bluuebunny/crossref_metadata_2025 huggingface dataset:
A Modified Sequential Extraction Technique and its Usefulness in Geochemical Exploration
Authors: Purushottam A. , Murty B. V. S. R. , Chandra S. , Subba Rao N. , Syamala Rao A. , Basu P. C. , Sood N. K.
Published: November 2024

Sequential extraction techniques for determination of trace metals associated with different phases in soils/stream sediments are being increasingly used for geochemical exploration in recent years. The existing techniques do not provide for the separate determination of Copper, Lead or Zinc present in the secondary mineral form, although in many soils and stream sediments, these metals exist in such phases. Based on laboratory studies, the sequential extraction technique suggested by Chao and Theobald (Jr) has been modified to include an additional step to provide for determination of Copper, Lead and Zinc present in their commonly occurring secondary mineral forms. Making use of the modified scheme, stream sediment samples from Ahobilam area in Cuddapah Proterozoic basin have been analysed. Metal contents of samples in the primary and secondary mineral phases were found to be good indicators for Pb and Zn mineralization in zones 2 and 3. Subsequent field check revealed Ph-Zn mineralization in t he above two zones.
Provenance Control of Diagenesis in Clayey Sediments in the Northern Part of Western Continental Shelf of India
Authors: Bhattacharya N.
Published: November 2024

Recent marine sediments coupled with sea-bottom cores, parting shales and insoluble clay residues of carbonate reservoirs in northeastern continental shelf of the Arabian Sea were investigated for studies of clay mineral diagenesis to evaluate respective roles of source conditions and environment of deposition. The material was also compared with those from selected weathering profiles on basalts and/or diabases. The data indicate an uniform distribution of montmorillonite and expandable mixed-layers with little kaolinite over the continental shelf diluted by sporadic occurrences of degraded illite and chlorite off the Saurashtra coast and beyond in the north and northwest upto the international boundary. These clays were derived by weathering from basalts/diabases and so have not responded to diagenetic changes even at depth. Occurrence of illite and chlorite mixed with montmorillonite and expandable mixed-layers could have resulted from material brought in by the Indus river. The factors of source and inheritance seem to have been the governing criteria for structural failure of these clays against diagenetic processes. However, clay mineral diagenesis indicates that hydrocarbons discovered in this area are independent of the associated clay mineral characters with regard to their genesis and entrapment.
A Proterozoic Intracratonic Basin, Dyke Swarms and Thermal Evolution in South India
Authors: Drury S. A.
Published: November 2024

The spatial and temporal relationships between mid-Proterozoic, intracratonic sedimentation in the Cuddapah Basin and earlier Proterozoic basic dyke swarms are analyzed in the context of thermal and mechanical models for crustal doming, erosion and subsidence. The dyke orientations imply that the Archaean crust of South India was thermally warped into an elliptical dome with a roughly E-W axis, under varying regional tectonic conditions. Thermal relaxation of this dome, after erosion and crustal thinning, laid the basis for sedimentation in the Cuddapah Basin, whose deepest part lay to the SW of its present outcrop. Late-Proterozoic sedimentation of the Kurnool rocks must have been initiated by a later, separate thermal event.
Ion Exchange Properties of Lateritic Soil from Calicut Kerala
Authors: Raymahashay B. C. , Bhavana P. R. , Rao K. S. , Mehta V. K.
Published: November 2024

The lateritic soils developed over Precambrian crystalline rocks near Calicut have relatively high Cation Exchange Capacity. At the same time, the soils are highly efficient for phosphate uptake. Both of these properties are traced to the presence of halloysite of intermediate hydration in the soils. Experimental results have been interpreted in terms of the structure of soil minerals.
Pressure - Temperature Estimates of the Iron Formations of Sivasamudram Area, Karnataka
Authors: Mahabaleswar B. , Anantha Murthy K. S. , Basavanna M.
Published: November 2024

Through a consideration of major element chemistry it is inferred that the orthopyroxenes and clinopyroxenes of the iron formations are ferrohypersthene and ferroaugite respectively, whereas the garnets belong to pyralspite series. The opx and garnets are rich in Mn content, which may be due to bulk composition of the host rock and oxygen fugacity. The P-T estimates give values of 7.5 to 8 Kbars and 607°C to 657°C.
Palaeocurrent and Clastic Dispersal Pattern of the Proterozoic Alwar Group around Jaipur, Northeastern Rajasthan
Authors: Singh S. P.
Published: November 2024

The Proterozoic Alwar Group of tje Jaipur area, northeastern Rajasthan, includes two formations: the Rajgarh Formation, predominantly comprising conglomerate-feldspathic quartzite-arkosic grit association with subordinate phyllite and schist; and Kankwarhi Formation, representing an interbedded sequence of thinly bedded quartzite, phyllite and schist. These sediments were accumulated in tidal flat and fluvial environments in a fault-controlled basin.

