bluuebunny/crossref_metadata_2025 huggingface dataset:
Ore Mineralogy and Fluid Inclusion Characteristics of Different Ore Associations from Malanjkband Copper Deposit, M. P. (India)
Authors: Panigrahi M. K. , Mishra B. , Mookherjee A.
Published: November 2024

Textural and paragenetic study of primary minerals (chalcopyrite, pyrite, magnetite, hematite, sphalerite, bornite, chalcocite and molybdenite) reveal intermittent fracturing, precipitation and dissolution phenomena with at least two recognizable stages: magnetite(I) - pyritc(I) - molybdenite (?) followed by pyrite(II) - chalcopyrite - sphalerite - magnetite(II) - hematite - bornite - chalcocite. Oxidation and supergene enrichment effects producing cuprite-malachite-native copper and chalcocite-covellite are moderate. Difference in the mineralogy of the oxidation zone and restricted occurrence of supergene enrichment are due to the variation in the primaty mineralogy of the ore.

The ranges of fluid inclusion homogenization temperature (maxima 160°-180°C) and fluid densities in the reef quartz and ore bearing vein quartz are more or less the same, with a wider range of salinity in the vein quartz ores. However, mixed aqueous carbonic inclusions are restricted to the vein quartz ores and hence points towards a difference in the fluid regime. Th vs. salinity and Th vs. density plottings rule out simple cooling and/or mixing processes in the evolution of the fluid but rather hint at immiscible two-fluid phase separation. The suspected presence of low temperature Iss-phases and the results of fluid inclusion microthermometty point towards an unexpectedly low temperature environment of ore deposition. The paragenetic sequence is suggestive of an increase in the Cuffe ratio and fluctuating fO2 conditions in the fluid during the main stage of mineralization.
Magnetic Anomalies and Basement Structure Around Vizianagaram, Andhra Pradesh
Authors: Radhakrishna Murthy I. V. , Polinaidu B. , Rao A. T.
Published: November 2024

Magnetic anomalies in an area of about 1500 sq km around Vizianagaram town in Andhra Pradesh bring out a shallow magnetic basement of charnockitic rocks, which is highly faulted. The magnetic basement exhibits horst and graben-like structures and broadly maintains conformable relations with the antiformal and synformal structures of the overlying khondalite suite of rocks. The development of these faults is attributed to the earlier folding of the Eastern Ghats and their refolding about a N-S axis to change their initial NE-SW trend to E-W and NW-SE in the nonhern part of Andhra Pradesh. The development of the horst-graben type structure is explained by movements of the faulted blocks along the fault planes at different stages or tectonic activity.
Locomotory Traces (Repichnia) from the Jurassic sequence of Kutch, Gujarat
Authors: Kulkarni K. G. , Ghare M. A.
Published: November 2024

Of the seventeen ichnoforms, many are dominantly associated either with fodinichnia or pascichnia. Such an association, suggests low to moderate energy conditions and shallow water environment of deposition. Replacement of Curvolithus by Gyrochorte reflect minor oscillations in sea-level. Facies variations are decipbered by studying percentage distribution of repichnia in relation to other ethological groups.
Pleistocene Benthic Foraminifera and DeepM
Authors: Gupta Anil K.
Published: November 2024

The evolution of Pleistocene deep-sea environments at Northern Indian Ocean DSDP Site 219 has been evaluated, using the quantitative analyses of deep-sea benthic foraminiferal fauna. The Pleistocene assemblages are dominated by Uvigerina proboscidea which shows remarkable frequency changes. The relative abundances of characteristic benthic foraminifera, and patterns of Species Diversity and Equitability have enabled identification of four events (C1-C4) of major faunal turnovers. These events have been inferred to represent intervals of fundamental changes in atmospheric oceanic circulation, most likely the cooling and intensification of bottom-waters due to major increase in polar ice volume.
Tectono-Stratigraphic Framework and Volcanic Geology of the South Delhi Fold Belt in Central Rajasthan
Authors: Gupta P. , Mukhopadhyay K. , Fareeduddin  , Reddy M. S.
Published: November 2024

The Delhi rocks are deposited in two sub-basins separated by a median inlier of Pre Delhi rocks. The Barotiya and Sendra Fonnations occupying the western sub-basin contain significant basic flows and tuffs with associated felsic volcanics. The eastern sub-basin recording a diachronous evolutionary history is the repository of the Rajgarh and Bhim sediments.

