bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid Inclusion Studies in Charnockites from Yercaud Area, Tamil Nadu
Authors: Asha Manjari K. G.
Published: November 2024

Massive charnockites from the Yercaud area in Tamil Nadu show petrographic evidence for post-metamorphic deformation. Fluid inclusion studies indicate a change in densities from 1.06 - 1.03 g/cm3 in the early carbonic inclusions to 1.17 - 0.90g/cm3 in the late carbonic inclusions. The wide range of density variations within each generation of fluids suggest that the syn-metamorphic fluids captured within inclusions could have been preferentially leaked out during post-metamorphic deformation.
Geochemistry of Carbonate Precipitation from the Ground Waters in Basaltic Aquifers: An Equilibrium Thermodynamic Approach
Authors: Pawar N. J.
Published: November 2024

The geochemistry of ground waters in the basaltic aquifers is considerably modified by the incongruent dissolution of augite and plagioclase from basalts. The analyses of the water chemistry data by using the WATSPEC aqueous-model computer programme for computing the ionic species abundances, the partial pressures of CO2 (PCO2) and mineral Saturation Indices (SIc and SId) suggest. that the ground waters are supersaturated with respect to calcite and dolomite. The modeling has indicated a state of equilibrium with respect to dolomite first followed by calcite. This state of equilibrium can be linked with the selective dissolution of augite leading to Mg-rich alkaline environment. which is also favourable for the formation of montmorillonite clays. The clays in turn act as a buffer and as a result the levels of Ca and Na do not exceed 1.8 mmol/L concentration. Due to the early dolomite saturation the Ca/Mg ratios areless than unity, whereas Na/Ca ratios are above unity suggesting precipitation of calcite and possibility of input from zeolites and mixing of difierent sources of water with local ground water.

The precipitation of calcite is under high PCO2 conditions related to degassing and diffusion of CO2 at the water-table and along cracks, joints and fissures in the basalts. The high PCO2, dissolved oxygen content, presence of contaminants and fluctuations in the water table suggest that the ground water has chemically evolved under open system conditions.
Stochastic Modelling of Lead - Zinc Deposit at Rampura Agucha, Rajasthan
Authors: Sahu B. K. , Bagchi J.
Published: November 2024

The irregularly spaced assay values of lead and zinc in different boreholes of Rampura-Agucha Pb-Zn deposit (Rajasthan), have been interpolated at equal intervals of one meter using cubic splines to obtain a constant lag, discrete spatial (time) series. The time series has been used subsequently for stochastic modelling of assay values along the drill holes. Univariate stationary models under the integrated autoregressive moving average scheme - ARIMA (p,d,q) - were established for each assay series along four borehole based on statistical analyses of their auto (acl-) and their partial (pacf) correlation functions. These models can be used for univariate forecasting of assay values at different distances. Among the candidate ARlMA (p,d,q) models, ARLMA (1,1,1)and ARIMA (1,1,0) were found to fit spatial distributions of Zn and Pb, respectiveIy, using the principle of parsimony.

Though linear stochastic models were developed for Rampura - Agucha Pb-Zn deposit, a brief review of the scope and use of non-linear stochastic model for modelling of complex ore mineralisation has also been attempted.

Geochemical interpretation has been carried out on the petrochemical data of the amphibolites interlayered with the footwall and the hanging wall rocks using partial correlation coefficients between various oxides. This has led to comprehensive characterisation of the geochemistry and mineralogy of the amphibolites.
Uranium Mineralization in the Siwaliks of Northwestern Himalaya, India
Authors: Kaul Ravi , Umamaheswar K. , Chandrasekaran S. , Deshmukh R. D. , Swarnkar B. M.
Published: November 2024

The Siwalik Group constituting about 6000m of fluvial sedimentary rocks of Middle Miocene to Pleistocene age has been under exploration for uranium over the last two decades using different techniques including exploratory drilling, mining. More than 350 uranium occurrences forming eight major clusters between Poonch (Jammu, Kashmir) in the west and Tanakpur (Uttar Pradesh) in the east have been identified. A majority of these occurrences are confined to three distinct stratigraphic horizons: (1) lower part of Upper Siwaliks corresponding to the upper part of Garchandi energy sequence; (2) upper part of Middle Siwaliks (the middle part of Garchandi energy sequence); and (3) upper part of Lower Siwaliks (Jwalamukhi energy sequence).

Uranium mineralization occurs as small peneconcordant lensoid bodies with the longer dimension of individual lenses traceable from a few tens of metres to 700m, sub-parallel to strike or dip. The average grade of different occurrences in Siwaliks varies from 0.02-0.06% U3O8 and thickness less than a metre to 4m. Uraninite, pitchblende, coffinite, and a variety of secondary uranium minerals including tyuyamunite, uranophane, bayleyite, andersonite, schoepite, liebigite, swarlzite, and schroeckingerite have been identified. Azurite and malachite are also associated in some of the uranium occurrences in Lower Siwaliks. The sedimentological, geochrmical, and tectonic attributes of the Siwaliks indicate a sedimentary uranium province.

