bluuebunny/crossref_metadata_2025_split huggingface dataset:
Charnockite-Gneiss-Complex Relationship in Southern Karnataka
Authors: Ramiengar A. S. , Ramakrishnan M. , Viswanatha M. N. 
Published: November 2024

Abstract
The charnockites of southern Karnataka occur at the fringes of the greenstonemigmatite terrain. The contacts of the individual pods and balls of charnockite with the associated migmatites are invariably diffuse. Replication of all types of migmatitic structures by the conformable charnockite masses and pods, and discordant 'tree-structure' of charnockites transecting the early rnigrnatitic fabric of the gneisses strongly suggest that the gneiss complex has been transformed in situ into charnockite without much attendant ductile deformation. The mineralogy of the transformation phenomenon reflects the transitional nature of the amphibolite-granulite facies boundary, rather than a craton-wide regional retrogression. These transformed charnockite buds probably represent nuclei of dehydration.
The major 2900-3000 m.y. thermal event in the gneiss complex, involving the high-grade supracrustal rocks, is correlatable with the progressive metamorphism of amphibolite to granulite facies in the region. This event probably culminated in the production of charnockite around 2600-2700 m.y.
The progressive metamorphism in Karnataka from green schist to granulite facies is shown to be the cumulative effect of polymetamorphism and regional synclinorial structure plunging northward. Post-Dharwar uptilting of the Peninsula has served to accentuate this vertical zonation. As a result deeper crustal levels are exposed southward, involving older supracrustal rocks. The high-grade terrain in Karnataka is, therefore, older than the greenstone terrain. The greenstones and granulites were not juxtaposed against each other because of their differing levels. Parts of the high-grade terrain later evolved into a mobile belt of charnockite-khondalite association. This mobile belt has been interpreted variously as geosynclinal orogenic belt, collision feature similar to the Circum-Pacific belts of the Himalayas, or as a transform zone. The continent-continent collision model is preferred.
The Geology and Origin of Magnomagnetite Deposits from Trap Area of Siberian Platform
Authors: Pavlov N. V. 
Published: November 2024

Abstract
Distribution and localization of iron-ore deposits of Siberian platform appears to be controlled by the disjunctive dislocations in the upper structural level of the platform, conjugated with deep faults in the basement. The peculiar features of the ores and near ore metasomatite composition indicate their connection with trap-magma. Ore-bearing solutions, responsible for the formation of magnomagnetite deposits, are likely to originate as a result of interaction of trap-magma rich in iron with halogene facies of the lower horizons of platform with the formation of iron chlorides. Geological data indicates, that magnomagnetite deposits formed at depths from 300 to 2000m from surface. The variable composition of magnomagnetites and different parageneses of accompanying mineral phases is probably related to different depths of formation.
Sm-Nd and Rb-Sr Ages for Archaean Rocks in Western Karnataka, South India
Authors: Drury S. A. , Holt R. W. , Van Clasteren P. C. , Beckinsale R. D. 
Published: November 2024

Abstract
A Sm-Nd whole-rock isochron age of 3020 ± 230 Ma for basal rnetavolcanics of the Kudremukh-West Coast greenstone belt and a Rb-Sr whole rock age of 3280 ± 230 Ma for the underlying granitoid gneisses are presented. These ages indicate that the filling of an ensialic basin with volcanic and sedimentary rocks began at around 3000Ma and confirm earlier studies which concluded that the dominant gneisses of Karnataka represent a major period of primary crust formation in the South Indian Craton at about 3300 Ma. Both the early granitoid gneisses and the younger metavolcanics were derived from unfractionated mantle sources which had not previously been depleted or enriched in LIL elements.
Crustal Structure Across the Narmada-Son Lineament, Central India from Deep Seismic Soundings
Authors: Kaila K. L. , Reddy P. R. , Dixit M. M. , Koteswara Rao P. 
Published: November 2024