Striking similarities are noted in respect of lithology, structure and metamorphism amongst the gneisses and schists of the Pre-Delhi rocks flanking the Delhi Supergroup and also of the median inlier. Structural imprints and contact relationship indicate that these gneisses and schists fonn the basement for the Delhi sediments. Migmatization related to orogeny suggests reactivation of a sialic basement, which along with the tectonic emplacement of basement slices in the Delhi stratigraphy argue in favour of an intra-cratonic development of the Delhi basin.

The western sub-basin shows bimodal volcanism and the various geochemical discriminants suggest an IATor MORB setting, but fail to make a choice between the two. Bimodal volcanism in association with shallow clastic sediments signify ensialic origin in a rifted mobile belt. Structural studies indicate large-scale dextral vergence with steep 'S' surfaces which are characteristic of oblique shear transpressive mobile belt.
Fluid Inclusion Studies in Apatite of the Sung Valley Carbonatite Complex, N. E. India: Evidence of Melt-Fluid Immiscibility
Authors: Jaireth S. , Sen A. K. , Varma O. P.
Published: November 2024

The Sung Valley carbonatite complex of Cretaceous age has a core of serpentinized peridotite rimmed by pyroxenite. The complex is intruded by small- to medium-sized bodies of uncompahgrite, ijolite, syenite and carbonatite. The carbonatites occur as stocks, lenses, dykes and veins. Apatite grains in the apatite-magnetite sovite are characterized by three varieties of apparently syngenetic primary inclusions: The type S (solidified) inclusions contain highly birefringent and anisotropic solids along with some gas and liquid; the co-existing type F (fluid) inclusions are of two types-low to moderate salinity gas-liquid inclusions (gas= 15 to 35% by volume) and high salinity gas-liquid inclusions with one or more daughter minerals (halite, sylvite, carbonates). Type S inclusions homogenize into a relatively viscous, melt-like liquid at temperatures between 740 and 806°C whereas type F inclusions homogenize into a liquid phase at temperatures between 177 and 488°C. The large variation in homogenization temperatures between type S and type F inclusions and the difference in their composition are interpreted to be the result of a liquid immiscibility between a volatilerich carbonate melt and a saline aqueous fluid, though contribution of necking down of some original inclusions in generating clusters of type S and type F inclusions cannot be ruled out completely.
Geology, Petrography and Systematic Stratigraphy of Pre-Ariyalur Sequence in Tiruchirapaui District, Tamil Nadu, India
Authors: Ramasamy S. , Banerji Ranjit K.
Published: November 2024

A new litho unit-Terani Formation is proposed. The lower part of the Uttatur Formation is found to be homotaxially equivalent to the Dalmiapuram Formation. A new geological map based on these units is presented.
Evaluation of Deformational and Depositional Controls on Pebble Characters - A Study of Bisrampur Conglomerate, Singhbhum, Bihar
Authors: Ghosh Anirvan , Bose Mihir K.
Published: November 2024

The conglomerate horizon near Bisrampur in Singhbhum, Bihar, on the flank of Archaean (Singhbhum granite) platfonn, manifests a highly mature pebble assemblage in an argillaceous to arkosic matrix. The triaxial pebbles in conglomerate show readily recognizable down dip preferred orientation of longest axes and a common graving lineation on pebble surfaces. Strain analyses indicate a feeble relative dominance of flat type pebbles and a possible non-random orientation pattern of the primary deposited nonspherical pebbles. Calculation of finite strain also suggests that the axial parameters of pebbles cannot be related to a single phase of deformation. Thus, there may be two factors involved responsible for triaxiality of pebbles, one prior to deposition and a later modification by feeble deformation. Although spatially associated to a strongly tectonised domain to the north, the conglomerate largely retains the primary depositional character controlled by mass flow on the basin flank. This behaviour may be resolved by protective character of the channel filling on continental slope.
Constraints on the Evolution of the Purana Basins of Peninsular India
Authors: Kale Vivek S.
Published: November 2024

