bluuebunny/crossref_metadata_2025 huggingface dataset:
Geology of the Contact between the Eastern Ghats Belt and North Orissa Craton, India
Authors: Mahalik N. K.
Published: November 2024

The contact region of tile Eastern Ghats Belt (EGB) with the North Orissa Craton (NOC) in Orissa State was studied and certain new observations have been made. The contact is represented by a wide zone affected by several east-west running faults with fault fragments of both blocks interfingcred with each other. Portions of the fault zone have later given rise to Gondwana graben in which coal-bearing sediments were deposited covering the contacts. The stratigraphic relation between the two crustal blocks was difficult of interpretation because of intermingling of the fault slices and concealment of the contacts by granitic intrusion, Gondwana sedimentation and lateritic cover.

The Eastern Ghats Belt (EGB) is made up of granulite facies rocks consisting principally of khondalites, leptynites, quartzites, gamet-biotite schists, basic granulites, charnockites and gneisses, all migmatized to different degrees. They could be distinguished into two different assemblages: the Rengali assemblage, forming the northernmost fringe of the EGB and the Angul assemblage lying to the south of the Gondwana graben. Both differ in their lithologic characteristics. The North Orissa craton, on the other hand, consists of several sequences of low-grade supracrustals with or without Banded Iron Formation (BIF) associated with granitic intrusion of more than one generation. At places within the fault zone between the two blocks there are typical intrusions of nepheline syenite and chromite-bearing ultrabasics.

A tentative geological account around the contact of the two major crustal blocks has been presented. It is believed that the Eastern Ghats granulite rocks formed earlier to the BIF-bearing supracrustals and associated granite intrusives. Migmatization, charnockitization and alkali plutonism etc. were late Proterozoic events in the EGB (1.0 Ga-0.8 Ga) related to deep seated fault tectonics along the contact.
Na-Poor Ferro-Augites and Ferro-Hedenbergites from Ferrosilite-Bearing Ferrosyenites of the Prakasam District in Andhra Pradesh, India: Further Evidences for a Tholeiitic Parentage
Authors: Leelanandam C.
Published: November 2024

The clinopyroxenes from the ferrosyenites in the Prakasam district of Andhra Pradesh are characterized by their subcalcic nature, enrichment in Fe with concomitant impoverishment in Mg, and low amounts of (calculated) Fe3+, Na, Al and Ti - features which specifically typify their subalkaline (tholeiitic) parentage. The acmite component is insignificantly low in the analyzed clino-pyroxenes (Na3.60-5.74 Mg10.01-27.09 Fe67.17-85.16) and bears no relationship whatsoever either with the hedenbergite component or with the calculated Fe3+ content. The results of the Fe3+ calculations were suspect, especially when the mineral analyses show low SiO2, low totals, Si+Al<2, and total cations more than 4 per formula unit of 6 oxygens. These strongly coloured green clinopyroxenes, commonly mistaken as sodium-rich acmitic pyroxenes, are indeed sodium-poorferro-augites and ferro-hedenbergites. The high Fe/Mg ratios in the clinopyroxenes (2.4-8.2; Ca43.3-45.6Mg5.8-16.0Fe39.6-50.5), coupled with the extremely high Fe/Mg ratios in the coexisting olivines (35.5-61.8; Fa97.3-98.5) and orthopyroxenes (3.6-11.8; FS78.2-91.3) are an indication of the very highly fractionated nature of the magma. Clinopyroxenes of comparable chemical characteristics are reported from ferrosyenitic rocks elsewhere in the world, which in contrast to these of the Prakasam district, are not cospatial with (feldspathoidal) alkaline rocks. The occurrence of ferrosyenites, containing Fe-rich orthopyroxene (eulite-ferrosilite) and inverted pigeonite, in the vicinity of alkaline rocks in the Prakasam district, is interpreted as purely fortuitous and merely coincidental, not having any genetic or causative relationship.
Application of Inversion Techniques on Marine Magnetic Data - Andaman Shelf
Authors: Sarma K. V. L. N. S. , Ramana M. V. , Murty G. P. S. , Subrahmanyam V. , Krishna K. S. , Chaubey A. K. , Malleswara Rao M. M. , Narayana S. L.
Published: November 2024

