bluuebunny/crossref_metadata_2025 huggingface dataset:
Tin and Rare Metal Pegmatites of the Bastar-Koraput Pegmatite Belt, Madhya Pradesh and Orissa, India: Characterisation and Classification
Authors: Ramesh Babu P. V.
Published: November 2024

The Bastar-Koraput Pegmatite Belt (BKPB) in southeastern part of the Bastar Craton of Penisular India extends over 80km in a NW-SE direction from Dantewada in the Bastar District of Madhya Pradesh to Salimi in thc Koraput District of Orissa. The pegmatites of BKPB are typically associated with tin and rare metal (Nb, Ta, Be and Li) mineralisation in the form of cassiterite, columbite-tantalite, beryl, lepidolite and amblygonite. Based on the study of over 200 pegrnatites in the Tongpal-Mundval-Dammoguda sector, the pegmatites of BKPB are characterised in terms of mode of occurrence, size, shape, internal zoning and mineralisation. Considering the mineralogy, internal zoning and associated mineralisation, the pegmatites of BKPB are classified into five types, viz., I-Simple, unzoned biotite or muscovite-microcline prgmatiles without tin and rare metal minerals, II-Partly differentiated, muscovite-microcline pegmatites with beryl, III-Fully differentiated muscovite-microcline pegmatites with beryl, columbite-tantalite and cassiterite, IV-Replaced lepidolite-albite-muscovite pegmatites with amblygonite, cassiterite, beryl anti colurnbite tantalite and V-Replaced muscovite-albite pegmatites with cassiterite and beryl. The five types of pegmatites have diagnostic sizes and shapes and form a paragenetic sequence with increasing internal evolution from types-I to V. Such a classification aids in prospecting for tin and rare metal minerals since pegmatitcs of types-III to V in BKPB are highly potential for these metals.
Alluvial Fan Qrigin of the Bagra Formation (Mesozoic Gondwana) and Tectono-Stratigraphic Implications
Authors: Casshyap S. M. , Tewari R. C. , Khan Abdullah
Published: November 2024

The Bagra Formation of the Mesozoic Gondwana sequence of Satpura basin has been considered as a facies equivalent of the underlying Denwa, and assigned a late Triassic age. The present study reviews the above contention, prompted by distinctive lithofacies assemblage, depositional setting and tectonic framework of the Bagra Formation, and its variable relationship with the underlying strata.

The Bagra Formation as a whole comprises conglomerate assemblage in the lower and middle parts and sandstones with intercalated lenses of shale in the upper part. The lower conglomerate facies occurring northward is clast - to matrix supported and poorly sorted; it is finergrained, better sorted, including thin lenses of cross-bedded sandstone southward in middle part of the formation. The overlying cross-bedded sandstone and shale facies is the most important assemblage in the distal south. The coarse grained nature of the sediments, the upward- fining distribution and lateral changes in gross lithofacies and stratification types, and paleocurrent data suggest that the Bagra conglomeratic sequence was deposited as an alluvial fan system that prograded southward from a highland source located immediately to the north. In sharp contrast, the fluvial system was directed dominantly northward and source area located southward for the underlying Permo-Triassic Gondwana sediments, including Denwa.

It is argued that a late Triassic age of the Bagra Formation is questionable, in as much as a substantial stratigraphic break in sedimentation is called for after the deposition of Middle Triassic Denwa. The Bagra may well be late Jurassic-early Cretaceous in age based on its relationship with the overlying JabaIpur Formation.
A Two Stage Model for the Development of Karitoran Shear Zones, District Lalitpur, Pradesh, Central India
Authors: Roday Prakash P. , Diwan P. , Pal Amiya
Published: November 2024

The rocks described as esmeraldites in the southern part of Centra1 Indian Bundelkhand granitic massif are suggested to the typically those formed by heterogeneous simple shear and by development of retarded runway shear instabilities in host granites.

The development of shear zones appears to have occurred under two different stress fields. The early stress field was subhorizontal and nearly equatorial with low values of ESE trending s3 and low ¯s in statistically isotropic material (elastic response). This produced positive dilational shear zones marked by intrution of pegmatite, filling en echelon tensile fissures. The early shear zones were converted into regular ductile shear zone at a later stage under a subhorizontal meridional stress field within highly compressive NNE trending s3 and high ¯s (viscous response within previously weakened zone). This produced a subvertical or steeply dipping ESE trending fabric. Only this two-stage model is able to explain the development of these zones. Finite strain determinations are made from deflected basic dykes, deformed quartz veins and based on the angular relationship between C and S surfaces. The dilation during early episode is indeteminate because of rotation during latershearing. The shear along fabric suggests that the foliation failed to rotate with rotating ?1 ?2 planes of the simple shear. The finite strains computed on the basis of angular departures between fabric and zone walls are therefore slightly underestimated.
Basal Aravalli Volcanism : Evidence for an Abortive Attempt to form Proterozoic Ensialic Greenstone Belt in Northwestern Part of Indian Shield
Authors: Raza M. , Khan Shamim
Published: November 2024

