bluuebunny/crossref_metadata_2025 huggingface dataset:
Tectonics of the Cuddapah Basin
Authors: Narayanaswami S.
Published: November 2024

The Cuddapah Basin in Andhra Pradesh is a remarkable tectonic and orogenic belt of the unfossiliferous Precambrian rocks of Peninsular India. The paper reviews the stratigraphy and structure of the rocks of the Cuddapah System and Kurnool Series as originally proposed by King and gives the author's conclusions on the detailed structure and tectonics of the Basin. A north-plunging low-amplitude asymmetrical synclinorium having a gently dipping western limb and intensely folded, overfolded and thrusted eastern limb is the major structural element. This is further complicated by a major domal upwarp across the middle of the basin marked by monocjinal flexures of the Kurnool strata in Gani Kalawa area; culminations and depressions at Jammalamadugu, Giddaluru and Srisailam plateau; Eshwarakupam dome of the lower Cuddapahs in the northern part of the Nallamalai hills; and granite domes of Vinukonda area in the north-east extremity.

The relation of the structural elements to the localization of mineral deposits in the Cuddapah Basin is discussed and the necessity for their precise interpretation for exploring the depth extension of the ore mineralization is stressed. The author recommends further detailed structural mapping, especially in the eastern half of the basin, for solving the unsolved problems in the Cuddapah stratigraphy and structure.
Pyroxene-Quartz-Magnetite Rocks from Satnur-Halaguru Area, Mysore State
Authors: Devaraju T. C. , Sadashivaiah M. S.
Published: November 2024

The pyroxene-quartz-magnetite rocks occurring in association with the charnockites and other rocks of the Satnur-Halaguru area, which were regarded by many of the early officers of the Mysore Geological Department as members belonging to charnockite series have been reinvestigated. The investigation has brought to light the occurrence in these rocks, of iron-rich minerals like, ferrohypersthene, eulite, hedenbergite, ferroactinolite, iron-rich garnet and the unusual occurrence of pyroxmangite and orthoclase, It is suggested from a detailed study of the field relation, petrology, mineralogy and petrochemistry that the pyroxene-quartz- magnetite rocks form a separate entity, representing metamorphosed iron-rich sediments, which except for their formation under similar metamorphic conditions namely, pyroxene granulite facies, have no relation whatsoever with the intimately associated charnockites of the area.
Reconsideration of Some Problems in the Archaean Complex of Mysore
Authors: Radhakrishna B. P.
Published: November 2024

The stratigraphy and age relationships of certain rock formations of Mysore are reviewed and the following points made out. (1) The Peninsular Gneisses as a whole are not intrusive into Dharwars. (2) The existing three fold classification of Dharwars has not taken into consideration the Dharwarian succession in Goa and north Mysore and requires to be revised. The Dharwar sediments were deposited in a narrow geosynclinal trough and did not extend very much beyond their present limits. (3) The name Champion Gneiss should be used only as a local name to designate the micaceous gneisses bordering the Kolar schists and not extended to other formations. (4) The charnockite terrain represents the lower most section of the Archaeans. The Dharwars occupy stratigraphically a higher position than the deep seated charnockites. (5) Basic dykes cutting across the gneisses and schists are pre Cuddapah in age. (6) The term Dharwar should be restricted only as a local name to the schistose rocks of Mysore. The crystalline schists of other regions may represent only a portion of Dharwar or be entirely different.
Geology of Devidhura Area, Almora, U.P.
Authors: Misra R. C. , Sharma R. P.
Published: November 2024

The area around the village Devidhura (79°52'22" : 29°25'30") covering about 250 square miles forms the subject matter of the present study. Two major tectonic units-the Almora nappe and the Krol nappe-separated by the Ladhiya Thrust can be recognized in the area. Crystallines corresponding to the Almora nappe have been thrusted over the sedimentary quartzites (resembling Nagthats) of the Krol nappe.
Summary of the Structural History of the Pre-Delhi Rocks around Sangat, Udaipur District, Central Rajastfian
Authors: Naha K. , Chaudhuri A. K. , Bhattacharya A. C.
Published: November 2024

The metamorphic and migmatitic rocks comprising the Banded Gneissic Complex, the Aravallis and the Raialos around Sangat (25° O5': 73° 45'), central Rajasthan, maintain a structural unity with no decipherable unconformity within them. The rocks have been involved in two generations of folding with the earlier set dominant in the eastern part. The early folds are isoclinal and reclined, with their axial planes dipping and fold axes plunging W to WNW. On these is superimposed a set of open, upright, NNE-trending folds resulting in a dispersal of the earlier axial orientation near Sangat. Further west, with increase in the intensity of the second deformation, the later folds become isoclinal, the earlier axial planes are rotated to vertical attitude, and the traces of the earlier folds are lost except for occasional sharply bent reclined fold hinges. Because of the diverse orientation of the foliation surfaces already folded by the first movement, the later fold axes also show a great variation in plunge.