The seven supracrustal, epicratonic Purana basins occupy more than a fifth of the area of Precambrian exposures in the Indian Shield. They are repositories of Proterozoic shallow marine sediments, resting unconformably on the eroded surfaces of the older rocks; and are preserved in an unmetamorphosed and marginally deformed state. These sequences have comparable characters though their mutual differences are quite significant, indicating that each one of the host basins had an independent evolutionary history.

The gross sedimentological contents, associated igneous rocks, structural and metamorphic features of the Purana basins and their geographical and temporal proximity with the Middle Proterozoic Mobile Belt are examined to evaluate the broad geotectonic framework within which they evolved. These "polyhistory, continental" basins are apparently analogous to the "Atlantic-type" passive continental margin systems associated with extensional tectonic regimes. The Bhima basin is an exceptional case of a "simple", transtensional, "pull-apart" type basin, while some of the others were probably initiated as "back-arc" basins.
Geochemistry of the Tertiary Formation at Pozhikkara Cliff Section, Kerala-Its Palaeoenvironmental Significance
Authors: Seralathan P. , Padmalal D.
Published: November 2024

The Tertiary sequence begins with fossiliferous marl and is overlain by carbonaceous clay, china clay and laterite. The thin (3 cm thick), hard, compact duricrust layer, which is found interbedded within the carbonaceous clays, shows abnormal geochemical anomalies. Major elements such as Fe, Mn and Ca and the trace element Co show about 2-3 fold and 1-2 fold increase respectively in the duricrust than the upper and lower sections. However, the content of Na, K, Ni, Cu and organic carbon show an opposite trend. Cd does not show any marked variation along the profile. The CaCO3 content is remarkably high in the duricrust and marl than the other layers. Fe and Mn contents are much higher in the laterite than china clay, other parameters do not show much variation. The high content of Fe, Mn, Ca and CaCO3 and low Ni/Co ratio and organic carbon content in the duricrust layer indicate an oxidizing environmental condition which existed at the time of the formation of this layer, while the converse trend of these parameters in the carbonaceous clays indicate the prevalence of a reducing condition.
Geothermal and Rheological Implications of the Crustal Earthquakes Within and West of the Arakan-Yoma Fold Belt (Northeastern India)
Authors: Cermak V. , Bodri L. , Saikia M. M.
Published: November 2024

The study area, which represents a boundary collision zone between the Indian and Euroasian plates, has been the focus of intense seismic studies for decades. Except for events that have been clearly associated with the underthrusting of the Indian plate. the data reported by the regional network in the Northeastern Regions of India indicate a layer of concentrated seismicity in the lower crust at a depth range of 30 to 40 km. The lithosphere rheology was assessed on the basis of the frictional failure in the brittle regime, and power-law steady-state creep in the ductile regime. Rheological profiles were constructed fora 1-0 crustal structural and thermal model. The rheological stratification of the lithosphere was compared with the earthquake depth distribution which indicated a reasonable confinement of seismicity to brittle horizons.
Syn-Sedimentary and Later Remobilised Epithermal Pb-Zn Mineralisation of the Great Limestone, Riasi, J & K - Signatures in Fluid Inclusions and Stable Isotope Compositions
Authors: Nayak B. K. , Sharma Rajesh
Published: November 2024

