bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and Petrography of the Quartz-Magnetite and Associated Rocks of Vemparala Area, Nellore District, Andhra Pradesh
Authors: Sastry A. V. R. , Vaidyanadhan R. 
Published: November 2024

Abstract
In the Nellore and Guntur districts of Andhra Pradesh a series of detached hills composed of interbanded quartz-magnetite rocks, garnetiferous quartzites, pyroxene granulites, hypersthene-magnetitites and ferruginous schists extend for 33 miles from Konijedu in the south to Vemparala in the north. This paper mainly deals with the structure and petrography of the northernmost group of these rocks at Vemparala.
In this area the rocks have been metamorphosed and folded, whose axial plane trace only (FI) can be recognised. These have been folded again (FU) with eastward dipping axial planes trending NNW-SSE accompanied by gabbroic and granitic intrusions. The third folding (FIll), in the nature of a cross-fold, is along axes plunging NNE. There are many faults trending roughly N-S and E-W.
Mapping of the structure of a part of the eastern margin of the Cuddapah Basin between Cumbum and Markapur by the authors has revealed the presence of an earlier fold axis trending NW-SE and plunging due NW and a later cross-fold trending NNE-SSW and plunging due NNE. A study of the region from here eastwards to the Konijedu-Vemparala area, a distance of about 60 miles, has shown that the earlier fold axes (or axial plane traces) vary in trend, but the cross-fold axes show fairly consistent trend and plunge due NNE. It is therefore suggested that this region as a whole must have been affected by one and the same set of tectonic forces during its last stage of deformation.
Application of Quantitative Petrographic Data in Mosaboni Copper Mine, Singhbhum District, Bihar
Authors: Talapatra A. K. 
Published: November 2024

Abstract
Detailed petrographic study of the rocks of the Mosaboni copper mine, Singhbhum district, Bihar, suggests that quantitative petrographic data may be successfully utilised here for locating the lode zones in the lower levels where exploration is going on. In this study the mineralogical compositional variation was drawn in the form of 'isopleth map' prepared with the modal percentage of important mineralogical constituents of all the samples collected from two vertical sections of the Mosaboni mine. The isopleth maps suggest that within the portion of the mine already worked, the mineralogical compositional variation of the country rocks shows close relationship with the lode zone. From the trend of mineralogical variation, it might be possible to extrapolate the position of the lode zone from any mine level to the nearby areas in the same level and at depths. Thus the petrographic data may guide the explorer in the right direction in such a mine.
The Petrology of the Lamprophyres of the Girnar Hills, Kathiawar, India
Authors: Subba Rao S. 
Published: November 2024

Abstract
The lamprophyres are found in the form of altered basic inclusions in the syenites of the Girnar Hills. On the basis of field and petrographic studies, the origin of the lamprophyres has been shown to be due to the reactions of the inclusions of basalt and gabbro with the syenites.
Note on the Blaini Boulder Beds of Tehri Garhwal, Kumaon Himalayas
Authors: Rupke J. 
Published: November 2024

Abstract
The Blaini boulder beds of parts of the N. W. Himalayas have been reappraised on the basis of a few exceptionally clear exposures during a short mapping programme. The identity of these beds is shown to be that of slumped beds with associated turbidity current effects in what probably constituted a phase of rejuvenation of the regional Himalayan basin. Consequently the former theory of Gondwana glaciation in Northern India with all its implications in the field of continental drift and pole wandering is disputed.
Areal Variation of Anorthite Content of Plagioclase Feldspars from the Vajrat Gabbro, Ratnagiri District, Maharashtra State
Authors: Gokhale N. W. , Chavadi V. C. 
Published: November 2024

Abstract
The paper deals with the plagiodases occurring in the gabbro pluton of Vajrat. 133 twinned plagioclase grains from 26 rock samples of these gabbros are studied on the 4-axes universal stage. The anorthite content and the twin laws of these plagiodases have been determined on the lines of Reinhard. Areal variation map is prepared for the anorthite content of the plagioclases, on the lines of Dawson and Whitten. Petrographic studies of the gabbros indicate that the gabbros of the more central parts of the pluton are distinctly fine grained ru. compared to the grain size of those forming the peripheral portion. The areal variation pattern of the anorthite content together with the petrographic characters of the gabbros suggest more than one period of igneous activity in the formation of the Vajrat gabbro pluton.
The Plutonic Concept
Authors: Ray S. 
Published: November 2024

