bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shrimp U-Pb Ages of Detrital Zircon in Sargur Supracrustal Rocks in Western Karnataka, Southern India
Authors: Nutman A. P. , Chadwick B. , Ramakrishnan M. , Viswanatha M. N. 
Published: November 2024

Abstract
New limits have been set on the age of the provenance and the depositional period of the oldest known Archaean supracrustal rocks (Sargur Group) in southern India. Detrital zircon grains from a pelitic schist and a quartzite within major tracts of supracrustal rocks older than their host regional grey orthogneisses (peninsular Gneiss, c. 3000-2900 Ma) have yielded U-Pb ages in the range 3580-2960 Ma. The data indicate that granitoid rocks in the age range 3580-3130 Ma were a significant component of the provenance of the sedimentary protoliths. Ages younger than 3130 Ma are attributed to effects of high-grade metamorphism during emplacement of the igneous precursors to the host orthogneisses. Exhumation of the granitoid provenance, deposition of the sedimentary protoliths, intrusion of major gabbroic and peridotitic complexes and possible basaltic volcanism represented by amphibolites in the tracts of supracrustal rocks took place in the period 3130-2960 Ma. This age range is at variance with previous suggestions that the Sargur Group represents early Archaean or primitive crust.
Carbonic Fluids in Granulites: Cause or Consequence?
Authors: Santosh M. 
Published: November 2024

Abstract
From a generally fluid-free deep crust, carbon dioxide influx may occur related to the highest thermal anomaly attending granulite formation. This would manifest itself as high density fluid inclusions captured within different minerals. The transition from H2O to CO2 dominated fluids and the concomitant increase in CO2 densities with metamorphic grade ohserved in regional amphibolite-granulite transitions, and the spectacular increase in the volume of CO2 recorded from gneiss-incipient charnockite reaction fronts suggest that carbonic fluids cause granulite formation by the dilution of pore fluids and resultant lowering of water activity. Conversely, carbonic inclusions can also result as a consequence of granulite formation. This involves H2O loss from pre-existing mixed CO2-H2O inclusions, by ductile strain-induced leakage during deformation, removal of H2O to form retrograde hydrous assemblages, or by the absorption of H2O in local anatectic melt fractions; in all these cases, pure CO2 "residue" will result.
CO2 influx need not necessarily manifest itself in charnockite formation alone; the major imprints of this process in aluminous metapelites could be stable isotope alteration. Highest density CO2 inclusions in a rock need not necessarily represent the peak metamorphic fluid; entrapment and evolution of fluids are dictated by the nature of post-metamorphic P-T-fluid history. Desiccation along structural pathways of enhanced fluid flow is a viable mechanism to destabilize hydrous minerals, but the potential of such a process in generating local melt pockets is a topic which merits further consideration.
Models for the generation of CO2 are diverse, and can be broadly grouped into internal and external sources. Stable isotope systematics of fluid inclusions and graphites from the southern Indian granulites attest to distinct pulses of external CO2 often copious and at timescales short of attaining isotopic equilibrium between the influxing fluid and the precipitating graphite. This study proposes a unified model which links Pan-African syenite-chamockite associations and incipient charnockitic alteration of gneisses. Fluid-rich igneous activity of subcrustal origin is envisaged to have contributed the heat and CO2 necessary to drive structurally-controlled dehydration reactions.
Syn-Metamorphic Carbonic Inclusions in the Satnur-Halgur Granulites, Karnataka, India
Authors: Srikantappa C. 
Published: November 2024

Abstract
Peak-metamorphic carbonic pore fluids have been observed in granulite facies rocks of the Satnur-Halgur area. The CO2 densities (1.045 to 0.900 g/cc) are consistent with the P-T metamorphic conditions, indicating syn-metamorphic nature of carbonic inclusions.
Ilmenites from Cox's Bazar Beach Sands, Bangladesh : Their Intergrowths
Authors: Ahmed Samsuddin , Pal Taraknath , Mitra Sachinath 
Published: November 2024

Abstract
About 52% of the samples of Cox's Bazar beach contain six textural types of hematite-ilmenite exsolutions,the commonest (∼83%) being the seriate type. Hemo-ilmenite with greater ilmenite contnet exsolves in a process of continuous exsolution mechanism, whereas more hematiterich phases (very common) exsolve discontinuously. The hemo-ilmenites (IIm45 Hem55 to IIm75 Hem25) are ferrimagnetic in nature. Modal analysis has indicated the percentages of pure ilmenite (exsolved + unexsolved type) and hematite (exsolved, both host and guest) to be 73.74% and 26.26% respectively. This result also corroborates with X-ray, Mossbauer and chemical analyses.
Changing Sedimentary Environments During Pleistocene-Holocene in a Core from the Eastern Continental Margin of India
Authors: Purnachandra Rao V. , Rao Ch. M. , Mascarenhas A. , Mohan Rao K. , Reddy N. P. C. , Das H. C. 
Published: November 2024