Palaeocurrent study reveals that sediments were transported by external agency (river) from southeast, south, and southwest, and were dispersed within the depository by offshore and onshore currents and also by across-slope currents. The dispersal pattern so obtained is in close agreement with a coastal environment and hence it is suggested that cross-stratification can be utilized for palaeocurrent studies and palaeogeographie reconstruction even in a tectonically deformed terrain.
A New Triassic Fish (Actinopterygii; Saurichthiformes) from the Yerrapalli Formation, Pranhita-Godavari Valley, India
Authors: Jain Sohan L.
Published: November 2024

Yerrapalli Formation (late Lower Triassic or early Middle Triassic) in the Pranhita-Godavari Valley is characterized by a fauna consisting of a capitosaur amphibian, dicynodonts and an erythrosuchid. The first piscine member, Saurichthys, is recorded from this formation.
Evaluation of Aeromagnetic Data and Regional Geological Interpretation for a Part of the Cuddapah Basin
Authors: Ramanamurthy M. V. , Reddy U. S. N.
Published: November 2024

Based on total intensity aeromagnetic profile data across the Cuddapah Basin, it is possible to distinguish the Cumbum and Bairenkonda Formations of Nallamalai Group. Further subdivision within individual intercalated dolomites and quartzites of Cumbum Formation is also found feasible. This discriminatory criterion can be used to guide mineral exploration, especially in the dolomites of Cumbum Formation. The magnetic variations along the strike of the Cumbum Formation is considered to be due to minor undulations in basin geometry, ref1ecting palaeogeography of pre-Cumbum period. The high magnetic response in Tadpatri and Vempalli Formations is mostly due to their association with basic volcanism.

All along the eastern margin of the basin, there is an ascending magnetic trend which coincides with a thrust. The geometry of Iswarakuppam dome is inferred to be asymmetric and with a tilt towards cast and/or controlled by a crustal fracture. The relative high magnetic response and discordant trend over Kurnool Group of rocks in the western part of the Kunderu Basin is attributed to the occurrence of the basement at shallow levels locally. Regional and areal trend surfaces have been estimated and causative magnetic responses due to basement and overlying metasediments are evaluated. For trend surface analysis, window sizes have been determined and computerization is suggested. From the LANDSAT imagery interpretation, a three stage basin evolutionary trend has been inferred.

A northwest-southeast tectonic break near Cumbum town is proposed, along which the basin oscillated, causing shallowing of the basin to the north and deepening to the south. Further, it is postulated that the northern and southern blocks tilted to east and west respectively moving on a northeast-southwest axis, resulting in the basement rise in the northwest and southeastern parts and gentle slope in the northeastern and southwestern parts in the area of study.
Geology and Ore Reserve Estimates of Rampura-Agucha Zinc-Lead Deposit, Bhilwara District, Rajasthan
Authors: Gandhi S. M. , Paliwal H. V. , Bhatnagar S. N.
Published: November 2024

Rampura-Agucha zinc-lead deposit, located 15 km southeast of Gulabpura in Bhilwara District, Rajasthan, forms a part of pre-Aravalli Banded Gneissic Complex (3.2 to 2.5 billion years old) consisting of gneisses. schists and intrusives of acidic and basic igneous rocks, that occupy predominantly the southeastern plain of Ajmer and Bhilwara. The sequence of rocks from hanging wall to footwall in the deposit is (a) garnet-biotite-sillimanite gneiss/schist, intercalated with amphibolite, calc-silicate, pegmatite and aplite, (b) graphite-mica-sillimanite gneiss/schist, (c) footwall garnetbiotite- sillimanite gneiss with interlayering of granite gneiss, amphibolite, calc-silicate and pegmatite, (d) granite gneiss. and (e) mylonite. The rock units show northeast-southwest strike with steep dips in hanging wall (75°-80° ) and moderate dips in footwall (60°-65°) towards southeast and are suspected to have undergone more than two stages of deformation. Structurally, the deposit is interpreted to represent a doubly plunging. isoclinal, synformal fold with steep northeasterly plunge (65°-70°) in the south and shallow southwesterly plunge (20°-22°) in the north.

Graphite-mica-sillimanite gneiss/schist forms the host for economic mineralization and have a strike extent of about 1400 m. The ore zone is massive, wider in the middle section with tapering ends on either side along the strike. The persistence of ore has been established upto a depth of about 350m and is still open in depth. The economic minerals occurring in this deposit, in the order of decreasing abundance are sphalerite, pyrite, pyrrhotite and galena. The dominant gangue minerals occurring within the ore zone are quartz, felspar, micas (sericite, chlorite and biotite), graphite and sillimanite with negligible amounts of garnet and amphibole. The genesis of mineralization remains unclear, but presently it is interpreted as a volcanogenic massive sulohide that has later been subjected to high grade metamorphism and tectonic disturbances. The total ore reserves have been estimated to be 61.10 million tonnes with 1.57 % Pb, 13.48 % Zn and 9.58 % Fe.
Crustal Structure Along Wular Lake-Gulmarg-Naoshera Profile Across Pir Panjal Range of the Himalayas From Deep Seismic Soundings
Authors: Kaila K. L. , Tripathi K. M. , Dixit M. M.
Published: November 2024

Deep Seismic Soundings along Wular lake-Gulmarg-Naoshera profile across Pir Panjal range of the Himalaya have delineated the Srinagar and Jammu synclines, each having a maximum sedimentary thickness of about 18 km. In the Srinagar syncline, the thickness of Karewas (velocity 2.8 km/sec) varies bctween 0.5 km to 1.1 km near Babarishi. Karewas are underlain by Triassic limestones (velocity 4.55 km/sec) having a thickness of 2.0km near Muquam, increasing to 3.6 km south of Sopur. Its thickness decreases to 1.2 km near Babarishi. The third layer with velocity 5.8 km/sec is inferred as Panjal Traps having a thickness of 2.5 to 3.0km. A system of 3 high angle faults is also indicated in the Srinagar valley. In the Jammu syncline, the exposed Murrees and Middle and Lower Siwaliks (velocity 3.8 to 4.6 km/sec) indicate a total thickness of about 3 km near Naoshera overlying the Waishnodevi limestones (velocity 5.8 km/sec). A number of low angle faults have been delineated in the Jammu syncline.