Uranium mineralization in Siwaliks is attributed to concentration of intrinsic uranium in the sediments derived from fertile Himalayan provenance and subsequent remobilisation by groundwater. Enrichment of uranium is controlled by sedimentary and lithological characteristics such as porosity-permeability barriers and abundance of reductants such as organic carbon, pyrite, and anaerobic bacteria. A secondary control by faults has also been observed at some places. Relatively higher concentrations of Se, Mo, Cu, Co, V, and Au have been noted in some of the uraniferous zones.
Neogene-Quaternary Sequence in Gujarat: A Review
Authors: Merh S. S.
Published: November 2024

The constituent rocks of Neogene are conglomerates, grits, silty sandstones, marls and argillaceous limestones. Marine Quaternaries are represented by the miliolite rocks of Saurashtra (Middle Pleistocene) and younger Holocene Rann sediments, mudflats and beach rocks. The transition of Neogene to Quaternary is not fully understood. Perhaps regressive conditions prevailed during the close of Pliocene and in the early Pleistocene. Evidences point to a bw strandline during the Lower Pleistocene. The Quaternary period is marked by two major transgressions-one in Ihe Middle Pleistocene and the other at the advent of Holocene. The Middle Pleistocene transgression gave rise to the miliolites, whereas the Holocene marine deposits are related to the last post glacial transgression.

The Neogene-Quaternary sequence requires further examination, particularly the so-called Pliocene, Plio-Pleistocene and Lower Pleistocene rocks. As the N-Q sea levels were related to climatic changes, a close scrutiny of the onshore continental record just above the marine Neogene rocks might provide some information towards fixing the nature of transition of Neogene to Quaternary. It would be essential to apply alternative criteria such as palaecmagnetic and therrnoluminiscence measurements and radicmetric age determinations for obtaining a clearer picture.
Status of Hydrocarbon Exploration in Western Offshore Basins, India
Authors: Mathur R. B.
Published: November 2024

Following the discovery of Bombay High field in 1974 by OiZ & Natural Gas Commission about 60 oil and gas strikes have been made including a couple of giant fields.

Western offshore comprises five contiguous sedimentary basins all of which are under active exploration. Hydrocarbon resources of 9.5 billion tonnes have been prognosticated in the area upto 200 m isobath, off the west coast of India. About 35% of these have already been established and sufficient scope exists for the continued thrust on exploration.

Two owned survey vessels capable of carrying out state of the art geophysical surveys coupled with inhouse computer facilities and expertise have dispensed with foreign dependence on seismic data acquisition, processing and interpretation faced in the seventies. Advanced techniques of 3-D surveys and evaluation of reservoir parameters from seismic have alteady found place for subtle exploration and exploitation needs.

Today Western offshore is the most active drilling area of the country. Ten offshore rigs owned by ONGC and 18 charter hired rigs are operating. About 250 km per year of exploratory and development drilling is being carried out currently which is likely toincrease 11/2 fold during the Eighth Five Year plan.

Starting from a meagre 0.4 MMT per annum the current production rate of over 20 MMT has been achieved from Western Offshore which-accounts for about 65% of the country's oil from indigenous sources.
Conglomerate Horizons in South-Central Rajasthan and their Significance on Proterozoic Stratigraphy and Tectonics of the Aravalli and Delhi Fold Belts
Authors: Sinha-Roy S. , Mohanty M. , Malhotra G. , Sharma V. P. , Joshi D. W.
Published: November 2024

The Proterozoic sequences of South-Central Rajasthan are contained in the Lower to Middle Proterozoic Aravalli and Middle to Upper Proterozoic Delhi fold belts. The stratigraphic relations within these fold belts as well as the basement-cover relations are beset with several problems. The conglomerate horizons have been studied to address some of these problems. Based on the conglomerate horizons, representing erosional unconformities, the Aravalli Supergroup has been sub-divided into three groups and the Delhi Supergroup of the South Delhi fold belt into two groups with constituent formations. These horizons are also useful in identifying three stages of basin evolution for the Aravalli fold belt. The Middle Aravalli Conglomerate is the most prominent representing mid-Aravalli hiatus, and corresponding to the Debari Transgressive Stage which followed the Delwara Rifting Stage in the Lower Aravalli in a system of ensialic distensional tectonics where triple-junctions and pull-apart basins are formed. The Upper Aravalli has been the Jharol Ocean Opening Stage, the oceanic/transitional crust having been consumed at a median ultramafic suture line during the formation of the Aravalli fold belt. The South Delhi fold belt has also multi-stage development history with the Barr Conglomerate representing the base of the youngest Delhi sequence.
Geophysical Methods for Subsurface Geological Mapping in Bethunmi-Dariba-Bhopalsagar Belt of Rajasthan-A Case Study
Authors: Gopal Ram , Agarwal R. N.
Published: November 2024

Geophysical Surveys employing, magnetic, self-potential and resistivity methods in Bethunmi-Bhopalsagar belt in Rajasthan have proved to be effective in identifying and mapping the various litho-units largely concealed under soil cover. An important discovery in the area was a striking closure of a local structure to the south of Dariba by magnetic suryeys. The disappearance of the graphitic mica schist and amphibolite to the south of Dariba may be explained by the structural closure brought out by these surveys rather than by faulting as invoked from geological evidences.
Sedimentary Structures in the Archean Sediments of Gadag Schist Belt, Karnataka
Authors: Chkrabarti C. , Reddy U. S. , Natarman W. K.
Published: November 2024

Gadag schist belt consists of more than 2000 m thick pile of sediments, least metamorphosed, and with abundant well preserved sedimentary sturctures, The principal types of structures are discussed and an attempt has been made to interpret the environment of deposition. Sedimentary structures and the lithotectonic sedimentary assemblage broadly indicate an unstable environment of deposition under geosynclinal conditon.
Application of Hornblende Fabric in Fold Analysis
Authors: Prasannakumar V. , Nair P. K. R.
Published: November 2024