Abstract
Sedimentological and geochemical investigations of the sediments in a core from the eastern continental margin of India, at a water depth of 1200m, revealed two distinct sediment types. The Late Pleistocene sediments are greyish-black in colour and consist of mud turbidites in the lower part and dolostone breccia in the upper part. They also consist of illite and chlorite-rich clay minerals with high organic carbon and sulfur. Organic matter is of dispersed nature. These are similar to black shales and are apparently formed by rapid burial of terrigenous organic matter by turbidites with intermittent reducing conditions during lowered sealeveIs. Dolostone fragments appear to have been transported by mass movement processes during the terminal pleistocene. The Holocene sediments: are moderate yellowish-brown in colour and with detrital vivianite nodules at the base. These sediments are clayey with mont-morillonite-rich, illite-poor clay minerals, lower organic carbon and sulfur contents and ferruginised pyrite grains, deposited under oxidising conditions. The marked changes in the sedimentary environments are attributed to climate and sealevel changes during Pleistocene and Holocene.
Spinifex-Textured Peridotitic Komatiite from Karighatta, Chitradurga Schist Belt, Karnataka
Authors: Srikantappa C. , Shankar B. N. , Vasudev V. N. 
Published: November 2024

Abstract
Ultramafic rocks of the Karighatta schist belt display spinifex texture and komatiitic chemistry indicating their volcanic origin.
Kimberlite Pipe in Lattavaram Area (A.P.) by Detailed Geopbysical Surveys: A Case History
Authors: Chayanulu A. Y. S. R. , Singh R. K. 
Published: November 2024

Abstract
Detailed magnetic (V. F.) and electrical resistivity surveys led to the discovery of one more hidden kimberlite pipe (P8) of dimensions 110 x 55m to the northeast of the known pipe P4 in Lattavaram area, Anantapur district, Andhra Pradesh. Detailed geophysical surveys can profitably be used for the location of hidden kimberlite bodies, in selected areas.
Oxygen and Carbon Isotopic Composition of Precambrian Carbonates from Karnataka and Tamilnadu, India.
Authors: Srikantappa C. , Valley John W. 
Published: November 2024

Abstract
Oxygen and carbon isotopic compositions for carbonate rocks from the Sargur Group in Kamataka and carbonates from the Madukkarai area in Tamil Nadu are reported. Carbonate rocks from both areas show preservation of sedimentary isotopic compositions. Bettadabidu carbonates have lower isotopic ratios (d180 = 15.8 SMOW ; d13C = 0.7 PDB) when compared to Madukkarai carbonates (d 180 = 20 SMOW; d 13C = 2.0 POB). Oxygen and carbon isotopic values exhibit positive correlation indicating a progressive devolatilization process during regional metamorphism. The range in d180 values demonstrates that large quantities of a homogeneous metamorphic fluid have not pervasively infiltrated either terrane.
Tectonic Reactivation in the Indian Ocean:Evidences from Seamount Morphology and Manganese , Nodule Characteristics
Authors: Mukhopadhyay Ranadhir , Khadge N. H. 
Published: November 2024

Abstract
The Central Indian Ocean Basin (CIOB) was subjected to tectonic reacti, vation in geological past which is unusual for a basin occurring on an apparently , single tectonic plate. ENE-WSW trending latitude parallel zone of reactivation across the central part of the basin is reported. Distinct difference in characters of seamounts, . manganese nodules and bottom sediment are found in this deformed central part as . compared to those from northern and southern parts of th'is basin. Much lower ratio of height to basal width (h/Wb) of seamounts; and presence of several guyots in this' ; central part are reported. Abundance of smaller. spheroidal, smooth textured nodules and absence of index radiolarian zone I fossil, coupled with sediment erosion of to several centimeters indicate activity of west-bound Antarctic Bottom Water (ABW) , and other turbulent water masses that later passed through the reactivated central part. The cause of this deformation is attributed to wrench.faulting as part of large scale tectonic reactivation during late Miocene.
Radiolarian Biostratigraphy of Early Pliocene Sequences, Car Nicobar Island, Northeast Indian Ocean
Authors: Sharma V. , Singh Surender 
Published: November 2024