The deeper crustal section is divided into three major blocks bounded by deep faults, the northern block being downfaulted with respect to the southern block. In the southern block, Moho is at a depth of 44km near, Main Boundary Fault, 57km under Pir Panjal range, 51 km under Babarishi. Moho is at a depth of 63 to 69km north of Muquam. Under the Great Himalaya, Moho starts rising from 78 km depth in the deepest part to 67 km under the Nangaparbat shot point.
Orthophosphates in the Shallow Groundwaters of South India
Authors: Sahgal R. K. , Ramesan V.
Published: November 2024

Detectable amounts of phosphates occur in the groundwaters of many parts of South India. Excessive concentrations occur in isolated parts either due to pollution of village wells or other cultural practices. The results of analyses carried out in 1982 and 1983 show significant differences indicating a general variability in the source. The excessive phosphate content in Chirala (10mg/l) and Bapatla (7mg/l) need further investigation. In most of the other areas, local geology and prevalence of phosphate bearing minerals play an important role in giving the observed phosphate content. Developing towns with no proper sewerage also show higher phosphate content in groundwater (e.g.; Karimnagar in Andhra Pradesh gives phosphate up to 1.5 mg/l).
Origin of the Palghat Gap in South India -A Synthesis
Authors: Subramanian K. S. , Muraleedharan M. P.
Published: November 2024

The east-west trending Palghat Gap across the Western Ghat hill ranges is a part of a well-defined low level landform along 10°45'N latitude in south India. The Nilgiri hills to the north and the Anai Malai-Palni hills to the south of the gap are marked by remnant plateau landforms representing a planation surface of Jurassic age. Field evidences are against block faulting and uplift of the hills to the north and south in post-Jurassic times to account for the elevation of the Jurassic surface and the evolution of a low level landform in between the hills. Results of recent studies do not support marine incursion in the gap area to carve out a low level landform.

It is put forward that crustal upwarp along an east-west axis coinciding with the Palghat Gap elevated the Jurassic surface; the brittle crustal rocks along the axis got ruptured by tensional stresses resulting from upwarping; and the ruptured rocks were eroded with comparative ease by fluviatile action. LANDSAT imagery (MSS Band 5 and 7) bears out the signature of an easterly flowing palaeo stream (Proto-Amaravati), which apparently dried up in post Mio-Pliocene times because of a change in the climatic pattern.

The upwarp of the continental crust is considered to be a natural response to correct the imbalance in equilibrium resulting from the erosion of crustal rocks and deposition of stupendous amounts of sediments in taphrogenic basins on the east coast. From the Plate tectonics angle, the elevation of the continental crust may be attributed to tremendous pressure exerted on the crust by vertical thermal plume activity related to Deccan trap volcanism.
X-Ray Fluorescence Analysis of Major, Minor and Selected Trace Elements in New IWG Reference Rock Samples
Authors: Govil P. K.
Published: November 2024

Major and minor oxides: SiO2, Al2O3, TiO2, CaO, MgO, Na2O, K2O, MnO, P2O5. Fe2O3(T) and a few selected trace elements Zr, Y, Sr, Rb, V, Ba, Cr. Ni, Co, Cu, Zn in the IWG standards AN-G. BE-N and MA-N have been determined relative to USGS geochemical reference samples and synthetic standards by using a PW1400 XRF analyser with P851 computer system in an attempt to get usable values for the standards.

Samples prepared in duplicate were repeatedly (ten times) analysed to check the reproducibility of the data which is within the range of ± 1.0 % of reported values for all the major and minor elements, ± 5% for trace elements and ± 10% for the trace elements at concentrations below 10 ppm. The average values are found to be in good agreement with the proposed values. The results on MA-N granite were found to be very reproducible and MA-N may be used as a replacement of USGS-Gl or G2 which are no longer available.
Algal Structures from the Upper Krol-Lower Tal Formations of Garhwal and Mussoorie Synclines and their Palaeo-Environmental Significance
Authors: Tewari Vinod C. , Fasiullah Qureshy M.
Published: November 2024

Algal pisolites, oncoids, columnar stromatolites and columnar layered stromatolites have been recorded from cherty dolomitic limestones from Upper Krol and Lower Tal formations. The algal mat facies show bird's eye structures and irregular fenestral fabric suggesting an intertidal supratidal environment of deposition for Upper Krol (D and E) Formation of Garhwal syncline. The basal Lower Tal Formation of Mussoorie syncline also represents a complex algal oncoidal-stromatolitic (protected tidal flat/lagoonal) facies with restricted circulation. The association of phosphorite with stromatolites and oncoids proves the phosphorite to be deposited in a shallow water environment. The presence of pyrite and associated black shales indicate an erobic condition.
Fluoride Ingestion into the Natural Waters of Hard-Rock Areas, Peninsular India
Authors: Ramesam V. , Rajagopalan K.
Published: November 2024

The Vedavati River Basin falling in the central part of Peninsular India is a typical drought prone hard-rock terrain. Many places in it show high fluoride content (maximum 11 ppm) in the ground waters. Detailed studies on the distribution and geochemistry of fluoride were conducted in the basin between 1974 and 1979. User oriented map showing fluoride distribution giving mean and standard deviation is compiled. The leachable fluoride in the soils is more significant in contributing the fluoride-rich water rather than the mere presence of fluoride-bearing minerals in the rock.
Occurrence of a Podocopan Ostracod Palmenella Mckenzii Sp. Nov. in the Marginal Water Bodies, East Coast of India
Authors: Annapurna C. , Rama Sarma D. V.
Published: November 2024