Disharmonic folding, curving foliation around the fold hinges, absence of planar surfaces oblique to the folded foliation, and folds following the competency rule prove that both the sets of folds were formed essentially by flexural slip. Early mullions unrollable on later axes also point to a flexural slip origin for the later folds.
Juras-Cretaceous Stratigraphy and Sedimentation Around Jabalpur, M.P., and Their Paleogeographic Implications
Authors: Chanda S. K.
Published: November 2024

The Lameta and jabalpur Groups, which are redefined and described in their type area, are separated by an unconformity at Dalpatpur. The unconformity grades to a paraeonformity of much lesser magnitude in the vicinity of jabalpur town. Local paleocurrents in the type area, directions of truncations and relative rates of change of stratigraphic hiatus across the unconformities and configuration of pre-trappean surface appear to be mutually related to each other. All these features suggest the existence of a westerly slope corresponding to Krishnan's' Narmada Trough' since the Jurassic period. While the Jabalpurs are the products of a typical flood plain in an interior basin, the Lametas appear to represent shallow marine sediments on the stable shelf. The terrigenous constituents of the Jabalpur Group are mainly derived from the pelitic metasediments in the east. The terrigenous constituents of the Lametas, on the other hand, represent a mixed assemblage of detritus derived from the local jabalpurs and pelitic metasediments. Diagenesis of the ]abalpur sediments mainly involves endogenic reconstitution. Exogenic cements in the lametas are mainly derived from the overlying Deccan Trap.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
A Note on the Mode of Eruption of the Deccan Trap Lavas with Special Reference to Kutch
Authors: Biswas S. K. , Deshpande S. V.
Published: November 2024

On the basis of detailed field mapping and available gravity data, certain conclusions regarding the mode of eruption of Deccan trap lavas are drawn.

In Kutch, the Deccan trap formation outcrops along the western and southern periphery of the mainland. The trap flows which rest disconformably over the Mesozoic rocks, are also seen to cover the eroded Mesozoic structures. They thin out towards the central and northern hills of folded Mesozoic rocks. Whereas basic dykes and sills are concentrated in these fold zones, a number of plugs occur close to the Deccan trap outcrops. Igneous plugs, seem to be related more to the trap than the tectonism. The dykes and sills are probably syntectonic whereas the trap flows are post-tectonic with respect to the Mesozoic folding. Three volcanic cone-like structures have also been discovered at the fringe of the Deccan trap outcrop, near Jada and Wehar. It is therefore, concluded that the trap lavas in Kutch have mainly erupted from Hawaiian type shield volcanoes. The lavas erupted from such volcanic centres periodically and flowed to the south down the paleoslope towards the main volcanic field.

Positive gravity anomalies are noted around well known plugs of Saurashtra which have long been considered as the eruptive centres along tectonic lines. Similar anomalies which could also be interpreted as the subsurface volcanic plugs or cones, are seen within the major rift zones of Western India like Cambay and Narmada grabens and faulted west coast. Thus, the Deccan trap lavas of Peninsular India too might have erupted from Hawaiian type shield volcanoes situated along the major fracture zones.
A System of Classification and Nomenclature of Granitic Rocks
Authors: Viswanathan S.
Published: November 2024

The paper proposes a system of classification and comprehensive kinematic-descriptive-genetic nomenclature of granitic rocks based on results of detailed petrographic studies of samples from the southern margin of the Canadian shield. Unlike the schemes currently in use that emphasise only the relative proportions of quartz, potassium-feldspar and plagioclase, the proposed classification recognizes the significance of several additional parameters: (a) biotite/amphibole ratios, (b) non-opaque calcic trace mineral contents (e.g., sphene, apatite, epidote), and (c) plagioclase compositions. Using these parameters, a new modal Quartz-Alkali feldspar-Plagioclase ternary diagram is presented. An example of a comprehensive kinematic-descriptive-genetic nomenclature of granitic rocks, derived from the proposed system is: 'late-kinematic, pink, slightly porphyritic, weakly foliated, medium- to coarse-grained, chloritized, muscovite-biotite-albite (An6)-microcline leucogranitic anatexite', The proposed system should prove useful in mineral exploration programmes aimed at locating rare-mineralic granitic bodies, and in inter-continental petrographic comparisons.
Wrench-Faulting and its Relationship to the Structure of the Southern Margin of the Sub-Himalayan Belt Around Ramnagar, Uttar Pradesh
Authors: Rao Y. S. N. , Rahman A. A. , Rao D. P.
Published: November 2024