Abstract
A study of the radiolarian assemblage from the Sawai Bay Formation (Early Pliocene) exposed in Car Nicobar bland shows the presence of age diagnostic radiolarian taxa. Based on the radiolarian zonation applicable for the tropical Indian Ocean, three radiolarian zones are identified in this formation. These, in ascending order, are: Phormostichoartus doliolum zone, P. fistula zone and Stichocorys peregrina Zone. The radiolarian events (first and last appearances) recognised in the Car Nicobar sequences are discussed in relation to those in the Central Indian Ocean Basin. The proposed radiolarian zones are correlated with the previously proposed planktonic foraminiferal zone in the study area, and an htegrated biostratigraphic scheme is presented.
Fossil Pigeonites and Exsolution Features in Pyroxenes from Ferrosyenites of South India
Authors: Babu E. V. S. S. K. , Leelanandam C. 
Published: November 2024

Abstract
Pigeonites are typically absent in slowly cooled plutonic rocks, and ortho-pyroxene is totally unkown in alkaline rocks. Ferrosyenites and ferrornonzosyenites of the Chimakurti (Andhra Pradesh) and Sivamalai (Tamil Nadu) areas in south India contain both ortho- and clino-pyroxenes exhibiting various exsolution and inversion textures. The present study on these textures demonstrates the rare presence of 'inverted pigeonites' suggesting very high initial crystallization temperatures for the host rocks and also offers unambiguous evidence for the sub-alkaline (tholeiitic) nature of the host rocks.
The Gold Content of Deccan Basalts Western Ghats, India
Authors: Oleinikov B. V. , Korobeinikov A. F. , Koroleva O. V. , Krishnamurthy P. , Kumar Anil , Gopalan K. 
Published: November 2024

Abstract
Sixty nine (69) samples of Deccan basalt flows from the Western Ghats representing the Wai, Lonavala and Kalsubai subgroups average 3.7 ppb of gold. Gold content shows limited variation from 3.0 to 5.8 ppb in 62 samples whereas they range from 1.4 to 2.7 ppb in 7 samples. Flows of the Wai subgroup show the maximum variation in gold abundances (1.4 - 5.8 ppb) and which may be related to the presence of primitive uncontaminated basalts (Ambenali)- lowest value-crust-contaminated basalts (Poladpur) and basalts derived from enriched-mantle sources (Mahabaleshwar). Gold appears to be insensitive to crystal fractionation or differentiation as basalts of different types such as the picritic, porphyritic, aphyric and giant plagioclase-bearing types found within a subgroup or formation have similar avcrages (3.6-3.8 ppb).
Deccan Tholciitic basalts contain higher amounts of gold than dome of the occean island (Hawaii) tholciitic basalts island are (Kurile-Kamchatka) tholciites, but contain values similar to those found in the Columbia River basalt province.
Heavy Metal Content in Suspended Particulates and Bed Sediments of a Tropical Perennial River and Estuary, Central Kerala, India
Authors: Padmalal D. , Seralathan P. 
Published: November 2024

Abstract
The tropical perennial muvattupuzha river and adjoining Vembanad estuary, Central Kerala, were surveyed for texture, organic carbon and heavy metals (Fe, Mn, Cu, Ni, Zn, and Cr) in suspended particulates and bed sediments. Sand is the dominant textural class in river, whereas mud, muddy sand and sand floor the estuarine substratum. Particulate organic carbon varies from 2.04-3.44% with a slight increase towards estuarine mouth. River sediments show low range of organic carbon (0.35 - 1.03%) while the estuarine sediments show 3-4 fold increase than that in the river. The concentration of Fe, Mn and Zn are in general higher in bed sediments than in suspended particulales. But Cu, Ni and Zn enrich in particulate phase. The overall variation of geochemical parameters is in general controlled by particle size as well as chemical desorption during estuarine mixing.
Alkaline Magmatism in the Eastern Ghat Belt - A Critique
Authors: Leelanandam C. 
Published: November 2024