Early Proterozoic mafic volcanic rocks, occurring at the base of Aravalli Supergroup of northwestern Indian shield, have komatiitic, tholeiitic compositions. In discrimination diagrams based on immobile minor and trace elements they show a close affinity with MORB, However, the immobile incompatible element patterns and element ratios resemble those of enriched continental tholeiites which erupt at the time of initial rifting. Geochemical and geological evidences suggest a transitional nature of basal Aravalli sequence between Archaean greenstone belts and younger continental suites. It appears that the basal Aravalli volcanism was an attempt to form a Proterozoic greenstone belt on the stable continental crust through lithospheric rifting and lava eruption. The attempt failed with cessation of volcanism, probably due to falling geothermal gradient and basin subsidence by sediment loading. The occurrence of similar rock associations in other shields of the world indicates the existence of particular tectonic-thermal regimes during the early Proterozoic.
Nearshore Coastal Sedimentation in the Early Cretaceous Ranipat Formation of Saurashtra Basin, Gujarat, Western India
Authors: Aslam M.
Published: November 2024

The Early Cretaceous Ranipat Formation of Saurashtra basin is divisible into three distinct lithofacies assemblages: 1) crossbedded sandstone facies assemblage characterised by coatse to medium-grained, planar and trough crossbedded sandstone with occasional thin layers of silty mud or reactivation surfaces; 2) plane-bedded sandstone facies assemblage composed of interbedded white to clean white, medium to fine-grained sandstone, siltstone and shale with a low-diversity of shallow water trace fossils; and 3) thin-bedded sandstone and mudstone facies assemblage characterised by interbedded fine to very fine-grained sandstone, small scale planar and trough crossbedding, horizontally bedded, ripple cross-laminated, way and lenticular bedding, flaser and herringbone crossbedding with the dominant ichnogenera being Skolitbos and Ophiomorpha. These lilhofacies assemblages indicate that the Ranipat sandstone was deposited in a tidal, intertidal, and shallow subtidal shoreline environment. The mineralogy, texture, and paleocurrent data also rcveal that the sediments were brought to the Ranipat basin, largely by southwesterly streams/distributaries, with occasional dispersal and redistribution by northwesterly to northerly oriented longshore and/or tidal currents of the nearby coastal environment.
Working Values for Major, Minor and Trace Elements for Meta-Basic Reference Sample (MB-H)
Authors: Rathi M. S. , Khanna P. P. , Mukherjee P. K. , Purohit K. K. , Saini N. K.
Published: November 2024

Proposal for the preparation of a metabasic reference sample (MB-H) from the Himalayas has attracted the participation of twenty four laboratories of repute from thirteen countries beside India. Tables of compiled data (1818 total individual results in all) are presented in this paper. Working values/information values have been assigned for 37 major, minor and trace elements including REEs after rigorous statistical as well as subjective data evaluation.
Geochemistry and Tectonic Significance of Late Archaean-Early Proterozoic Metabasalts from Bacheli, Bastar District, Madhya Pradesh
Authors: Khan M. W. Y. , Bhattacharyya T. K.
Published: November 2024

The fine grained, massive metabasalts of Bacheli-Kirandul areas, Bastar district, M.P., characterized by a greenschist facies mineral assemblage have been studied for their major, trace and REE geochemical distribution pattern. On Jensen's AFM Plot and diagrams of relatively immobile elements; these metabasalts fall in the tholeiitic basalts to basaltic andesite field.

Large scatter in Na2O/K2O, K/Rb and RblSr ratios suggest to alteration effects, while high MgO content ascribes to the oxidative diagenesis. Relatively immobile and HFSE element discriminant diagrams point to an island arc/convergent plate setting. The depletion in Nb and Ta relative to Th and LREE in these samples may be relict from a previous tectonic event.

Inferences drawn from geochemical tectonic discriminant diagrams have been evaluated in the light of additional geological data, and an ensialic rift setting for these volcanics is envisaged.
Multi-Mode Generation of Carbonate Tabular Intraclast Deposits: Unnamed Proterozoic Formation, Maharashtra
Authors: Sarkar Subir , Chakraborty Partha P. , Bose Pradip K.
Published: November 2024

Breccia and pebbly massflow products are present in abundance in basin slope deposits of an unnamed marine Proterozoic fonnation in Maharashtra. Seven distinctive genetic modes have been identified and attributed to slump, slide, spring sapping and evaporite dissolution. The clasts are tabular in form and intraclastic in origin. The observations suggest caution against the prevailing tendency to equate occurrence of tabular intraclasts with shallow depositional regime. In order to ascertain their sedimentological significance, a clear understanding of their genetic processes is thus warranted.
Origin of Polyphase Gneisses Associated with the Krishnarajpet Greenstone Belt, Dharwar Craton
Authors: Rama Rao P. , Diyakara Rao V.
Published: November 2024

Hornblende, biotite and feldspar rich gneisses (HG, BG and FG respectively), in that order of formation are associated with the Krishnarajpet schist belt in Dharwar craton, a greenstone belt coeval with, and similar to, the Holenarasipur and Nuggihalli schist belts. These gneisses show compositional differences with SiO2, K2O and Rb increasing and TiO2, Al2O3, Fe2O3, CaO, MgO, Sr, Zr and Ni decreasing from HO to SO and FG. The overall REE is more in BG (SREE = 332.90), while it is similar in HG (SREE = 173.36) and FG (SREE = 159.03) with comparable LREE/HREE ratios (BG = 12.71; HG = 10.26; FG = 10.95). The overall chemistry of the three phases suggests a single source of origin for all the phases. While the field characteristics suggest successive origit from HG to BO and FG, the chemical signatures also support this mode of origin from HG to FG through BG. Available geochronological data on the gneisses indicate that probably the HG, a partial melt of the mafic schists of the greenstone belt, wns recycled at lower crustal levels in Late Archaean foming BG and FG. The time gap between the phases appears to be less but no detailed age data exist on the different phases to support this.
Holocene Deep-Sea Benthic Foraminifera and Watermasses in the Indian Ocean and the Red Sea
Authors: Gupta Anil K.
Published: November 2024