On the basis of detailed field studies. the authors postulate that there is a wrenchfault on either side of the Kosi River, and that both of them pass into thrusts along the southern margin of the Sub-Himalayan belt.
Copper Mineralisation in the Ultrabasic Complex of Nuggihalll, Hassan District, Mysore State
Authors: Radhakrishna B. P. , Achuta Pandit S. , Prabhakar K. T.
Published: November 2024

The paper records an interesting occurrence of chalcopyrite and other sulphide minerals associated with the ultrabasic complex of Nuggihalli. Exploratory work carried out in the area for copper is described. The need for a closer observation of ultramafic and related rocks as potential sources for copper in the country is stressed.
The Geomorphology of the Vindhyan Plateau, Central India
Authors: Choubey V. D.
Published: November 2024

In Central India, the rocks belong to two groups, Vindhyans of lower Palaeozoic or late Precambrian age and the Deccan Trap lava flows of Cretaceous-Eocene age. The study of the geomorphology has led to the conclusion that after the deposition of the Vindhyans in a shallow inland sea, the country was uplifted. peneplaned and subsequently greatly dissected by a later cycle of erosion. Much later, the old and mature Vindhyan topography was buried beneath the lava flows and the associated sediments.

As denudation proceeded, erosion removed the lavas and sediments in places, laying bare the old land surface beneath. Thus the former topography of mature hills and flat valleys has been resurrected. With the partial removal of the lava flows: the remnants of the Cretaceous peneplain exist at an elevation of about 1950ft. At a lower surface of 1450 ft.,-the lavas rest on a planation surface developed particularly on the weaker rocks in a much more widespread younger cycle. The subvolcanic surface is reconstructed in detail and shows that the current drainage is superimposed on the pre-Deccan trap topography; and after the removal of the lavas, the rivers are tending to revert to the pre-Deccan trap drainage system. The current valley cycle. where the basalts have been removed, is largely coincident with the lower erosion surface, but it is now coming under attack from a newer cycle working up from Narmada and Ganges rivers.
Mineralogy and Petrochemistry of the Differentiated Sill Around Gwalior City, Madhya Pradesh
Authors: Varadarajan S. , Verma V. K.
Published: November 2024

Mineralogical and petrochemical characteristics of the differentiated sill, occurring at the highest horizon of Morar Stage, Gwalior System (Cuddapah age), around the city of Gwalior, Madhya Pradesh, are detailed. Petrographically the sill, composed of dolerite which is sparsly porphyritic, tends to be quartz dolerite in higher levels. The occurrence of micropegmatitic texture is proportional to the amount of hornblende present in the rock. Chemical nature of the chilled margin reveals that the undifferentiated magma was tholeiitic. Differentiation in the sill is of limited extent and is considered to be the result of the combined processes of fractional crystallisation, crystal settling and mild convectional currents.
Mineralogical Studies on the Bauxites from Shevaroy Hills, Tamilnadu State
Authors: Krishna Rao G. , Borreswara Rao C. , Syam Sundar Y.
Published: November 2024

Bauxites of Shevaroy hills were analysed for their mineralogical composition adopting X-ray and differential thermal analyses, heavy mineral and microscopic studies. Gibbsite and goethite are the ubiquitous and major constituents while boehmite, hematite, lepidocrocite, kaolinite, halloysite and quartz are present in minor amounts in certain samples only. There is a variation in the abundance of these minerals with the grain size of the bauxite. Magnetite, ilmenite, zircon, rutile and garnets are the heavy minerals present.
Geology of Bhotang Sulphide Deposit, Rangpo, Sikkim
Authors: Mukherjee N. K. , Dhruva Rao B. K.
Published: November 2024

The Bhotang sulphide deposit, situated near the border town of Rangpo, Sikkim was explored in detail during 1957-59. The copper-lead-zinc lode is exposed in a hill scarp over a strike length of about 400 m. with a strike of N 50°E and a dip of 65°SE. The lode is folded into a sinistral drag fold plunging ENE and is faulted along the anti-clinal axis. The ore body shows pronounced zoning along strike and across the Width. It has a strong pitch of about 50° towards south. The pitch and zoning of the ore body and the faults in the area have a significant bearing on the planning of development and exploitation of the deposit.