A strong stratigraphic control is exhibited by the sporadic Pb-Zn occurrences in the Great Limestone of Riasi, J & K. Fluid inclusion thermometry and stable isotope data suggest their remobilisation and concentration in the fractures developed in the host-rock at the time of orogenic movements and the final deposition may be due to the mingling of at least two fluids; one epithermal; generated due to orogenesis and the other, meteoric water.
Crenulation Cleavage Development in Pukhri Formation of Chamba Area, Western Himachal Pradesh, India
Authors: Bhola A. M.
Published: November 2024

The geometric and tectonic significance of crenulation cleavage in Pukhri Formation (mainly pelitic sequence with interbedded thin quartzitic layers) of Chamba area, is studied by taking into account modifications taking place in original class 1-3 fold layers by three theoretical models viz. i) Homogeneous flattening ii) Shearing along the axial plane of folds iii) Volume reduction in multilayers. Theoretical model studies supported by the study of cleavage microstructure and microlithons in microfolds of Class 1-3 pairs point out that volume reduction model is most appropriate in explaining the development of crenulation cleavage, its intensity and frequency in the Chamba area.
Tectonic Strain Ratio Computed from the Mean Shape of the Ellipsoidal Passive Particles
Authors: Roday Prakash P. , Katpatal Yashwant B.
Published: November 2024

All methods of computing Rs. the tectonic strain ratio from the various means (of axial ratios of ellipsoidal particles that undergo deformation homogeneously with the matrix-the passive particles) such as arithmetic (̅Rf). geometric (Rg) or harmonic (H) fail to adequately express the real values of Rs. Using the data given by Lisle (1979) for simulated conglomerates, it is shown that ̅RfH = H+̅Rf÷2-(H+̅Rf)-1 is closest to Rs if Rs > Ri. For Ri > Rs (2φ > 90° in a given principal plane), R' (given by ̅Rfa-̅Rfa-2/̅Rfb-̅Rfb-1 or by ̅Rfa-̅Rfa-1/̅Rfb-̅Rfb-2, depending upon whether Rib > RSb or Ria > RSa respectively) gives the value of k and the values of a and b that are closest to that of the superimposed Rs. The data are tabulated and also plotted on a conventional Flinn diagram.
A Mid Holocene Strandline Deposit on the Inner Shelf of Cochin, West Coast of India
Authors: Purna Chander Reddy N. , Durga Prasada Rao N. V. N.
Published: November 2024

Beach sediments with a phi mean size varying from 1.07 to 2.9 are well to moderately sorted and to a great extent negatively skewed. On the inner shelf, the sediments exhibit a wide range (0.9φ and 10φ) in mean grain-size. While most of the inner shelf is covered with fine silts and clays, sandy sediments occupy a linear belt in the outer parts (-25 to -30 m) of the shelf. These moderately sorted sands are considered to be relict and deposited during a standstill of the Holocene transgression. The CM pattern suggests that the sandy sediments in the inner shelf like the beach sands were deposited under high energy conditions. The well-preserved sands indicate that the existing hydrodynamic conditions on the inner shelf are neither strong enough to rework the sediments nor transport the modern river-contributed fine sediments to the outer parts.
A Mathematical Approach to the Petrogenesis of the Upper Siwalik Conglomerates (L. Pleistocene) of the Jammu Region, Northwest India
Authors: Mohan Chander , Gundu Rao C.
Published: November 2024

In sedimentary petrography, interpretation of the source and process from the response data i.e., characteristics of the deposited sediment is a convention. The best suited mathematical technique in such an exercise is 'Principal Component Analysis'. Applying this technique to the Upper Siwalik Conglomerates of Jammu region, northwest India (Lower Pleistocene, Cromerian) five components were extracted representing 68% of total variation in the conglomerate system. Components C1, C2 and C4 were identified with erosion and transporting processes (size, size sorting and shape), C3 with composition (quartzite and sandstone pebble proportions) and C5 with depositional processes (orientation and packing). Also, the analysis suggests that instead of three values of each of size and size sorting, and four values of shape used in the investigation, one measure of each of size, size sorting and shape is quite sufficient to explain the total variation in the petrographic properties of the Upper Siwalik Conglomerates of Jammu region.
Neotectonic Movements in the Loharkhet Area, District Almora, Kumann Fiimalaya
Authors: Pant P. D. , Goel O. P. , Joshi Mallickarjun
Published: November 2024

