bluuebunny/crossref_metadata_2025 huggingface dataset:
Mineralogy of Saurashtra Miliolites
Authors: Baskaran M. , Somayajulu R. L. K.
Published: November 2024

The results of CaCO3, carbonate minerals and quartz measurements on 114 miliolites (some of which are dated) and of sedimentatogical and clay mineral studies on select (10-20) samples are reported and discussed.

The miliolite deposits are predominantIy calcite (CaCO3 range = 50.2 to 100 %, mean 86.8 %) with aragonite and quartz as minor components. None of the measured parameters show any trend/pattern between coast and inland which, coupled with field observations indicate that long distance (< 100 Km) eolian transport was unlikely.

Despite the fact that miliolites rest on Deccan trap basalts and several local and Narbada and Tapti river sediments as well as the near coastal sediments of Saurashtra are enriched in clay mineral smectite, the miliolite clays show the dominance of illite which is principally generated by weathering of granites and brought by the Indus river. This observation implies that the processes responsible far bringing Indus clays to Saurashtra region when the miliolites were formed (60 Kyr - 200Kyr) are not operative in recent times.
Microstructural Studies and Distribution of Mineral Matter in the Macroscopic Ingredients of Coal, Jharia Coalfield, India : An Appraisal of SEM Study
Authors: Singh Mahendra P. , Singh R. M. , Chandra D.
Published: November 2024

Scanning Electron Micrography of the Jharia Coals has been attempted with a view to decipher the enigmatic microstructural features and diversities in distribution of mineral matter in the banded constituents and coal. A wide variation has been observed in the distribution of mineral matter in coal lithotypes. The mineral matter is most abundant in durain; abundant in c1arain and dull clarain, less abundant in bright clarain and vitrain; and rare in fusain. The order of abundance of the mineral matter may be put as; Durain > Dull Clarain > Clarain > Bright Clarain > Vitrain > Fusain.

The microstructural relation of mineral. matter with coaly substances reveals that in durain and elarain, mineral matter is associated as massive impregnation, superficial infilling of micropores and filling of cavities. In vitrain, this occurs mainly iS superficial inlilling of pores, superficial mountings, and in and around cavities. In c1arain mineral matter is mainly confined to dull bands, while bright bands contain sporadic mineral matter. Fusain is almost devoid of inorganic contamination. At places, however, mineral matter is observed filling the cavities of cell fibres and cell lumina.
Sulphide are Mineralisation in Archaean Volcanogene-Sedimentary Ensemble of Ganacharpura, Kolar Greenstone Belt, Dharwar Craton, India
Authors: Vasudev V. N. , Mukherjee Ananda Deb
Published: November 2024

Stratiform pyrrhotitic sulphide ores occur at Ganacharpura which forms a part of mafic volcanic and volcano-sedimentary terrain of the Archaean Kolar greenstone belt. The ores are interbanded with graphite-quartz-sericite schist and are metamorphosed and deformed along with the associated rock types of the area. Dominant ore mineral is pyrrhotite while chalcopyrite, pyrite, sphalerite, galena, magnetite and mackinawite are present in subordinate amounts. The mineral chemistry of the co-existing sulphide phases indicate equilibration at 587°C and 4.98 Kbar total pressure. The fugacities of sulphur and oxygen, reflected in various sulphide assemblages varied considerably, but the fluid composition during metamorphism was essentially internally controlled instead of being externally imposed. The co-existing pyrrhotite, pyrite and magnetite indicate log fs2= -2.4 and log fo2= -17.8 during culmination of metamorphism. It is suggested that the ores are of volcano-sedimentary type and are later modified by mobilisation/remobilisation during diastrophism. The arc-forming metals and sulphur have probably been derived from volcanic exhalations.
Anorthosites and Associated Rocks of Nellore-Gudur, South India
Authors: Kanungo D. N. , Chetty T. R. K. , Mallikarjuna Rao J.
Published: November 2024

Structural, petrographic and geochemical characters of several anorthosite bodies exposed over a length of eight km in the eastern margin of India are presented. From the asymmetry of parasitic folds and cleavage/bedding relationship in the host rocks, it is concluded that these were emplaced into anticlinal cores of isoclinally folded Precambrian schistose formations.

Textural variation from centre to border, mafic enrichment towards the margins. alignment of linear structures combined with steeply dipping foliation of arcuate nature parallelling the boundaries. suggest that anorthositic bodies are plug-shaped and viscous magmatic fluid moved vertically upwards. The progressive variation in mineralogy. grain-size and some of the major oxides is attributed to flow differentiation.
Decisive Controls in the Formation of the East Coast Bauxite Deposits of India
Authors: Ramam P. K.
Published: November 2024

The formation of lateritic bauxite deposits is, by and large, governed by the cumulative effect of several controls. Salient amongst them are: (i) favourable source rock, (ii) effective porosity, (iii) high rainfall, (iv) good drainage, (v) tropical climate, (vi) low to moderate topographic relief, (vi i) prolonged stability, and (viii) presence of vegetation. Despite a general consensus on these causative factors to promote bauxitisation, the decisive controls, still remain to be discerned. A synthesis attempted from this angle in respect of the East Coast Bauxite (EeB) deposits of India has brought to focus the effective permeability of the source rock and a congenial geomorphic base, preferably unidirectional, of low to moderate slope angles (3° to 15°) as the decisive controls in their formation. These, in turn, are dependent on the structural history of the terrain.
Genesis of Two Zoned Pegmatites of the Bihar Mica Belt: A Fluid Inclusion Study
Authors: Santosh M.
Published: November 2024