Analysis of the total intensity magnetic data over the western Andaman shelf has been carried out for determination of depth to magnetic basement using the Analytical signal and Werner Deconvolution methods. The basement depths are refined with optimisation procedure of iteration modelling. The depths Derived from these methods match well with the acoustic basement mapped by the seismic reflection survey across the Andaman shelf. The interpretation by these methods demonstrates the rapid utility in virgin areas forderiving the first order basement configurationquickly. The gradual slope of the basement from west to east on the western Andaman shelf may be attributed to the ongoing process of the subduction of the older crust in the Sunda Trough.
Geochemistry of Early Proterozoic Mafic and Ultramafic Rocks of Jharol Group, Rajasthan, Northwestern India
Authors: Abu-Hamatteh Z. S. H. , Raza M. , Ahmad T.
Published: November 2024

The deep water Jharol sediments of Aravalli Supergroup host sporadic bodies of mafic-ultramafic. rocks. Field evidence suggests that at least some of these rocks are extrusive in nature. Low to medium grade metamorphism and intense deformation has obliterated the original mineralogy and texture of these rocks. The ultramafic rocks are relatively more altered (serpentinized) with highly disturbed geochemical composition which cannot be used for petrogenetic interpretations. On the other hand, the mafic rocks are relatively less altered with some relict plagioclase feldpars. Geochemically, these mafic volcanics are Mgand Fe- rich tholeiites.

These tholeiites have nearly flat to slightly enriched REE patterns (about 30 to 40x % chondrite La and 20 to 25x % Chondrite Yb), with (LalYb)N ratio ranging between 1.29 and 1.54 and (GdIYb)N ratio ranging between 0.97 and 1.07. All samples show slight to strong positive Eu anomaly. Immobile incompatible-element geochemical patterns and other binary plots suggest that these tholeiites have enriched chemistry and that grobably they have been derived from enriched source(s) and resemble closely with within plate and initial rift tholeiites.

Trace elements, including REE based petrogenetic modelling indicate that (a) the source had about 3x% chondoritic REE abundances with nearly flat to slightly depleted pattern and (b) that these rocks were generated by about 8 to 12% partial melting of the modelled source followed by some olivine and clinopyroxene fractionation. Field as well as trace element characteristics indicate rift related (lithospheric extension) generation of these basalts with some influence of asthenosphere (deep mantle) on the lithospheric source(s) as indicated by positive Nb and Sr anomalies.
Mineralogy, Geochemistry and Genesis of Clay Deposits in Belgaum, Dharwad and Chitradurga Districts, Karnataka
Authors: Devaraju T. C. , Khoshroo Ali , UGARKAR A. G.
Published: November 2024

A dozen clay deposits occurring in the districts of Belgaum, Dharwad and Chitradurga of Karnataka State have been studied. ln Dharwad district, while the clay deposits derived from greywackes/phyllites are dominated by kaolinite, those derived from the acid metavolcanics contain illite as the sole clay mineral. In Belgaum and Chitradurgadistricts the deposits are kaolinitic, characterised by poor crystallinity and near absence of illite.

Chemically, the clay deposits studied have relatively high silica and low titania. The transformation of precursor rocks to clay deposits which was brought about by insitu chemical weathering and subsequent reworking of the weathered products under tropical climatic conditions was accompanied by enrichment of Al, Zr and Cr and removal of Sit Fe. Ni, Cu and Zn. Presence of relicts of nearly all the major and accessory minerals native to the precursor rocks, in all the litho-units of clay profiles is in agreement with such an interpretation.
Sedimentological and Clay Mineral Studies of Kumbla-Shiriya Estuary, West Coast of India
Authors: Narayana A. C. , Suresh Kumar K. N.
Published: November 2024