Abstract
The crustal structure along Ujjain-Mahan profile reveals a layered structure in the vertical direction and block structure in the lateral direction. This profile from north to south is divided into four crustal blocks: I (Ujjain-Sanwer), II (Indore-Dorwa), III (Dorwa-Tapti) and IV (Tapti-Mahan) which were relatively displaced up or down during different times along deep faults bounding them and extending up to the Moho discontinuity. The depth to Moho varies between 37 to 42 km along the entire length of the profile with a velocity jump of 7.3 to 7.8 km/sec across the boundary. It is concluded that during Precambrian, blocks I and II north of Dorwa were downthrown with respect to block III leading to the development of the Vindhyan basin in that region. Blocks III and IV being uplifted at that time, formed the land part and hence no Vindhyan sedimentation took place there. Subsequently during Gondwana times, reverse tectonic movement resulted in downfaulting of block III where Gondwana sedimentation took place. During this period, blocks I and II formed the land part and hence no Gondwanas were deposited there. A shallow refraction boundary at a depth of 8 to 12 km has also been observed along this profile with a velocity jump from 6.0 to 6.9 km/sec, which may represent the Conrad discontinuity in this region.
In the Ujjain-Dorwa section comprising blocks I and II, under a thin cover of about 100 m of Deccan Traps, there lie Cretaceous Lameta beds (200m thick) and Vindhyan quartzites (lOa m thick) and Bijawars (200 to 300 m thick). Thus the total sedimentary thickness above the crystalline basement is hardly 600metres in this region. On the other hand, the Dora-Mahan section, consisting of blocks III and IV, has a maximum thickness of about 1.7 km Gondwana sediments underlying 400 metres of Deccan Traps. This hidden Gondwana basin is believed to be a northwestward continuation under the Deccan Trap of the exposed Gondwana-Godavari graben.
A Study on the Time Relations Between Movements, Metamorphism and Granite Emplacement in the Middle Proterozoic Delhi Supergroup Rocks of Rajasthan
Authors: Roy A. B. , Das A. R. 
Published: November 2024

Abstract
The Delhi Supergroup rocks, an important tectonic-stratigraphic unit of the Aravalli Mountains, are affected by multiple folding and polyphase metamorphism. Three generations of deformational structures have been recognized in these rocks (DFI, DF2 and DF3). DFI structures which include a set of isoclinal folds with penetrative axial planar schistosity, were deformed successively by DF2 and DF3 folding movements. Microtcxtural studies of rocks yielded evidence for two metamorphic events-a progressive metamorphism (M1) rising upto epidote amphibolite facies, followed by a retrogressive phase (M3) under greenschist facies condition. Field and microscopic studies indicate that both DF1 and DF2 structures were formed during Ml phase, and DF3 structures were formed during the retrogressive phase (M2). The metamorphic climax of M1 phase was during the early phase of DF2, and the granites emplaced coevally with this event indicated ca. 1450 Ma Rb/Sr isochron age. No definite relationship could be established for the 850-700 Ma secondary (mineral) ages with DF3 deformation and M2 metamorphism.
Mass Spectrometric Diagnostics of Plasmas - Negative Ions in an Oxygen Glow Discharge
Authors: Krishna Kumar S. V. 
Published: November 2024

Abstract
An introduction to mass spectrometric diagnostics of plasmas with an emphasis on the study of glow discharge plasmas is presented. Relative intensities of the negative ions present in a pure oxygen plasma has been studied as-a function of gas pressure, discharge current and reduced electric field (E/N) using a quadrupole mass spectrometer. The variation in the intensity of different negative ions is attributed to the gas phase reactions involving electrons, neutral species, excited molecules, positive ions and negative ions.
Textural Studies on the Ores of Amjhore Pyrite Deposit, Rohtas District, Bihar, India
Authors: Pandalai H. S. , Chandra D. 
Published: November 2024

Abstract
The pyrite ore body at Amjhore occurs as a horizontal to sub-horizontal 'bed' composed, in part, of a hard massive variety and, in part, of a more friable disseminated variety of ore. Microscopic studies reveal that the disseminated ore is made up chiefly of large spherules of pyrite (100,.μm to 1200,.μm in dia.) in a matrix of shale containing also dispersed subhedral toeuhedral pyrite (4,.μm to 30 μm in size). Occasionally, large isolated hexahedral grains of pyrite are also present in the disseminated ores. The microscopic studies indicate development of pyrite spherules from initially close-spaced growth nuclei (perhaps of the precursor-mineral pyrite). The spherules and hexahedra of pyrite fuse together to give fise to the massive variety of ore which show such textures on etching. The textural studies alone cannot, however. be used to infer the exact genesis of the deposit.
Archaean Stromatolites from Dodguni Belt of Karnataka Craton, India
Authors: Baral Mohan C. 
Published: November 2024