Two pegmatites, namely, Bandarcbua and Kharonia, show ideal mineralogical zoning with a massive quartz core surrounded by a muscovite plagioclase-perthite quartz and muscovite-quartz zone. Aqueous two phase inclusions with 40% vapour and three phase inclusions with C02(liquid)+CO2 (gas)+H20(liquid) occur as primary inclusions in quartz from the feldspathic zone. Aqueous three phase inclusions with NaCl daughter mineral coexisting with gaseous inclusions with 60-80% vapour occur as pseudosecondary inclusions in quartz from the feldspathic zone and as primary inclusions in quartz from the muscovite-quartz zone. Quartz from migmatitic gneisses show the common occurrenee of monophase carbonic inclusions. Heating-freezing data assign CO2 densities of 0.81-0.90 g/cm3 for the peak metamorphic fluids which were entrapped at 4.2 Kb pressure at a temperature of 680°C. The feldspathic zone crystallized from moderate density (0.6 g/cm3) and salinity (10 wt, % NaCI) fluids. Coexisting H20 and CO2-H20 inclusions record a temperature of 630°C and a pressure of 2.4 Kb for the equilibration of the feldspathic zone. Subsequent adiabatic decompression resulted in the boiling of fluids with enhanced density (1.O g/cm3) and salinity (32 wt, % NaCl). Boiling, which precipitated bulk of the mineralization, occurred at temperatures of 360°C to 320°C and at pressures of 110-90 bars, corresponding to 1100-850 metres depth. The fluid characters suggest a probable relationship between regional metamorphism and the genesis of the mineralized pegmatites of the Bihar mica belt.
Mineral Chemistry of the Silicate Mineral Phases of Banded Iron-Formation of High-Grade Region, Karnataka
Authors: Mahabaleswar B.
Published: November 2024

Analytical data on the silicate mineral phases, namely, orthopyroxene, clinopyroxene, lamellar pyroxene, pyroxenoid, gamet, amphibole and biotite of ironformation from high-grade region, Karnataka are presented. It is inferred that Opx and Cpx of the iron-formation are ferro-hypersthene and ferro-augite respectively, whereas the pyroxenoid is a pyroxferroite. Garnets belong to pyralspite series. Amphiboles are represented by grunerite, edenite and ferroan pargasitic hornblende. Lamellar pyroxenes are represented by clinopyroxene and orthopyroxene containing lamellae which are Ca-poor and Ca-rich respectively. The lamellar nature of the pyroxene appears to be related to silica activity, P-T and oxygen fugacity. Orthopyroxene and garnet are rich in Mn content, which may be due to bulk composition of the host rock and oxygen fugacity. Pressure and Temperature estimates give values of 7 to 8 kbars and 600° to 650°C.
Banded Iron-Formation and Associated Manganiferous Horizons of the Sargur Supracrustals, Southern Karnataka
Authors: Janardhan A. S. , Shadakshara Swamy N. , Capdevila R.
Published: November 2024

High-grade Archaean Sargur supracrustals are made up of quartzites, pelites, carbonates, BIF and manganiferous horizons and have been metamorphosed to upper amphibolite facies. The BIF and manganiferous horizons form thin but persistent bands. Iron-manganese-carbonate association is characteristic. Ten samples of BIF and spessartine-rich manganiferous horizons were analysed for major, trace and rare earth elements. Low trace and REB abundances characteristic of these bands agree well with the data of Archaean iron-formations elsewhere. Chemistry of Sargur BIF is distinctly different from that of the Algoma and Superior types. The positive Eu anamoly shown by the iron-formation indicates oxygenic conditions. The low content of some trace elements indicates shallow water environment of deposition. The REE concentrations of manganiferous-horizons are relatively higher than that of the BIF with anomalous behaviour of Ce and Eu. The present data show that the iron and manganese separation had taken place even in the Early Archaean.
Depositional Environments and Tectonic Settings of the Cherty Iron-Formations of the Canadian Shield
Authors: Dimroth Erich
Published: November 2024

Two types of cherty iron-formations of the Canadian Shield are distinguished by their environmental and tectonic setting. Platform iron-formations form major stratigraphic units, hundreds of meters thick, and continuous for hundreds of kilometers, in some, but not ~[l all, Early Proterozoic geosynclines. Their sedimentary textures and structures indicate deposition in shelf environments ranging from the peritidal zone to well below wave base. They occur at the top of platform sequences and are overlain by black shales and turbidites.

Pelagic iron-formations generally form small units, rarely over 10 m thick and rarely continuous for over 10 km. They are intercalated between submarine volcanic rocks, between black shale, or between siliciclastic or volcaniclastic turbidites. Gradations between pelagic iron-formations and turbidites prove that the pelagic iron-format ions were deposited by settling from dilute suspensions.