Four sediment facies viz., sand, clayey sand, sandy clay and silty clay occur in Kumbla-Shiriya (K-S) estuary. Sediments have formed from bottom suspension and graded and uniform suspension as a result of variable hydraulic conditions in different parts of the estuary. Kaolinite+chlorite is the dominant clay mineral followed by montmorillonite and illite. Gibbsite, goethite and quartz also occur in minor quantities. It appears that the abundance and distribution of clay minerals in the estuary are controlled by the geology of the source area and the water circulation pattern within the estuary.
Spectral Mapping of Siwalik Sediments of a Part of Jammu Foothills
Authors: Dey B. K. , Mitra D. S. , Agarwal R. P. , Dotiwala S. F. , Prasad D. N.
Published: November 2024

The satellite and ground based spectral data corresponding to the six reflected radiance bands of Landsat Thematic Mapper (TM) are analysed to determine their utility in mapping the possible lithologic variations wihtin the Siwalik sediments of J&K foothills. The satellite reflectance values plotted along a selected image profile identified subunits within the Lower Siwalik, Pammdal and Nagrota, which were not identified by conventional field mapping. The field reflectance studies also confirmed their presence. The variation may reflect a possible lithofacies change wihtin the units. The technique developed may provide a rapid reconnaissance tool for preparing lithofacies map.
Morphometric Appraisal of Slope Instability of Chilla Landslide, Garhwal Himalaya
Authors: Mehrotra G. S. , Dharmaraju R. , Prakash S.
Published: November 2024

A major landslide occurred in January 1990 on the left bank of Tal river, near Chilla in Hardwar district which raised a part of the river bed by 6-8 m. It has emerged as successive rotational slide forming numerous radial and longitudinal cracks with tension cracks on the slopes near the escarpment. The present paper highlights the geological, geomorphological and morphometric parameters to identify the factors responsible for instability of slope. A detailed morphometric assessment of the slide area has also been carried out with a view to prepare a zonation map of slide area in terms of instability. The study has been found very useful to understand the mechanism of the slide area and also to suggest suitable recommendations for control measures at proper locations in the slide area. The future behaviour of the slide area can also be assessed.
Gemstone Mineralization in Southern Kerala, India
Authors: Menon Radhi D. , Santosh M. , Yoshida M.
Published: November 2024

Within the gem field in southern Kerala and adjacent Tamil Nadu region, extending over an area of 70 X 35 sq km, a variety of precious and semi-precious stones occur such as chrysoberyl (cymophane or "eat's eye", and alexandrite varieties), ruby, sapphire, emerald, topaz, zircon, and amethyst. The primary mineralization occurs within zoned, complex pegmatites of Pan-African age, emplaced within granulite facies metapelites (khonda1ites), and variably weathered and lateritised. Gemstone deposits of secondary type are associated with stream gravels and placers.

Preliminary fluid inclusion results provide evidence for the involvement of CO2-enriched felsic melts which interacted with the aluminous supracrustals in the formation of the pegmatite-hosted gem mineralization. Thennal decrepitation offluid inclusions under high vacuum, extraction and quantification of the fluids from inclusions indicate the presence of variable amounts of CO2 in quartz (72.7 ppm), garnet (141.2 ppm) and chrysoberyl (51.6 ppm). The carbon isotopic composition of CO2 in quartz indicates a 'Juvenile" magmatic nature, with d13C va1ue of -8 per mil. The gem-bearing pegmatites may therefore represent cryptic pathways through which large volumes of felsic melts migrated, a process which can be correlated to deep-seated extension in the Gondwana crustal fragments during the PanAfrican.