The ore body has been proved over a vertical extent of 275 m and a strike length of 200 m in the lower levels; and because of erosion in upper horizons, the strike length is gradually reduced to 90 m. The ore body has an average width of 5 m. The drives in different mine development levels indicate a width of about 1.5 m with a total copper-lead-zinc content of 4.90%.
Dadikar Granite: A Study on a Precambrian Intrusive Body in Relation to Structural Environment in North-Eastern Rajasthan
Authors: Gangopadhyay P. K. , Das D.
Published: November 2024

The Precambrian Delhi group of rocks in north-eastern Rajasthan is associated with a few granite bodies. Among these the Dadikar granite near Alwar city is intrusive into the Delhi metasediments. Both the granite and the Delhi rocks are deformed and recrystallised under the common plan. The Dadikar granite had been emplaced within an overall domal structural framework of the Delhi rocks. Any radiogenic age determination of this granite must be interpreted in the light of the field relationships between the granite and country rock.
The Mode of Occurrence, Petrography, Metamorphism and Origin of Amphibolites of Devgad Baria Panchmahals District, Gujarat State
Authors: Narayana B. L.
Published: November 2024

Amphibolites occur towards south and south-east of Devgad Baria town in the Panchmahals district of Gujarat State, in the form of disconnected bands showing concordant relationship with the rocks of the Banded gneissic complex and passing into striped varieties, and also as caught-up patches in the granitic intrusive bodies. Mineralogically, the former type is a quartz and plagioclase bearing amphibolite, while the latter is only plagioclase-bearing.

The quartz-amphibolites are shown to be para-amphibolites on the basis of their intimate association with the impure calcareous metamorphosed sedimentary rocks, lack of relict igneous textures, absence of sphene and plagioclase, high modal percentage of quartz, and low weight percentage of TiO2 and Al2O3 showing a near concordance with the alumina content of marbles of the area. On the other hand, the plagioclase-amphibolites show, in addition to the disconnected sill-like form, relic sub-ophitic texture, high proportion of sphene and high weight percentage of TiO2 and Al2O3 indicating their primary igneous nature.
Mineralogy of the Fuller's Earth of Rajasthan, India
Authors: Singh Indra Bir
Published: November 2024

The paper incorporates the results of grain size and mineralogical investigations carried out on the clays of the Eocene Fuller's earth formation, collected from various localities in Rajasthan. The major clay mineral is palygorskite-attapulgite, The heavy mineral assemblage suggests a metamorphic provenance. The depositional environment of this Fuller's earth formation seems to be in alkaline, hypersaline coastal lagoons.
Detrital Radiolarian Cherts in the Subsurface Murree Formation of Suruin-Mastgarh Anticline, Jammu & Kashmir State
Authors: Khan K. N. , Raju A. T. R.
Published: November 2024

Detrital ferruginous chert rock fragments containing many radiolaria have been observed from one of the lithic arenite core sample of the Murree formation in a deep exploration well drilled on Suruin-Mastgarh anticline near Jammu. The age of these radiolarian cherts may range from Jurassic to Eocene. Presence of such reworked radiolaria in the Murree sediments indicates uplift of the main Himalaya providing partially material for the Murree sediments.
A Review of Geochemical Studies on Some Precambrian Plutonic Complexes of India
Authors: Sankaran A. V.
Published: November 2024

The important results of the application of trace element geochemistry to petrogenetic problems of the Indian Precambrian are reviewed. Such studies have gained importance only recently. Except for two major terrains comprising the Singhbhum granite in Eastern India and the Peninsular gneisses in Southern India, numerous rock complexes in other terrains have not been investigated in detail. The few available trace element data have provided insights into the emplacemental history of the Singhbhum and Soda granites and the associated mineralisation, and have also contributed to a better understanding of the nature of the Peninsular gneisses and some of the granites occurring within. The available data suggest a crustal heterogeneity in the Indian shield with respect to the granitophile elements.
Peninsular Gneissic Complex of the Dharwar Craton - A Suggested Model for its Evolution
Authors: Radhakrishna B. P.
Published: November 2024