Archean supracrustal sequences contain only pelagic iron-formations, but both types and their transitions occur in some Early Proterozoic geosynclines. These transitions prove that both types are genetically related.
Determination of Manganese in Pyrolusites by Neutron Activation Analysis Using Low Flux 241Am-Be Neutron Source
Authors: Batra R. J. , Garg A. N.
Published: November 2024

A neutron activation analysis method based on thermal neutron irradiation from 241Am-Be source is suggested for the determination of Mn in pyrolusites. The method uses 55Mn (n, γ) 56Mn reaction and counting of 0.847 MeV γ-rays on NaI (Tl) detector coupled with single channel analyzer. The method has been employed for the analysis of pyrolusites and results were found in good agreement with those from conventional chemical methods. The method is fast, non-destructive and economic and can be used for the determination of Mn in its ores.
Game Theory Analysis of a Groundwater Contamination Dispute
Authors: Dagnino Aldo , Hipel Keith W. , Fraser Niall M.
Published: November 2024

Environmental disputes arise due to opposing views of various groups about their environmental concerns and their economic or developmental interests. Bargaining constitutes a very effective mechanism to resolve environmental disputes and to reach a compromise solution among decision makers. A new game theoretic model for analyzing bargaining situations in which more than two decision makers are involved is presented in this paper. The model is referred to as the Cooperative Conflict Analysis System (CCAS) and is based on concepts from conflict analysis and bargaining theory. To demonstrate how the model can be effectively used in practice, it is applied to a real world environmental dispute involving the petrochemical groundwater contamination of the Cohansey Aquifer in the State of New Jersey in the U.S. Additionally, the Zeuthen's bargaining model is employed to analyze the conflict from a different perspective.
Granulite Facies Rocks of Brazil: A Review of their Geologic Setting, Geochronological Evolution, Petrographic and Geochemical Characteristics
Authors: Iyer S. S. , Choudhuri A. , Cordani U. G.
Published: November 2024

An attempt to assemble the available data on the granulite facies rocks spread around Brazil is made with a view to discuss their geological setting, geochronological evolution, petrographic and geochemical evolution. The isotopic ages of the granulites fall into different groups ranging from Archaean to Late Proterozoic. The geotectonic evolution of these rock types is discussed in terms of their being either fragments of geochemically differentiated lower crustal layers or eroded segments of modern Cordilleran (Himalayan) type collision belts. The geochemical feature of the rock types demonstrates the non-systematic fractionation of trace elements.
Rare Earth Element Geochemistry of the Munnar Carbonatite, Central Kerala
Authors: Santosh M. , Thampi P. K. , Iyer S. S. , Vasconcellos Marina B. A.
Published: November 2024

Rare earth element abundance in carbonatite associated with the 740 Ma old alkaline complex of Munnar is reported. High values of La (up to 232 ppm) and Ce (up to 261 ppm), moderate Sm (upto 11 ppm), with low Tb (up to 1.1 ppm), Yb (upto 3 ppm) and Lu (up to 0.6 ppm) are observed, comparable with similar values for carbonatites from other regions. The chondrite normalised patterns exhibit a steep slope from LREE to HREE, with (La/Lu)cn ranging upto 191. A genetic model involving CO2 degassing from the mantIe and ion exchange reactions with deep crustal rocks is envisaged, with the carbonatites probably representing a late immiscible fraction that separated from a polymerized alkali silicate melt. REE geochemistry of the carbonatite substantiates the view of a Late Precambrian alkaline magmatic regime in this part of the Indian Shield.
Geomorphological and Quaternary Geological Studies Along the Coastal Plain in Parts of Cannanore and Kasargod Districts, Kerala
Authors: Krishnan Nair K.
Published: November 2024

The area studied represents coastal plain of Kerala forming parts of Cannanore and Kasargod districts. The coastal plain in this area is narrow, having an average width of about 6 km and consists of depositional landforms. Five depositional surfaces and one erosional surface, each characterised by a particular morphology and lithostratigraphy are identified in the coastal plain. The strandlines and sand barriers throw some light on the nature of the former coastal plain and the marine regression. The shell-bearing black clay deposit below the flood-plain deposit is an evidence of palaeolagoonal environment.

Fringing the coastal plain, towards east, are laterite-capped plateaus which represent remnants of a former planation surface. This surface is seen developed over the Mio-Pliocene (Warkalli) Formation as well as over the crystallines and is tentatively dated as the Pliocene surface. An attempt is made to discuss the neotectonic activity along the coastal plain with the help of geomorphic data.
Evolution of the Western Ghats, India- A Simple Model
Authors: Subrahmanya K. R.
Published: November 2024

The nature of origin of Western Ghats is being debated for several decades. In the light of modern developments in the field of earth sciences, this paper postulates that the western margin of India originated due to a combination of the following factors:

a) Crustal doming and rifting which preceded the drifting of the Indian subcontinent, resulting in an initial escarpment along the western margin of India.

b) Recession of the Ghats to the east due to marine erosion;

c) Withdrawal of the sea during the glacial period exposing part of the continental shelf as a coastal plain.

d) Development of westerly drainage.

e) Fluvial erosion of western ghats and coastal plain, and

f) Gradual post glacial rise in sea level resulting in drowned valleys, estuaries and lagoons.

This model is substantiated by a few evidences and offers a satisfactory explanation for the controversy concerning the origin of western ghats.
Gravity Field and Its Significance to the Origin of the Bengal Anorthosite
Authors: Mukhopadhyay Manoj
Published: November 2024

The Bengal anorthosite is the only known major anorthosite occurrence in India outside the Eastern Ghats province. The characteristic Eastern Ghats gravity 'high', however, continues northward across the Bengal anothosite. Recent gravity mapping shows that this anorthosite is associated with a Significant positive anomaly of 20 mgal amplitude and 25 km width. The gravity high also extends far another 100 km westward into the Chhotanagpur gneissic terrain. Gravity interpretation suggests a more mafic phase of the anorthosite underlying its southern part, the mafic mass being of gabbroic composition. The mafic mass is inferred to have the form of an inverted cone, at least 3.3 km thick, below a thin veneer of anorthositic rocks, but its thickness reduces westward inside the Chhotanagpur gneisses where the mafic mass assumes a more tabular form. Two large granitic stocks, upto 1.8 km thick and 20km wide, are inferred to have intruded the country rocks to the immediate south of the anorthosite suite. The granites are supposedly derived by palingenesis of in situ leptynites.
Quaternary Valley-Fill Deposits of the Ravi Drainage Basin in Chamba, Western Himalaya: Definition, Lithostratigraphy and Depositional Framework
Authors: Joshi D. D. , Tandon S. K.
Published: November 2024