The distribution of Holocene deep-sea benthic foraminifera in 19 core top samples from the Indian Ocean and the Red Sea is examined to understand the faunal-watermass associations. Relative percentages of significant taxa have enabled to identify distinct assemblages associated wth different watermasses in the Indian Ocean and the Red Sea. The first assemblage in the Indian Ocean is marked by the dominance of Nuttallides umbonifera. This assemblage is found below 4000 m where bottom water is highly carbonate-undersaturated and is influenced by Antarctic Bottom Water (AABW). The second assemblage is characterized by Uvigerina hispido-costata dominance with Cibiddes wuellerstorfi as a subsidiary species. This assemblage is associated with the lower tongue of North Indian Deep Water (NIDW) between 2500 and 4000 m water depths. U. hispido-costata has higher abundances at sites lying below upwelling zone off the Arabian coast in relatively high dissolved oxygen deep water. The third assemblage is dominated by Uvigerina proboscidea between 1500 and 2500 m depth. Globocassidulina pacifica/subglobosa, Pullenia bulloides and C. wuellerstorfi are secondary constituents. This assemblage characterizes high productivity regions (equatorial belt) with relatively low oxygen levels in deep water. The Red Sea Deep Water (RSDW) assemblage is dominated by Bolivina subreticulata and characterizes highly saline, warm, oxygen-poor deep water. Other species of this assemblage are Textularia agglutinans, Astrononion umbilicatulum, Miliolinella subrotunda and Ophthalmidium acutimargo.
Formation and Tectonic Evolution of Granulites from the Biligiri Rangan and Niligiri Hills, S. India: Geochemical and Isotopic Constraints
Authors: Janardhan A. S. , Jayananda M. , Shankara M. A.
Published: November 2024

The granulites of the Biligiri Rangan (BR) and Niligiri Hill ranges are characterised by distinct field, geochemical and isotopic signatures. The B.R. Hill granulites contain a significant metasedimentary component (pelite-BIF-Mn-horizons), whilst metasediments are rare in the Niligiri granulite terrain. Lithologic and structural continuity between the two terrains cannot be demonstrated as they are separated by E-W running Moyar shear zone. Isotopic data suggest that B.R. Hills and Niligiri granulites have had different pre-crustal histories. Sm-Nd model TDM ages and U-Pb zircon concordia upper intercept age suggest that the protoliths of B.R.Hill quartzo-feldspathic charnockites accreted at 3.4Ga. On the other hand, Sm-Nd model TDM ages indicate that the magmatic protoliths of Niligiri granulites differentiated from mantle at 2.6 Ga.

Geochemical data from the B.R. Hills charnockites, particularly low-Mg numbers (0.2-0.3), low content of transition and HFS elements and strongly fractionated REE patterns with HREE depletion, suggest that their magmatic protoliths were derived by partial meltingof young, hydrated oceanic crust, in which garnet and amphibole were important residual phases. The high content of transition elements together with low total LREE and less-or unfractionated REE patterns of the B.R. Hills mafic granulites imply the derivation of their protoliths from long term depleted mantle sources. On the other hand the high Mg numbers (0.5-0.6), high content of transition and HFS elements, moderately fractionated REE patterns with HREE enrichment suggest that the protoliths of the Niligiri granulites are interpreted to have formed by melting of metasomatized mantle wedge with olivine and spinel as residual phases.

The Niligiri terrain was accreted onto the Dharwar Craton at C.2.6 Ga and the two terrains witnessed a common major granulite event at 2.51 Ga.
Distribution of Iron Cations in Natural Chromites at Different Stages of Oxidatio - A57Fe Mossbauer Investigation
Authors: Pal Tapan , Moon Hi-Soo , Mitra Sachinath
Published: November 2024

57Fe Mossbauer spectroscopic investigation of natural chromites from two chromite deposits of India (Sukinda and Byrapur) documents partly inverse spinel structure arising out of oxidation. The spectral fitting was based on allowing a disordering distribution of Fe2+ and Fe3+ ions at tetrahedral (A) and octahedral (B) sites. Mossbauer investigation of the samples taken from the physico-chemically distinct two horizons of Sukinda viz. brown are and grey ores, and Byrapur area revealed three types of iron ion distribution as: Fe2+(A), Fe3+(A) and Fe2+(B) (GC-group); (b) Fe3+(A1), Fe3+(A2) and Fe2+(B) (BC-2 group), and (c) Fe3+(A1), Fe3+(A2) and Fe3+(B) (BC-1 group).

The distribution pattern of iron cations at A and B sites was linked to the degree of oxidation. The stages of oxidation could be modelled from normal to inverse fonn. A model suggesting 'electron localisation' at the B-sites makes the intermediate stage. Iron site occupancy determined by Mossbauer spectroscopy of the presently studied samples indicates that these fall under three groups of oxidation stages. An early stage of oxidation is shown by samples of group GC, intermediate stage by group BC-2 and final stage by BC-1 group of chromite samples. The imprint of progressive oxidation manifested by Fe cation site occupancy has been correlated with the Fe2+/S:Fe ratios, obtained for each group of samples.
Rank Evaluation of the Neyveli Lignite Deposit on the Basis of Reflectance Parameter
Authors: Singh Alpana , Singh D. B.
Published: November 2024