The relationship between the gneisses and the greenstone belts of the Dharwar 'Craton is reviewed. Arguments for and against considering the gneisses as forming the basement, are presented and the evidences critically evaluated. Stages in the evolution of the craton are traced. The suggested model envisages the recognition of an older greenstone sequence, largely mafic and ultramafic in character followed by a major differentiation episode in the earth's upper mantle giving rise to a tonalite magma. The bulk of the gneisses forming the Peninsular gneissic complex is assigned to this major event which has not been repeated subsequently. The variations shown by the Peninsular gneisses are indicated to be the result of intimate mixing and interaction of the tonalite magma with the pre-existing mafic and ultramafic lavas and associated sediments. The banding and migmatitic character of the Peninsular gneisses is ascribed to plastic flow in response to relatively small directed stresses.

The suggestion is made that the greenstone belts of the Dharwar craton be split into two major stratigraphic units - an older, composed of mafic and ultramafic rocks of distinct chemical character, and a younger geosynclinal pile with a lower volcanic phase and an upper well-developed sedimentary phase. While the gneisses show an intrusive relationship with the older group, they form the basement for the younger group of lavas and sediments deposited in long linear basins. The suggested model explains a large number of related facts, reconciles the different views, and takes into account the prevailing conceptions of the evolution of the early crust in other parts of the world.
Geochemical Studies of the Precambrian of India: Suggestions for Future Research Work
Authors: Viswanathan S. , Radhakrishna B. P.
Published: November 2024

A critical evaluation of the scope, nature, and results of the geochemical researches so far conducted on the Precambrian of India, when viewed against the background of contemporary global trends, reveals that India lags very much behind countries like Canada, the U.S.A., South Africa, and Australia in this important discipline. To remedy, and even reverse this rather unfortunate situation, the paper proposes some major research projects aimed at elucidating (I) the geochronological evolution of the Indian Precambrian; (2) geochemical affinities and evolution of Early Precambrian volcanic-plutonic complexes; (3) nature of the Indian protocrust; (4) evolution of Iron formations and related chemical sedimentary rocks; (5) bio-geochemistry of the Indian Precambrian; (6) geochemical facies of granitic complexes; (7) Precambrian ore genesis and metallogeny in India; (8) evolution of Precambrian carbonatite complexes; (9) episodes of Precambrian volcanism and plutonism; (10) nature of 'cratonization' in Peninsular India; (11) core-mantle-crust differentiation in the Indian sub-continent; and (12) plate-tectonic regimes in the Precambrian of India, and related metallogenic provinces.

As fundamental geochemical researches on the Indian Precambrian are extremely relevant to India's planning for socio-economic uplift, because the results can be applied to projects aimed at locating new ore deposits, the paper emphasises that unless the Government of India sets up expeditiously a National Institute of Precambrian Geochemistry, it would be impossible for India to plan meaningful mineral exploration programmes in the future, and to catch up with the tremendous advances made in the western world. The structure of such an institute is outlined in Table I of the paper.
Rb-Sr Age Determinations for the Mount Abu Granite and Related Rocks of Gujarat
Authors: Crawford A. R.
Published: November 2024

The mount Abu Granite of south-western Rajasthan and related 'Erinpura type' granites in Gujarat give Rb-Sr total rock ages of about 735 m.y. They are therefore of the same age as the Malani Igneous Suite of western and south-western Rajasthan and not older as previously believed. Though possibly updated by re-heating related to emplacement of that Suite, it seems more probable that the two were emplaced at about the same time. This could have taken place in a tectonic environment created by sinistral shear of what are now northern and southern Peninsular India along the Narmada-Son lineament, with bending of the southern end of a rectilinear Aravalli orogenic belt by major fault drag.
A Petrological Study of Charnockites and Associated Rocks East of Chipurupalle, Srikakulam District, Andhra Pradesh
Authors: Perumal N. V. A. S.
Published: November 2024

Geological mapping of a 300 sq km area forming part of the Eastern Ghats, east of Chipurupalle, supplemented by modal analyses, optical petrographic data, and chemical analyses of seven whole-rock samples and a garnet, show that (1) basic charnockites of the area represent igneous rocks of noritic composition metamorphosed to granulite facies, and (2) some rocks of the area that resemble intermediate charnockites are metamorphosed hybrid rocks derived from assimilative reaction between basic magma and pelitic sedimentary rocks.