Abstract
Most of the Archaean rocks in India have been commonly referred to as having originated at plutonic or hypometamorphic depths. Data exist to prove that the Archaean crusts were decidedly thin and hotter. Thus, metamorphism in the remote Archaean time took place under lower load pressure around 4-7 kb and under higher temperature around 650°C-750°C. As the crust thickened metamorphism in depth took place under higher pressures and lower temperatures.
The Khondalite tract along the East Coast of India has mineralogical, petrological and structural singularity to prove that it was metamorphosed under the former set of P-T conditions.
This khondalite belt shows a trend of 'facies' variation which is strongly contrasted with the variation in Hietanen's Barrovian or other types. A new 'facies series' and metamorphic' type', viz, 'Khondalite type' is hence proposed to be added to Hietanen's eight 'types' of metamorphism.
Paleocurrent Studies in the South-Eastern Part of Gangpur Series
Authors: Kanungo D. N. , Mahalik N. K. 
Published: November 2024

Abstract
Paleocurrent analysis of the south-eastern part of the Gangpur series, made from cross-bedded structures in the quartzites of Raghunathpalli and Birmitrapur stages, shows that during the deposition of the older Raghunathpalli stage, the currents were flowing in a north-north-east direction and at a later period during the deposition of upper Birmitrapur stage the current direction was predominantly north-north-west.
A new method has been suggested for correction of tectonic tilt of paleocurrent data.
Arsikere Granite-Its Petrography and Mode of Emplacement
Authors: Narayana Das G. R. 
Published: November 2024

Abstract
Arsikere granite, with its porphyritic and aplitic phases, shows sharp contact with the surrounding gneisses but is concordant with its trend (NNW-SSE) only slightly deviating (NW-SE) from the gneisses. Marginal inclusions of gneiss, amphibolite and folded quartzsericite schist occur. Mineralogically, though similar to the enclosing gneiss, the granite consists of two generations of quartz and felspar. Chemically the granite is more acidic than the gneiss indicating an influx of SiO2 and alkalies. The study of the Arsikere granite massif indicates that it is formed in situ, from the pre-existing rock which in the area is the gneiss of the Peninsular gneissic complex, through mobilisation.
Clay Mineralogy and Trace Element Geochemistry of Subathu, Dharmsala and Siwalik Sediments in Himalayan Foothills of Northwest India
Authors: Bhattacharya N. 
Published: November 2024

Abstract
265 analyses from 108 selected samples of Subathu, Dharmsala and Siwalik sediments by X-ray diffraction, emission spectroscopy, flame spectrophotometry and gamma ray spectrography are presented in this report. Dominant clay minerals of the Subathu, Dharmsala and Siwalik sediments are respectively moderately degraded illite and chlorite; degraded illite, vermiculite and expandable mixed-layers; and montmorillonite, kaolinite and highly degraded illite/chlorite. Trace and minor elements in clays are divided into non-detrital diadochic substitutions (B, Ba, Sr, Ga, Sc, Zn, Ge and Pb) and detrital elements as diadochic impurities (Be, P, Mn, Cu, Mo, W, Zr and V). Distribution of Li, Na, K, Rb and Cs and that of U and Th seem to be related primarily to weathering in source areas. It appears that mineralogy and crystal chemistry of clay minerals have dominating influence in selective geochemical partition of trace elements.
Joint Patterns and their Significance to the Tectonic History
Authors: Narayana M. S. , Sastry A. V. R. 
Published: November 2024

Abstract
On the basis of the relative intensity of the tectonic disturbances in the Medivada-Vaddadi area in Visakhapatnam district of Andhra Pradesh, the area is subdivided into two domains, homogeneous and inhomogeneous, for the purpose of the study of joints, The subdivision of this contiguous area into two distinct domains is corroborated by applying the Snedecors F-test for the equality of variances for the variables - strike and dip of the joints and the test for the equality of covariances for the variates - strike and dip taken together.
Only in the inhomogeneous domain there is superposition of the low-angled joint pattern on the pre-existing joint pattern consisting of three sets of joints - J1, J2, J3.
The first order joints J1, J2 and J3 might have probably formed during the folding of the beds, and the second order joints with low dips were formed during the readjustment of stress after the folding, jointing and faulting.
The application of the results of the study of the joints to the mineralised zones in areas of superimposed tectonic deformation is indicated.
Significance of Small-Scale Deformation Structures Around Jawad, Udaipur District, Rajasthan
Authors: Naha K. , Halyburton R. V. 
Published: November 2024

