bluuebunny/crossref_metadata_2025 huggingface dataset:
Metamorphism of the Dalma Mafic Rocks
Authors: Bhattacharyya D. S. , Dasgupta D.
Published: November 2024

The Precambrian Dalma metabasalts stretching for more than 200km represent original oceanic tholeiites. The metabasalts can be represented by eleven different groups of mineralogical assemblages ranging from low greenschist to high amphibolite facies. Spatial distribution of these six groups indicates increasing P-T conditions from east to west.
Early Lower Carboniferous Conodonts from the Syringothyris Limestone of Kashmir
Authors: Savage Norman M.
Published: November 2024

Conodonts from the lower part of the Syringothyris Limestone exposed near Aishmuqam in the Liddar Valley, Kashmir, include Clydagnatlllls gilwernensis Rhodes, Austin, and Druce, Polygnathus communiscommunis Branson and Mehl, Bispathodusstabilis (Branson and Mehl), and Bispathodusaculeatusplumulus (Rhodes, Austin, and Druce). The fauna is of early lower Carboniferous (early Tournasian) age.
Petrography of the Lower Oligocene Limestones of Anklesvar Oil Field, Cambay Basin, Gujarat
Authors: Hardas M. G. , Srivastava D. C. , Maindarkar M. M.
Published: November 2024

The limestones of Dadhar Formation (Lower Oligocene) in the Anklesvar oil field of Cambay basin, provides a typical example of erosional transgression. Interbedded with grey, fossiliferous shales and fine grained sandstones, these carbonate layers have been found to be biomicrudites comprising foraminiferal shells, glauconite, terrigenous sand, silt and clay, microspar patches and development of pseudospar in fossil shells. The above assemblage, especially the glauconite and recrystallized microspar and pseudospar, typically indicates a transgressive marine environment, characterised by calm, weak and shortlived currents. Most earlier workers have invoked a regressive phase for the deposition of this limestone but recent microfaunal studies and the salinity data point to an inner neritic environment transgressive phase.

The petrography provides evidences to reveal a marine environment of shallow tidal sea, wherein the marine incursion must have been characterised by tidal effects and reworking of the older sediments.
High Alumina-Magnesium Sedimentation in the Javanahalli Schist Belt, Karnataka, India
Authors: Narayana B. L. , Subba Rao D. V. , Govil P. K.
Published: November 2024

High alumina, magnesium and iron-bearing sediments represented by cordierite-anthophyllite rocks occur in association with amphibolites. calc silicate rocks and banded magnetite quartzites, within the Javanahalli schist belt, Karnataka. Their chemical composition is anomalous. The abundance levels of elements like Fe, Mg, AI, Ni, Cr, Co, Rb and Sr indicate that probably they represent metamorphosed chemical sediments generated by volcanogenic exhalative activity.
Lead Age Measurements on Galenas from Peninsular India
Authors: Venkatasubramanian V. S. , Jayaram S. , Subramanian V.
Published: November 2024

Measurements of lead isotope ratios on some Indian galenas and calculation of single-stage model ages were presented in a previous paper. Techniques have been improved since then, and more samples from some of these areas and several new samples have been measured. The present measurements cover a wide age-span, Eocene to Archaean (~3300 m.y.) and the Pb-isotope abundances are not inconsistent with a 2-stage evolution of lead which show an episodic change in μ-value at ~ 3000m.y. Model ages and μ-values have been calculated using single and double-stage models and an attempt made to interpret these values.
Textural Analysis and Mineralogy of the Black Sand Deposits of Visakhapatnam-Bhimunipatnam Coast, Andhra Pradesh, India
Authors: Ramamohana Rao T. , Rao Ch. Shanmukha , Sanyasi Rao K.
Published: November 2024

Textural analysis reveals that the black sand samples are well sorted. negatively skewed, mostly mesokurtic and unimodal in distribution with the Mean Size of the grains falling mostly within the fine sand. The opaques and non-opaque heavies in a weighted average sample constitute 78.1% and represent the full range of minerals found in the rocks of the Eastern Ghats. The marked preference of a particular heavy mineral to a certain sieve fraction can be related to the grain size of the heavy mineral in the source rocks. The occurrence of thin layers of black sand in the stream channels inland. the non-disappearance of any unstable heavy mineral in the deposits, suggest that the black sands are derived from the highland area.
The Chromites of Byrapur, Karnataka
Authors: Sahu K. C. , Nair A. M.
Published: November 2024

Chemical study on clean chromites reveals enrichment of chromium and iron due to alteration. Physico-chemical properties show that alteration has enhanced the cell-edge, reflectivity and specific gravity but reduced the microhardness of the mineral. The reemplacement and subsequent instability of tectonic conditions might be the ultimate cause for the shift of Byrapur chromites from aluminian to ferrian field of composition.
Coal-petroleum Relation and Its Significance for Petroleum Exploration
Authors: Raghavendra Rao V.
Published: November 2024

Geological and geochemical studies of the two previous decades stress the significance of carbonaceous material as probable source of oil and gas accumulations in many parts of the world. The Shebelinka field, Donetz basin, U.S.S.R., the gas fields in the northwest Siberian basin, the giant Groningen gas field of the Netherlands, hydrocarbon accumulations in the Viking graben of the North Sea and the offshore oil and gas fields of the Gippsl and basin of southeastern Australia are some examples.