Quaternary deposits in the Himalaya fall into two major categories: Group 1-lntra-montane basinal fills occurring in various tectonic zones, and valley-fill sequences of limited width along the linear extent of major Himalayan drainages and Group 2-Sub-montane basinal fills in the foot-hills zone. The Mangla Formation (250m thick) is being defined from one of the major Himalayan drainages-the Ravi river. It is divided into six members representing paraglacial fan and braided stream deposits. The 'glacial' history of the sequence has been inferred from the physical environment of the terrain. and by relating the deposits to the gross geomorphological features.

Attempts to correlate the Mangla Formation with the glacial deposits in the Himalayan region, particularly Swat Kohistan and the southern slopes of the Dhauladhar range, are beset with difficulties in the absence of a proper chronology of Quaternary glacial events in the Himalaya. Two major ice advances have been interpreted in the Dhauladhar Range. In the absence of datable materials, no meaningful temporal relationships can be established for the ice advances.
Iron-Titanium Oxide Minerals In The Mayurbhanj Basic Intrusion, Orissa, India
Authors: Das S. K. , Mukherji S.
Published: November 2024

Electron probe data arc presented for coexisting ilmeno-magnetite and hemoilmenite for three samples along with the two published analytical results. The Mol % ulv and hem are plotted in T-fo2 diagram and compared with the results of DubJabera and Skaergaard. The oxides of the five samples equilibrated at 710°C to 1050°C with fo2 ranging between 10-9.2 to 10-17.5 atm. The lower temperature of formation indicated by three samples is probably due to external granule exsolution process and high water content of the magma which is responsible for widespread deuteric and hydrothermal alteration of the genetically associated rock types.
Analytical Studies of Stream Sediments of Sri Lanka for Identification of Gold-Bearing Areas and Delineation of Ultramafic Bodies
Authors: Ramakrishnal R. S. , Dharmadasa D. , Brooks R. R. , Ryan D. E.
Published: November 2024

Trace element analyses of stream sediments in Sri Lanka have been carried out to identify existtncc of ultrarnafic rocks in areas other than those demarcated as serpentinite zones. Residual soil analysis was used to confirm the results of delineation of a scrpentinite zone by photogrammetric study. Inter-element correlations are shown to be significant in these studies. The analyses also indicate anomalous levels of gold (>20 ng/g), along the Highland Group and the Highland-Eastern Vijayan boundary as demarcated by Abeysinghe.
U-Th-Mo Mineralisation in Quartz Syenite from Maturigiri-Dhurakantagiri, West Garo Hills District, Meghalaya, India
Authors: Basu A. N. , Sharma G. S. , Varma H. M. , Dhana Raju R. , Dougall N. K. , Raju N. V.
Published: November 2024

At Maturigiri and Dhurkantagiri, mineralised coarse-grained quartz syenite bodies (up to 10 x 2 m) occur as intrusives along the NNW-SSE trending joints in the gneissic country rock. Mineralogically. the quartz syenite is characterised by over 50% K-feld-spar, lesser plagioclase, quartz, mica, garnet and chlorite, together with accessory uraninite, monazite, molybdenite and pyrite. Uraninite occurs as euhedral to subhedral inclusions and mineralisation is syngenetic. Two types of monazite, Th-poor and Th-rich, are present. Molybdenite occurs as veins along fractures and appears to be of late hydrothermal origin. The mineralogical and textural features suggest that quartz syenite was formed from a residual melt of granitic magma of crustal origin.
An Interpretation of Regional Structures of Kumaun-Garhwal Himalaya Based on LANDSAT-I Imagery
Authors: Goel O. P. , Garhia S. S. , Mehta J. S. , Kandpal G. C.
Published: November 2024

A preliminary study and interpretation of LANDSAT-I imagery, covering a large area of Kumaun-Garhwal Himalaya. lying between 79° - 80°30' East longitude and 29°0' - 30°30' North latitude, reveals the presence of four dominant directions of lineaments trending NS, NE-SW, NW/WN-SE/ESE and E-W. The lineament fabric of the region represents axial directions of major folds, regional strike trends of thrusts and of transverse or strike-slip faults. The study is supplemented by detailed structural analysis of mesoscopic folds, planar and linear features present in rocks of three sections of the Kumaun Himalaya and it is suggested that the deformation in rocks of the region was the result of both compressional, tensional, and vertical uplift.
Effects of Industrial Effluents on the Water Quality of River Hindon, District Saharanpur, U.P.
Authors: Singhal B. B. S. , Mathur R. P. , Singhal D. C. , Mathur B. S. , Minocha V. K. , Seth A. K. , Sinha S. K.
Published: November 2024

To assess quantitatively the effect of organic load from the Star Paper Mill on the quality of Hindon water, a dissolved oxygen sag model is developed by using Streeter-Phelps equation for a stretch of 7 km down-stream of the paper mill effluent and Hindon confluence. The critical DO deficit and critical time for minimum dissolved oxygen have been computed. The study reveals that severe anaerobic condition prevails in the river between a distance of 2.2 km to 3.6 km from the confluence of Paper Mill effluent with the Hindon river. The sag in dissolved oxygen curve is not fully apparent in the observed model; though the occurrence of reducing condition is correlated by field observations.
Environmental Geology of Peninsular River Basins of India
Authors: Subramanian V. , Biksham G. , Ramesh R.
Published: November 2024

An attempt is made to evaluate the environmental geology of non-Himalayan rivers of India. These twenty river basins including eleven medium basins together drain nearly 25 per cent of the sub-continent. The annual transport of suspended sediments and dissolved salts by these rivers have been estimated to be around 370 million tonnes and 61 million tonnes respectively. The rate of physical erosion among these basins range from 799 tonnes/km2/yr to 16 tonnes/km2/yr. Similarly, chemical erosion ranged from 110 tonnes/km2/yr to 22 tonnes/km2/yr.