Gem recovery in Kerala, despite vast untapped potential, is largely done through illegal means. We emphasize the need for a gem industry in the State, and the requirement to bring the local prospectors under the fold of artisans so as to make use of their experience and expertise, in gem prospecting.
Specific Yield Evaluation: Barind Area, Bangaladesh
Authors: Jahan Chowdhury Sarwar , Mazumder Quamrul Hasan , Ghose Shyamal Kumar , Asaduzzaman M.
Published: November 2024

Proper planning of groundwater exploitation policy in Barind area, Bangaladesh needs the knowledge about the specific yield of the aquifer, whose computed values vary from 8 to 32% with a general decreasing trend from north towards central portion but the southern portion has better specific yield value than the central portion. On the basis of specific yield variation the area is divided into: Zone-I: includes Dhamoirhat, Patnitola, Mohadevpur, Manda, eastern side of Tanore, southern side of Godagari and Nawabganj, Shibganj and Bholahat thanas (specific yield values > 15%); Zone-II: covers the area of Niamatpur thana and the rest part of Nawabganj thana (specific yield valle 10-15%) and Zone-III: includes Nachole thana and the rest of Gomastapur thana (specific yield values <10%).
Porphyroblasts-Matrix Microstructural Relationships from the Crystalline Thrust Sheets of Satluj Valley, Himachal Pradesh
Authors: Gururajan N. S.
Published: November 2024

The crystalline thrust sheets of the Lesser and Higher Himalayan region of the Satluj valley, Himachal Pradesh, contain porphyroblasts of gamet, chloritoid, staurolite, kyanite and albite. The inclusion trails in the prophroblasts indicate that the porphyroblasts overgrew during various stages of S2 crenulation cleavage development related to D2 deformation. The sites for nucleation and growth of porphyroblasts are provided by deformation partitioning. The dissolution of porphyroblast margins is not common as suggested by other workers. Metamorphism during D1 was low grade.
Geological and Structural Features of Gulabgarh Area, Kashmir Himalaya with a Brief Note on the Study of Associated Granitoids
Authors: Koul A. K. , Fotedar B. K.
Published: November 2024

The Gulabgarh region of Kashmir Himalaya presents an interesting area in providing the complete geological section from Salkhalas to Tertiaries which are traversed by two tectonic planes viz., the Murree Thrust in the south and the Panjal Thrust in the north. An attempt has been made in this paper to present pragmatic classificatory models of granites after comparing the tectonic groups of the present area with the classic areas elsewhere in the world.
Grain Size and Petrography of Mesozoic Rocks of Saurashtra Basin, Gujarat, Western India
Authors: Aslam M.
Published: November 2024

A provenance study was conducted on the Mesozoic rocks of Saurashtra basin, Gujarat, in which grain size, mineralogy and petrographical features of sandstones were integrated to arrive at an consistent interpretation.

Textural parameters suggest progressive variation in that mean grain size increases from Than (0. t 98 - 0.117 mm), Surajdeval (0.257 -0.213 mm), through Ranipat (0.5 -0.378 mm), to Wadhwan (0.716 - 0.469 mm). The bulk of the sandstones demonstrate positive (+) skewness in Than and Surajdeval implying that sandstones include greater admixture of fine sediments, as aganist those of Rani pat and Wadhwan which show excess of coarse admixture. By and large, the Dhrangadhra sandstone is moderately to well sorted (s I=0.52 - 0.84 f).

Petrographically, three types of sandstones constitute the Dhrangadhra group of formations, namely, quartzarenite, subarkose and sublitharenite, consisting of quartz, feldspar, lithic-fragments, and mica in order of abundance. Groundmass material consists of cementing material and matrix. Heavy minerals show a preponderance of granet, zircon, tourmaline, staurolite, rutile and epidote. The study reveals a mixed provenance, comprising of acid igneous, metasedimentary rocks of the Aravalli highlands outcropping in the northeastern part of the study area.
Subsurface Flow of Water and its Structural Control in the North Ganges Floodplain of Bangladesh
Authors: Khan Aftab Alam , Sattar Golam Shabbir
Published: November 2024

The surface configuration of the north Ganges floodplain, covering the region Godagari. Rajsbahi (Paba-Boalia), Durgapur, Puthia and Charghat has been determined. The central region of the investigated area shows some prominent north-south elongated elevated zones and an east-west elongated depressed zone. The rest of the investigated area is marked almost by the flat and sloping surface. The subsurface structural configuration has been inferred taking into account the prominent basement faults and the regional geologic cross-sections. It is inferred that the investigated area is located on the downthrown segment bounded by faults. However the region located nearCharghat where the river Ganges has taken almost 90° swing, is relatively an uplifted block.