The paper reviews studie, on relationship between coal and petroleum and points out their relevance to oil exploration in Nigeria and India.
Terraces, in the Himalayan Tributaries of Ganges in Uttar Pradesh
Authors: Khan A. A. , Dubey U. S. , Sehgal M. N. , Awasthi S. C.
Published: November 2024

The Ganga system in Garhwal Himalaya comprises of Alaknanda followed by Bhagirathi, Bhalangana, Mandakini, Pindar, Atta Gad and Jalkhur with their terraces. Alaknanda is the trunk stream and the others are tributaries. The Alaknanda and its tributaries include terraces of three domains: glacial, fluvio-glacial and fluvial deposits in three distinct environments in Pleistocene, late-Pleistocene and Holocene. Stratigraphic succession of terraces and sequential stages of valley development in the Ganga system of Garhwal Himalaya has been worked out. There was continuous decrease in rate of uplift of Himalaya from early to late Holocene, as evidenced by the conspicuous divergent disposition of older terraces and convergence of younger terraces all along the length of the Alaknanda river.
The Age of the Earth According to the Hindu Calendar
Authors: Murthy S. R. N.
Published: November 2024

We reproduce below an article by Sri S. R. N. Murthy detailing the basis of measurement of time as per the Hindu Calendar. It will be seen from this that the ancient Hindu philosophers had an expansive view of time and had recognised the cyclic nature of events. According to them each cycle or KALPA was of 4.3 billion years duration. We are, as per this calendar, about two billion years old in the present Kalpa, The basis on which such calculations were made by the Ancient Hindu Philosophers of India should prove to be of interest to our readers.
Sapphirine, Kornerupine, and Sillimanite + Orthopyroxene in the Charnockitic Region of South India
Authors: Grew Edward S.
Published: November 2024

Sapphirine, kornerupine, and the associations sillimanite-orthopyroxene and sillimanite-gedrite are reported from 23 localities (or areas of closely spaced localities) in Fermor's (1936) charnockitic region and in transitional zones to Fermor's non-charnockitic region in south India (Andhra Pradesh, Tamil Nadu, and southern Karnataka). The rocks containing these minerals and mineral associations are believed to have a pelitic sedimentary precursor. They are in general closely associated with khondalite (garnet-sillimanite gneiss), quartzite, and calc-silicate rocks, and less commonly with metabasites of presumed metavolcanic origin. However, the sapphirine occurrences in the Sittampundi anorthosite complex, where sapphirine and sillimanite-gedrite are found in reaction zones between anorthosite and chromite layers, are an exception. Assemblages of sapphirine with garnet and sillimanite are not rare, but sapphirine in direct contact with quartz, which has not previously been reported from south India, was found at Paderu, Vishakhapatnam District, A. P. Kornerupine occurs with sillimanite at three localities but with orthopyroxene only at Ganguvarpatti, a new locality for kornerupine. Temperatures and pressures calculated from pyroxenes, garnets, and feldspars in associated rocks suggest that sapphirine, kornerupine, and sillimanite-orthopyroxene crystallized at 800-850°C and 6-10 kbar in the charnockitic region and sapphirine at 780°C in a transition zone between the granulite and amphibolite-facies near Sargur. Water partial pressure during the metamorphism was significantly less than total pressure. Regional differences in pressure are reflected in the distribution of mineral assemblages: sillimanite-orthopyroxene is found in Madras and Andhra Pradesh, but is conspicuously absent in the Palni Hills, where spinel-cordierite is an important assemblage. Sapphirine and sillimanite-orthopyroxene (and sillimanite-gedrite) are restricted to rocks relatively rich in Al2O3 with high Mg/Fe ratios relative to khondalite. Kornerupine appears to be confined to rocks containing boron. These special rock compositions (except Sittampundi) are believed to reflect unusual compositions of the precursor pelitic sediments rather than changes in chemistry during metamorphism.
Palaeogeographic Reconstruction of the Jaffna Peninsula, Sri Lanka
Authors: Senaratne A. , Dissanayake C. B.
Published: November 2024

The study of the tonal variations of aerial photographs showing the vegetational cover in the Jaffna Peninsula of the north of Sri Lanka clearly points to the progressive formation of spits and lagoons. The contrasting tonal variations of the vegetation found in the emerging lands of different ages can be used to some extent effectively in the delineation of lands in a chronological sequence as exemplified by studies in the Karativu island.
The Early Precambrian Crust with Reference to the Indian Shield: An Essay
Authors: Glikson A. Y.
Published: November 2024

The existence of several greenstone generations and of continuous transitions between gneiss-greenstone terrains and granulite terrains in the Indian Shield allow a unique insight into the structure and evolution of the Archaean crust. The long standing controversy on granite-greenstone relations reflects contrasting basic assumptions, methods and criteria. Many of the problems reflect the uncertain significance of Rb-Sr ages, which often represent thermal resetting events. Correlations between volcanic units in separate greenstone belts and between shallow and deep crustal zones should be soon enabled by U-Pb and Sm-Nd isotopes. The concept of greenstone belts as primary basins is not applicable to the oldest supracrustals whose remnant enclaves and xenoliths are distributed on all scales throughout the Peninsular Gneiss. The oldest directly identifiable rocks in south India consist of ultramafic-mafic-anorthosite-pelite-chert assemblages of the Sargur Group intruded by ca 3.3 Gyr gneiss. While sialic nuclei may have been present, a pre-existence of regional sialic crust is inconsistent with the petrological, geochemical and isotopic characteristics of the dominant tonalite-trondhjemite components of the Peninsular Gneiss. The gneisses are extensively imprinted by a ca 3.0 Gyr thermal event which reset Rb-Sr systematics, but left least-reset isotopic 'windows' such as around Hassan. The age of the discrete depositories in which the Dharwar Supergroup volcano-sedimentary successions accumulated remains to be clarified. These rocks were possibly deposited in rifted zones floored by Peninsular Gneiss blocks, older greenstones and simatic gaps. The formation of charnockites and the generation of K-rich adamellites about 2.7-2.6 Gyr ago may have been genetically linked and appears to have been essentially imprinted on the older gneiss-greenstone system. Repeated thermal rises at infracrustal levels during the Proterozoic resulted in isotopic resetting of Rb-Sr systems in the Eastern Ghats granulite-gneiss belt. The temporally unique nature of the Archaean Era and major unresolved questions are pointed out.
Carbonatite-Alkaline Complex of Mundwara
Authors: Narayan Das G. R. , Sharma C. V. , Navaneetham K. V.
Published: November 2024