The optic direction Y in hornblende in the lower amphibolite facies rocks of the southern part of the Chitradurga schist belt is parallel to the hinge lines of the earliest folds. Hornblende orientation and the temporal relations between crystallisation, folding and formation of foliation point to ENE- WSW compression at the time of deformation.
Siwalik Mammalian Faunas from Ramnagar (J. & K.) and Nurpur (H.P.) and Lower Limit of Hipparion
Authors: Nanda A. C. , Sehgal R. K.
Published: November 2024

Recent collections of mammalian fossils from the Siwalik sediments of Ramnagar (J.& K.) and Nurpur (Kangra, H. P.) indicate the presence of Chinji Fauna in the red bed sequence exposed in the vicinity of Ramnagar, but in Nurpur despite the dominance of the red clays which are usually considered as characteristic for the Lower Siwalik Subgroup, the fauna indicates an age equivalent to the Middle Siwalik. The mammalian fossils collected by the earlier workers are reinterpreted and the fossils, which include Propotamochoerus hysudricus. Merycopolamus dissimilis and Bramatherium megacephalumminus, are found to be indicative of Middle Siwalik age rather than the Lower Siwalik or the Lower-Middle Siwalik transitional age as was considered earlier. Hipparion (includes Hipparion and Cormohipparion) has been recorded by all the workers in Nurpur and now its arrival in India is considered at about 10m.y. The 12.5 m.y. dispersal event of hipparion in the Old World is found missing in the Siwalik Group. Though hipparion has been recorded from the so-called Lower Siwalik sequence of Kalagarh, U. P. but so far it is not recorded from the type section of Chinji in Potwar and in Dang Valley, Nepal. In the present collection, the presence of hipparion along with Dicoryphochocrus vinayaki, Hydaspifherium megacephalum, etc. from Nurpur is indicative of the Middle Siwalik age for the Nurpur Local Fauna. It is inferred that the red clays considered characterisitic of the Lower Siwalik are time transgressive and even the fauna colIected by earlier workers from Haritalyangar (Himachal) and Kalagarh (U.P.) is (at least a part of it) of Middle Siwalik age.

Ramnagar Fauna, recently collected by the authors, is true Chinji Fauna and is characterised by the presence of Dicoryphochoerus haydeni, Conohyus chinjiensis, Anthracotherium punjabiense, Dorcabune anthracotherioides, Hemimeryx pusillus, Giraffa priscilla etc. In Ramnagar area the Lower Siwalik Subgroup and the underlying Murree Formation have a conformable contact and fauna collected at the base of the Lower Siwalik Subgroup is found to be of Chinji age. So there are all possibilities that upper part of the Murree Formation may be of Kamlial age (i.e., lower part of the Lower Siwalik).
Taxonomy and Intraspecific Variation of Macrocephalites Formosus (Sowerby) from the Jurassic Chari Formation, Kutch, Western India
Authors: Bhaumik Debasish , Datta Kalyanbrata , Jana Sudipta Kumar , Bardhan Subhendu
Published: November 2024

Macrocephalites Zittel, 1884, an important genus in Kutch biostratigraphy, shows considerable diversity at species level. Macrocephalites formosus (Sowerby) is one species which shows a wide range of variability of different morphological characters. A detailed statistical analysis of the principal biocharacters of 140 individuals collected from different localities of Kutch was made to assess quantitatively the range of variation of the species.  "Macrocephalites chariensis (Waagen)", which was previously designated as a separate species, is demonstrated here to be a variant of Macrocephalites formosus and is incorporated into the latter species. An attempt is made to delineate the generic characters of Macrocephaliles and describe the diagnostic characters of the species M. formosus in detail. The variability of the species has no obvious adaptive significance.
India and Ur
Authors: Rogers John J.W.
Published: November 2024

Estimates of stabilization ages of the world's Precambrian cratons reveal a pattern in which all blocks stabilized at ages = 3.0 Ga occur in one area of the end- Paleozoic supercontinent Pangea. These blocks center around India, where at least two cratons (Western Dharwar and Singhbhum) show evidence of crustal growth terminating at or before ~3.0 Ga. This concentration of =3.0-Ga blocks is regarded as an Archean supercontinent referred to as "Ur."
Some Contributions to the Stratigraphy of the Yerrapalli Formation, Pranhita-Godavari Valley, Deccan, India
Authors: Dasgupta Kasturi
Published: November 2024

The mappability, distinctive lithology and fossil content of the Yerrapalli Formation of the Pranhita-Gcrdavari valley, Deccan, India show that it is a vatid lithostraligraphic unit of the rank of Formation. The vertebrate fossils give all early Middle Triassic age. The Gondwanas of Pranhita- Godavari valley provide one of the most complete Triassic Gondwana sequence in India as well as in the world. The importance of the Middle Triassic continental deposits of the valley in stratigraphic correlation is also discussed.
Geochemistry of Archaean Arenites Formed by Anoxic Exogenic Processes-An Example from Bababudan Schist Belt, India
Authors: Arora M. , Naqvi S. M.
Published: November 2024