The Neyveli field is well known for Tertiary lignite deposits in India. The reflectance of organic constituents (humioite macerals) has been measured to find out organic maturation level (rank) of the main lignite seam lying either at same time level or at different time levels in space. The deposits are of sub-bituminous C stage (ASTM) with the mean refectance (Ro max. in oil) range from 0.34 to 0.42% (average 0.39%). Evidences from rank study indicate that the quality of lignite deteriorates towards southern part of the field.
Magnetic and Sedimentological Studies of Netravati and Gurpur River-Bed Sediments, West Coast of India
Authors: Manjunatha B. R. , Shankar R.
Published: November 2024

Magnetic susceptibility and sedimentological studies have been carried out on Netravati and Gurpur river-bed sediments along the west coast of India to throw light on the distribution and movement of magnetic minerals in the riverine environment. The sediments studied are coarse to fine sands, platy to leptokurtic and poorly to well sorted. Granule to medium size sands dominate in the upstream segment. whereas very fine sand and silt+clay are either absent or of negligible importance. Netravati river-bed sediments have a two-fold higher bulk susceptibility than Gurpur sediments because the Netravati drainage basin has magnetite quartzites, amphibolites and garnetiferous biotite gneisses in contrast to granitoids found in the Gurpur drainage basin. This trend of susceptibility is seen for the 13 particle size fractions studied.

Magnetic minerals are concentrated in poorly sorted, fine grained sediments of Netravati river and in leptokurtic sediments ofGurpurriver. They are particularly enriched in the size range of 0.063-0.125 mm and to a lesser extent in the >4 mm fraction. Downstream decrease in susceptibility of both bulk samples and particle size fractions reflects on the vicinity or otherwise of sampling sites to the source of magnetic minerals in the drainage basin.

On the basis of bulk susceptibility data, it is.estimated that about 87% of sediment in the Netravati main river is derived from Kumaradhari river and 13% from Netravati (upstream) tributary. However. about 78% of particles >0.35 mm in size in Netravati main river are contributed by Kumaradhari river and 22% by Netravati (upstream) tributary. The bulk susceptibility of Ourpur river sediments shows that the Venoor hole is the dominant sediment contributor (83%) to the main river when compared to Hosangadi hole (17%). In contrast, Hosangadi hole contributes ca. 63% of the fine particles (0.55-1.0 mm) to the Gurpur main channel. This discrepancy could be attributed to the higher susceptibility of coarse fraction (> 1 mm) of Gurpur (main) river when compared to its tributaries.

Magnetite is the most important mineral that accounts for nearly a half of the susceptibility. Magnetite weight percentage and susceptibility are significantly correlated (r=O.50). About 21 % of the suspectibility is explained by ilmentite and garnets. Amphiboles, pyroxenes and other weakly magnetic minerals account for ca. 27% of the susceptibility. The residual fraction, censtituting ca. 60% of sample weight, explains only 8% of the susceptibility of samples.
X-Ray Diffraction Study on Neogene Shales from the Patharia Anticline, Eastern Bangladesh, with Emphasis on Smectite Clay Dehydration and Implications
Authors: Badrul Imam M.
Published: November 2024

Mineralogical composition of Neogene shales from the Patharia structure, as determined by X-ray diffraction analysis, includes quartz, illite, kaolinite, clllorite and mixed layer illite/smectite as major and feldspars as minor components, with calcite, dolomite and siderite in tsace amount. High degree of tectonic stress rather than the above mineralogy is believed to be responsible for high density of shales from the patharia-5 well. Progress illillitization of randomly interstratified illite/smectite is the rnost important diagenetic change observed with increasing burial depth. Transition from random to ordered inter layering in illite/smectite is suggested to have taken place at about 3000 m in the Palhuria- 5 well. Considering the huge volume of shale in the Neogene Group, sliicctitc dehydration, as a result of diagenetic conversion to illite, appears to have made available significant volume of interlayer water for migration into the pore water system in the subsurface. This may have played important role in the generation of overpressure at depth as well as structural shaping of the Patharia anticline.
Geochemistry, Age and Origin of Perur Granite, Chittoor District, Andhra Pradesh
Authors: Divakara Rao V. , Subba Rao M. V. , Rama Rao P. , Pantulu G. V. C.
Published: November 2024

The homophanous coarse-grained granite near Perur, Chittoor district, Andhra Pradesh ranges in composition from granite (normative) to granite-quartzmonzonite (chemical) and records a Rb-Sr whole rock isochron age of 2549 ± 39 Ma. Variation observed in the major and trace element concentrations (SiO2 = 67.09-73.83%; Al2O3 = 12.76-14.51%; total iron = 2.31-4.97%; MgO = 1.03-3.66%; Cr = 7-102 ppm; Rb = 169-223 ppm and Sr = 128-423 ppm) and the low CaO (less than 2%) in the granite suggest that it is a crustal remelting (CR) type granite formed by the anatectic remelting of an intermediate source rock. The high total REB (201.38-245.63 ppm), their well fractionated nature (LaN/YbN= 17.83-22.32) and the negative Eu anomaly of the granite support that the source rock was intermediate in composition having hydroxyl-bearing minerals like biotite and hornblende.