Abstract
Folds of different style and orientation, bent hinges of folds, curved lineations on folded or planar foliation, folds torn to form boudins and tectonic inclusions of diverse shapes, chocolate-tablet boudins, interference patterns like mirror-image type folds, irregular domes-and-basins and eyed folds-all these small-scale structures provide ample evidence for superposed deformations in the Precambrian terrain around Jawad in the Udaipur district, Rajasthan. Variation in the attitude of foliation, axial planes and axes of small folds of different styles and the related lineations finds a rational explanation in the tectonic model drawn from the geometry of directly observable structures.
On Textural Characteristics of the Muth Quartzite of Spiti and Kuti Regions, Central Himalayas
Authors: Dasgupta Pradeep Kumar 
Published: November 2024

Abstract
The upper member of the Muth Quartzite from the Pin valley of Spiti and Kuti valley in Northern Kumaon consists of super-mature quartz arenite with a typical bimodal distribution. Remarkably well rounded coarse grains of sand (-1f to 1f are set in very fine sand to coarse silt fractions (3f to 4f).
The frequency distribution of grain size conforms cIosely to that found in typical deflationary desert flats. An aeolian origin for the upper member of Muth Quartzite is indicated.
Precambrian Geochronology of Peninsular India
Authors: Pichamuthu C. S. 
Published: November 2024

Abstract
Geochronological data for the Precambrian formations of such a large region as Peninsular India are still far too few. However, with the available data, certain broad generalisations can be made regarding their relative ages, correlation, and stratigraphy.
Mysore, Kerala, Singhbhum, and Bundelkhand contain rocks nearly 3000 m.y. old. which probably represent the nuclei around which grew the continental mass of the Peninsula. The Dharwar craton appears to be the most ancient part of the Peninsula. The existing age determinations do not help, however, in determining which is the oldest rock formation in this region.
The Eastern Ghats belt was formerly considered to be about 1600 m.y. old, but it is now known to contain rocks ranging in age from 2100 to 2600 m.y. The base of the Cuddapahs is about 1400 m.y. old, and the Kurnools about 1150 m.y. Southernmost India contains rocks of a wide variety of ages. Some are very ancient being over 3000 m.y. old. There are also evidences of 500 m.y. and 700 m.y. events which have been recognised in Ceylon.
In Rajasthan many formations are now known to be much older than previously thought. The base of the Aravallis appears to be about 2500 m.y. old and the Delhis 1800 m.y. The Bundelkhand and Berach granites are of the same age (2555 ± 55 m.y.). The Banded Gneiss Complex has components varying in age from about 2100 to 950 m.y. The base of the Vindhyans is probably 1400 m.y. old, and the Upper Kaimur Series about 910 m.y. No dates are available for fixing the upper age limit of the Vindhyans. They probably span the Precambrian-Cambrian boundary.
A Note on the Trace Element Contents of Carbonatites of a MBA Dongar and Surrounding Areas, Chhota Udaipur
Authors: Sethna S. F. 
Published: November 2024

Abstract
The note incorporates trace element analyses of carbonatites from Amba Dongar and surrounding areas. Mineralogical study indicates that pyrochlore is the only diagnostic mineral present in some of these rocks. Though the rare earth minerals proper are absent, the analyses reveal a fair concentration of the rare earth elements. It is therefore concluded that these elements are mainly contained in calcite and ankerite. Also, some calcareous rocks of dyke-like nature from Bakhatgarh and Dehi, suspected to be carbonatites, have been analysed. However, their trace element contents do not conclusively prove them to be so.
Petrographic Study of Some Indian Phosphorites
Authors: Krishna Rao N. , Rao G. V. U. 
Published: November 2024