Sandy matrix of QPC of Archaean Bababudan schist belt is distinguished, by the abundance of well rounded detrital pyrite, uraninite, chromite, zircon, rutile and micas, and clasts of fuchsite quartzite. Presence of detrital pyrite and uraninite in mature arenites deposited during the initial stage of shallow stable basin, indicate the anoxic nature of ambient atmosphere. Compositional characteristics such as the abundance of Al2O3, K2O, MgO, Cr, Ni, Co, Zr, V, Sc, Rb, Sr and ?REE reveal that only restites could survive intense chemical weathering and strong hydrodynamic action. High to moderately fractionated REE patterns (LaN/LuN-10) with essentially negative Eu anomalies of the matrix of QPC, typically resemble the Archaean arenitic and pelitic rocks. These characlcristics of the QPC indicate removal of mafic-ultramafic and other unstable constituents of provenance to the deeper part of the basin. Silicic and other resistive part of provenance were deposited on the margin of the basin. Geochemical parameters of these rocks show that initial anoxic stage was changed to rhythmically oxidizing environment, in which very thick oxide facies of BIF got precipitated. Stable tectonic condition was changed to active margin setting, in which immature Kaldurga polymictic conglomerate (KCM) with greywacke matrix was deposited. Available data on various rock types of the Bababudan basin, demonstrate that the composition of atmosphere changes in tectonic setting and depositional environment resulted in the deposition of sediments of divergent type in the basin at various stratigraphic levels.
Petrography and Geochemistry of the Pipe-7 Kimberlite, Anantapur District, Andhra Pradesh, India
Authors: Mallikharjuna Rao J. , Nirmal Charan S.
Published: November 2024

The diamond-rich Pipe-7 kimberlite found about l0km east of Lattavaram in Anantapur district, Andhra Pradesh in south India is an elongated dyke - like body, that extends over a length of 450 m and has a maximum width of 25 m. It is porphyritic in texture and contains sub-angular to rounded xenoliths of peridotite, garnet-clinopyroxene rocks, websterite, amphibolite, metabasic rocks and granite. Petrographic studies reveal that it is porphyritic in texture and contains euhedral to sub-hedral altered olivine. phlogopite, garnet, clinopyroxene (chrome diopside), chromite, perovskite and ilmenite which are the uneqvivocal primary liquitlus phases whereas serpentine, chlorite, phlogopite, calcite, amphibole, magetite, monticellite, clay minerals and others represent secondary alteration assemblages. Chrome-diopsides and garnets represent an important megacryst suite.

The Pipe-7 kimbeerlite has higher CaO and lower MgO, Al2O3, K2O and iron contents compared to rhe other six known kimberlites in the vicinity. Fe/Mg ratio in coexisting garnets and clinopyroxenes, indicates the equilibration temperature for (a) the nodules to be 1040 - 1070°C and for (b) the megacrysts of garnet and clinapyroxene to be 1350°C respectively.

Pyrope garnets from titis kimberlite show a positive correlation between CaO and Cr2O3 and are similar in nature to those of the low calcium garnets reported from the diamondiferousSouth African kimberlites.
Strain Transition and Microstructural-Fabric Analysis of Qaurtz-Mylonites Exposed within Pratapnagar Nappe Garhwal Himalaya, India
Authors: Bhatt S. C. , Saklani P. S.
Published: November 2024

The Pratapnagar Thrust sheet in the Lesser Garhwal Himalaya consists of massive, white mylonitized Pratapnagar Quartzite and is delineated at its base by the Pratapnagar Thrust which brings this rock group to rest over the parautochthonous Argillocalc-arenite Group.

The estimated three-dimensional finite strain (¯Ss) in the specimens located close to the Pratapnagar Thrust was 0.937 while away from the thrust it was 0.412. The quartzite exposed within the mylonitized zone of Pratapnagar Thrust underwent non-coaxial (= simple shear) deformation revealed by asymmetrical (unpopulated) C-axes girdles and rotation of mylonitic foliation (S3), lineation (Lm) and C-axes girdles, The variable orientation of C-axes girdles, mylonitic foliation, lineation and microstructural shear indicators (asymmetrical porphyroclasts and pressure shadows) noticed within the rock exposed along the thrust zone indicate sinistral (-ve) sense of shear movement (NE-SW) with respect to N. The quartzite away from the thrust were initialy subjected to coaxial (= pure shear) deformation as is indicated by scattered globular and tabular host quartz grains and symmetrical cross and small circle girdle patterns of C-axes. The microstructural transition and asymmetrical orientation of C-axes fabrics indicate that the mylonitized Pratapnagar Quartzite was formed by deformation under ductile flow and low grade metamorphic conditions.
Desert Quaternary Formations and their Morphostratigraphy: Implications for the Evolutionary History of the Thar
Authors: Dhir R. P. , Rajaguru S. N. , Singhvi A. K.
Published: November 2024

Morphogenetic manifestations and stratigraphy of the Quaternary alluvial and aeolian formations of the desertic tract of Rajasthan have been described. The stratigraphy is based on a study of deep sections (-15 m) from different locations. Additionally, well-logs have been used to prepare the isopach maps of these formations. It is inferred that during the major part of the Pleistocene, the region witnessed widespread alluvial sedimentation. Though the region was well-watered then, the presence of large masses of lime coupled with negligible in-situ weathering suggests, that over-all the environment must have been predominantly semi-arid. Presence of nodular and lithic calcrete bands suggests an episodic character of this sedimentation. The form and distribution of surficial calcretes (including polycyclic lime nodules) suggest several cycles of calcrete formation.