Among the rivers considered, the chemical composition of water indicates that Cauvery carries a large silica load (39 ppm), while the TDS is low (172 ppm), whereas Sabarmati has the highest TDS (352 ppm). Krishna waters show the highest alkalinity. In all the rivers, conductivity shows good correlation with TDS. Sediment chemistry indicates that Cauvery river sediments are most siliceous while that of Godavari are least siliceous. In both these cases, average SiO2 is higher than the Indian average river sediment. Similarly, Fe in southern river sediments is very high while P is very low compared to the Indian or world average. Apparently local geology (Shield area hard rocks in southern India and Deccan Traps in central India) control the water and sediment characteristics of the peninsular rivers.
Godavari Basin - A Geophysical Study
Authors: Mishra D. C. , Gupta S. B. , Rao M. B. S. V. , Venkatarayudu M. , Laxman G.
Published: November 2024

Detailed gravity and magnetic surveys in and around the Godavari basin have helped in delineating the subsurface structures which, in turn, facilitated reconstructing its evolution. The general NW-SE trend of the magnetic and the gravity anomalies towards north takes a swift turn along an E-W line south of Bhadrachalam. This may be attributed to a deep-seated fault dividing the basin into Godavari and Chintalapudi sub-basins. The same fault may be responsible for limiting the southern extent of Pakhal sediments. A similar deep-seated fault north of Bhadrachalam along the Mailaram 'high' is also indicated. Modelling of some critical gravity and magnetic anomalies indicates the maximum thicknesses for Gondwana and Sullavai sediments as 4.5-5 km and 1.5-2 km respectively. A large gradient in the Bouguer anomaly on the eastern side of the Gondwana basin suggests the existence of a long continuous normal fault which is the master fault of the Gor.dwana rift valley. The other side of the basin is characterised by variations in the gradient of the Bouguer anomaly suggesting enechelon faulting.

The Gondwana basin is flanked on either side by heavy rocks of density 2.95 g/cm3 between the depths of 6km to 13 km which might be due to the block uplift of the lower crust forming the 'shoulders' of the rift valley or large sub-basic intrusions in the region. The definite magnetic anomalies in this region providing a high susceptibility of 0.1-0.2 emu almost at the same depth as obtained from the Bouguer anomaly further substantiate them. The subsequent uplifts of the basin is apparent from 'highs' in Bouguer anomaly inside the basin such as around Chinnur which shows sharp gradients on either side suggesting faulted margins. The Regional Bouguer anomaly separated from the observed field along a few representative profiles suggests the presence of a high density (3.1 g/cm3) material along the Moho between the depths of 30km to 38km.

The magnetic data reveals several basement ridges and intrusions as far west as. Manthani and Sirpur-Kagaznagar which are transverse to the general trend of the Gondwana basin and almost parallel to the eastern ghat trends suggesting that they may be the subsurface reflections of eastern ghat orogeny. A well-defined magnetic anomaly in the Chintalapudi sub-basin suggests the depth to the basic intrusion in the basement as 3.1 kilometres. There are high magnetic anomalies along the Precambrian faults defining the Purana basin suggesting basic intrusions along them. The basin as a whole depicts a high heat flow specially its southern part which might be due to several intrusive bodies as inferred from the magnetic and the gravity studies. The Godavari basin is a typical rift structure formed during the Gondwana period. The high density material along the Moho and in the upper crust suggests the diapiric upwelling of the asthenosphere as the main cause for the development of a typical continental graben in this region and subsequent uplifts along the shoulders.
Implication of Shale Diagenesis on Cementation of Reservoir Sandstones in the Neogene Surma Group of the Bengal Basin, Bangladesh
Authors: Imam Md. Badrul
Published: November 2024

Late Fe-calcite and quartz overgrowths are the two most widespread and important cements in the Surma sandstones and are most responsible for damaging their reservoir properties. This paper suggests that the burial diagenesis of Surma shales has significantly influenced the cementation of adjacent sandstones by supplying ion charged water expelled during shale compaction and dewatering. The diagenetic conversion of smectite to illite layer in the illite/smectite mixed layer clay mineral in the Surma shales release Si4+ and Ca2+ that migrate up with expelled water and form important sources of quartz overgrowth and late calcite cement respectively in the overlying sandstones. This is compatible with the correlatable relation between the higher degree of illitization plus greater volume of shale and the zone of increased sandstone cementation in the deeper subsurface. The ferroan nature of the calcite cement may have been related to the availibility of Fe2+ ions, also released by the illitization reaction. The diagenetic dissolution of calcite in shales in the subsurface and its migration upward may have been an additional source of the late Fe-calcite cement in the Surma sandstones.
A Note on the Occurrence of Ortho-Amphibolites on the Inner Shelf off Bhatkal, West Coast of India
Authors: Siddiquie H. N. , Karisiddaiah S. M. , Subrahmanyam V.
Published: November 2024