The Rb-Sr whole rock age (2459 ± 39 Ma) of the granite is similar to that of Closepet, Lepakshi and Hyderabad granites suggesting that this granite has formed along with the other K-rich granites by extensive crustal remelting during the Archaean-Proterozoic Transition (APT).
Mineralogy and Textural Features of Settupalle Syenites, Prakasm District, Andhra Pradesh
Authors: Srinivasan T. P. , Chalapathi Rao N. V.
Published: November 2024

The Settupalle igneous complex is characterised by syenitic variants with distinct mineralogic assemblages. The variable perthitic patterns, nature of plagioclase, fayalite-quartz assemblage in Settupalle syenites clearly suggest that the Settupalle igneous complex has evolved under fluctuating pressure and temperature conditions. The mineral chemistry of K-feldspar and plagioclase suggests that K-feldspar assemblage in these rocks indicates their subsolvus nature. The probable crystallization sequence of rocks is fayalite clinopyroxene syenite (FC-Syenite) - fayalite quartz syenite (FQ-Syenite)-hornblende syenite - quartz syenite - nepheline syenite in that order.
Arrested Charnockite Formation in the Palghat Region, South India
Authors: Ravindra Kumar G. R. , Srikantappa C.
Published: November 2024

Exposures of in-situ charnockitisation of gneisses in widely varying geological associations, related to differing mechanisms of dehydration and prograde metamorphism, are recorded from the Palghat region, southern India. Mineral reactions in gneiss-charnockite prograde profiles indicate hornblende + biotite breakdown in the presence of quartz to produce orthopyroxene within structurally controlled and/or compositionally modified portions of the gneisses. Chemically the gneisses and arrested charnockite zones are granitic in composition whereas the associated banded charnockites (regional granulites) are tonalitic to granodioritic in composition, Geothermobarometric data indicate high temperature and high pressure early granulite-facies (regional granulite) metamorphism at 780 - 880°C and 9-10 Kbar. The fluid species in both types of charnockites and gneisses are characterised by CO, and mixed CO2-H2O inclusions.

The banded charnockites largely pre-date major deformation and the early Palaeozoic time of development of arrested charnockites. A definite time gap between the formation of banded charnockites and arrested charnockites is indicated. Arrested charnockites in the Palghat region are formed along (1) structurally controlled zones, (2) in compositionally favourable zones of modified paleosomes, (3) in melt portions of migrnatitic gneisses and (4) along margins of invading alkaline dykes. These are interpreted as different processes triggered by emplacement of igneous bodies and movement of CO2, enriched melts through the crust, producing sequential interrelated events like dehydration, partial melting, metasomatism and wall-rock alteration, leading ultimately to charnockite formation. The present field dispositions of arrested charnockite are inferred as only an expression of varying response of rock types to changing physico-chemical conditions (e.g. PT and fluid regime) with time during metamorphism.
Additional Agnostid Trilobites from the Middle Cambrian of Kashmir
Authors: Shah S. K. , Parcha S. K. , Raina A. K.
Published: November 2024

A new agnostid genus Trilagnostus from Middle Cambrian of Kashmir is described in addition to Pagetia griesbachi and Pagetia sp. from the same level at the Solvan-Menevian boundary. Diplagnostus is also being reported and described in the same succession at the top of Menevian. This form helps in demarcating the Middle - Upper Cambrian boundary in the sequence.
Age of Deccan Volcanism Across KTB in Krishna-Godavari Basin: New Evidences
Authors: Raju D. S. N. , Jaiprakash B. C. , Kumar Arun , Saxena R. K. , Dave Alok , Chatterjee T. K. , Mishra C. M.
Published: November 2024

The latest Paleontological data suggest that the duration of Deccan trap eruption in Krishna-Godavari basin varies from place to place and could be anywhere between <0.5 Ma and 6 Maacross KTB. Three groups of fossils viz., Planktic foraminifera, Nannoplanktics and Dinoflagellate cysts suggest that the initiation of volcanism was during latest Maastrichtian within the upper part of Abathomphalus mayaroensis Zone, Micula murus Zone and Triblastula utinensis Zone between 67 and 66.5 Ma. There are conflicting evidences in dating the upper age limit of the volcanics probably due to diverse methods employed in calibration of forarniniferal and nannoplanktic scales or selective retrieval of very small sized planktics of zones P0 and P1 in well cuttings.
Neogene Planktic Foraminiferal Biochronology of the Central Indian Ocean DSDP Sites 237 and 238
Authors: Singh A. D. , Srinivasan M. S.
Published: November 2024

Qualitative and quantitative planktic foraminif~raal nalyses of the Central Indim Ocean DSDP Sites 237 and 238 provided 34 important events during the Neogene. A comparison of the chronoIogica1 succession of ihese planktic foraminiferal events, with the other tropical Indian Ocean and Southwest Pacific DSDP Sites reveals remarkable similarity. Therefore, these Neogene foraminiferai events [First Appearance (FA) and Last Appearance (LA)] are considered as synchronous within the tropical Indo-Pacific except Gq. dehiscens LAD, Gr. margaritae FAD, range of Gr. tumidaflexuosa, Gr. crassaformis FAD, Gr. truncatulinoides FAD, and Gs. obliquusLAD, which are diachronous reflecting their paleobiogeographic control. Stratigraphic ranges of planktic foraminifera enabled recognition of 20 zones from the late Early Miocene to Pleistocene.

Two hiatuses (NH3 at Site 238 and NH4 at Site 237) associated with severe carbonate dissolution were identified. These hiatuses havealsobeen recordedatabout the same stratigraphic intervals in several deep sea sections in the Pacific and represent an important oceanographic event, useful for inreroceanic correlation.
Petrological and Geochemical Constraints on the Petrogenesis of the Jaspa Granitic Pluton, Lahual Region, NW Himalaya
Authors: Rameshwar Rao D. , Sharma Kewal K.
Published: November 2024

Several granitic plutons were emplaced in the Lesser and Higher Himalayas of India during early Paleozoic. Jaspa pluton of Lahual region is one such pluton, where the granitoids are intrusive into the low-grade Haimantas made up of phyllitic and quartzitic rocks. The petrochemical studies of the Jaspa granitoids show two successive phases of intrusion. The early phase is dominated by Biotite-Muscovite Granite (BMG) of Ordovician age. Compositionally these rocks are similar to the biotite-granites of Shingo-La of Higher Himalayan range, which are around 50 km to the north of the BMG rocks. The younger phase is represented by tourmaline bearing leucogranites (TLG), which occur as minor phase generally along the marginal parts of the BMG rocks.