Thermoluminescence dating of aeolian sands sampled from 28 to 65 metre depths suggest that the antiquity of the aeolian dynamism extends to atleast 100 ka B.P. The period from c.25 to 50 ka B.P. consistently shows the presence of wetter interludes with weaker aeolian dynamism, a fluvial redistribution of sediments and formation of nodular calcretes and gypcretes. The last major aeolian activity peaked at LGM in the Sahara, the Australian and the Kalahari deserts. However, the evidence on Thar suggests a peak in aeolian activity post-dating the LGM.
Geochemistry and Petrogenesis of Dolerite Dykes In and Around Kolar Schist Belt, South India
Authors: Sahoo Jayaram , Balakrishnan S.
Published: November 2024

The Kolar Schist Belt and adjoining areas of Dharwar Craton are considered to be accreted terranes. Two distinct sets of dolerite (diabase) dykes, trending E-W and N-S are found in the area. The major minerals in the dykes are plagioclase feldspars (50-65 mol. % anorthite) and c1inopyroxenes (augite, sub-calcic augite and magnesian pigeonite).

The Kolar dyke samples are essentially tholeiitic except for one sample which resembles a basaltic komatiite. Mineral, as well as, whole rock chemistry of the dyke samples indicate an iron enrichment trend. The modelling of major and trace elements of Kolar dykes suggest that their parental magmas must have been derived from Fe- enriched sources with higher Fe/Mg ratios than primitive mantle. Source for parental magma to the basaltic komatiite dyke has been inferred as garnet lherzolite, whereas, for all others it could be komatiite with variable Fe/Mg ratios.

The Kolar dyke samples are enriched in light rare earth elements (LREE) and have variable abundances of heavy rare earth elements (HREE) relative to chondrites. The modelling of major, trace, and rare earth element data indicate that the generation of parental magmas took place from sources similar to komatiites, by low percentages (<30%) of partial melting, within the lithosphere at pressures less than 3GPa. Magmas representing the dyke samples could have undergone small extents of fractional crystallisation and assimilation of granitoids. It is suggested that the partial melting of lithospheric sources is related to its stretching and elevation of geothermal gradient, possibly, as a result of intrusion of picrite/kornatiite melts into the lithosphere.
Fluid Inclusion Evidence for Amphibolite-Granulite Facies Transitional Metamorphism in Delhi Supergroup of Rocks
Authors: Sachan Himanshu K.
Published: November 2024

The Deri-Ambaji massive sulphide deposits are associated with the Precambrian rocks of Delhi Supergroup. Detailed fluid inclusion studies of quartz associated with the host rock of sulphide deposit as well as with ores show high density CO2 (1.05-1.08 g/cm3) as the dominant fluid phase and C02-H20 (0.94-0.98 g/cm3) and minor H2O inclusions are also present. The isochore for the high density fluid inclusions indicate the pressure limit of 7.5 Kbars, at the upper temperature limit 800°C, which is in accordance with the estimation by mineralogic thermobarometery. The lower P-T limit is of 2.5 Kbar at 500°C, which indicates that the transition of upper amphibolite to granulite facies of metamorphism has taken place in the area. The P-T path delineated from combined mineralogical and fluid data is characterised by T-convex nature, which is indicative of isothermal crustal uplift, probably promoted by extensional tectonics.
Indications of Hydrocarbon Generation in the Coal Deposits of the Rajmahal Basin, Bihar: Revelations of Flourescence Microscopy
Authors: Singh Mahendra P. , Singh Prakash K.
Published: November 2024

Application of Fluorescence microscopy to the organic petrological study of Rajmahai Coals has been done with a view to have a correct qualitative and quantitative assessment of the Liptinite constituents of these low rank coals. The study has revealed the presence of hydrogen rich constituents which were recorded as mineral matter under white incident light due to their greater resemblance to clay minerals, being dark grey to black in colour. These constituents are bituminite, flourinite and exsudatinite which occur in considerably high concentrations and are proved to be a kind of expelled hydrocarbons. Further, it has been observed that the concentration of these expelled secondary constituents is much higher in the basal parts of the coal seams suggesting high activity of their generation in the over-pressured zones of the coal seams. Besides, the study suggests that the "birthline" or maturation level desired for the generation of liquid hydrocarbon is 0.5% Ro mean.
Ground Water Quality in Weathered Singhbhum Granite around Karanjia, Southern Bihar, India
Authors: Mahato Dharun
Published: November 2024

Selected samples of well and spring waters from the weathered profiles of Singhbhum Granites show strong control of soil mineralogy. Felspars, mica, quartz and some mafic minerals in the bed rocks weather to kaolinite rich top soils in the cultivated lands. Soils at higher slopes are lateritic. Lime concretions are common and quartz is ubiquitous.

The HCO3/SiO2 mole ratio in the waters is in the range predicted for alteration of augite to kaolinite and plagioclase to montmorillonite. The silica level is above quartz solubility and generally below solubility of amorphous silica. Kaolinite and potassium are thermodynamically stable in ground water environment.
Cyclic Volcanism and Sedimentation in the Mahakoshal Greenstone Belt, District Sidhi, Madhya Pradesh
Authors: Tripathi S. C. , Mishra M. N.
Published: November 2024

Several ordered cycles of volcanism and sedimentation have been recorded from the Mahakoshal greenstone belt in the eastern part of the Sidhi district, Madhya Pradesh. Each cycle is characterised by pillow lava-pahoehoe toes, bomb agglomerate. volcanic breccia and tuff, culminating with the deposition of massive chert under quiescent conditions. The volcanics and the sediments exhibit linear distribution and were deposited as a result of eruptions along ENE-WSW trending fissures, parallel to the margins of the belt. The deposition of volcanics and sediments took place over thin Archaean sialic crust where tholeiitic magma differentiated at a depth of less than 15 km.
Origin of Grunerite Schist-Hosted Magnesite Mineralization in Copper Mountain Area, Sandur Schist Belt, Karnataka
Authors: Krishna Rao B. , Hanuma Prasad M. , Vasudev V. N. , Sethumadhav M. S.
Published: November 2024