Two types of carbonatite dykes - alvikite and beforsite are associated with (the Mundwara alkaline igneous complex. Petrochemical and mineralogical studies indicate enrichment of alkalies and niobium. Pyrochlore is noted in beforsites along with dolomite, apatite, barite and flourite, whereas calcite, ankerite, heamatite, aegirine, apatite and barite are noted in the alvikites. The presence of both metasomatic as well as intrusive syenites are noticed. Higher content of Nb is noted in the syenites containing sphene, aegirine and magnetite.

The presence of annular fractures around the plutons and the arcuate shatter zone with breccia on the outer margins of the Mer pluton indicate upwarping and later intrusion of carbonatites through the Erinpura granite. High P2O5 and Nb content of the soil samples around Mer Pluton suggest possible existence of a carbonatite plug below.
Mantle Convection Pattern under India: Relevance to Lonar Crater, Girnar Node and Peri-Indian Volcanism
Authors: Crawford A. R.
Published: November 2024

The mantle convection pattern under India as calculated by H-S Liu shows only two points of upwelling, which correspond with the Lonar crater and the Girnar circular complex. This suggests that Lonar is more likely to be endogenic rather than of impact origin. The Ramgarh crater, having no such correspondence, is more likely to be an impact. The pattern also shows upwelling in the vicinity of the Taftan volcano of southeastern Iran.
Ree Geochemistry of Pink Granulites from North Arcot District, Tamil Nadu
Authors: Kutty T. R. N. , Anantha Iyer G. V. , De Poli E.
Published: November 2024

Petrography, mineral chemistry, major elements as well as Rb, Sr, Ba and REE geochemistry of pink granulites and the associated charnockites have been studied. Pink granulites are prograde rocks metamorphosed under granulite facies condition. There is no genetic relation between potassic pink granulites and tonalitic charnockites and their geochemical evolutionary trends are distinctly different. K/Rb ratios are in the same range, although abundance level of K and Rb in pink granulites is high. Charnockites have higher Sr and lower Rb/Sr. Pink granulites have variable Sr level, high Rb/Sr and variable Ba/Sr indicating heterogeneity in the parent rocks. REE abundance level in pink granulites shows wide variation; non-uniform but negative Eu anomaly, strong fractionation with respect to LREE, positive slope after Gd and lower ∑LREE/∑HREE ratio (5 to 26). Charnockites have coherent REE patterns, with strongly fractionated LREE and slight positive Eu anomaly and higher ∑LREE/∑HREE (30-70) ratios. Field relation, mineral paragenesis, whole rock chemistry, Sr-isotope ratios and REE geochemistry strongly support sedimentary parentage for the pink granulites. The highly fractionated REE patterns of the associated charnockites reflect not only igneous inheritance but also the effect of granulite grade metamorphism.
Gravity Field and Tectonics in Karanpura-Daltonganj Coalfields, Eastern India
Authors: Verma R. K. , Mukhopadhyay M. , Ashraf M. H.
Published: November 2024

Both coalfields are marked by significant gravity 'lows'. Maximum sedimentary thickness present is of the order of 1. 75km below the surface under the Karanpura and 0.8 km under the Daltonganj coalfields. The two coalfields, are characterized by prominent normal faults at their southern margin. The throw of the faults may be few hundred metres, Within the individual coalfields, basement faults appear to be associated with younger Gondwana sediments on the surface. The areas occupied by youngest Gondwanas do not necessarily represent the deepest part of the coalfields. This is noted, in general, for nearly all coalfields of the Damodar Valley. Differential movement appears to have occurred during Gondwana times under the coalfields resulting in either single-walled or double-walled grabens.
Deformation Structures in Pegmatite, Aplite and Quartz Veins in Delhi Group Rocks
Authors: Bhola A. M. , Varadarajan S. , Khosla Virender
Published: November 2024

Pegmatite. aplite and quartz veins of varying dimensions occur in association with pelitic schists, calcareous rocks, quartzites, amphibolites belonging to Ajabgarh Formation, Delhi Group in the Narnaul area and act as important structural markers.

The polyphase nature of deformation of the rocks with which these veins occur, is shown by rotation of boudins, presence of overturned tight isoclinal folds resembling F1, presence of F2 folds and refolded folds shown by quartz veins, refolding of limbs of folded pegmatites by folds resembling F3. Features like boudins, pinch and swell structures shown by quartz veins and pegmatites at the limbs and along the axial planes of F1 folds with S1 development in the host rock and attenuation and disruption of limbs of tight folds resembling F1 shown by these veins also point to significant amount of flattening during F1 folding phase and longitudinal stretching in the late stage of their development. Slippage in the later stages of deformation phase (F3) is also distinctly borne dy displaced aplite veins.
A New Approach to the Lithostratigraphy of the Cenozoic Sequence of Kerala
Authors: Raha P. K. , Sinha Roy S. , Rajendran C. P.
Published: November 2024