The BMG rocks in comparison to TLG rocks have relatively high concentrations of CaO, MgO, TiO2, Fe2O3(T), Nb, Zr, Sr, Pb and Th and low concentrations of SiO2, Na2O, P2O5, Rb,Ga and U. They distinctly plot as two geochemical populations on different variation diagrams. The BMG rocks are characterised by enriched REE concentrations and show fractionating bends, while the TLG rocks have low REE concentrations and show less fractionated trends and depleted HREE pattern. The field, petrographic and geochemical studies suggest that the two phases of Jaspa pluton, the BMG and the TLG rocks were generated from the partial melting of the continental crust in which two chemically different source types were involved.
Morphological Variations in Some Islands in the Gulf of Mannar, India
Authors: Ramanujam N. , Mukesh M. V. , Sabeen H. M. , Preeja N. B.
Published: November 2024

Islands in the Gulf of Mannar are sedimentary landforms developed during the low strand of sealevel during the last interglacial period. The reefs commenced to grow along with the pace of rising sea level. Islands such as Van, Koswari, Kariashuli, Viangushuli inTuticorn region can be called as Tuticorin group of islands. The size, shape and orientation of the reef along with the wave parameters are crucial in determining the development and instability of the islands. Oval or elliptical shape of the reef, small reef area and orientation along with the major wave direction are favourable for the development of the islands, The non-elliptical shape, bigger size of the reef and irregularity in rim topography are hindrances to their development. Apart from the said factors the sea level rise and mining of reef materials are also causative factors.
Geological Evolution and Uranium Mineralisation of Chhinjra Area, Kulu District, Himachal Pradesh
Authors: Sen D. B. , Kumar Suresh , Gangadharan G. R.
Published: November 2024

Several shear-controlled and fracture-filled/disseminated type uranium occurrences are known in the Rampur Window. This paper presents the geology and genetic aspects of fracture-filled type of mineralisation in Chhinjra area on the basis of recent stratigraphical, geochronological and tectonic data. Based on the angular unconformity between Manikaran quartzites and overlying chlorite phyllites, the geological evolution of Chhinjra area has been reconstructed in two stages: Pre-unconformity and post-unconformity. Each stage is characterised by different phases of deformation with typical structural style and accompanying mineralisation processes. Four major tectonic events can be recognised here, namely 2500 Ma, 1200 Ma, 700 Ma and 55 Ma. Each event has left its imprint on the rocks as well as uranium mineralisation of Chhinjra area.
Neogloboquadrina, Pulleniatina and Sphaeroidinellopsis-Sphaeroidinella Lineages in the Northern Indian Ocean: Their Paleoceanographic Relations and Biostratigraphic Significance
Authors: Singh A. D.
Published: November 2024

The evolutionary gradation and ancestor-descendant relationship within planktic foraminiferal lineages Neogloboquadrina, Pulleniatina and Sphaeroidinellopsis-Sphaeroidinella, from DSDP sites 214, 219 and 237 (Northern Indian Ocean) are discussed. The study suggests that the evolutionary diversification among these lineages are closely linked with the major oceanographic changes during the Neogene. The phyletic lineages are placed within chronologie framework in order to find out the reliability of vital taxa of these bioseries for biostratigraphic correlation.
Lamprophyre Dykes in the South Delhi Fold Belt Near Pipela, District Sirohi, Rajasthan
Authors: Fareeduddin  , Kirmani I. R. , Srivastava B. L. , Reddy A. B. , Bhattacharjee J.
Published: November 2024

Lamprophyre dykes are reported from the southern part of the South Delhi Fold Belt (SDFB), near Pipela, about 3 km SE of Sarupganj in Sirohi district of Rajasthan. They occur as sub-volcanic intrusives in the Ajabgarh supracrustals and follow a WNW -ESE to E-W trends. They show porphyritic and panidiomorphic textures with biotite and magnetite occurring as euhedrru phenocrysts ina cryptocrystalline matrix. One large Jamprophyre body shows acompositionallayering. Widespread alteration (chloritisation of biotite and potash depletion) suggests that they are not cogenetic with the post-Cretaceous, fresh lamprophyres of the Mundwara area. Probably these dykes are emplaced during the waning stage of the Late Proterozoic tectonomagmatic cycle of the South Delhi Fold Belt.
Chemical Variations in the Tertiary Carbonates Of Southwestern Kutch, Gujarat - A Statistical Approach
Authors: Kumar Arun , Ratha D. S. , Nandy Partha
Published: November 2024

Tertiary carbonates from Kutch have been analysed for chemical constituents such as Ca, Mg, Mn, Fe, Sr, Ba and insoluble residue. Vertical distribution of these elements shows a gradual decrease in Ca and Sr and increase in Mn, Fe, Ba and insoluble residue from older to younger beds. R-mode factor analysis of chemical data is interpreted. The first factor loaded on IR-Mn-Fe-Ba is considered to be the effect of clastic deposition, chemical co-precipitation and adsorption by clay minerals. The second factor loaded on Ca, Sr, Ba and Mg explains their syndeposition, leading to the formation of limestones.
U-Pb Isotopic Study of Zircons from a Few Granitoids of Delhi-Aravalli Belt
Authors: Sivaraman T. V. , Raval U.
Published: November 2024