Magnesite mineralization in the Copper Mountain areaofthe Sandurschist belt occurs scattered in a 5 km long and 50 to 200 m wide grunerite schist unit of Late Archaean age. Magnesite occurs mostly as less than a cm to about 50 cm thick parallel to subparallel veins. The veins are confined to gently dipping joints and tensional fractures transecting the steeply dipping bedding and schistosity of the host rock. Magnesite is cryptocrystalline and is associated with minor amounts of dolomite/magnesian calcite, calcite, cryptocrystalline silica and iron oxyhydroxides. Magnesite veins are essentially of cavity filling origin. Field setting, rock and mineral chemistry and stable isotope data indicate that magnesite was precipitated at ambienttemperatures from descending meteoric waters enriched in biogenic and atmospheric CO2 and Mg2+, the latter derived from the upper weathered portion of the host grunerite schist.
Calcite Fabric from the Southern Part of the Chitradurga Schist Belt, Karnataka
Authors: Prasanna Kumar V.
Published: November 2024

On the basis of calcite orientation, the temporal relations between crystallisation, folding and formation of foliation in the Chitradurga schist belt are attempted. Stress orientation at the time of deformation and spatial orientation of the hinge lines of syncrystallisation folds have been determined. While syntectonic recrystallisation seems to be the dominant mechanism, pressure solution and intracrystalline deformation might also have played a role in fabric development.
The Magnitude of Hiatus and Sea Level Changes Across KIT Boundary in Cauvery and Krishna-Godavari Basins, India
Authors: Raju D. S. N. , Jaiprakash B. C. , Ravindran C. N. , Kalyansunder R. , Ramesh P.
Published: November 2024

A Major hiatus of varying time span ofiess than 1 Ma to greater than 30Ma encompasses the Cretaceous/Tertiary boundary (KTB) in several parts of the Cauvery, Krishna-Godavari (KG) and other pericratonic basins of India. The succession in the north and northeastern parts of Cauvery basin is apparently continuous, whereas in other areas of this basin, either the sediments of Late Maastrichtian or Middle-Late Maastrichtian or even Middle Campanian-Maastrichtian are unrepresented due to erosion/nondeposition. A north-northeasterly tilt within the Cauvery basin with some tectonic blocks subsiding is inferred during Late Maastrichtian. An additional event of global significance that occured across orvery close to the KTB in KG basin is volcanism within alimited duration of 3.8 to 5.5 Ma equivalent to Deccan volcanism. The succeeding transgression in Paleocene-Early Eocene was in pulses at levels ranging from Zone PI-P7. This hiatus appears to be linked with the rise of a giant hot mantle plume just prior to the eruption of Deccan volcanism during Abathompalus mayaroensis Zone of Latest Maastrichtian around 66.5Ma to 67.5Ma.
Copper Mineralization in Machanur Area of the Dharwar Craton, Karnataka
Authors: Koti M. V. , Tenginkai S . G. , Ugarkar A. G.
Published: November 2024

Copper mineralization in Machanur is confined to the fracture and breccia zone (shear zone) traversing mainly pink porphyritic granite of the Closepet granite suite (2,400-2,000 my.) including minor diabase dykes and pegmatites, The mineralization is fractule-controlled cavity filling epiigenetic hydrothermal type. The associated wall-rock alterations are chloritization, saussuritizalion, sericitization and silicification of the host-rocks. The  mineralization consists essentially of chalcopyrite and pyrile with subordinate bornite, chalcocite, covellite, digenite and linnaeitc. Native copper occurs but rarely. Hematite(specularite) and magnetite are commonly associated with the mineralization. Three stages of mineralization have been inferred. It is suggested that the second stage has been dominated by precipitation of chalcopyrite. The paragenetic scquence is suggestive of high fO2 condition in fluid at the beginning and progressive increase of Cu/Fe ratio and high fS2 condition in fluid during the main Cu deposition stage.
Mineralising Fluid Ascent Direction in the Sulphide Assemblage of Mosaboni, Singhbhum, Bihar
Authors: Nayak B. K. , Panchapakesan V.
Published: November 2024

Distribution pattern of fluid inclusion homogenisation temparatures and assay of copper ores hove been uscd to ascertain the mineralising fluid ascent direction. Thetrigonametric relationships to calculate the parameters of this direction have been derived which show that the bearing of ascent of ore fluids isN 53.°E-S 53°W having plunge 38° and rake 77°. There is high probability of encountering rich ores underneath 30th level in a direction opposite to fluid ascent at selected locations.
Petrofacies, Provenance and Tectonic Setting of Nimar Sandstone (Lower Cretaceous), Rajpipla-Jobat Area
Authors: Akhtar K. , Mujtaba Khan M. , Ahmad A. H. M.
Published: November 2024

The Nimar Sandstone were studied with a view to understanding the nature of the Narmada  basin and its tectonic setting during an important event which took place on a global scale. The sandstones are predominantly quartzarenitcs composed mainly of several varietics of quartz, mica, rock fragments, feldspar and heavy minerals derived from the underlying Plecambrian basement. An integrated approach suggests that the Nimar Sandstone was derived from fault-bound uplifts of continental basement rocks and accumulated without much transport in the incipient rift belt of the Narmada basin.
Organic Matter and Carbonate in the Southwest Continental Shelf of India
Authors: Mohan P. M. , Victor Rajamanickam G.
Published: November 2024