Distinguishing characters relating to carapace and soft parts of a new podocopan ostracod, P. mckenzii inhabiting the shallow backwaters of Bimili and lower reaches of the Vasishta Godavari estuarine system on the east coast of India, are described.
Cachar Earthquake of December 31, 1984 is it a Signal for the Beginning of Seismic Activity?
Authors: Gupta Harsh K.
Published: November 2024

The Cachar earthquake of December 31, 1984 is significant on two counts: i) It occurred in a region identified to be experiencing dilatancy stage precursory to a large earthquake by Gupta and Singh (1980), ii) An earthquake of magnitude exceeding 6 has occurred in the vicinity of the Shillong Plateau after a lapse of four decades. This may be signal of beginning of a seismically active period in the vicinity of Shillong Plateau similar to the one between 1869 and 1943 when six large earthquakes occurred in this region.
Pellatispira (Foraminiferida) from the Upper Eocene Kopili Formation of Garo Hills, Meghalaya
Authors: Samanta Bimal K.
Published: November 2024

The foraminiferal genus Pellatispira Boussac is represented by P. crassicolumnata Umbgrove, P. inflata Umbgrove, P. irregularis Umbgrove, P. madraszi (Hantken) and P. orbitoidea (Provale) in the Upper Eocene Kopili Formation of Garo Hills, Meghalaya. This is the first record of such an assemblage from the Indian region. Vacuolispira Tan is treated as a synonym of Pellatispira Boussac, while Biplanispira Umbgrove is considered as generically distinct from Pellatispira. The larger foraminiferal fauna of the Kopili Formation exhibits a close affinity with that of Upper Eocene succession of Indonesia.
The Deformation and Strain Analysis of the Gandemara Conglomerate from the Archaean Iron-Ore Group Rocks, District Singhbhum, Bihar
Authors: Srivastava Deepak C.
Published: November 2024

The Archaean I.O.G. metasediments exposed near Gandemara have undergone three successive deformational phases, D1, D2 and D3 of varying intensities. The quartzite pebbles from oligomictic conglomerate arc considered as the markers for finite strain analysis. Strong correlation between major and minor axes of the ellipses (sections of the pebbles along XY, YZ and XZ planes) and good linear fitting to the axial-ratio plots imply that these markers came from the same population. High values of fluctuation 'f' and nearly symmetric Rf/f patterns (IYSM values) indicate large initial axial-ratios (Ri >Rs) and random predeformational fabric respectively. The axial-ratios of strain ellipses (Rs) in XY, YZ and XZ sections are 1.5, 1.83 and 2.5 respectively and these correspond closely with the ß values. The three dimensional strain analysis reveals that most of the pebbles have undergone flattening (?=0.2 to 0.4) corresponding to the low amounts of strain (es =0.6 to 1.0). Available structural relations and evidences from strain analysis strongly suggest that the conglomerate has been dominantly deformed during D1 phase and subsequently modified during D2 phase.
Distribution of Calcareous Nannoplankton from the Sedilnents of the Northwestern Continental Shelf of India
Authors: Shankaranarayana Guptha M. V.
Published: November 2024

Fifty-four snapper samples from the northwestern continental shelf of India have yielded fifteen species of calcareous nannoplankton along with a few reworked ones. Among the species encountered, Gephyrocapsa oceanica was most predominant, being distributed in all the stations. The patchy and sparse distribution of nannoplankton suggests that the flora has undergone intense grazing. Low diversity of nannoplankton indicates a marginal environment.
Stratigraphy of the Purana Supergroup Around Ramgundam, Andhra Pradesh
Authors: Chaudhuri A.
Published: November 2024

Middle and Late Proterozoic Purana Supergroup at Ramgundam in the Pranhita Godavari valley is separated from the underlying granites and gneisses of the Basement Complex and the overlying Gondwana Supergroup by two major unconformities. Evidence is adduced to show that two other major unconformities divide the Purana sequence into three chronologically independent units correlatable with the Mallampalli Subgroup and the Mulug Subgroup, two major divisions of the Pakhal Group, and the Sullavai Group in adjacent areas, viz., Mancherial and Mulug.

Both the Subgroups of the Pakhal Group comprise of silici-clastics at the base and are followed by carbonates while the Sullavai Group is constituted entirely of siliciclastics. Detailed section measurements show rapid facies variation, both lateral and vertical, to be a characteristic feature of the Pakhal formations. Formations in the Sullavai Group are regionally more uniform in character.
Lonar Crater, India: A Crypto-Volcanic Origin
Authors: Subrahmanyam Burra
Published: November 2024

One of the largest natural crater in the world is situated at Lonar (J9°59'N : 76°31'E) in the Buldhana district, Maharashtra. The crater is located in Deccan basalts and controversy exists about its origin. The earlier theories suggested a volcanic eruption. Morphological resemblance with other terrestrial craters, physical evidences like the identification of very high pressure shock deformation features and shatter cones have favoured an impact origin. Bore holes drilled could not establish a sufficient thickness of brecciated zone which is a prerequisite for an impact crater. Gravity and magnetic (Vertical Force) measurements favour a crypto-volcanic origin for the crater associated with a volcanic pipe or a carbonatite plug.
Petrology of the Carbonatites and Associated Rocks of Sung Valley, Jaintia Hills District, Meghalaya, India
Authors: Krishnamurthy P.
Published: November 2024

In Sung Valley, (Lat : 25°31' -25°36'N : Long; 92°05' -92°10'E) the Shillong Series rocks comprising mainly quartzites and phyllites are intruded by a N-S trending, roughly oval shaped body of pyroxenite covering an area of about 35 km2 and into which the following genetically related rock types have been emplaced in order of decreasing age and abundance. Peridotites (stock-like bodies), ijolites (ring dyke and plug like), carbonatites (incomplete cone sheets) and syenites (sheets, dykes and veins). Minor dykes and veins of magnetite-serpentine rock, ijolite and melilite-bearing types with a rough radial disposition are also present. Fenitization, due to both ijolites and carbonatites, has affected older rocks resulting in wollastonite-rich aegirine-augite bearing rocks, K-feldspar-aegirine-augite veins and oversaturated potassic syenites.