Abstract
Long, straight columnar stromatolite structures showing concentric arrangement of laminae in cross-sections are reported from the dolomitic marble of Chitradurga Group from Dodguni, An Archaean age, not less than 2600Ma and not more than 3000 Ma (the minimum and maximum possible age-limits of the Chitradurga Group) has been assigned to the stromatolite-bearing horizon. Presence of organic microstructures and organic carbon in the sediments provided the earlier indirect and controversial evidence of primitive life in this area. The find of these stromatolites undoubtedly confirms the existence of Archaean life in the Dodguni belt.
Geochemical Studies of Soil, Bedrock and Stream Sediment Around Base Metal Mineralization in Tiranga Hill, Bhilwara District, Rajasthan, India
Authors: Bheemalingeswara K. , Deb M. , Banerjee D. M. 
Published: November 2024

Abstract
The Tiranga Hill is located in the southernmost part of the 25 km long Pur-Banera mineralized belt in the Bhilwara District of Rajasthan. Exploration by Government agencies has revealed low grade Pb-Zn-Cu sulfide mineralization along this Early to Middle Proterozoic metasediments and meta-volcanics, regionally metamorphosed to amphibolite facies. At Tiranga, the mineralization occurs within a metamorphosed banded iron-formation spatially associated with spectacularly-folded banded magnetite quartzite (BMQ) bands.
The soils, neglecting the effects of ancient workings, are highly anomalous in Pb and Zn and also to certain extent in Cu. The major anomalies coincide spatially with the cores of synformal folds in BMQ bands, suggesting structural control of the richer parts of the mineralization. The Tiranga soils display strong interelemental correlations between Cu, Pb, Zn, Ag, Fe and Mn, The base metals display similar dispersal behaviour in soils and stream sediments. Their relative mobility in the weathering zones of Tiranga Hill is : Zn &gt;Cu &gt;Pb. Somewhat surprising, however, is the lower concentration of Fe and Mn as well as Ni and Cr in the soils compared to the bedrock.
Angular Unconformity, Structural Unity Argument and Sargur-Dharwar Relations in Bababudan Basin
Authors: Ramakrishnan M. , Viswanatha M. N. 
Published: November 2024

Abstract
Recent mapping by the authors in southern Bababudan has confirmed tbe angular unconformity between the Dharwar cover and Sargur-Peninsular Gneiss basement. The original structural trend of Sargur Group is preserved in an unmodified form in the low strain zone near Kalasapura. In the structural domain of eastern Bababudan with its N-S trends, the underlying Sargur enclaves retain their old N-S orientation but with minor rotation and enhancement during Dharwar overprinting. The apparent structural unity between the basement and cover, therefore, is due to the repetition of a stress regime similar to that of Sargur during the later Dharwar orogeny, which is a common feature of most Archaean cratons. Even in such domains of superposed deformation, the Sargur Group is lithologically distinct from the Dharwar cover rocks and occurs as a train of migmatised enclaves in Peninsular Gneiss, whereas the Dharwar cover forms a large athwart-lying fold belt with mature basal conglomerate preserved in the unaffected parts. These are prima facie evidences for separation of the Sargur and Dharwar into two distinct orogenies. Structural unity per se, divorced from regional stratigraphic considerations, is apt to be grossly misleading in interpreting the geological history of multiple deformed terrains.
Application of Gas and Water Chemistry to Various Geothermal Systems in India
Authors: Saxena V. K. 
Published: November 2024

Abstract
Gas and water studies on sixteen geothermal manifestations (34-97°C) from four geothermal provinces of India have been used to evaluate the reservoir temperatures. The pH of deep thermal waters and partial pressures of CO2 gas have been estimated at probable rock-water equilibrium temperatures. Sub-surface temperatures for geothermal manifestations as estimated by gas and silica geothermometers range from 50 to 163°C and show a good correlation.
Unusual Composition from the Cumulate Section of Andaman Ophiolite
Authors: Ray K. K. , Sengupta S. , Van Den Hul H. J. 
Published: November 2024