Twenty five sediment samples, from seven traverses, were collected from the southwestern continental shelf of India. A variation in the organic matter from zero to 1 1.26% and carbonate from 7 to 96% is noticed. The stations located off the river mouth areas show high amount of organic matter and low amount of carbonate content, whereas outershelf sediments display high amount of organic matter and carbonate contents. However, in between these two zones, at the depth of 35 to 65 m, the concentration of organic matter and carbonate is found to have a considerable decrease in amount. It is inferred that this zone might be a paleo beach environment admixtured with present day marine environment.
Snout Fluctuation Study of Chhota Shigri Glacier Lahaul and Spiti District, Himachal Pradesh
Authors: Kumar Surendar , Dobhal D. P.
Published: November 2024

The snout fluctuation of Chhota Shigri Glacier has been examined for the period of 1962 to 1989. This period can be characterised as one of general retreat. The morainic levels at different positions and altitudes show the past extension of the glacier, eventhough then is no documented record of past advance and retreat of the glacier. But on the basis of the different morainic deposits the nature of past extension and deglaciation history of the glacier can be inferred. There are six such morainic levels recognised in the field. On the basis of these deposits the total retreat of glacier is calculated as about 2.5 km. since its break from the main Chandra Valley glacier, The present fluctuation study (1 962- 1989) shows that the glacier has been almost retreating expect in 1987 when it advanced about 17.5m. The totd recession of glacier during the period of 26 years was about 195m with an average rate of 7.5m/yr.
Groundwater Recharge Process Model in a Granitic Terrain - A Long Term Analysis
Authors: Narasimha Reddy T. , Prakasam P. , Subrahmanyam G. V. , Nageswara Rao T. , Prakash Goud P. V. , Harish K. , Gurunadha Rao V. V. S. , Gupta C. P.
Published: November 2024

Dulapally watershed in granitic terrain covers about 34 sq. km lying north of Hyderabad City in semi-arid tropics. Groundwater recharge has been estimated considering the soil-plant and agroclimatological conditions from daily rainfall and pan evoporation data during 1974 to 1990. The average annual recharge over 16 years worked out to be 124 mm. The temporal variation of the recharge estimates have been validated through simulation of well hydrographs in a nested squares finite difference aquifer model by feeding them as temporal input during transient condition.
A Geophysical Approach to the Problem of Seismicity in the Indian Shield
Authors: Reddi A. G. B.
Published: November 2024

An earthquake is but a culmination of stress build-ups that go on over a period of time at various brittle-ductile transitions located mainly within the crust. Mapping such transitions must therefore form an integral part of any effort at understanding the seismicity of a region. However, this aspect has been grossly neglected, most of our concerns so far revolving round faults and allied structures that only provide a mechanism for stress dissipation as distinguished from stress accumlation.

As a matter of fact, any holistic approach to the problem must invariably include within its ambit an investigation of the thickness and composition of the crust on the one hand and surface heat flow on the other, since these are known to have a direct bearing on the seismic propensity of a region. For instance, a thicker than average crust or a higher than normal heat flow (with consequent thinning of the lighter upper crust) could signify a potential seismogenic area. The same thing could be said of areas where strong rheological stratification is suggested at depth by the presence of say, low velocity layers, seismic reflectors or electrical conductors.

There is a distinct possibility of many of these situations finding expression in gravity maps which could consequently provide a very reasonable basis for effctive selection of areas for detailed follow-up, by more complex methods. Adopting this principle, a broad geophysical strategy has been mooted for the active consideration of geoscientists in the country. While it may be debated and improved upon in regard to detail, its overall implementation as a national project is an imperative dictated by the ominous prospect of a more and more common recurrence of earthquakes in the peninsula in the years ahead.
Braided-Fluvial Depositional Model of Late Triassic Gondwana (Mahadeva) Rocks of Son Valley, Central India: Tectonic and Paleogeographic Implications
Authors: Tewari R. C.
Published: November 2024

About 800 m thick late Triassic Gondwana (Mahadeva) rocks of Son valley, central India are composed of pebbly to gritty, very coarse to coarse and medium sandstone, and thin to thick beds of grey, micaceous and red shale. Sandstone bodies are channel-shaped to sheet-Like and multistoreyed, characterised by large scale trough and planar cross-beds. Interbedded shale beds are laminated. Palaeocurrent analysis based on 192 measurements of trough cross-bedded cosets reveals northwesterly (321° ± 46°) palaeodrainage and palaeoslope throughout the late Triassic Gondwana sedimentation.

Lithofacies characters, nature and geometry of sedimentary structures and palaeocurrent attributes suggest that the late Triassic Gondwana rocks of the Son valley area were deposited by a widespread system of bed load (braided) streams which flowed dominantly from southeast to northwest. Indeed, there is uniformity in the northwesterly palaeolope during Permian and Triassic Gondwana sedimentation in this area. Implicitly, the Gondwana basin under study should have extended northward down the palaeoslope beyond its present limit across the north boundary fault (? Narmada - Son lineament).
Delineation of Faults, Using Deep Seismic Sounding Refraction Data, West Bengal Basin
Authors: Reddy P. R. , Koteswara Rao P. , Venkateswarlu N. , Prasad A. S. S. S. R. S.
Published: November 2024