A lithostratigraphic classification of the Cenozoic sedimentary sequence of the coastal plains of Kerala has been developed through an analysis of the exposed and subcrop litho-facies and their interrelationship based on sedimentologic parameters. The entire Cenozoic sequence is designated as the Malabar Supergroup comprising the Vembanad Formation (Quaternary-Holocene) and the Warkalli Group (Tertiary) separated by an unconformity marked by laterite. The Warkalli Group comprises the Ambalapuzha, the Quilon and the Mayyanad Formations from top to bottom. The Ambalapuzha and the Mayyanad Formations are basin margin fluvial and deltaic facies comprising sandstones, clays and lignites, and having a wedge of calcareous platform facies of the Quilon Formation. With the thinning out of the Quilon Formation (calcareous facies) in the eastern margin of the basin, the distinction between the constituent formations of the Warkalli Group disappears. Thus the purely terrigenous sediments in the eastern and southern margins of the basin form a single non-classifiable unit, the Warkalli Formation.
Deccan Trap Intrusion: Magma Mixing in the Chakhla-Delakhari Sill, Chhindwara District, Madhya Pradesh
Authors: Sen Gautam
Published: November 2024

Strong variations exist in compositions of olivine, plagioclase and pyroxenes within individual hand specimens of this differentiated sill. Such intergrain variations and zoning features were studied with the electron microprobe. These compositional variations can be explained by mixing between liquids that have undergone different degrees of differentiation at different parts of the sill. The mixing effect is illustrated with respect to phase equilibria in the anorthite-saturated surface forsterite-fayalitesilica in the system CaAl2Si2O8-Mg2SiO4-Pe2SiO4-SiO2. It appears that the mixing of these differentiated liquids has occurred along the surface pl + o1 + Ca-poor px + 1 in the natural multicomponent equivalent of the simple system.
Computer-Assisted Trend Surface Mapping-An Aid to Geochemical Exploration in the Sargipalli Lead-Zinc Mine Area, Sundergarh District, Orissa (India)
Authors: Roy A.
Published: November 2024

Computer-aided trend surface mapping of the Pb values from the Sargipalli Pb-Zn mineralized belt (Orissa) revealed that the fourth-degree surface (trends and residuals) is of utmost significance for prediction of further promising pay zones of the unexplored extension areas.
Uranium Mineralization in Singhbhum Shear Zone, Bihar II. Occurrence of 'Brannerite'
Authors: Krishna Rao N. , Rao G. V. U.
Published: November 2024

Composite grain-aggregates of titanium and uranium oxide phases resemble, both in texture and composition, those described as 'brannerite' grains occurring in quartz-pebble conglomerate-type uranium deposits such as those of Witwatersrand in South Africa and Blind River in Canada. The grain-aggregates contain variable amounts of quartz, rutile, anatase, uraninite, brannerite (s.s), pyrite, galena and hematite. Intimate inter-growths of uranium-rich and titanium-rich phases are observed. 'Brannerite' grains are secondary in origin, both detrital and metamorphic ilmenite being the antecedent mineral. They have been formed by the action of uranium-bearing solutions on ilmenite under conditions which favoured (i) alteration of ilmenite to titania by removal of iron (ii) simultaneous precipitation of uranium from solutions as uraninite and (iii) adsorption of uranium by titania. This can take place under both reducing and oxidizing conditions.
Erosion Intensity in a Mountain Watershed in the Himalayan Region
Authors: Narayan Devendra , Tandon S. K. , Joshi D. D.
Published: November 2024

A simple method for mapping of erosion intensity in a mountain watershed based on assignment of qualitative indices to various categories of geomorphic features, mean ground slopes and lithological cum structural state of the bedrock is proposed.

A preliminary case study has been conducted in a part of the Ravi drainage basin in the Himalayan region. The major geomorphic features observed are fill-cut and strath terraces, alluvial fans, landslides, small talus cones and debris-flow deposits. The slopes range from 4° to 41° and have been divided into seven classes consisting of 6° intervals each. Lithologically, the area consists of phyllite, quartzite, slate, limestone, conglomerate and granite. An erosion intensity map of this region indicates that most of the high erosion areas lie close to the main river and their distribution is controlled mainly by the recent drift material and the valleyside slopes.

Although this method is qualitative, it can be useful for a preliminary evaluation of erosion intensity. and for delimiting high erosion areas for environmental planning.
Geochemistry and Petrogenesis of Basic Dykes of Agali Area, Palghat District, Kerala
Authors: Sinha-Roy S. , Radhakrishna T.
Published: November 2024

A basic dyke swarm trending ENE-WSW traverses the Agali area of north-central Kerala. The geochemistry of these dykes suggests that they are transitional in character between continental and oceanic basalts. and are akin to one of the magmatic phases of the Deccan volcanics. They have been derived from a tholeiitic magma generated by partial melting of a heterogeneous mantle containing minor amounts of phlogopite and apatite. Fractionation of clinopyroxene. magnetite and plagioclase is indicated. The present study supports one of the earlier suggestions that these dykes are related to the rifting of the western continental margin of India.
Opaline Silica in Tertiary Sediments of Kerala
Authors: Ghosh Swapan K. , Raha Pulak K.
Published: November 2024

Smooth and well rounded grains of opal are recorded in the Tertiary sediments exposed in Trivandrum and Quilon districts and from deeper levels in the subsurface sediments near Ambalapuzha, in Alleppey district of Kerala. The clear to translucent opal grains vary in size from 0.05mm to about 3mm. Opaline casts of fossil tests with characteristic shapes and organic structures on their surfaces suggest organic activity in selective precipitation of opal inside fossil tests. Silica infillings in partly broken shells of gastropods were also observed. Difference of pH level in porewaters and inside the fossil tests favoured by organic decay in them is considered to be the main controlling factor for their formation.
Micro-Lineament Analysis and the Palaeostress Environment in Ishwarakuppam Dome Area, Cuddapah Basin, Andhra Pradesh
Authors: Ramasamy S. M. , Sinha Manohar , Devaprasad C.
Published: November 2024