Abstract
Mafic and acid cumulates from Andaman ophiolite contain hornblende and magnetite as primary cumulus phases. Four samples with higher SiO2range, contain in addition apatite and quartz crystallised from intercumulus liquid. These have lower Ni, Cr and higher total REE abundances than ophiolitic gabbros and plot away from the field of ophiolitic cumulates in the AFM diagram. Strong negative Eu-anomaly is in striking contrast to ophiolitic cumulates.
No volcanic rocks are associated with these cumulates. Volcanic rocks occurring in a different thrust slice are similar to 'transitional' ridge basalts. It is suggested that the cumulates have crystallised from melts more evolved than ridge tholeiites and possibly from melts similar to basaltic andesites of Andaman ophiolite. in a shallow magma chamber.
Genus Worthoceras Adkins from Cretaceous Deposits of Tiruchchirapalli District, Tamil Nadu, India
Authors: Vartak A. V. , Ghare M. A. 
Published: November 2024

Abstract
Paper reports the presence of the genus Worthoceras Adkins from the Utatur Group, Cretaceous deposits of Tiruchchirapalli, Tamil Nadu. The genus is represented by three species, viz., Worthoceras vermiculian, W. gibbosum and Worthoceras sp. aff. W. rochatianum. History and phylogenetic position of the genus is discussed in detail. Authors following Henderson (1973), place the Wortoceros species under the family Scaphitidae and consider the genus Otoscaphites Wright as an evolutionary form in the lineage Eoscaphites-Scophites.
Estimates of Palaeodiameters of the Earth through Geological Time
Authors: Ahmad F. 
Published: November 2024

Abstract
Palaeozoic palaeopoles deduced from palaeomagnetic data and from the distribution of glacial deposits are in accord for some of the south polar positionst confirming that it was in the north-west of Morocco in the Cambrian. In Upper Permian the pole had moved to the south-east of South Africa, almost in the middle of Antarctica in the Pangaea assembly used here. The Cambrian North Pole, was similarly in Antarctica and migrated to the Verkhoyansk region in the Permian.
Palaeontological data show unequivocally that India was not involved in long distance drift and collision with the northern continents, as advocated by plate-tectonics protagonists. Instead, it existed in its present relationships with the other continents since at least the Cambrian, and may be earlier. The 'Indus Suture' concept is not valid and Chinese geologists, on the basis of their work in the area, are emphatic on the point. Pangaea, thus, existed as a large, composite super-continent comprising the entire existing continental crust, and both the poles were located over this landmass.
The pole positions indicated above go to suggest that in the Upper Permian, the Earth, with the North pole near Verkhoyansk and the South Pole south east of South Africa was 55-60% of its present diameter. The Cambrian diameter, measured similarly, was smaller. For other Palaeozoic periods, the diameter can be similarlyestimated reasonably accurately.
This suggests that the Earth is expanding, and it is probable that the rate of expansion has progressively accelerated through time.
Archaean-Proterozoic Boundary in India
Authors: Radhakrishna B. P. , Ramakrishnan M. 
Published: November 2024

Abstract
Greenstone belts in India are predominantly Archaean with minor development in Proterozoic. The important greenstone belts of India, like the Dharwar of South India, Iron-Ore Group of Eastern India and Bailadilla Group of Central India, are of Late Archaean age and show characteristics transitional to Proterozoic. The end of the Archaean is marked by a burst of granitic activity.
Two independent continental blocks-a southern Peninsular Block and a northern Foreland Block are recognised. The Early Proterozoic successions in India are formed in rifted basins fringing these two Archaean cratonic blocks. These Early Proterozoic cover-rocks and the Archaean basement have invariably been deformed together in Middle Proterozoic, pointing to substantial crustal shortening. The narrow continuous fold belts like those of Aravalli, Delhi, and Satpura, mark the sites of the coming together of the different continental blocks to form a single Indian continent as we see today. A comparable situation is that of the Great Lakes Tectonic Zone of Central North America. Geological, geochronological, geochemical, palaeo-magnetic and palaeobiological considerations which help in demarcating the boundary are outlined.
Ideally, in order to more precisely demarcate the stratigraphic boundary, specific rock units have to be identified in the rock succession in each of the regions. Present data is insufficient and the available maps are on too large a scale to permit identification of boundary stratotypes.
Aeromagnetic Evidence of Crustal Structure in the Granulite Terrane of Tamil Nadu-Kerala
Authors: Reddi A. G. B. , Mathew M. P. , Singh Baldau , Naidu P. S. 
Published: November 2024