A systematic analysis of refraction data obtained in West BengaI basin, has been carried out to bring into focus the utility of the seismic refraction data in delineating fault zones. The study clearly points out the different conspicuous signatures present in the refraction travel time data, associated with the shallower fault zones affecting the top sedirnentry column and the crystalline basement.
Evidence of Palaeoclimatic Fluctuations in Miliolite Rocks of Saurashtra, Western India
Authors: Patel M. P.
Published: November 2024

Detailed studies of various miliolite occurrences of Saurashtra have revealed fluctuations in the palaeoclirnate witnessed in the course of deposition and consolidation of the dune material during Middle and late Upper Pleistocene. The entire process of formation of miliolite rocks is indicative of alternating arid and humid phases. During protracted arid phases strong wind actions were effective whereas during brief wet phases fluvial erosion & deposition and pedogenesis were brought about. The various evidences in support of palaeoclimatic fluctuations include: (i) the presence of erosional surfaces separating the miliolite deposits by intercalated redsoil horizons, cross-beddedand horizontally bedded miliolite deposits, two cross-bedded miliolite sequences with reversed dips and the two superimposed unidirectional cross-bedded miliolite sequences with different angles of dipin the coastal cliffsections, (ii) the occurrence of intercalated red beds and fluvial debris (sand/silt/gravel) within miliolite sequences as seen in some of the river and well sections, together with slope-wash debris between two miliolite layers substantiating small scale intervening periods of quiescence, (iii) a well defined junction between the two different major cycles of aeolian accumulation marked by the surfaces of non-deposition, erosion and honeycomb weathering at the top of the lower cycle as encothered in some of the well sections, (iv) burial of animal burrows by a younger cycle of miliolites devoid of animal burrows in some exposures and (v) the presence of diagenetically formed coated grains, vadose calcite silt around the ooliths & intraclasts, and its occurrence between two generations of cement in thin section also provide aclue to the minor breaks in diagenetic environment.
Pliocene - Pleistocene Benthic Foraminifera and Abyssal Circulation Changes at Arabian Sea DSDP Sites 220 and 223
Authors: Gupta Anil K. , Roy Abhra , Naik Pradyumna , Chatterji Santanu
Published: November 2024

Pliocene-Pleistocene benthic foraminifera were analysed from arabian Sea Deep Sea Drilling Project (DSDP) sites 220 and 223. At site 220 the most dominant taxon is Nuttallides umbonifera showing peak abundances in the Early Pliocene, Early and latest Pleistocene possibly representing intervals of highly carbonate-undersaturated bottom waters. The species diversity [H(S)] and equitability (E') trends show inverse relationship with N. umbonifera percentages. At relatively shallower site 223, the benthic assemblage is dominated by Cibicides wuellerstorfi, Oridorsalis umbonatus and Uvigerina hispido-costata through Plio-Pleistocene. N. umbonifera shows peak abundances only in the beginning of the Pliocene. This species shows an abrupt decrease to near extinction near the Plio-Pleistocene boundary and occurs very rarely and sporadically in the Pleistocene at site 223. C. wuellerstorfi and O. umbonatus show increased percentages in the earliest Pliocene, late Early Pliocene, and a short lived peakin the Early Pleistocene (samples 2-5), indicating presenceof relatively warm, oxygenated, and less corrosive bottom water at this site. The peaks of U.hispido-costata at site 223 are inferred to reflect intervals of high surface productivity due to intense upwelling off the Arabian coast.
Fluid flow during contact metamorphism: Petrographic evidence from the uranium prospect at Tummalapalle in the southwestern part of Cuddapah Basin, India
Authors: Dhana Raju R. , Roy Madhuparna , Panda Arjun , Vasudeva Rao M.
Published: November 2024

In the uranium prospect at Tummalapalle in the southwestern part of Cuddapah basin, fluid flow during contact metamorphism is documented in a vein-mineral-assemblage of a metadolerite intruding the carbonate rocks and shale of the Vempalle Formation of the mid-Proterozoic Lower Cuddapah Supergroup. The minerals in the vein are calcite, quartz, Mg-chlorite and Fe-chlorite formed in that order due to fluid-infiltration-driven volatilization reactions involving CO2- and H2O- fluid having an external source in the nearby sedimentary rocks. The observed sequential vein-mineral assemblage is considered as a petrographic evidence of 'infiltrating fluid mechanism during metamorphism', proposed first by Ferry (1980), as well as for 'batch volatilization' of Valley (1986).
Mineral Chemistry of Mafic Chain Silicate Minerals in the Torappadi Layered Complex of the Southern Granulite Terrain
Authors: Ray Jyotisankar
Published: November 2024

The chemistry of the mafic chain silicate minerals in the Torappadi layered ultramafic-mafic complex occurring in the southern granulite terrain of the Indian shield has been presented. The pyroxene compositions are found to be sympathetically related to the whole-rock chemistry; further the orthopyroxenes are discriminated to be metamorphic in terms of chemical parameter. All amphiboles of the complex are 'calcic' and their compositions spread from magnesio-hornblende to edenitic homblende/tschermakitic hornblende depending upon the rock-chemistry. Pyroxene geothermometry (assuming complete disordering) using different methods reveals a comparatively large range for a particular rock (up to 181°C). Amphibole geothermometry, on the other hand, gives consistent temperature values (716°-804°C) which has been taken as the range of temperature of equilibration of the whole complex. Estimation of pressure with amphibole-compositions yields a mean value of 4.16 kb. It has been suggested that Torappadi rocks correspond to shallow level - low pressure granulite equivalent to a depth of ca. 10- 17 km.