Stress environment of Ishwarakuppam dome area, Cuddapah Basin, has been interpreted through micro-lineament analysis. The strain history suggests deformation under horizontally disposed maximum and least principal stress axes having WNW-ESE and NNE-SSW orientations.
Algal Genus Aethesolithon from Neogene of Little Andaman Island
Authors: Venkatachalapathy V. , Gururaja M. N.
Published: November 2024

The paper records the occurrence of the red alga Aethesolithon from the Neogene limestone of LittIe Andaman Island in the Bay of Bengal. Two species of the genus are described. The new find is significant, for it is the first of its kind from Andaman area and is suggestive of its common occurrence between Andaman and Pacific regions in Miocene.
The Origins of the Closepet Granites and the Implications for the Crustal Evolution of Southern Karnataka
Authors: Friend C. R. L.
Published: November 2024

The origin of the late Archaean Closepet granites by in situ anatexis of amphibolite facies Peninsular gneisses is discussed.

The Closepet granites which are essentially post-tectonic, cut the high-grade metamorphic fabrics found in the Peninsular gneisses. They show no effects of the regional deformation and of the foliation, forming events found in the Peninsular gneisses. Additionally, the granites have escaped metamorphism except in the south where they are statically overprinted by charnockite. Since the charnockite may be shown to be syn- and post-Closepet granite it follows that there may be two granulite facies events: (1) belonging to the evolution of the Peninsular gneiss; and (2) the late-stage formation of charnockite, which is in some places static whilst in others may be accompanied by deformation.

The Closepet granites may thus be used to clearly separate the charnockite from the early evolution of the Peninsular gneisses.
Experimental studies on Magnesite Genesis - Application to the Magnesite Deposits Associated with Ultramafic Rocks
Authors: Venkataramana P. , Kutty T. R. N. , Anantha Iyer G. V.
Published: November 2024

Previous experimental studies on magnesite formation which are confined to temperatures greater than 250°C, do not explain all the field and petrographic observations in natural situations where magnesite is associated with ultramafic complexes, as at Dodkanya, Mysore district, Karnataka.

A series of experiments were conducted using natural samples (rock and mineral powders) as starting materials. The experimental temperatures were varied from 35° to 300°C at intervals of approximately 50°C and normal and elevated pressures (500 and 1000 bars). At higher pressures, the XCO2 in the fluid phase was also varied.

These studies have shown that magnesite and quartz can be formed directly by the interaction of CO2-bearing water vapour and ferromagnesian minerals (olivine, orthopyroxene) without passing through the intermediate serpentine stage. The temperature conditions at which these reactions take place is between 150 and 250 °C at 500 bars total pressure with XCO2 in the fluid phase greater than 0.015. The presence of Na+ salts enhances these reactions.

The presence of calcite-aragonite-quartz-aluminous hydroxide gel-limonite (birbirite) cap rock intersected by a network of magnesite veins in Dodkanya and surrounding areas has been explained on the basis of experiments with natural hornblende, the major Ca2+-bearing mineral in hornblende-peridotites. Hornblende, under hydrothermal conditions, breaks down to calcium silicate hydrate (CSH). CSH, being unstable in the presence of CO2, inverts to CaCO3 (calcite/aragonite) and quartz. Mg2+ in trace quantities stabilises aragonite.
Carbonates of Chiknayakanhalli Schist Belt, Karnataka
Authors: Devaraju T. C. , Anantha Murthy K. S.
Published: November 2024

Carbonates of the Chiknayakanhalli (CN halli) area include (i) dolomite, (ii) limestone, (iii) ankerite and (iv) calc-schist. Of these, dolomite is the most widely developed rock. chemically the CN halli carbonates cover a wide range from almost pure calcite and dolomite-ankerite to Mg-limestone, shaly limestone and cherty limestone/dolomite/ankerite. In their trace element content, the rocks are typically much depleted in comparison with carbonatites. Available evidence indicates overall primary chemical sedimentary deposition of the carbonates in a barred basin with a gradual rise in salinity, pH, temperature and Mg:Ca ratio of the environment. Evidence of dolomitization is limited to the border zones between limestone and dolomite and there is no recognizable indication of organic activity.
New Fossil Finds from the Manjra Valley, Central Godavari Basin, India
Authors: Badam G. L. , Sathe V. G. , Ganjoo Rajinder
Published: November 2024

New fossil material suggests that the Manjra valley was occupied, in part, by Middle Palaeolithic man from late Pleistocene to terminal Pleistocene.
Inter-Relationship of Tectonism and Sedimentation in the Jharia Basin
Authors: Mukhopadhyay Abhijit
Published: November 2024

The Jharia Coal Basin is composed of 2900 m of fresh-water Gondwana sediments deposited on the mature pediplained Archaean basement. The consistent fresh water features of the sediments indicate that the sedimentation kept pace with general subsidence. From the analysis of lithological attributes it can be postulated that there were longer intervals of rapid subsidence when fluviatile sediments were deposited; these alternated with shorter intervals of relative tectonic quiescence or slower rate of subsidence, favourable for the development of the regional coal seams. The subsidence was maximum during the Upper Barakar and Barren Measure times.
Geology of Karara Volcanic Vent, Rajasthan
Authors: Ranawat P. S. , Dashora R. S.
Published: November 2024