Abstract
As conventional mapping of near-surface geology has been completed already on a certain scale for most part of the country, the primary objective of the on-going National Aeromagnetic Survey seems to lie in uncovering the structural configurations at depth by producing relief maps at one or more levels within the crustal column, although such maps cannot but be tentative and open to revision in the light of new data.
This exercise has been attempted for the peninsular segment south of 12°N latitude resulting in the production of a map of a relatively shallow magnetic basement. A filtered (low-pass) anomaly map is also presented that apparently reflects a deeper simatic layer and, therefore, the Moho, by implication. The area seems to be composed of a mosaic of independent crustal blocks involved in relative vertical movements. A graben is indicated sub-parallel to the west coast extending into the Gulf of Mannar and possibly beyond into Sri Lanka. The Palghat-TiruchirapalJi region is also downfaulted suggesting a junction of profound structural dislocation between the granulite terrane and the Karnataka craton. An overall increase in crustal thickness towards north and east is also inferred. The gravity rise towards the Tamil Nadu coast (in striking contrast with the uneventful fatI in magnetic values) may have to be explained in terms of lateral changes in crustal and subcrustal parameters rather than in terms of a simile rise of the Moho.
These results should hopefully encourage the generation of subsurface maps of structure even for the rest of the country based on aeromagnetic and other ground geophysical data, thus, ushering in a new chapter of Indian geology in three dimensions.
2.9 b.y. Rb-Sr Age of the Granulite Facies Rocks of Satnur-Halagur and Sivasamudram Areas, Karnataka, South India
Authors: Mahabaleswar B. , Peucat J. J. 
Published: November 2024

Abstract
Preliminary Rh-Sr isotopic studies of the granulites occurring SW of Kabbaldurga were undertaken to verify the possibility of an earlier granulite facies event. The Rb-Sr data obtained gives an imperfect isochron age of 2950 ± 234 m.y. with an initial ratio of 0.7032 ± 22 (MSWD = 52). The age obtained may correspond to subconcomitant protolith-metamorphism age or metamorphism alone. The high error may be due to non-cogenetic nature of the rocks analysed or a small disturbance of the Rb-Sr system during the 2500 m.y. high-grade event. The present study indicates probability of the occurrence of an early granulite facies event prior to 2500 m.y.
Radiolarian Occurrences in Surface Sediments of the Indian Ocean in Relation to Bottom Water Circulation
Authors: Sharma V. , Mahapatra A. K. 
Published: November 2024

Abstract
Occurrences of radiolaria in the surface sediments collected at 22 stations in the Indian Ocean are noted. While some samples contain abundant radiolaria, others show extremely poor concentration, or, are practically devoid of them. A distinct relationship is found between radiolarian abundance and deep water current systems. It is suggested that the occurrence of radiolaria is largely controlled by currents which are responsible for dissolving radiolarian skeletons. The assemblage is dominated by warm-water species and also contains a few cold-water forms. The cold-water species are believed to be transported by the Antarctic Bottom Waters (AABW) to the present area.
Geology and Structure of the High-Grade Rocks from Punalur-Achankovil Sector, South India
Authors: Radhakrishna T. , Mathai John , Yoshida M. 
Published: November 2024

Abstract
The Punalur-Achankovil sector is a southwestern segment of the high-grade granulite terrain of South India. It is characterised by charnockite and garnet-biotite. Quartz-feldspar (GBQF) gneiss with minor occurrences of sillimanite and graphitebearing gneiss and basic granulite. Structurally. The terrain has undergone three phases of intense deformation and metamorphism and a late less intense deformation. The first deformation (D1) has disrupted original depositional layering with development of quartzo-feldspathic bands; the accompanying metamorphism (M1) is represented by granulite facies sillimanite-bearing gneiss and basic granulite. The second deformation (D2) resulted in isoclinal folding and the corresponding metamorphism (M2) produced large neosome now represented by the GBQF gneiss. Lithologies representing the D3-M3 event are the charnockite and minor granite bodies developed under high-grade metamorphic conditions; open to tight" asymmetric folds are characteristic of this deformation. The final deformation (D4) is less penetrative and is characterised by open folds. Structural data from the area do not indicate any major shear zone features nor does the region constitute an intercratonic suture belt as suggested earlier. The topographic expression along Achankovil-Punalur represents only a neotectonic lineament.