Abstract
Almost all the feldspaihoidal alkaline complexs of the Eastern Ghat granulite belt are virtually restricted to its western margin, arid are significantly confined to the junction zone between the catonic and mobile belt regions. The presence of subordinate amounts of quartz syenite in preponderantly nephe1ine syenite plutons is ascribed, among other causes, to the dominant role of crustal contamination by initially undersaturated magmas. The not-so-common ferrosye nites, though cospatial, are not comagmatic with nepheline syenites. White ferrosyenites represent the late stage derivatives of tholeiitic magmas, nepheline syenites correspond to the end stage differentiation products of malignites/melteigites. The so-called "alkalic stamp" for rocks purported to be gabbros, in the vicinity of alkaline plutons, is realised as merely a myth. The longevity or propensity for rejuvenation of alkaline magmatism and carbonatite emplacements of mantle origin, in abyssal faults, is fairly well established. The possibility of the presence of isotopically distirict subcontinental mantle reservoirs in a part of the belt is discussed. Some general characteristics of the feldspathoidal complexes are summarized the need for studying them on modern lines to understand their precise petrogenetic schemes and exact crystallization histories is outlined.
Ball and Pillow Structure in the Miliolite Formation of Saurashtra, Gujarat and its Significance
Authors: Garhia S. S. 
Published: November 2024

Abstract
Ball and pillow structure present in the calcarernties of the Miliolite Formation, occuring in the river sections of Mangrol-Veraval arca in southern Saurashtra are described. The calcarernties deposited under shallow subaquous marine environment along tide dominated rivers. These tide dominated rivers were highly charged with sediments and the hydrodynamic conditions were of high energy regime. The occurrence of ball and pillow structures in the calcarenites indicate a rapid and sudden input of sediments along the tide dominated rivers probably under storm conditions.
Petrology, Petrochemistry and Genesis of the Alkaline Rocks Associated With the Ambadungar Carbonatite Complex, Baroda District, Gujarat, India
Authors: Srivastava Rajesh K. 
Published: November 2024

Abstract
The present paper describes the petrology, protochemistry and genesis of alkaline rocks related to the Ambadungar Carbonatite Complex. These alkaline rocks have been classified as tinguaite, phonolite/phononephelinite, melanephelinite and syenite/nepheline syenite. The porphyritic variety dominates in the area and important phenocrysts are aegirine/aegirine-augite. feldspars, nepheline, hauyene, analcite, and minor mealnite. Chemically they are undersaturated. In the tight of new petrological and chemical data presented. the alkaline rocks of Ambadungar are shown to be genetically related to the Carbonalite-Nephelinite magmatism. These are inferred as products of liquid immiscibility from a parental carbonated nephelinilic magma.
Geochemical Changes in Basalts Across Rhe Archaean-Proterozoic Boundary-An Evaluation of Dalma Basalts from Eastern Indian Shield
Authors: Bose Mihir K. , Chakraborti Manas K. 
Published: November 2024

Abstract
Geochemical characteristics of Dalma basalts from the Proterozoic Singhbhum basin of eastern Indian shield have been evaluated in the perspective of basalt geochemistry across the Archaean-Proterozoic Boundary (APB) in greenstone belt association. Most of the incompatible elements and element ratios in Dalma basalts clearly establish their depleted geochemical signature comparable to the late Archaean greenstone belt basalts. Like their late Archaean counterparts, the Dalma basalts have La/Yb = 2.50, La/Ta = 19, Ti/V = 18 and Zr/Y = 2.6. This ultrabasic and potash-poor tholeiitic association of Singhbhum basin differs remarkably from calc-alkali basalts-potassic felsic rocks assemblage of Proterozoic greenstone belts. Convincing lithotectonic association and geochemical behaviour are strongly indicative of a back-are setting for Dalma volcanism. However, due to partly modifying influence of subduction zone elements on primary primitive composition of Dalma basalts, an apparent are association is imposed in terms of certain element ratios. Taken together, the lithoassociation and geochemical data suggest that basalt magmatism in early Proterozoic Singhbhum basin is broadly similar to those found in many late-Archaean greenstone belts. Dalma basalts do not appear to fit a generalised pattern of secular m~mt1e evolution across the APB. Further, it is observed that geochemical signatures of basalts are controlled by local tectonics which persist across a preconceived discrete time plane.
A Study of Gem Varieties of Corundum from Parts of Thmkur and Mysore Districts, Karnataka
Authors: Panjikar Jayshree , Chandrashekhar H. , Muniswamaiah M. , Ahmed Nazeer 
Published: November 2024