U -Pb isotopic analysis of zircons of three granitoids from Chhapoli, Kishangarh and Ajmer localities in the Delhi fold belt of Rajasthan, shows that these granitoids have been emplaced around 1700 Ma and were thermally disturbed at -70 Ma resulting in Pb loss in these zircons. Later studies by other workers on rhyolites, carbonatites and lamprophyres from Rajasthan and Gujarat, corroborate the -70 Ma event which was possibly a period of intense regional magmatic activity in this region. This Cretaceous thermal episode, when evaluated in the light of the paleogeography of the Indian plate, strongly suggests that the reactivation of this part of the subcontinent may be due to: (a) the continental breakups along the west coast at ~80 and 64 Ma, (b) plausible passage of this part of the Indian continental lithosphere (CL), over the Reunion mantle plume between 80 to 60 Ma and (c) the earliest phase of the India - Eurasia Collision. It is also found that the existing knowledge of the geophysical anomalies (such as geothermal signatures, seismicity, gravity, magnetic and electrical conductivity) over the Delhi Aravalli mobile arm (DA-MA), Kutch, Jaisalmer- Mari- arch (JM-A), and Cambay graben - the latter two being parts of the NNW-SSE trending Madagascar-Dharwar mobile arm (MD-MA)- also support this inference.
Mineralogy and Genesis of Ironstone Ooids, Subathu Formation (Eocene) in the Tal Valley, Garhwal Himalaya
Authors: Mundepi Anil K. , Bagati T. N.
Published: November 2024

The physico-chemical and X-ray diffraction analysis of the oolitic ironstone belonging to the lower part of the Subalhu Formation (Eocene) reveal the presence of major berthierine and chamosite with minor amounts of hematite, limonite and rarely glauconite. Quartz. polycrystalline quartz, siderite and chert are important accessories .

The ironstone ooids having the alternate coalS of berthierine/chamosite and ferric oxide were formed under changing physico-chemical conditions. Mineralized solutions containing iron and silicates replaced the carbonate ooids and other detritus during diagenesis. The ooids were fractured and distorted due to intergranular solution readjustment during compaction and later tectonics.
Nature and Palaeoweathering of Source Rocks and Palaeoclimates for the Gondwana Sandstones from Pranhita-Godavari Valley, Andhra Pradesh
Authors: Sayyed M. R. G.
Published: November 2024

The Gondwana sediments from the Pranhita-Godavari valley were analysed for major elements and some petrographical characters to find out the nature of the source of rocks, their palaeo weatbering and the palaeoclimatic conditions. The results of this study indicate that source rocks were mainly granitic in composition which had undergone K-metasomatism. Most of the major elements show large fractionation and mobilisation during weathering and transport while the intensity of weathering was highly variable under humid to subhumid climatic conditions.
A Semi-Quantitative Approach to Detect Aquifers in Hard Rocks from Apparent Resistivity Data
Authors: Muralidharan D.
Published: November 2024

Resistivity sounding technique is conventionally adopted for ground water exploration in hard rock areas. From the interpretation and layer parameter evaluation alone, deciphering the actual depth to aquifer zone and delineating the thin high yielding fracture zones is found to be difficult. In many cases, the high yielding zones are found to be well within the bedrock signal part of the sounding curve. A non-conventional way of examining the apparent resistivity data of soundings was attempted for the soundings conducted over different hard rock terrains. The interpretation yielded a factorial depth relation with the yielding aquifer zones hidden in the bedrock signal. This approach has been used successfully in many areas of investigation. A theoretical base for the observed depth relation is at developmental stage.
Accretionary Evolution of the Ramagiri Schist Belt, Eastern Dharwar Craton
Authors: Zachariah John K. , Mohanta Manoj K. , Rajamani V.
Published: November 2024

The gold mineralized Ramagiri Schist Belt is a volcanic dominated, late Archaean belt in the eastern Dharwar Craton. Based on the lithological association, mode of occurrence of rocks, geochemical characteristics of mantle derived rocks and the metamorphic grade of rocks, the belt is divided into three blocks that are tectonically interleaved with and surrounded by granitic rocks of distinct histories. The eastern block has amphibolite facies rocks, dominantly basic metavolcanics having light rare earth element (LREE) depleted patterns with minor banded ferruginous quartzite (BFQ). The central block includes mafic and felsic volcanics, pyroclastics, gabbroic and felsic dykes, argillites and BFQ. The volcanic rocks as well as the intrusives have LREE enriched patterns. The central block has dominantly greenschist facies rocks. The western block is made up of fine grained metabasalts with well preserved pillow structures at places, and retrogressed chlorite-actinolite and chlorite-carbonate schists in shear zones, serpentinite and BFQ. These rocks have flat to moderately LREE depleted patterns. The associated serpentinite is of residual origin, probably representing obducted pieces of Archaean oceanic lithosphere. Available age information and required tectonic settings of the volcanics necessitate subduction related magmatism and corroborate the idea of crustal genesis by accretionary processes in the eastern Dharwar Craton during late Archaean.
Mid-Continental Rift - A Hypothesis
Authors: Baride M. V.
Published: November 2024

The paper presents a new hypothesis on the possibilities of the opening up of a Mid Continental Rift (MCR) in the southern block of the Indian Shield based on the background data on seismic centres, continental rift, and seismo-tectonic studies.