Abstract
This paper incorporates results of textural and mineratogical study of phosphorites from Mussourie and Maldeota in Uttar Pradesh, and Kanpur, Maton and Birmania in Rajasthan. In Uttar Pradesh phosphorites, the phosphatic mineral collophane occurs in pelletal, interstitial and massive form. Different types of pellets - ovulitic, oolitic, encased, nucleated and polynucleated, are encountered. Most of the collophane is isotropic, rarely cryptocrystalline or microcryptocrystalline. Calcite, muscovite-sericite, clay, quartz and chert are the principal gangue associates. In phosphorite from Kanpur collophane lacks pelletal arrangement and occurs in the form of irregular bands in limestone. Maton phosphorites consist of nodules and large pellets of micro- and cryptocrystalline collophane enclosed in a matrix of chert and calcite, while in Birmania collophane occurs both in the form of dispersed pellets and bands in limestone.
Infra-red spectra of pure collophane samples from each of the localities show the presence of structural (OH) and (CO3) groups. This coupled with the chemical analysis shows that the samples from Maldeota and Birmania can be called carbonate-hydroxyl-fluorapatite, while those from Kanpur and Maton fall in the range of fluoiapatite. Calculation of ionic composition of the collophanes shows that C replaces P, further the direct relationship observed between H2O+ and Ca/P+C ratio indicates the possibility of PO«^*(OH)4 substitution. The unit cell dimensions fall in between those of fluorapatite, hydroxylapatite and francolite. Substitution of C for P reduces slightly the average refractive indices.
It is interesting to note that collophane from Maton and Kanpur areas which occur in precambrian formations approach fluorapatite in composition while those from later horizons (Birmania - late Palaeozoic, Mussourie and Maldeota - Mezozoic) are carbonate-hydroxyl-fluorapatites.
Isogon Patterns for Minor Folds and Some Effects of Deformation in the Banded Ferruginous Quartzites from the South Eastern Bababudan Hills, Mysore
Authors: Niyogi R. K. , Baral M. C. 
Published: November 2024

Abstract
Convergent isogon patterns for the minor folds in the Banded Ferruginous Quartzites of southeastern Bababudan Hills reveal that at least some of the bands are flexurally folded, but the thickness of individual bands does not remain constant throughout a fold. Hence these are not ideal parallel folds; and apart from flexure, processes like compression also played a role. Divergent isogons indicate differential compression. In multilayered sequences isogon patterns are more controlled by thickness than composition. Even though the folds are flexural, they are propagated for long distances due to alternate divergence and convergence of isogons. Bands of different compositions respond differently to the deformation. Magnetite is more competent than quartzite. Thickness also controls folding in that thinner the magnetite band the lower is the order of folding shown by it.
Ore Genetic Significance of Geochemical Trends During Progressive Migmatisation Within Part of the Singhbhum Shear Zone, Bihar
Authors: Banerji A. K. , Talapatra A. K. , Sankaran A. V. , Bhattacharyya T. K. 
Published: November 2024

Abstract
Study of the trends of geochemical migration of some major and minor elements during progressive migmatisation within part of the Singhbhum shear zone supports the view that apatite-magnetite, uraninite and copper sulphide deposits and the associated wall rock alterations are related to processes of migmatisation therein. During migmatisation extensive mobilisation of elements took place when Si, Al, Na and small quantities of Ga, U and Zr were introduced into the pre-existing basic metavolcanics within the shear zone, and Fe, Mg, Ca, K, Ti, Mn, P, Ba, Rb, Sr, Li, Ni, Co, Cr, V, Cu, and Y were expelled from these rocks. The addition of the former group of elements brought about transformation of these rocks, into felspathic schists and gneisses (the soda-granites) while the expulsion of the latter group of elements from these rocks and their addition to the migmatising fluids caused progressive changes in the chemical composition of these fluids. At the closing stages of the process these fluids were transformed into mineralising solutions that gave rise to apatite-magnetite, uraninite and copper sulphide deposits and to extensive sericitisation, chloritisation, biotitisation and silicification within the shear zone. The various elements, present in traces, entered the crystal lattices of these minerals, in accordance with their geochemical preferences and in proportion to their concentration in the mineralising solutions. The resulting deposits should be regarded as 'metasomatic hydrothermal'.
Albitized Slates from the Upper Kaladgi (Precambrian) Formations, Lokapur, Bijapur District, Mysore State
Authors: Govjnda Rajulu B. V. , Chandrasekhara Gowda M. J. 
Published: November 2024