Abstract
The occurrence of corundum in Southern Karnataka is known from a long time in its complex geological environment, especially at the margins of the Clospet pluton. Although the exploitation for corundum has been going on since a long time, no systematic approach was made to study the gemmological characters of the mineral. In this paper the geological and gemmological characters of the gem varieties of corundum from parts of Tumkur and Mysore Districts are described.
Is the Simplipal Complex a Product of Shallow Plume Tectonics?
Authors: Banerjee P. K. , Ghosh S. 
Published: November 2024

Abstract
The Simlipal basic volcanics share two common features with the Newer Dolerite dyke swarm (within the Singhbhum-Keonjhar granite) and the Ongarbira volcanics and Dangoaposi lavas occurring along its western margin: their freedom from intense folding movements and from granite intrusion; although Simlipal's tectonic and chronologic frame with grits and sandstones alternating with basic volcanics still awaits solution. The geologic and isotope geochronologic data available from these suites do not rule out the possibility that these could be broadly contemporaneous eruptions and emplacements. Judging by the uniform spread of the dykes over approx. 20,000 sq km of granite country, the forcing of all these eruptions by a plume head, spreading below the Singhbhum continental lithosphere near the transition between Proterozoic I and II is suggested as a tectonomagmatic model, to be tested in future against high resolution isotope geochronological dates and dependable REE and Nd-Sr geochemistry for defining the eruptive events of this terrain.
Factorial Correspondence Analysis of Spatially Related Multi-Metallic Data along Gangpur-Singhbhum Metallo-Tectonic Belt
Authors: Roy A. , Saha A. K. , Sarkar S. N. 
Published: November 2024

Abstract
Correspondence analysis, using the concept of joint probability distribution of two random variables, individual samples and chemical variables, was applied to two sets of multi-metallic data from Mosaboni copper mines (18th, 21st & 25th revels) and Sargipalli lead-zinc mine falling within the Gangpur-Singhbhum metallo-tectonic belt. The analysis results factor loadings for individual samples and variables, which when plotted as points on two-dimensional coordinate (factorial) axes with the same origin recognize distinct geochemical domains characterised by natural groupings or clusters of samples and variables. The simultaneous variation of trace elements in these two data sets with sample locations (background/anomalous) seems to reflect overall trends of geochemical evolution of base metal mineralisation in the region.
Geochemical Trends in the Sediments and Manganese Nodules from a Part of the Central Indian Basin
Authors: Banakar Y. K. , Jauhari Pratima 
Published: November 2024

Abstract
Geochemical analyses of eighteen surface sediment samples collected from an area between 1°-15° S latitudes and 73°-87° E longitudes exhibit significant variation in their chemical composition. Distribution patterns of the major and minor elements suggest a probab Ie removal of a portion of Fe, Ti, Mg and Cr along with major portions of Mn, Ni, Cu and Zn as authigenic ferro-manganese colloids to the sediments.
The rare earth elements (REE) exhibit nearly an order of magnitude enrichment in the nodules compared to the surrounding sediments. The positive Ce anomaly in the Nodules (~0.25) is associated with negative Ce anomaly (0.04) in the host sediment indicating its oxidative scavenging preferentially by Fe-hydroxide colloidal floes incorporating into the nodules. The shale (NASC) normalised patterns and end member ratios of REE indicate middle REE(MREE) ennchment over light REE(LREE) and heavy REE(HREE) in both nodules and sediments. The preferential uptake sequence of REE in the nodules could be given as MREE&gt;LREE&gt;HREE.
Geostatistical Modelling of Lead-Zinc Mineralisation at Rajpura-Dariba (Rajasthan) - A Case Study
Authors: Sarma D. D. , Bahadur Subash , Moharana L. , Selvaraj J. B. 
Published: November 2024

Abstract
Geostatistical modelling of the South lode of Rajpura-Dariba lead-zinc mineralisation has been carried out based on the assay values of 49 borehole cores. From the variograms constructed, the structure of Zinc and Lead mineralisations of this lode can bedescribed by spherical models as: ?(h)=2.01 [Spr(h/a)]; for h=a=50 m for the variable Pb and ?(h)=13.50 [Spr(h/a)]; for h=a=50 m for the variable Zn. The variogram for Zn is more stable than for Pb. Based on the above models, kriged estimates, corresponding variances and standard errors were obtained for Zinc and Lead variables in respect of 315 blocks of ore each measuring 15 m × 15 m. From the results, it has been observed that there is close agreement between the observed assay values and the krigedestimates. 68% and 95% confidence limits corresponding to ±10s and ±1.960s limits were worked out fora sample set of kriged estimates on the assumption that Pb and Zn variables follow Gaussian distribution. The results are presented.