It is suggested that, due to locking at the northernmost part, there is progressive NE-E drifting of the Indian subcontinent and, therefore, a rotational movement is taking place with the southern tip moving faster than the main land. This has created a major weak zone along Ongole to Cutch. Due to this movement, fractures will open up along the Narmada-Son. This will also give rise to major seismicity along and adjoining Ongole to Cambay areas resulting in MCR along Narmada-Son lineament in geologic time.
Gondwana Palynostratigraphy from Drill-Core Studies in Coastal Tamil Nadu and Pondicherry
Authors: Tiwari R. S. , Vijaya  , Tripathi Archana
Published: November 2024

The palynoflora of subsurface coal-bearing sequence in cores from boreholes TC-1 and TC-2 in Kandmanglam and Marakkanam area, Tamil Nadu and Pondicherry Union Territory has been found to be rich in pteridophytic spores. The palyno-assemblage is assignable to the Coptosporo cauveriana Zone of Aptian age. The findings add to our knowledge of Gondwana coal deposits along the east coast of India.
Occurrence of Fluorapatite in Granitic Veins from the Kerala Khondalite Belt, Southern India
Authors: Braun I. , Raith M.
Published: November 2024

This paper presents the first description of fluorapatite in rocks of the Kerala Khondalite Belt in southern India. The fluorapatites occur either dispersed or aggregated in granitic and pegmatitic veins which intruded into high-grade metamorphic gamet-biotite gneisses. Microtextures indicate an exclusively magmatic origin for the fluorapatites and the strong zoning of F and OH points to a change in fluid/melt composition during apatite crystallization. The P-T conditions of melt crystallization are estimated to be in the range of 750-800°C and =5 kbar. The origin of the fluorapatite bearing melts is poorly known. It is suggested that they formed either through fluid-absent incongruent melting of a F-rich biotite or during a late stage of fractional crystallization of a granitic parent magma. Additionally, we report a single occurrence of a monazite-rich quartzmonzodiorite vein. Field observations indicate an emplacement subsequent to the fluorapatite bearing granites and pegmatites. The occurrence of magmatic andalusite and cordierite in this rock points to a crystallization at low pressures (P = 3 kbar).
Fluorapatite from Alkaline Pegmatites of the Kerala Khondalite Belt: A Petrologic and Fluid Inclusion Study
Authors: Rajesh H. M. , Santosh M.
Published: November 2024

We report the occurrence of primary apatite crystals in association with graphite within alkaline pegmatite dykes in the Kerala Khondalite Belt (KKB). Petrologic and X-ray diffraction studies identify the mineral to be fluorapatite. Fluid inclusion studies show that the fluorapatites contain abundant CO2-rich inclusions with densities in the range of 0.85-0.72 gcm-3. A subsequent generation of trail-bound CO2-HP inclusions with low salinity were entrapped along hydraulic cracks. The abundance of CO2-rich inclusions, and the intimate association of fluorapatite with fluid-precipitated graphite suggest that the pegmatite dykes hosting fluorapatite were rich in CO2-dominated fluids. We identify that among the magmatic conduits proposed for the transfer of CO2-rich fluids in granulite processes in the KKB. the fluorapatite and graphite bearing pegmatites reported in this study form important examples.
Geophysical Discovery of Archaeological Sites at Nelakondapally in Andhra Pradesh, India
Authors: Atchuta Rao D. , Ram Babu H. V. , Rao Ch. Rama
Published: November 2024

The discovery of a hemispherical shaped Maha Stupa, the largest known in South India belonging to the 2nd to 6th century A.D., Buddhist monastic order at Nelakondapally (Khammam district, Andhra Pradesh), has marked the area for further exploration for cultural sites and objects. The Department of Archaeology and Museums, Government of A.P., has been actively pursuing exploration in this area using conventional methods and brought to light some important archaeological findings indicating the importance of the area for elucidating the full structural details of the dwelling complexes and other cultural objects. With a view towards creating awareness among the archaeologists on the use of geophysics in archaeology, an experimental geophysical survey has been carried out using magnetic, electrical and electromagnetic methods, in an area near Nelakondapally. These surveys have brought out geophysical anomalies resulting in the discovery of sites and objects of archaeological interest. This paper describes the survey and the results which led to the discoveries.
Petrology and Geochemistry of Kimberlite Pipe 11 of Chigicherla Area, Anantapur District, Andhra Pradesh, South India
Authors: Murthy D. S. N. , Dayal A. M. , Natarajan R. , Balram V. , Govil P. K.
Published: November 2024

Newly discovered kimberlite pipe 11 of Chigicherla area of Andhra Pradesh consists of two generations of olivine with phlogopite, spinel. perovskite, melilite etc., A comparative study of chemical characterstics of pipe 11 with those of pipe 1,2,3,4 and 5 of Wajrakarur- Lattavaram area and pipe 10 of Chighicherla indicate that Zr-Hf, Nb-Ta, Th-U have a high degree of correlation. The ratio of Ba/Nb( <10), Z/Hf( -50) and Nb/Zr (>0.5) are similar to the Group-I kimberlites. The chondri te normalised REE pattern of pipe 11 is similar to the other kimberlites and shows enrichment in LREE. Spider diagram of incompatible elements indicate similarity with those of many oceanic island alkalic basalts or other types of alkalic intraplate volcanics. They are highly enriched in incompatible elements. Major elements, Ce/Yb and La/Yb ratios suggest that the formation of kimberlite is due to low degree of partial melting of ultrabasic source along with an earlier subducted oceanic lithosphere.