Carbonatites are mainly sovites with minor beforsite and types rich in magnetite and apatite are present. Average abundances of trace elements (values in ppm) characterizing carbonatites such as Bu (549), Sr (3134), La (50-100), Ce (489), Y (50), Nb (372), Zr (179) and P2O5 (5.7) wt% are comparable to those found in reported intrusive carbonatites. The weathered mantle of the carbonatites and the contact zones between carbonatites and pyroxenites have resulted in soils rich in pyrochlore, apatite and magnetite. It is postulated that the carbonatites may be differentiates of an ijolitic magma, in turn derived (liquid immiscibility?) from a parental mela-nephelinite or alkali picritic magma. The ultramafic suite could represent the cumulates from such a picritic source.
Deformational and Crystallization History of the Delhi Group Rocks, Around Narnaul, Haryana, India
Authors: Bhola A. M. , Varadarajan S.
Published: November 2024

The regional metamorphic rocks of Precambrian age belonging to the Delhi Group, around Narnaul, show complex deformational-crystallization history. The first deformation phase, F1 of Delhi orogeny produced isoclinal folds overturned towards southeast plunging in NNE-SSW directions associated with most pervasive foliation S1. The later deformation phases, F2, tight to open folds, and F3, open folds produced crenulation cleavages S2 and S3 (rare). These three deformational events have been correlated with the crystallization periods of the more important minerals in pelitic schists and amphibolites.

The study reveals that mineral assemblages were identical during the first and second deformation phases. The index minerals garnet, staurolite, kyanite, hornblende started forming either during F1 folding or immediately after F1 and continued till the close of F2 folding with incipient crystallization of micas during F3 phase. Mineral assemblages in the pelitic schists display a single staurolite-kyanite zone. Mineralogical reactions ,indicate metamorphism under amphibolite condition below 650°C with minimum temperature 540°C and pressure 5.5 kb (PL =Ptotal) in this part of the Aravalli belt.
Mineralogy and Chemistry of Manganese Nodules from the Southern Part of Carlsberg Ridge
Authors: Karisiddaiah S. M.
Published: November 2024

Petrographic study indicates that the nucleus of nodules is generally composed of clay, volcanic glass, basalt fragments, and earlier nodules. Polished sections indicate typical collomorphic globular segregations and partly crystalline oxides of todorokite. Scanning electron micrographs indicate that they are made up of small and large botryoids; and occasional platelets of todorokite, within cavities formed due to post depositional recrystallization. X-ray diffraction patterns do not show any peaks of todorokite due to poor crystallinity, while d-MnO2 is seen in all the nodules studied. The nodules analysed show: Mn 15.01-21.40%, Fe 10.07-20.10%, Cu 0.07-0.32%, Ni 0.32-0.57%, Co 0.07-0-21%, and also have a Mn/Fe ratio less than 2. The nodules are of hydrogenetic, secondary origin, source being volcanogenic.
Chitradurga Schist Belt - An Archaean Suture (?)
Authors: Naqvi S. M.
Published: November 2024

Chitradurga schist belt is a 450 km long linear feature of Archaean age and composed of several types of volcanic and sedimentary rocks. It has been deformed by 3-phases of folding rendering elucidation of stratigraphic sequence complicated. The volcanic rocks range in composition from Spinifix Textured Peridotitic Komatiite (STPK) to rhyolite. Volcanism appears to have occurred, at least at two diflerent stratigraphic levels in the belt. The STPK, basalt and rhyolite suites are not genetically related with each other, except in Gadag, where basalt-rhyolite may be cogenetic phases of the same suite. Chemogenic sediments have a higher order contribution and enrichment from volcanogenic exhalative component. Graywacke sedimentation is recognized at two stratigraphic levels. The graywackes of the central part of the belt and those from the Gadag part of the belt differ very much from each other in their abundance of rock fragments, plagioclase/K-feldspar and Na2O/K2O ratios, Fe2O3, MgO, Cr, Ni, Zr, Rb and Sr abundances. Detrital mineral content and REE pattern of the graywackes of the central part are similar to those from other areas of the world of the same period and appear to have been derived from mixed, but predominantly tonalitic source. Gadag graywackes, on the other hand, appear to have had a predominantly volcanic source. Folded BIF horizons too are inferred to form a significant part of the source areas. Gadag part of the belt is the youngest as the Bagewadi-Kodkal conglomerate contains porphyritic granite pebbles along with rhyolites. This progressive younging and widening of the belt to the north is governed by the attitude of the axial plane foliation and plunge of the fold axes. It also probably reflects the style of the opening of a rift in the Archaean continental crust. Gravity data support such a rift origin. Horizontal EW compression is an essential feature of the Chitradurga schist pointing to its being a probable late Archaean suture.
Structural Geometry of the Dharwar Rocks near Chitradurga
Authors: Mukhopadhyay Dhruba , Baral Mohan C.
Published: November 2024

The major structure south of Chitradurga is a southerly closing, very steeply plunging, nearly vertical fold (Chitradurga Fold) defined by the BIF horizons. This is a second generation structure and the dominant schistosity with NNW-SSE strike is parallel to the axial plane of this fold. The first generation structures are represented by minor folds only. They have variably oriented axes and their axial planes are bent by the major Chitradurga Fold. The strike of the third generation axial planes varies from NNE-SSW to ESE-WNW, and the axes are generally steeply plunging.