Abstract
Detailed studies of the Kaladgi pelites occurring along the contacts of dolerite dykes, near Lokapur reveal interesting metamorphic and metasomatic changes. Due to contact metamorphism the pelities have been metamorphosed into hornfels. They have also been subjected to albitisation and silicification due to metasomatism, as revealed by chemical analyses.
Planktonic Foraminiferal Biostratigraphy of the Early Tertiary of the Rakhi Nala Section Sulaiman Range, West Pakistan
Authors: Samanta Bimal K. 
Published: November 2024

Abstract
Of the four Formations, the Ranikot, the Dunghan, the Ghazij and the Khirthar, constituting the early Tertiary succession exposed in the Rakhi Nala, a river in the Sulaiman Range, West Pakistan, only the upper Dunghan Formation, the lower part of the Ghazij Formation and the upper Khirthar Formation have yielded good planktonic foraminifera. A total of seventy-nine species and subspecies of planktonic foraminifera, including two new species, are identified, The range of stratigraphically significant species perinits recognition of eight planktonic foraminiferal zones in the sequence. Between the fifth and sixth faunal zones there is an interval with reworked Upper Cretaceous planktonic foraminifera in the lower part and rare, indeterminable planktonic foraminifera in the upper. The Rakhi Nala zones are compared and correlated with those established by Bolli in Trinidad. On the basis of the planktonic foraminiferal content, the upper Dunghan Formation is dated as Middle Palaeocene to lower Lower Eocene, the lower part of the Ghazij Formation as middle Lower Eocene and the upper Khirthar Formation as middle Middle Eocene to Upper Eocene in age.
Stratigraphy and Microfauna of Car Nicobar Island Bay of Bengal
Authors: Srinivasan M. S. , Sharma V. 
Published: November 2024

Abstract
The paper gives a complete stratigraphic sequence of Car Nicobar strata for the first time since the work of Schwager. The Sawai Bay formation (consisting of a mudstone member and a limestone member) and the Malacca limestone formation belonging to Archipelago Group are proposed with their type localities defined at Car Nicobar island. Based on the known stratigraphic ranges of planktonic foraminifera, the following three zones are distinguished in ascending order: (1) Globorotalia tumida flexuosa zone, (2) Globigerina nepenthes zone, and (3) Globorotalia multicamerata-Pulleniatina obliqueloculata (s.s.) zone. An Early to Middle Pliocene age is assigned to Schwager's Car Nicobar foraminifera based on planktonic foraminiferal evidence. A comparison of the zonation of Car Nicobar island with zones proposed by Banner and Blow shows that Banner and Blows' sequence is most applicable, and is used in the present work as a basis for comparison.
Petro-Mineralogical Variation of Two Vindhyan Sections Around Sagar (M.P.), India
Authors: Babu S. K. , Durge M. V. 
Published: November 2024

Abstract
The petromineralogical variations in the Rewa Series of the Proterozoic Vindhyan quartzite, have been studied by the authors, in two Sections from Ranipura and Garhpera, Sagar District, Madhya Pradesh. On the basis of various mineralogical and petrographic parameters, the two sections have been divided into three zones at Ranipura and the section at Garhpera into two zones vertically. The boundaries vary slightly between the two sections. When a correlation is attempted between the two sections, a lateral variation in between the demarcated zones is seen.
Petrology of the Leptynites and Garnetiferous Granite-Gneisses Around Garbham, Srikakulam District, Andhra Pradesh
Authors: Bhattacharyya C. 
Published: November 2024

Abstract
Petrography, mineralogy and chemistry of leptynites and garnetiferous granitegneisses of Garbham area have been described. On the basis of texture, structure and mineral assemblage, the leptynites have been classified mainly into three types A, B and C, all of which have been formed by the granulite-facies metamorphism of sediments of appropriate compositions. A fourth type of leptynite has been shown to have formed by migmatisation of khondalite; with increasing migmatisation-granitisation, this is locally converted into one-feldspar (Kvfeklspar) garnetiferous granite-gneiss. One-feldspar garnetiferous granite-gneiss has been locally formed by the granitisation of khondalite and quartzite. Two-feldspar garnetiferous granite-gneisses are predominant and have evolved by the granulite-facies metamorphism of sediments, possibly shale and/or greywackes, followed by granitisation in the form of K-feldspathisation. Two-feldspar garnetiferous granite-gneisses are suggested to be essentially the variants of acid charnockites. Both the acid charnockites and garnetiferous granite-gneisses suffered K-feldspathisation, the latter having been also locally derived by K-feldspathisat ion of acid charnockite.