The occurrence and the flow of grownd water in the investigated area have also been determined. The area covering Paba-Boaliaand Godagari is characterized by short distance recharge and infiltration from the near surface sources for the groundwater occurrence and movement, while the occurrence and the movement of groundwater in the region of Charghat, Puthia and Durgapur depend on the long distance recharge and infiltration from a few near surface sources.

The water table coutour maps both for the dry and the rainy seasons show some prominent diverging patterns. The water table fluctuation map shows that the zone of minimum fluctuation coincides with the zone characterized by diverging pattern. This anomalous situation has been interpreted as due to relatively higher hydrostatic pressure and the existence of an effective barrier of clay of about 50 feet thick oriented in the north-south direction across Charghat, between Soalia and Puthia, and between Paba and Durgapur.
Magnetic Profile Across Gulf of Mannar
Authors: Murty G. R. K. , Satyanarayana Y. , Pradeep Kumar T.
Published: November 2024

A study of the spectral analysis and two-dimensional modelling of magnetic data collected along the track of 200 km traversing the southern part of the Gulf of Mannar indicates the presence of an anomalous body within the basement. The total field magnetic anomaly along the track is well explained by variations in the topogrphy of the anomalous body of normal polarity and uniform magnetisation. The model shows a topographic relief of about 6 km. The presence of volcanic vents in this area suggests that the anomalous body could be more basic in nature having high susceptibilty values.
Basemetal Mineralization Along the Gurji Stream near Askote, Kumaun Himalaya
Authors: Farooq S. , Hasan N.
Published: November 2024

Surface indications of basemetal mineralization were detected in the granitic gneisses along the Gurji Stream near Askote in Pithoragarh district of Kumaun Himalaya. The sulfide minerals occur in the form of stringers and disseminations. Investigations reveal that the mineralization is hydrothermal in nature and is controlled by the structural patterns of the host rocks. Mineralogy of the altered zone and textural relationships of the sulfide minerals indicate a high temperature of the hydrothermal fluids. The similarities in the nature of sulfide mineralization, the mineral assemblages, paragenesis and associated wallrock alteration with the mineralized zone in low-grade schists at Brigaon near Askote suggest that the two mineralized zones are cogenetic.
Clay Minerals as Indicators of the Provenance and Palaeoclimatic Record of the Kashmir Loess
Authors: Dilli K . , Pant R. K.
Published: November 2024

The provenance of Kashmir loess and its palaeoclimatic significance has been probed using minerological techniques. As many as ten palaeosols (buried soils) have been recognised within the loess profiles. Their mineralogical composition is almost uniform throughout the profilcs. Qu'artz is the dominamt mineral (>60% of the total) and is followed by feldspar and pyroxene suggesting that the loess is derived primalily from a region where both acid and basic rocks and their equivalent metamorphic derivatives predominate. The clay mineral suite consists principally of illite and stnectite, which are negatively correlated. Kaolinite and chlorite are also present (<10% each of total). elemental composition of the different lithounits generally correlate well with the mineralogical data. These studies suggest that the loess was derived from the rocks within the valley itself. Crystallinity parameters of illite are found to be very sensitive to Quaternary climate change and are correlated with deep sea palaeoclimatic record.
Middle Archaean Age of Sargur Group by Single Grain Zircon Dating and Geochemical Evidence for the Clastic Origin of Metaquartzite from J. C. Pura Greenstone Belt, Karnataka
Authors: Ramakrishnan M. , Venkata Dasu S. P. , Kroener A.
Published: November 2024

