures and oxygen fugacities equilibrated in a T-fO2, field very near to FMQ (Fayalite-Magnetite-Quartz) buffer curve, lending support to its genesis in the upper crust, more being of igneous sources rather than metamorphic.
Granitoid Rocks of Wangtu Gneissic Complex, Himachal Pradesh: An Example of In situ Fractional Crystallisation and Volatile Action
Authors: Rameshwar Rao D. , Sharma Kewal K. , Gopalan K.
Published: November 2024

The Wangtu Gneissic Complex (WGC) of Himachal Himalaya represents the basement rocks which remained more or less in its original realm. The unique feature of this complex is that the various phases of deformed and undeformed granitoids are exposed in the area. The complex has a peripheral zone of augen gneisses and core of non-foliated granitoids comprising of Coarse Porphyritic Granites (CPG) and Fine Grained Granites (FGG).

In the field the FGG rocks have sharp intrusive contacts with CPG rocks. At places they are entrapped or have protrusions into CPG rocks. Compositionally they represent syenogranites. They are peraluminous to meta-aluminous with Sr initial ratio of 0.705. The major and trace elements of these rocks show unimodal distribution pattern on different variation diagrams. They along with rare earth elements show marked fractionation trends, with a significant negative Eu anomaly. The rocks more or less define an isochron, representing Rb-Sr age of 1895±64 Ma.

The petrochemical studies favour a fractionated rather than multiple intrusions of magma. The studies suggest that fractional crystallisation of parental magma gave rise to early formed CPG rocks and the residual melts resulted in the crystallisation of FGG rocks. The last formed granitoids, the FGG rocks are interpreted as the final residue which crystallised rapidly after build-up and loss of fluids and volatiles which migrated to higher levels to form pegmatite phase in the aureol zone. The Rb-Sr systematics in the present case indicate that the granite have primary crystallisation melts derived from the deep crustal levels around 1895±64 Ma.
Factor Model for the Genesis of Manganese Deposit, Balaghat, M.P.
Authors: Nayak B. K. , Acharya B. C. , Sahoo R. K.
Published: November 2024

Complex system of geochemical variables obtained from manganese ores of Balaghat mine, M.P., is simplified by using R-mode factor analysis of correlation matrix. Eighteen major oxides and trace elemental variable have been expressed in terms of the three common (rotated) factors and genetic interpretations of these factors have been brought out in relation to the manganese deposit.
Geochemistry and Rb-Sr Chronology of Upper Jurassic A-type Granite, Tangmarg region, Kashmir Himalaya
Authors: Rameshwar Rao D. , Sharma Kewal K. , Gopalan K.
Published: November 2024

The present paper deals with petrochemistry and geochronology of granite pluton that intrudes the Agglomerate Slate-Panjal Trap sequence in Tangmarg region of Baramulla district, Kashmir Himalaya. This granite body henceforth called 'Tangmarg Granite' contains biotite, amphibole and rare pyroxene as mafic minerals and shows higher abundances of Zr, Nb, Ga, Y and REE, and lower AI, Mg and Ca contents. The geochemical signatures suggest the granite to be chemically distiIict from most of the orogenic granites (M-, I- and S-types) and points to their Anorogenic nature.

The six point whole rock Rb-Sr isochron of the Tangmarg granite gives an age of 161 ± 5 Ma, with Sr ratio of 0.714. The small size of the pluton points to limited melt generated from a partial fusion 'event' of short duration. Such a melt is attributed to pressure release due to reactivation of the faults that were formed during Permo-Triassicrifting event.
Petrographic and Facies Evaluation of Middle Siwalik Subgroup of Jammu, Himalaya
Authors: Pandita S. K. , Bhat G. M.
Published: November 2024

This paper embodies the results on the study of depositional environment, provenance and tectonic setting of Middle Siwalik Subgroup of Jammu region. The data obtained on lithofacies, sedimentary structures and nature of contacts between various lithofacies, suggest multiple episodes of avulsion and abandonment of the channel system for a new course in braided river system. Four variable plot of quartz types shows that these sediments have been derived from low rank metamorphic source. The detrital modes (quartz, feldspar and lithic fragments) plotted on complementary ternary diagrams (QFL and QmFLt) indicate that these sediments have been shed from recycled orogens, transitional arc and transitional continental provinces.