The total magnetic intensity map of the area shows that the inner shelf to a depth of 50m is marked by a zone of magnetic closures. The occurrence of offshore ortho-amphibolites and the qualitative interpretation of the magnetic map indicate the extension of onshore rocks (or the amphibolites and associated rocks of Precambrian (?) and intrusions of Deccan Trap age) under a thin cover of sediments to the offshore to a depth of about 50 m.
Textural and Mineralogical Studies of the Beach Sands from Fort Cochin to Chellanam, Kerala
Authors: Purandara B. K. , Unnikrishnan V. P. , Srinivas Gupta C. , Dora Y. L.
Published: November 2024

In general most of the beach sediments from the area under study are medium sand-sized, unimodal, moderately sorted, nearly symmetrical and mesokurtic in terms of their grain-size distribution. The standard deviation shows minor variations from September to December. The heavy minerals commonly found in these sediments in the order of decreasing abundance are hornblende, opaques, hypersthene, garnet, mica, sillimanite, augite and diopside. The percentage of quartz in the light mineral fraction varies from 57% to 99%. The provenance of these beach sands is believed to be the rocks of the Western Ghats - charnockite and gneissic terrain.
The Central Himalayan Gneisses in Northern Pakistan
Authors: Broughton R. D. , Windley B. F.
Published: November 2024

The Central Himalayan Gneisses on the northern margin of the Indian plate in the Hazara and Lower Swat areas of N. Pakistan comprise; orthogneisses with minor schists, amphibolites and calc-silicates, overlain unconformably by a cover sequence of graphitic and calcareous schists, marbles and minor amphibolites. These rocks are bounded to the south by a major thrust (equivalent to the Himalayan Main Central Thrust), and to the north by lhe Main Mantle Thrust (Indus Suture). To the south of the MCT there is a thrust slice of basement paragneisses with no relics of cover. The dominant gneissose foliation parallels the main thrusts, and is modified by numerous, large-scale N-S trending open folds.

The ortho- and para-gneisses and cover sequence are isofacial, and underwent two phases of metamorphism, prior to 35 Ma. Mineral equilibria indicate conditions for the cover sequence in the range 550-620°C and 8.0-8.9 kb, and for the paragneiss basement at ~650°C and 6.7-6.8 kb. The two pressure ranges come from different thrust slabs. These data indicate an average cooling rate of ~17°C my-1, and an average uplift rate of ~0.8 mm yr-1 over the last 35 My, for the relic cover sequence.
Tectonics of the Main Central Thrust in Garhwal Himalaya, U.P
Authors: Bahuguna V. K. , Saklani P. S.
Published: November 2024

The Main Central Thrust in Garhwal Himalaya is characterized by a duplex system. The relationship between the minor duplexes with the major Central Crystalline Duplex is investigated with the help of branch-line maps and balanced cross-sections. A probable model for the thrusting is suggested. Development and growth of Central Crystalline Duplex was caused by the repeated cyclic straining in the hanging-wall during the emplacement of thrust sheets. The contraction of the minor duplexes, namely, the Bhagirathi, Bhilangana and Mandakini varied from - 55.8% to -138%.
Bone Histology as a Tool for the Search of Dinosaurs
Authors: Mathur U. B. , Pant S. C.
Published: November 2024

Morphologically unidentifiable bone fragmenls from Jurassic of Jaisalmer (Raja-sthan) and Infratrappean of Kutch (Gujarat) were recently identified to be dinosaurian by their histological examination under petrographic microscope. This was feasible because the tissue structure of dinosaur bones is different from other contemporaneous vertebrates. It is characterised by the occurrence of dense Haversian systems of many generations in greater part of cortex. The note deals with the structure of Haversian System, its mode of occurrence and the methodology for identifying dinosaur bone fragments. It is hoped that the knowledge of bone histology will help in the discovery of new horizons and localities in India where only a few occurrences are known so far.
Delhi Volcanics in Parts of Central Rajasthan and their Significance
Authors: Gupta P. , Mukhopadhyay K. , Bose Utpal
Published: November 2024

The Proterozoic Delhi Supergroup of rocks along the Aravalli orographic axis in central Rajasthan encloses thick linear piles of syn-sedimentary volcanics. The volcanies are low-potassic oceanic tholeiites derived from mantle source. The repository basin was ensialic to start with and was partially rifted to facilitate magma upwelling concomitant with sedimentation. Structural stratigraphic and chemical characters of the volcanics militate against the possibility of its being allochthonous slices of an oceanic crust.
Geomicrobiology as an Aid to Prospecting: A Critical Study from Malanjkhand and Zawar Base Metal Deposits, India
Authors: Shrivastava J. P. , Alexander P. O.
Published: November 2024

Cold extractable and total Cu, Zn and Pb in soils arc faithful pointers to concealed mineralisation. Geomicrobiological studies have failed to give positive results. Thiobacillus ferrooxidanS, T. nevellus, T. permetabolis, T. thiooxidans, T. thioparus in soils over the mineralised zones were not detected in the present study. But cultures grown in P.D.A. media have shown quantitative differences for the mineralised and non-minearalised soils. Several possible reasons for this negative geomicrobiological response are discussed which include: deficiency in Mo and organic carbon in soils. unfavourable pH of soils/water, lack of moisture and water-logging among others. More detailed study of soil geomicrobiology minerai exploration is suggested.
Mineralogy and Element Variations in the Vindhyan Stromatolites, Central India
Authors: Kumar S.
Published: November 2024