The middle Archaean J. C. Pura greenstone belt of Sargur Group underlies the Dharwar angular unconformity along the Kibbanahalli arm of Chitradurga schist belt. It consists essentially of periodotitic komatiite (serpentinite), basaltic komatiite (dark amphibolite), rare BIF and minor metaquartzite. In view of the ongoing debate on the origin of Sargur quartzite as to whether it is a chemogenic, biogenic or detrital-rich chert or quartz arenite, the study of J. C. Pura metaquartzite is important as it will have a direct bearing on the depositional setting of the metaquartzite in particular, and the Sargur association in general. In the absence of primary sedimentary structures, accessory zircons in the metaquartzite provide the main clue to its origin. Euhedral zircons with minor rounding of pyramidal terminations in the metaquartzite suggest little mechanical corrosion and negligible sedimentary transport. These zircons are interpreted as detrital grains and the host rock as siliciclastic in origin. Geochemical parameters like Al2O3 vs TiO2, SiO2 and K2O, trace element spider plots, REE patterns and La/Sc ratio indicate a significant continental contribution, low Fe and Mn content, low TiO2-normalised values and variable Co/Zn and Ni/Zn ratios preclude major sea water hydrothermal activity. The proximal provenance indicated by euhedral zircons did not apparently have a significant felsic volcanic component since such rocks are neither present witnin the schist belt nor found as enclaves in the surrounding gneisses. Furthermore, the Sr, Zn, Y, Yb values of the metaquartzite are lower than that of felsic volcanics and pyroclastics, thereby ruling out their prevalence in the source area. The most likely source would therefore be the widespread early Archaean continental crust of southern India made up of granitoids. The metaquartzite was probably deposited as quartz arenite in shallow marine enviroment close to the continent. The associated pillowed komatiite also lends support to this environmental interpretation.

Euhedral zircons from J. C. Pura metaquartzite were dated by single grain evaporation technique which yielded a Pb-Pb age of 3230 ± 5 Ma. This date representing the maximum age of the Sargur metaquartzite is fully in accord with previous Sm-Nd model ages and SHRIMP U-Pb zircon ages (ca 3200 Ma) of Sargur rocks from nearby areas. The Sargur Group is pervasively intruded by gneisses and granites around 3000 Ma. Still older gneisses seen in the neighbourhood such as the Gorur gneiss of 3300 Ma age may constitute a possible basement to the Sargur supracrustals and represent widespread early Archaean granitic crust of the Dharwar craton.
A Study on the Plant Communities in Relation to Copper Mineralisation around Rakha Mines, Singhbhum Copper Belt, Bihar
Authors: Chand Gyan , Venu P.
Published: November 2024

Results of the plant distribution pattern with reference to copper mineralisation in Singhbhum copper belt, Bihar are presented. In the heart of mineralised zone, Hyptis suaveolens or Croton roxburghii dominates. In areas under moderately high level of copper, the dominant species is not uniform and some of these stretches are dominated by Hyptis suaveolens or Croton roxburghii while other have shown Cymbopogon martini or Anogeissus latifolia or Shorea robusta or Diospyros melanoxylon. In contrast, sampling zone containing low levels of copper (around 200 ppm and less) is dominated by either Evolvulus aislnoides or Lantana camara or Woodfordia fruticosa. Areas that contain low copper values are also demarcated by Blumea oxyodonta and Polygonum plebejum. Overall analysis indicates that species varied in the copper tolerance and plants like Hyptis suaveolens and Croton roxburghii dominate when log copper values reach around 4.0. Species like Acacia torta, Diospyros melanoxylon and Holarrhena antidysenterica showed their maximum numbers when log copper values are between 2 and 3. It is suggested that the species combination and community structure are dependent on substrate copper levels.
Distribution of Calcium Carbonate in the Sediments of the Visakhapatnam Shelf, Central East Coast of India
Authors: Murty P. S. N.
Published: November 2024

The distribution of calcium carbonate in Visakhapatnam shelf sediments is controlled by the mollusca shells and shell fragments and foraminifera. The high concentrations near the river mouths are indicative of the detrital contribution also. The concentrations decrease from top to sub-bottom levels due to more dilution by the detritus from the adjoining area and less deposition of non-detrital calcium carbonate in the geological past.
Holocene Sea Levels of Visakhapatnam Shelf, East Coast of India
Authors: Mohana Rao K. , Rao T. C. S.
Published: November 2024