Thrusts, fold axes and fault zones in the Loharkhet area in the northern part of Almora district in Uttar Pradesh, record reactivation during Neogene times. Several alluvial and colluvial deposits in the area are being vertically and horizontally offset, and tilted by active folding and faulting. The recent movements along the Ravetiganga overturned anticline and Dulam Gadhera- and Vongarh-Gason-faults have not only uplifted the Nasati-Rithabagar block by about 103 m, but have shifted also the original confluence of the Sarju and Ravetiganga rivers by 11 km southwestward.

The ESE-flowing Gurkhula Gad and Mehar Gad streams have been deflected towards SSE direction by the recent strike-slip movements along the Kaphlikot-Ramari Fault. The Ramari landslides fan has been displaced vertically by 3 m along this fault. Terraced toe of the colluvial cone of the Badiyakot landslide has been displaced dextrally and uplifted by 18 m along the NNW-SSE striking Ghatia Gad Fauh.

The geomorphic expressions of the various tectonic zones indicate both vertical and strike-slip displacements. Rejuvenation of the earlier mature terrain is borne out by topographic changes that have taken place in the recent past. The topographic development indicates continuing uplift in some sections of Vaikrita (MC) Thrust and Berinag Thrust and the zone of the Ravetiganga overturned anticline. Relatively higher rate of uplift is observed for the MCT zone.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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>LREE>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

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.
Biometric Study of Lepidocyclina (Nephrolepidina) from Kutch, Saurashtra and Quilon (India)
Authors: Saraswati Pratul Kumar
Published: November 2024

The biometric parameters of Lepidocyclina (Nephrolepidina) from the Oligocene - Early Miocene sections of Kutch, Saurashtra and Quilon are studied to evaluate their biostratigraphic importance. Following the biometric concept L. (N.) isolepidinoides is identified in the Early Oligocene sequence of Kutch and L. (N.) sumatrensis from the Early Miocene sections of Kutch, Saurashtra and Quilon. The nephrolepidines of Kutch appear to show agradual sustained change withintelVal of arrested evolution. The average value of parameter - A stagnated at about 42% during Oligocene and increased to nearly 46% in Early Miocene times. The value of C increased from 1.7 in Early Oligocene to 2.6 in Late Oligocene and 3.9 in Early Miocene. During this interval F increased from 1.2 to 2.7. The parameters A, C and F are found to be most dependable in inferring the relative age of the nephrolepidine assemblages from the studied localities. The staggering values of E and dc prevent them from a reliable use in biostratigraphy.
Surface Microtextures of Heavy Minerals from the Bay of Bengal off Gopalpur, Orissa
Authors: Bhatiacharyya Samit , Sengupta Ranadhir
Published: November 2024

Microtextures of heavy minerals separated from the seabed samples collected from the inner shelf off Gopalpur, Orissa are identified under SEM and interpreted to prepare a process-response environment model. Dominance of features induced by mechanical process is noted though textures born of chemical processes depending on residence time are also common over the heavy grains. While microtextures of aeolian and glacial origin are absent in the minerals, recycling of heavies like ilmenite, rutile, garnet and spinel is evident from presence of features induced by both mechanical and chemical processes. Zircon and monazite are the only minerals in the studied suite that bear textures almost exclusively of mechanical origin. Derivation from a single provenance is suggested for these two minerals.
Geochemistry of Amphibolites from the Nellore Schist Belt, Andhra Pradesh, India: An Example of Back-Arc Basin Low-K Tholeiitic Magmatism
Authors: Satyanarayan K. , Dhana Raju R. , Kanungo D. N.
Published: November 2024