Fluorspar veins in Karara area occur in a variety of pyroclastic and flow rocks. represented by volcanic breccias, lapilli tuffs, and welded tuffs including ignimbrite. Lavas produced are of the nature of basalt. andesite, trachyte, dacite, and rhyolite along with their border line varieties.
Tertiary Fishes and Molluscs from the Kuksho Formation of the Indus Group, Near Nyoma, Ladakh
Authors: Sahni A. , Srikantia S. V. , Ganesan T. M. , Wangdus C.
Published: November 2024

A collection of Tertiary fishes and molluscs from the Kuksho Formation of the Indus Group near Nyoma, Ladakh are described, The fish families represented are: Siluridae, Channidae and Cyprinidae. The fishes are associated with dextrally coiled gastropods and unionid pelecypods.
Diamond Mines Near Raichur
Authors: Sakuntala S. , Krishna Brahmam N.
Published: November 2024

Information relating to diamond mining in Raichur region (Karnataka State, India), as recorded by some foreign and Indian chroniclers in the fifteenth century, is brougbt to light and critically analysed. The places Alibenchi and Nelaha near Raichur are identified as the sites where ancients worked for diamonds. Supporting evidence is furnished by the presence of one diamond, known as 'Raichur Diamond', in the Museum of the Directorate of Department of Mines and Geology (Government of Andhra Pradesh), Hyderabad. The geological implications of this finding are discussed and a detailed geological study of the region for locating kimberlite pipes is suggested.
Changes in the Fluvial Regime of Western Maharashtra Upland Rivers During Late Quaternary
Authors: Rajaguru S. N. , Kale V. S.
Published: November 2024

Recent geomorphological, archaeological, palaeontological and carbon -14 dating of alluvial deposits and the observations on buried as well as exposed channel deposits of Upper Krishna, Bhima and the Upper Godavari rivers of Western Maharashtra have brought out five major phases of fluvial activity, since late middle Pleistocene. These rivers were dominantly aggrading during theTermial late Pleistocene (c 40.000-11,000 yrs. B.P.) and incision predominated during the major port of the Holocene. These changes in the fluvial activity can be explained in terms of climatic changes of the late Quaternary period.

The present study disproves the earlier view that the late Quaternary geomorphic history of the study area has been stable and uneventful.
Contact Metamorphic Granophyres of Partial Melting Origin Adjacent to Dolerite Dykes in Karnataka
Authors: Ramakrishnan M. , Bhattacharyya Samit
Published: November 2024

Granophyric rocks produced at the contact of post-Dharwar dolerite dykes in the host gneisses and granites of Peninsular Gneissic Complex stand out conspicuously at the weathered dyke margins in the vicinity of Hole Narsipur, Karnataka. The degree of development of granophyric texture is variable, and with its progressive increase, there is a shift in the host rock composition from granodiorite to alkali granite. Since there is no possibility of addition of potash from the dolerite to the granodiorite (the reverse is commonly the case) to cause this potash enrichment in host rocks, the origin of granophyres in the contact zones is attributed to partial melting rather than metasomatism or assimilation. This view is consistent with experimental evidence that partial melting of sodie gneisses (tonalites, trondjhemites and even granodiorites) results in the production of more potassic rocks like adamellites and alkali granites. The production of granophyres in the present case is, therefore, taken as a textural evidence for the partial melting of quartzofeldspathic gneisses. Similar phenomena are observed at the contact of Skaergaard intrusion of Greenland and Newer Dolerite of Singhbhum in eastern India.
Petrology and Geochemistry of the Oddanchatram Anorthosite and Associated Basic Granulites, Tamil Nadu, South India
Authors: Janardhan A. S. , Wiebe Robert A.
Published: November 2024

Preliminary studies of the Oddanchatram anorthosite body, the largest of the bodies lying along a 100 km linear; on the northern slopes of Patni hilI ranges, show that it has all the chemical and mineralogical characters of Proterozoic massif anorthosites. Plagioclase compositions reveal two types: a) primary plagioclase of An60 and b) secondary plagioclase with An94 occurring as breakdown product of garnet. Estimates based on primary pyroxenes indicate intrusive temperatures between 960°C-1000°C; pressures of 5.3 kb. based on garnet breakdown products suggest a steep geothermal gradient. The chemistry suggests that the parental magma was unusually feldspathic; primary hornblende indicates a higher H2O content of the magma.
Paragenesis of Uraninite and Associated Ore Minerals in the Precambrian Oligomictic Conglomerates from Walkunji, South Kanara District, Karnataka, India
Authors: Aurora S. N.
Published: November 2024

Mineragraphic study of the Early Proterozoic uraniferous oligomictic quartzpebble conglomerate of Walkunji reveals 'three types of uraninites, designated as U-I, U-II and U-III respectively. Textural and mineralogical characteristics indicate . that (i) U-I with plenty of filled-in fractures is subrounded to rounded in shape, detrital, allogenic and oldest in the sequence; (ii) U-II and U-III are authigenic with fine-grained U-II, occurring as fillings in gangue minerals, and appear to be hydrothermal; and (iii) colloform-textured U-III (pitchblende) is the youngest formed at low temperature due to remobilization of earlier phases. In addition, a little detrital, partially altered brannerite occurs with anatase.