During the second deformation, folds formed at different stages and their geometry was modified by rotation in the subsequent stages of progressive deformation. The axes of the minor folds show a wider range in orientation than the direction of maximum elongation in the rocks, and there is often an angle between the two.

The distribution of the bedding plane poles in the projection diagrams of most of the sectors indicate steeply plunging ß (F2). The major Chitradurga Fold shows a conical geometry with a subvertical cone axis and very small apical angle.
Copper metallogeny in the Jogimardi Volcanics, Chitradurga Greenstone Belt
Authors: Anantha Iyer G. V. , Vasudev V. N.
Published: November 2024

Massive volcanic-hosted sulphide deposits, within the Jogimardi volcanic suite (JVS) are Cu-rich with minor Zn and Pb and form an important early phase in the evolution of the late Archaean Chitradurga belt. The deposits are concordant stratabound lenses in the bedded mafic tuffs emplaced as submarine volcaniclastites. The JVS is an integral part of the Chitradurga antiform flanked by synclines on either side. The stratiform massive and vein-type sulphide deposits of the JVS are confined to the eastern limb of the antiform.

The volcanic rock succession in the JVS consists of 85% tholeiitic basa1ts; 12% low silica variolitic andesites and 3% of rhyolites. The basalts are quartz-normative tholeiites, not known to occur in MORB environment. Unlike those of MORB, in their major, minor and REE geochemistry, the basalts related to massive sulphide deposits are almost identical to back-arc basalts generated in an ensialic marginal basin environment.

The thermal and chemical environment of ore formation are determined based on fluid inclusions data and d34S pyrite values of individual sulphide phases. These data indicatce that the ores were deposited under anoxic chemical environment at a temperature of 350°C within a pH range of 5 to 7 corresponding to proximal facies conditions. The stratiform sulphide ore body in the area is located in the vicioity of a fracture controlled stringer/stock-work ore zone - 'a hydrothermal discharge vent' in the pillowed basalts of tholeiitic composition which confirms the proximal nature of the deposit.

Uranogenic and thorogenic lead isotope studies on the galenas of Ingladhal stratiform sulphide bodies indicate that they are not of mantle origin but derived from the basement gneisses, dated at 3 b.y.

Geologic setting, preservation of quench plagioclase textures in the pillowed basalts and volcanogenic synsedimentary nature of the stratiform sulphide deposits indicate that the sulphides were deposited initially in the JVS prior to folding and regional greenschist facies metamorphism.
Identification of Titanomagnetites by Simple Magnetic Techniques and Application to Basalt Studies
Authors: Radhakrishnamurty C.
Published: November 2024

Some members of the titanomagnctite solid solution series, xFe2TiO4 (1-x) Fe3O4, have specific magnetic properties by which their presence in basalts could be inferred from one or two simple measurements. The titanomagnetite with x = 0.56 shows a characteristic constricted hysteresis loop in a low-field (10 Oe) at room temperature, while pure magnetite has a sharp peak in susceptibility at about 120 K. The presence of even other members, when occurring with one unique composition in basalts, could be identified by observing the change in either susceptibility or coercive force between 77 and 300 K. For x = 0.1, the susceptibility of the mineral at 77 K will be 1.3 times the value at 300 K. The coercive force for x = 0.7 is 50 Oe at 300 K and it attains a value of 1800 Oe at 77 K. Howewr, often a basalt sample contains more than one type of magnetic grains which will be revealed by a superposition of the individual characteristic features in some cases.

The techniques used for the study of the magnetie grains in basalts are described briefly. Results obtained using these techniques on samples from different volcanic provinces like East African Rift, Columbia River basalts, Deccan traps, Rajmahal traps and some Precambrian basalts, indicate that while titanomagnetite with up to x = 0.6 is fairly common and pure magnetite is rare in the younger basalts, the converse is the case in the older basalts. Some implications of such results are pointed out.
Crystal Growth of Zircons in Puttetti Syenite: Nature of Fluids and Implications on CO2 Activity
Authors: Santosh M.
Published: November 2024

Fluid inclusion studies in a number of doubly polished plates of zircons showing interesting features are documented. The equilibrium balanced shapes of inclusions and their pattern of distribution are suggestive of slow growth rate, largely controlIed by stacking mechanism, resulting in completed layerites. Development of tensional fractures which eventually healed by dendritic growth and typical necking-down textures of long tabular inclusions are recorded. Thermometric studies show tbat the early fluids were of high density (0.90-0.85 g/cm3)CO2 type with probable traces of CH4 and/or N2, entrapped at a pressure of 4.5 Kb. The fluids evolved into pure CO2 (O.83 - 0.68 g/cm3) and to mixed CO2-H2O around 650°C and 3.7 Kb due to formation of vapour phase, while a fraction of the melt was sti!l present. The composition of fluids recorded suggests repeated CO2 activity in south India with a peak during Late Precambrian-Early Palaeozoic times, effecting the generation and emplacement of alkaline plutons.
Hydrometric Implications of Morphometry and Geology: A Study of Lower Ramganga Catchment
Authors: Jawat J. S.
Published: November 2024