Geochemistry of ortho-amphibolites from the Degapudi-Kalichedu area of the Nellore Schist Belt (NSB), an Archaean greenstone belt in southeastern India, has indicated their affinity to a low-K tholeiitic magma derived from an LIL-enriched, apatite-bearing mantle by about 5-20% partial melting, followed by fractional crystallization. Amphibolites range from high-Mg-type early differentiates (massive amphibolite and actinolite schist) to low-Mg-type middle-stage differentiates (schistose amphibolite, hornblende schist and related gametiferous hornblende schist). During and subsequent to the generation of their parental magma, the early crystallizing mineral phases are oli vine-clinopyroxene-plagioclase-magnetite-apatite. A back-arc or marginal basin palaeotectonic setting is indicated for NSB by geochemistry of these amphibolites, with precursors of high-Mg-type emplaced in a narrow basin associated with mature subduction zone system and of low-Mg-type in a wider basin associated with youthful subduction zone system.
Groundwater Management in Parts of Saltora Block, Bankura District, West Bengal
Authors: Sikdari P. K. , Dasgupta N. , Sarkar S. S.
Published: November 2024

Hydrogelogical investigation of the area around Saltora reveals the presence of groundwater under shallow water table condition within the Precambrain anorthositic country rock. VES study indicates that the water is stored within the weathered residuum and the underlying fractured rocks within a depth of 69 m. The groundwater flow is guided by the topography and the fracture system. Chemically the groundwater is suitable for drinking and irrigation purposes. The cardinal aquifer parameters such as permeability, transmissivity and specific yield are oflow order and hence water harvesting structures should be supplemented with groundwater abstraction structures to increase agricultural production and thus the economy of the area. Since the area is drought prone traditional methods of irrigation such as flooding must be ruled out and water should be transported from the source to the field by lined channels or pipes to minimise conveyance and evaporationallosses. Drip irrigation may also be adopted.
Temporal Distribution of Benthic Foraminifera Across KTB in Krishna-Godavari Basin, India
Authors: Jaiprakash B. C. , Soodan K. S.
Published: November 2024

The abundance, survivorship and extinctions of smaller benthic foraminifera across Cretaceous/ Tertiary Boundary in a well section GS-II-A in Krishna-Godavari basin appears to be a reflection of tolerance and responses to major geological events such as basinal rise, sea level drop, hiatus and widespread Deccan volcanism. During the terminal Cretaceous the marine environment possibly suffered declining CaCO3 level and anoxic conditions.

Towards the top of Cretaceous (Zones M -16/17), smaller calcareous benthic foraminifera show a decline in relative abundance of the order of 35 %. The relative abundance oflow O2 tolerant arenaceous foraminifera shows a gain of 20% to 25%. A hiatus of the order of less than 8.5Ma encompasses KTB. A major transgressive phase after an anoxic stage above KTB hiatus reestablishes equable conditions for the proliferation of smaller calcareous benthic foraminifera. This relative decline of calcareous benthic foraminifera and survival abilities of arenaceous benthic foramini fera is suggestive of gradual and possibly stepwise elimination process under ecological stress over a prolonged period caused by a chain of KTB events.
Grain Size Distribution and Mineralogy of the Suspended Sediments of Mahanadi River
Authors: Chakrapani G. J. , Subramanian V. S.
Published: November 2024

Considering the enormity of sediment load transported by the Mahadnadi river (approximately 15.74*106 tonnes/year), a,study has been conducted to uncover the groinsize distribution mid clay minerals present in the suspended load which is found to be poorly sorted, mostly fine skewed and very leptokurtic. Increasing water discharge not only increases mean size but improves the sorting of sediments. Sediment size ranges from 1-25 μm and are mostly derived from the sedimentary formations in the basin. Thc Hirakud dam constructed in the Mnhanadi river basin traps coarser scdirnents. Illite is the dotninant clay mineral followed by knolinite, chlorite and montniorillonite. Futher, clays do show preferences to specific size ranges.