Among the sulphides, melnicovite-pyrite and pyrite-marcasite are the most dominant followed by galena pyrrhotite and marcasite. The oxide sulphide mineral assemblage suggests that mineralization was primarily strata-bound in the initial stages followed by hydrothermal phase and ended with remobilization that resulted in the formation of U-lIl. The textural relationships among different ore minerals indicate the following paragenetic sequence: U-I, brannerite, pyrite, melnicovite-pyrite and gel. pyrite (oldest); U-II, arsenopyrite, pyrrhotite-marcasite, chalcopyrite, galena, sphalerite and molybdenite; and U-lIl, gel-pyrite and marcasite (youngest).
Geochemistry of Jahaj-Govindpura Volcanics, Bayana Sub-Basin, Northeastern Rajasthan
Authors: Singh S. P.
Published: November 2024

The Jahaj-Govindpura Volcanics - the youngest formation of the Rajalo Group in the Bayana sub-basin, comprises lava flows, agglomerates, volcanic breccias, tuffs, and quartzite interbeds. Volcanics have been fed by feeder dykes which clearly cut the underlying rocks. Plots of geochemical data from this volcanic suite reveal that compositionally they are transitional between aikali basalt and tholeiite. They resemble high-K2O continental tholeiites.
Rb-Sr Age of the Tusham Ring Complex, Bhiwani, India
Authors: Kochhar N. , Pande K. , Gopalan K.
Published: November 2024

Acid volcanics and associated granites from the Tusham Ring Complex in northwestern India yield a well defined Rb-Sr isochron corresponding to an age of 754±20 Ma (?=1.42 x 10-11 yr-1 ) and an initial Sr composition of 0.7131±0.0025. This is in good agreement with the age of the Malani suite of igneous rocks of western Rajasthan.
Organa-Geochemical Studies of Proterozoic Stromatolitic Phosphorite and the Intercolumnar Dolomite from the Aravalli Group, India
Authors: Banerjee D. M. , Klemm Ursula
Published: November 2024

Stromatolitic phosphorites and carbonates from the Proterozoic Aravalli sediments of Western India, have been subjected to organo-geochemical studies, involving a modified gc-ms technique. The stromatolitic phosphorites have an average value of 0.22% TOC which is significantly different from the average TOC value (0.64%) for all types of phosphorite from the Indian subcontinent. With only a few exceptions, the isoprenoids-pristane and phytane and the n-alkanes, account for about 30% of the total amount of volatiles (1-20 ppm). Normal alkanes occur in the range of n-c12 to n-c31 with maxima between n-c17 and n-c21 . No odd/even predominance has been observed. Besides pristane and phytane, other isoprenoids identified in these rocks are iSO C16 and iSO-C18. The low pristane to phytane ratio of 1.14 suggests a reducing micro-environment within the laminae of shallow-water cyanobacterial/algal stromatolites. The phosphate is assumed to be precipitated within the pore-waters under anoxic conditions through the activities of biological agents, which is supported by geological and geochemical data. The overall basinal environment, however, remained oxidizing, as is evident from the associated sedimentary structures.
Origin of White Sands from Prakasam District, Andhra Pradesh
Authors: Rao A. T. , Sankara Pitchaiah P.
Published: November 2024

White sands in Prakasam District, Andhra Pradesh, occur as a narrow zone extending 45 km in length and 3-4 km in width between Karlapalem and Chinnaganjam. The origin and provenance of white sands are worked out based on geology and textural analysis of the white sand belt. The textural parameters and the gradational changes in the white sands support interpretation of the depositional environment as belonging to a beach system. The sub-angular to sub-rounded shape of the grains and appreciable amount of feldspars in the white sands suggest that they have undergone transportation locally and originated from a nearby source. It is established that the Gondwana sandstones exposed around Pavalur and Budavada were the source rocks for the white sands and they were deposited as a near shore bar.
Geomorphic Processes in the Formation of (Red) Sands at Bhimilipatnam, Visakhapatnam District, Andhra Pradesh
Authors: Prudhvi Raju K. N. , Mahalakshmi K. B. , Prasada Raju P. V. S. P. , Krishna Bhagavan S. V. B. , David Emmanuel B.
Published: November 2024

The (red) sands at Bhimili with an areal spread of about 7 km2 and a height of 90 m above M.S.L. adjoining the beach (sea) has a dome like form. Within this, a typical badland topography has been formed. Three horizons of red, white to brownish and white to yellowish sand occur beneath white sand at the top, The red sands are fine-grained. White to brownish sands are coarse and show partially cemented parallel laminations. White to yellowish sands at the bottom, are coarse and pebbly, and stone lines within them occur inclined towards the sea, with small pebbles to boulders at different heights above M.S.L. and at different distances from the sea. A part of the bed of a major stream in the badland is a uniform wave-cut rocky platform, at a height of 7 m above M.S.L.

The height (7 m) of the rocky platform confirms that the sea level was possibly higher. It is inferred that the white to yellowish sand horizon may be a beach deposit, the white to brownish sands to be coalesced dune deposits and the red sand to be of aeolian nature. Statistical values substantiate mixed populations in the dune environment.
On the Tonalitic Suite of Khammam, A.P.- A Study of Mineral Correlation as Petrogenetic Clue
Authors: Maitra Monoj
Published: November 2024

Extensive occurrence of granitoid suite comprising tonalite-granodiorite and granite around Khammam, A.P. is reported. Correlation between mineralogical attributes (free from close table effect) having petrogenetic significance has been achieved through statistical procedure. It is indicated that members of the suites are interrelated by a broad fractionation history.
Chitradurga Metallogeny - A Case Study for Regional Metallogenic Analysis
Authors: Mishra R. N.
Published: November 2024

Chitradurga schist belt has traditionally been accepted as a long and narrow curvilinear Archaean geosynclinal pile, cratonised long ago. Important economic minerals are gold ore at Gadag, Bellara, Ajjanahalli and Honnemaradi; antimony at Chikkanayakanahalli; copper-lead-zinc and pyrite at Ingaldhal; iron and manganese ores at the western margin of the belt; limestone and dolomite around Dodguni, Chikkanayakanhalli and Javanahalli; barytes and fuchsite quartzite around Ghattihosahalli.