Total stream length (ΣL) and relief ratio (Rr) are the most significant morphometric parameters, which have been used to define allometric change of hydrometric parameters i.e. stream discharge (Q) and silt delivery (S) as: Q = a+b (ΣL) and S = a b (Rr). The allometric models are largely controlled by bedrock lithologies. The lower Ramganga catchment in the central. U.P. Himalaya was employed as a natural laboratory for the above investigation.
A New Species of the Genus Physa from the Deccan Infra-Trappean Beds of Andhra Pradesh, India
Authors: Ayyasamy K. , Ganesan V , Narasimham C. V. L.
Published: November 2024

The paper records the find of a new species of the genus Physa, occurring in the infra-trappean beds of Andhra Pradesh, India. Discussions on the distribution, phylogenetic significance and the stratigraphic importance of this new find are presented.
Modelling of Trace Element Behaviour in Hydrothermal Brines
Authors: Menon A. G. , Anantha Iyer G. V.
Published: November 2024

Details of a new method to mode1 trace element distribution in hydrothermal ore deposits is outlined. The behaviour of Pb2+ at 100°, 200° and 300°C has been highlighted as a function of solution parameters fs2 fo2, and pH.
Stable Isotope Systematics in Tree Cellulose as Palaeoenvironmental Indicators - A Review
Authors: Ramesh R. , Bhattacharya S. K. , Gopalan K.
Published: November 2024

Stable isotope ratios of hydrogen, carbon and oxygen in tree cellulose have been recently demonstrated as potential indicators of past climate, However, a number of problems remain to be solved before isotope dendroclimatology can be used for routine reconstruction of palaeoclimate. Here we review the existing Literature, with a special reference to the Indian context and identify key problems that deserve immediate attention.
Wind-Sculpturing of the Vindhyan Sandstone in the Bhopal Region, M.P.
Authors: Mathur S. M.
Published: November 2024

Wind-sculpturing of the Karauli Quartzite (Rewa Group, Vindhyan Supergroup) at several localities in the Bhopal region has produced rock monuments like monad-rocks, inselbergs, etc., with tunnels boring through some of them. These monuments are found as isolated rock masses of various shapes and sizes standing above land surfaces that have reached base level of erosion. The highly jointed, horizontally bedded and fractured quartz-arenite rests over massive but softer sandstone which is first eroded causing overhang of the former. Eventual collapse of the overhanging rock masses and their ultimate removal leaves 1he soft but massive horizon underneath unprotected. Repetition of the process over eons of time has produced these natural monuments; the most remarkable group is seen at a locality known as Bhim Baithka. Several of these natural sculptures have developed tunnels and passages that pass right through them in the softer sandstone towards t he base. where the action of the sand- and particle-laden wind is most destructive.
Geochemistry of the Gabbro-Tonalite-Trondhjemite-Granite Suite of the Ezhimala Pluton, North Kerala
Authors: Sinha-Roy S. , Ravindra kumar G. R.
Published: November 2024

The Ezhimala pluton emplaced in possible Sargur-equivalent sequence in North Kerala is a differentiated suite showing a continuous compositional range from gabbro to granite through tonalite and trondhjemite. Geochemistry indicates that the suite is the product of diapiric emplacement of magma generated at shallow depth and of fractional crystallization in which the major participating phases were hornblende and plagioclase. Biotite and Fe-Ti oxides were minor fractionating minerals. There is an indication that this suite is one of the many igneous bodies of variable composition which are the products of important magmatic event in the Kerala region, in late Proterozoic and early Palaeozoic times.
Geology and Geochemistry of Tertiary Clay Deposits in South Kerala
Authors: Ghosh Swapan K.
Published: November 2024

The sedimentary clay deposits in south Kerala are the source of excellent quality kaolinite, formed due to weathering of arkosic sediments of Tertiary and crystalline Precambrian rocks. It has been possible to differentiate two such kaolinite beds in south Kerala based on mineralogy, chemistry and field relationship. At places, the two kaolinite beds are separated by sandstone-clay intercalations. The upper clay bed contains higher amount of impurities of quartz, goethite, hematite and gibbsite. The concentration of these impurities decrease at depth and vary horizontally having no consistent pattern. Study of sedimentary structures within the kaolinite beds, presence of kaolinite pseudomorph of feldspar still maintaining crystal faces, and lignite bed, support the hypothesis that the beds were deposited after a short and rapid transportation in a fluctuating flow regime. The lower elay bed, underlying the sandstone, is impoverished in both quartz and iron minerals. The source material for this clay deposit is the pre-Miocene weathered regolith extensively developed on Precambrian chalnockite- khondalite suites of rocks. After burial, ferric iron oxide from these beds was leached away in a reducing environment. The variation of mineral content and its chemistry in the kaolinite beds, have been related to spatial difference in micro-environment in the stratigraphic horizons in the geologic past and at present.
Uranium Mineralization in the Carbonate Rocks and Sandstones from the Subuk-Rishi Area of Sikkim Himalayas
Authors: Siddiqui A. S. , Dhana Raju R.
Published: November 2024

In a number of radioactive occurrences near the contact of Buxa and Gondwana rocks in the Subuk-Rishi area of Sikkim Himalayas. uranium mineralization, in the form of hydrothermal veins and disseminations of brannerite-davidite, is recorded in the carbonate rocks of the Buxa. Group (Older Palaeozoic) and quartz arenite of the Lower Gondwana Subgroup. The carbonate rocks are intermediate between a pure limestone and a pure dolonlite, and are phosphatic with P2O5 upto 17wt. %, reflected in essential apatite. Radioactivity is relatively more in carbonate rocks than in sandstone, and there is an apparent increase of U with P in both the rock types.
Regional Groundwater Flow Investigations in Visakhapatnam Basin, Andhra Pradesh
Authors: Jagannadha Sarma V. V. , Narayana Swamy A.
Published: November 2024