The Holocene sea level changes in the shelf areas off Visakhapatnam was studied from sediment distribution pattern and shallow seismic profiling. Morphological features on the shelf indicate a Late Pleistocene regression down to about -130 m below the present sea level. A major stillstand of the transgressive sea was recorded at about -80 m where coarse carbonates and shallow water fauna predominate. During this period algal barrier reefs with reliefs varying from 2 to 8 m were developed between -85 m (10790 ± 170 years B.P.) and -100 m (12530 ± 170 years B.P.). Buried reefs observed at about -60 m give a clue for a possible strandline at this depth. Coarse clastic sand patch having mean size of around 1.0 Phi between -20 to -30 m suggests another strand line. The sea level rise during Holocene transgression seems to be discontinuous with temporary pauses.
The Origin of the Iron Ore deposits of Donimalai area of Sandur Schist Belt, Karnataka State, India
Authors: Murthy P. S. N. , Chattterjee A. K.
Published: November 2024

Donimalai area is located in the SE portion of the Sandur Schist belt of Precambrian age. There are 6 ore deposits comprising 9 ore bodies having more than 150 million tonnes of high grade hematite ore in Donimalai area.

Banded Iron Formation (BIF) is the host rock for the iron ore deposits. Basaltic rocks, shales with tuff, dolerite and quartz veins are other important litho-units in this area. Principaly the BIF consists of alternative bands of iron oxides and chert belonging to oxide facies.

Hard laminated ore, medium hard laminated ore, soft laminated ore, friable powdery ore and blue dust are the major ore types with minor occurences of lateritic/limonitic ore and shally ore.

Leaching of silica has resulted in the origin of friable ore and blue dust. Leaching of silica followed by enrichment of iron oxide by the circulating solutions has given rise to hard laminated ore, medium hard laminated ore and soft laminated ore depending upon the degree of enrichment. Shaly ore occurs at the contact of deposit 1 with shale. It is formed due to the enrichment of shale by iron-rich solutions, Original material of shale has been replaced followed by enrichment of iron oxide giving rise to shaly ore.

Laterite ore/laterite occurs parallel to the surface of the ground with a thickness varying between 2-10 meters. They also occur along steeply dipping fault planes upto depths of 100-150 meters. parallel to the bedding. Geomorphic evolution of planation surface around 1000 mt. R.L. was responsible for the formation of flat surfaced laterites/lateritic ores. Activity of solutions along fault planes parallel to bedding has caused lateritisation/limonitisation at deeper lavels also.
Rb-Sr Systematics of Granitoids of the Central Gneissic Complex, Arunachal Himalaya: Implications on Tectonism, Stratigraphy and Source
Authors: Dikshitulu G. R. , Pandey B. K. , Krishna Veena , Dhana Raju R.
Published: November 2024

Precambrian Central Gneissic Complex (CGC) in the Kameng district of Arunachal Pradesh comprises the oldest Sela Group thrusting over the Bomdila Group, with the Salari Group being the youngest. Augen gneiss of the Bomdila Group, granite of the Salari Group and hornblende granite gneiss of the Sela Group define Rb-Sr isochron ages of 1914 ± 23, 1536 ± 60 and 481 ± 23 Ma, respectively. The 481 Ma age on the hornblende gneiss from the oldest Sela Group is attributed to the resetting of Rb-Sr clock due to tectonic imprint of the Main Central Thrust (MCT). The 1914 Ma age of the augen gneiss, the oldest reported so far from the Arunachal Himalaya, is either the emplacement age or latest metamorphic event. The 1536 Ma old emplacement age of the granite intruding the black shale of the Salari Group disproves the hitherto considered Gondwana age for the black shale, and, thus, necessitates revision in its chronostratigraphy. (87Sr/86Sr)i of the hornblende granite gneiss and Salari granite is high (0.719 and 0.709) indicating a crustal source for these, whereas it is low for the augen gneiss (0.703) suggesting an inherited signature of the upper mantle source together with some crustal contamination. Rb-Sr whole-rock isochron ages from the Arunachal Himalaya are correlatable with those reported from other parts of the Indian Himalaya. These cumulatively point to at least three major periods of activity in the Himalaya at ca. 2060 ± 250, 1530 ± 90 and 530 ± 75 Ma.
Hydrogeology of Madras City Aquifers
Authors: Ballukraya P. N. , Ravi R.
Published: November 2024