The Lower Vindhyan stromatolites are dominantly made up of dolomite while the Upper Vindhyan stromatolites are made up of calcite. Sr shows sympathetic relationship with CaO and K2O with Al2O3. Three distinct assemblages of stromatolites belonging to the Kajrahat Limestone, the Fawn Limestone and the Bhander Formation show different trace element distribution.
Tectonic and Stratigraphic Framework of the Lead-Zinc Sulphide Mineralisation at Zawarmala, District Udaipur, Rajasthan
Authors: Singh N. N.
Published: November 2024

The carbonate-hosted lead-zinc sulphide mineralisation of Zawarmala belongs to the early Proterozoic rocks of the Aravalli Supergroup. The floor of the Aravalli sedimentation was a peneplained Archaean basement whose antiquity, as revealed by the recent Sm/Nd isotope studies, dating back to 3.5 billion years ago. The sedimentary package of the Arava11i Supergroup represents a sequence showing a distinct dichotomy in its depositional and lithological characters. The sulphide mineralisation is entirely confined to the near-shore shelf sequence which shows diverse lithofacies association of carbonates, black shales, argillites and arenites. By contrast, the distal (deep water) facies rocks which do not show any sign of syngenetic mineral deposits of any kind, is a totally carhonate-free sequence of argillites with thin bands of arenites.

The Aravalli Supergroup includes two groups separated by an unconformity marked by conglomerates and palaeo-erosional surfaces. The lead-zinc sulphide ores are confined to the carbonate sequence which occurs in the Upper Aravalli Group. Studies on the host rocks and the orebodies indicate a common plan of deformation and metamorphism. The geometry of the ore lenses suggests a very strong influence of the second deformation (AF2). This is also apparent in the trend surface maps showing distribution pattern of the metals-lead and zinc. Localisation of sphalerite, galena, and pyrite-bearing orebodies indicates differential mobilisation of these minerals in response to repeated deformation and metamorphism under a low temperature condition. The present study reveals a polygenetic history of the Zawarmala ore-bodies comparabte with those proposed for 'Alpine or Mississippi ValIey' types.
The Mid-Proterozoic Vindhyan Macrobiota from Chopan, Southeast Uttar Pradesh
Authors: Maithy P. K. , Babu Rupendra
Published: November 2024

Macrobiota comprising body fossils and trace fossils are reported from the Semri and Kaimur Groups of the Vindhyan Supergroup exposed around Chopan. Carbonaceous compressions of Chuaria minima and Tawuia dalensis, impressions of Sekwia excentrica and moulds of Longfengsahnia chopanensis sp. nov. are reported from the Rohtas Limestone Formation, Semri Group. Beside these, Longfengsahnia stiplala and epirelief of trace fossils belonging to possibly annelids are reported from the Ghurma Shale Formation of Kaimur Group. The macrobiota record indicates that during the Rohtas time free planktonic forms were present in the entire Vindhyan region particularly the genus Chuaria which may be considered as an index fossil of that period.
Alveolina from Western Kutch-Systematics, Distribution and Stratigraphic Significance
Authors: Ray A. K. , Ghosh C. C. , Nag S.
Published: November 2024

Alveolina of Kutch Middle Eocene limestones and marls is identified as A. elliptica var. nuttalli. The variety is shown to have a characteristic shape (expressed as a ratio of polar and equatorial diameters), and more or less fixed number of flosculinised whorls; the variation in the development of non-flosculinised whor1s on the flosculinised ones is attributed to an ontogenetic development correlated with size increase. The variety shows a clear case of lateral facies variation, occurring in two 'apparent' horizons in deeper parts of the basin with vertical absence in between, but continuing throughout the rock unit in marginal shallower parts. The facies-governed nature of this larger benthic foraminiferal species and its presence in the Kutch Paleogene sequence without the earlier glomalveoline forms are considered important aspects in stratigraphic studies.
Trace Metals in Ferromanganese Nodules and Host Sediments of the Indian Ocean
Authors: Ghosh Swapan K.
Published: November 2024

Ferromanganese nodules and host sediments collected from Indian ocean were successively treated with distilled water, acetic-acid buffer, acidic solution of H2O2, Oxalic acid buffer and citrate-bicarbonate-dithionile solutions, to relate the partitioning of trace elements, and their chemical association with iron and manganese oxide phases.

Based on the selective dissolution analysis of samples, it is suggested that host sediments contain higher abundance of crystalline oxides of iron and manganese than that in ferromanganese nodules. It was, however, observed that most of trace metals in sediments are concentrated in non-crystalline ferric hydroxide, although its concentration is less than crystalline ferric oxide. Nodules contained much higher abundance of trace metals, both in their crystalline and in non-crystalline phases.

In addition to the crystalline and non-crystalline iron and manganese oxides, a significant amount of trace metals occurs as substitutions of Ca and Mg in carbonates, and also as absorbed ions and as loosely bonded ions. Presence of carbonates and status of crystallinity of oxides of iron and manganese are identifiable by selective-dissolution analysis as proposed in this work.
A Geophysical Appraisal of the Purana Basins of India
Authors: Ramakrishna T. S. , Chayanulu A. Y. S. R.
Published: November 2024