Salient features of the zonation of metals and minerals show a trend from the central to peripheral areas in the belt:

Cu, Pb, Zn, Pyrite ? Au, Ag, Sb, As ? Fe, MD, Carbonates ? Barite, Fuchsite Quartzite, Kyanite ? Feldspar, Quartz, Corundum.

The appropriate name for the container of this varied mineral spectrum across the time and space concept, could be 'metallogen'. The significant features of mineral zones in the Chitradurga metallogen; could prognostically lead to search for ore and the speculative size-up of the mineral in a futuristic perspective, thus forming a basis for a Resource Base. Regional metallogenic analysis thus opens up new vistas for future mineral appraisals. Chitradurga metallogen could thus form a subject for case study.
Accumulation of Oil in Coal-Bearing Strata North of Ahmedabad
Authors: Desikachar S. V.
Published: November 2024

The main oil sands of the Cambay Basin in the area north of Ahmedabad are in the Kalol Formation of upper Eocene age. The lower coal slit member of this formation can be identified all over the basin. In the fields north of Ahmedabad, this unit comprises mainly of coal and is identified as the reservoir unit. Hydrocarbon accumulations are found within high pressure lenses of poorly permeable silts within the coals. Study of the nature and environment of deposition of the reservoir rocks and a study of the development of the Kalol structure vis-a-vis the depositional and structural history of this part of the basin with the help of palaeostructural profiles and the production performance of the reservoir rocks provide some indication of the nature of distribution and accumulation of hydrocarbons in the area.
Bababudan - A Late Archaean Intracratonic Volcanosedimentary Basin, Karnataka, Southern India
Authors: Chadwick B. , Ramakrishnan M. , Viswanatha M. N.
Published: November 2024

The stratigraphy of the volcanosedimentary rocks of the late Archaean Dharwar Supergroup that make up the Bababudan basin is described in terms of six lithostratigraphic divisions, in ascending order, the Kalasapura, the Allampur, the Santaveri, the Mulaingiri, the Jagar and the Mundre Formations, the Jagar and the Mundre Formations being lateral equivalents. The three lower formations, each varying in thickness from a few metres to about 2000m, are dominated by metabasaItic rocks with local cross-bedded quartzites, including the basal quartz-pebble Kartikere Conglomerate which unconformably overlies the basement Peninsular Gneiss (c. 3100 Ma) in the south; the western, northern and eastern boundaries of the basin arc steep faults. The Mulaingiri Formation (200-1500m) is dominated by banded ferruginous cherts interbedded with phyllites, the Jagar Formation (? up to 2000m) comprises poorly exposed metabasaltic rocks and phyllites on the west of the basin, and the Mundre Formation, restricted to the northeast, contains the KaIdurga Conglomerate with a lower division dominated by clasts of Dharwar cover and an upper division dominated by clasts of Peninsular Gneiss basement: the conglomerate passes laterally into phyllites and crossbedded quartzites. The Mundre Formation is intruded by small bodies of pre- or syn-tectonic granite s.l.

The lithostratigraphic formations thicken from west to east indicating greater subsidence of the basin in the east, with the thickest accumulations marked by the Kaldurga Conglomerate (7 up to 5000 m) in the northeast. Sedimentary facies suggest that relatively shallow, intertidal or nearshore, marine environments persisted throughout most of the depositional and volcanic phases of basin development with banded ferruginous cherts and interbedded phyllites accumulating in areas (also relatively shallow ?) starved of terriginous detritus. The Kaldurga Conglomerate built out as a composite, shallow marine and alluvial cone into a rapidly subsiding part of the basin, detritus being provided by erosion of uplifted cover and basement to the north and northeast.
A Compilation of Sr and Nd Isotope Data on Mexico
Authors: Verma Surendra P. , Verma Mahendra P.
Published: November 2024

A compilation is given of the available Sr and Nd isotope data on Mexican volcanic-plutonic terranes which cover about one-third of Mexico's territory. The available data are arranged according to a subdivision of the Mexican territory in terms of geological provinces. Furthermore, site and province averages and standard deviations are calculated and their petrogenetic implications are pointed out.
Rb-Sr whole-Rock and Mineral Isochron Ages of the Tirodi Gneiss, Sausar Group, Rhandara District, Maharashtra
Authors: Sarkar S. N. , Trivedi J. R. , Gopalan K.
Published: November 2024

Six whole rock samples of the Tirodi gneiss belonging to the basal part of the Sausar Group rocks in the Dongri Buzurg area yield a good Rb-Sr isochron corresponding to an age of 1525±70 Ma and an initial Sr ratio of 0.7148±0.0033. Mineral isachrons for two of these rocks give concordant but younger ages at 860 Ma in good agreement with the previously reported K/Ar ages on minerals separated from the Sausar Group rocks. The 1525 Ma event is interpreted to mark the main phase of regional metamorphism of the Sausar Group of rocks including the granitization of the basal Tirodi unit. The deposition of the sediments of the Sausar Group and their basement must therefore be even older. The good agreement of the RblSr and K/Ar mineral ages at about 860 Ma indicates the latest thermal overprint on the Sausar - rocks, The regional metamorphism of the Tirodi gneiss at about 1500 Ma ago is also reflected in the Rb/Sr and K/Ar mineral ages of the Amgaon gneiss and Dongargarh granite to the east of the Tirodi gneiss.