The study of regional groundwater flow in an area plays an important role in the exploration, exploitation and conservation of groundwater resources. This paper deals with the investigations of horizontal groundwater flow made in Visakhapatnam basin of Andhra Pradesh state using water table and hydraulic gradient as criteria. In general. it is observed that movement of groundwater follows the trend of surface drainage. An attempt is made to apply hydrochemical approach to the interpretation of groundwater movement in the unconfined conditions of the region.
Crocodilian Remains from the Miocene of Kachchh, India
Authors: Sabale A. B. , Vijayasarathi G.
Published: November 2024

Crocodilian fossil remains from the Miocene sediments of Kachchh including a well-preserved skull, mandible with few teeth intact, numerous vertebrae and a few scutes are described. This is the first record of fossil Gavialidae from the Miocene of Kachchh.
Strain Analysis in the Basal Unit of Delhi Supergroup in Kishangarh Area (Rajasthan): As Deduced from Deformed Pebbles
Authors: Srivastava H. B. , Gairola V. K.
Published: November 2024

The arkosic quartzites overlying the rocks of Aravalli Supergroup along an unconformity cum thrust contact, exhibit strong deformation resulting in preferred dimensional orientation of the pebbles. The three dimensional strain is of constriction type where the mean value of k varies from 1.33 to 6.52 from locality to locality. The shapes of the pebbles prior to deformation were mainly of constriction type. The path of pebble deformation has been traced. The strain in these pebbles is related to folding and later thrusting (gliding) during the first phase of deformation.
Stratigraphic Relations of the Precambrian Rocks in the Salumbar Area, Southeastern Rajasthan
Authors: Mohanty S. , Naha K.
Published: November 2024

Around Salumbar in the Udaipur district, Rajasthan, the Banded Gneissic Complex (BGC). the Aravalli metasedimentary rocks, the Dudar Gneiss and the Lakapa Granite Gneiss have been involved in the same style and sequence of muhiple deformation. The oldest rocks are the migmatites forming the BGC, which underlie the Aravalli metasediments with an unconformity marked by a conglomerate. Rare relict pre-Aravalli structures in the BGC, and the conglomerate containing gneissic pebbles provide incontrovertible evidence for a part of the BGC being the original basement. Identical structural style and sequence of the basement gneisses wilh those of the metasedimentary cover rocks, however, point to mobilization so that they could take part in the earliest deformation affecting the metasediments in a ductile manner. The Dudar Gneiss has formed by migmatization of the Aravalli rocks synkinematically with the first deformation, whereas the Lakapa Granite Gneiss has been emplaced as a syn-to late-tectonic intrusion.
Structure and Tectonics of Exposed Tertiary Rocks Between Narmada and Kim Rivers in South Gujarat
Authors: Agarwal C. G.
Published: November 2024

The Tertiary rocks of the area between Narmada and Tapti rivers have undergone folding, faulting and partial erosion, whereas those of the adjoining area of Cambay basin to the north lie undisturbed,  technically, under the cover of Quaternary deposits. The exposed Tertiaries have been found to be folded into twelve linear anticlinal folds, plunging southwest and at times northeast as well, and invariably faulted along their southeast limbs. These faults are of reverse type and hade due northwest. The deformation was in all probability due to differential vertical basement fault-block movement caused by compressive forces related to the collision of the Indian Plate with the Asian Plate.
Geological Aspects of the Banded Iron-Formation of Bihar and Orissa
Authors: Chakraborty K. L. , Majumder Tapan
Published: November 2024

The metamorphic age (2.55-3.07 Ga) of BIF of Tomka-Daiteri belt has been established from Sm/Nd data which seemingly indicates that the sedimentation age of BIF is older than Singhbhum granite (3.12±0.OI Ga). Intrusive evidences of Singhbhum granite into BIF have been documented. An older age of the GorumahisaniBadampahar- Tomka Daiteri-Malayagiri BIF with respect to that of Jamda-Koira Valley is supported.

The BIF, consisting predominantly of magnetite-chert, magnetite-jasper (BMJ) hematite-jasper (BHJ) or martite-quartz (BMtQ}form part of a sedimentary succession, underlain by quartz-arenite or lithic wacke and interlayered with altered volcanic tuff (shale ?). Magnetite, hematite and chert were primary precipitates in the BIF. No primary carbonate, silicate or sulphide have been noticed to occur in these rocks excepting sporadic occurrence of carbonate pseudomorphs in the underlying quartz-arenite.

Primary sedimentary structures like current ripples, syneresis cracks, penecontemporaneous deformation structures (e.g. folds, faults, micro-brecciation, pods, etc.) and diagenetic recrystallization features are described.

Similar to other world deposits of Precambrian and Archaean age, the BIF of Bihar and Orissa are also deficient in major, trace (TE) and rare earth elements (REE). Mineralogical composition and geochemistry suggest that they belong to the oxide facies iron-formation, Low concentration of Al203, CaO, MgO. MnO and of Zr, Cr, Ti, V, Ni and Cu in the BIF with respect to their abundance in. the interlayered pyroclastics presumably suggests a non-volcanogenic source of iron and silica. Eu/Sm ratio (0.541.01) indicates an Archaean age for the BJF. A shallow water marine environment is predicted for the deposition of BIF.