Out of the six Purana basins, namely Cuddapah, Kaladgi, Bhima, Pakhal, Chattisgarh and Vindhyan, Cuddapah, Pakhal and Chattisgarh appear to be filled with rocks of higher than normal density, whereas the other three comprise low density rocks. Their gravity picture, however, are not found to be simple highs or lows as to be expected from their densities but are distorted by both deepseated causes as in the case of Cuddapah, Chattisgarh and Vindhyan basins, as well as the overlying sediments as in the case of Pakhal basin. Major earth movements appear to have been associated with Cuddapah, Pakhal, Vindhyan and Chattisgarh basins whereas Kaladgi and Bhima basins represent mere depressions. The thickness of sediments in these basins is estimated to vary from 2 to 10 km.
Petrology of Lamprophyres from Parts of East Garo Hills and West Khasi Hills Districts, Meghalaya
Authors: Raghavan Nambiar A.
Published: November 2024

Lamprophyres occur as dykes and veins in the Precambrian gneisses and granitoid country rocks along and in the vicinity of tbe Nongchram Fault Zone in East Garo and West Khasi Hills Districts of Meghalaya. They arc genetically associated with feldsputhie ijolites, tinguaites and carbonatites. They are typically melanocratic and contain leucocratic ocelli, spherical or sub-spherical in shape with a centrally disposed core of carbonates and alkali feldspar, mica and clinopyroxene-rich lining. The carbonate-rich inner zones of these zoned ocelli are interpreted as space originally occupied by a gas phase, whereas the outer zones represent late stage liquids. The mineralogy and chemical parameters of these lamprophyres coupled with the common presence of ocelli and megacrysts of mafic minerals and their genetic association with sodic alkaline rocks and carbonatite classify them as alkaline lamprophyres. Petrographically, the holocrystalline rocks can be classified as camptonites and the chilled dyke margins as monchiquites.

The occurrence is suggestive of rift-related alkaline magmatism. These alkaline and related rocks together with the ultramafic-alkaline-carbonatite complex of Sung Valley may constitute an ill-defined alkaline province. Their genetic link with Sylhet Trap volcanics cannot be ruled out, as eruption of alkali basalts is generally followed by alkaline intrusions.
A Note on the Occurrence of Ptilophyllum Flora from the Chintalapudi Sub-Basin, Pranhita-Godavari Valley, Khammam District, Andhra Pradesh
Authors: Lakshminarayana G. , Kutumba Rao N.
Published: November 2024

Ptilophyllum flora comprising Ptilophyllum cutchensis Cladophlebis denticulata,Cladophlebis Sp. Araucarites cutchensis, Araucorites Sp. (?) Elatocladus Sp. is reported from the buff siltstones and claystones of Dammapeta area, Chintalapudi sub-basin, Khammam District, Andhra Pradesh. The floral assemblage clearly indicates that the Dammapeta beds' belong to the Upper Gondwana, possibly Gangapur Formation and not Kamthi Formation (Lower Gondwana Group), as hitherto believed.
Granite-Molybdenite System of Ambalavayal, Kerala: Part I. Geochemistry and Petrogenesis of the Granite
Authors: Santosh M.
Published: November 2024

The 595 Ma old granite pluton punctures Precambrian low-alumina trondhjemites and occurs spatially related to the Moyar and Calicut fault-lineament. Mineralogically, it is a quartz-alkali-feldspar granite. Molybdenite occurs as disseminated flakes in the granite and associated pegmatites and as flaky aggregates in quartz veins. K: Na : Ca relationship suggests an adamellitic composition, whereas SiO2 vs. Log10K2O/MgO proportions confirm its alkaline nature. In Harker variation diagrams, the oxide weight percentages show overall magmatic trends. Among trace elements, the notable features are low large ion lithophile element contents, moderate to high transition element levels and extremely high light rare earth element values. High SiO2, K2O and Na2O values, with low abundance of Ba, Rb and Sr and enrichment of Nb and Zr are typical features comparable to alkali granites elsewhere. The Rb, Nb and Y characteristics denote a within-plate affinity. Petrochemical features indicate derivation of the granite from an alkali-enriched partial melt through quartz and alkali feldspar fractionation. The extremely high K/Rb values imply a K-enriched, Rb-depleted deep crustal source. The enrichment of LREE and HFS elements indicate an active role of CO2-rich volatiles in the petrogenetic regime.
Granite-Molybdenite System of Ambalavayal, Kerala: Part II. Nature of Mineralization, Sulphur Isotopes, Fluid Characteristics and Genetic Model
Authors: Santosh M.
Published: November 2024

The alkali granite pluton of Amba]avayal in Wynad district, Kerala, carries an 800m wide zone of disseminated molybdenite mineralization. Molybdenite also occurs as flakes and flaky aggregates in pegmatites and quartz veins. XRD and geochemical data indicate the molybdenite to be hexagonal 2H1 polytype. The general mineralogic and geochemical features of the granite are consonant with those of granite molybdenite systems in general. The sulphur isotope values in five molybdenite separates range from -1.62 to + 1.54 ‰, denoting a narrow spread and a single igneous source. Fluid inclusions commonly occur in quartz associated with the granite, pegmatites and quartz veins. Heating-freezing studies show that the granite quartz entrapped high density (0.90-0.95 g/cm3) CO2-rich fluids at pressures of 4.5-5.2 Kb. Coexisting CO2 and CO2-H2O inclusions in pegmatites yield a P-T estimate of 2.2 Kb and 500°C. Fluid inclusions in the mineralized quartz veins show that the ore-forming fluids (with a maximum salinity of 15 wt. % NaCl) were heterogeneous and the molybdenite precipitation was triggered by adiabatic decompression and 'boiling' at temperatures of 340-360°C and vapor pressures of 110-150 bars. The cooling curve of the granite constructed from combined P-V-T data shows a T-convex path, implying near-isolhermal upward movement of the granite magma. The data are consistent with a genetic model linking magmatism and metallogeny with extensional tectonics in the late Precambrian.