Subsurface lithological mapping has shown the presence of a crystalline rock ridge along the east coast of Madras City, and the aquifer above this ridge shows some characteristic features distinct from those on the western side. The presence of a fresh water ridge along the coast has checked the intrusion of sea water even though water levels are as low as 3m below mean sea level at certian places. Several pockets of brackish ground water have been identified which have been established as due to the presence of tanks and depressions therein. Identification of marine sands below the alluvium in some places gives an idea of the marine transgression that had occurred during Tertiary periods. Studies indicate that most of the alluvium is of estuarine origin, and that the crystalline ridge along with part of the east coast may be updergoing slow uplift.
Orbicular Structures from a Diorite body within the Granitoid Complex of Nellore Schist Belt
Authors: Srinivasan K. N. , Roop Kumar D.
Published: November 2024

A diorite body spread over an areaof 10 sq km, with proto-orbicular and orbicular structures is recorded for the first time near Rapur, Nellore district, Andhra Pradesh. It occurs within the post-tectonic granitoids emplaced along the thrust zone between Nellore Schist Belt and the Proterozoic Cuddapah Basin. It is 'proto-orbicular' in nature with concentric rims of felsics and mafics, having radial and tangential arrangement of plagioclase and biotite respectively. Orbicules are of both crystallothrausmatic and esboitic. The core and matrix are by and Iarge similar in composition. Graphic sand granophyric textures point to igneous origin of the orbicular diorite and the associated granitoids.
Xenotime Placers in Parts of Mahan River Basin, Surguja District, Madhya Pradesh
Authors: Rai S. D. , Banerjee D. C.
Published: November 2024

Several inland placers containing commercially viable resources of xenotime have been described from the Chhotanagpur granite gneiss terrain of Gumla district, Bihar and Raigarh district, M.P. Recent surveys in the adjoining western sector of Surguja district, have confirmed xenotime as a significant minor constituent (3-5 %) in the heavy mineral assemblages (1-4 %) of the various tributaries , of Mahan river.

The assemblage is typical characteristic of a granite migmatitic provenance. Geomorphologically, few of these occurrences are developed over limited extents as poorly sorted sediments in low order, less mature streams having steeper slope and smaller depth with an insignificant flood plain development. Mineralogically, the heavy mineral assemblages consist of ilmenite ± garnet (10-40 Wt%) with monazite (40-70 Wt%), zircon (10-20 Wt%) and magnetite (traces to 5 Wt%). A few of these placers are being investigated as potential sources for Yttrium as their heavy mineral suites, quantitatively, have a higher total content of xenotime and nronazite for upgradation to a marketable product acceptable to the chemical industry.
Fluidized Sediment Movements and Deposition - A case study from Bisrampur, Singhbhum Dt., Eastern India
Authors: Das Subhasish , Manta Santansua
Published: November 2024

Critical studies of a part of Singhbhum basin around Bisrampur, Singhbhurn district, Bihar, show that the metasediments (considered to belong to the Dhanjori Group) lie unconformably above the Singhbhurn Granite. However a few tongues of the granite that occur within the metasediments have been explained as thrust slices of the basement within the cover rocks. Though three phases of deformation have been recorded here, and the general outcropgattern has been largely controlled by the second phase of deformation, there has not been any marked change in the spatial disposition of the coarser clastics. The shape of pebbles within the conglomerate, though often triaxial, cannot be correlated with the deformational history. This calts for original triaxiality of the pebbles. The high proportion of clastmatrix indicates that they were deposited under a two phase flow mechanism: a gravity mass flow aided by a high turbulent flow. Relatively high amounts of solid material in the fluid with variable particle size can create such a turbulent motion and the resultant scattered dispersion possibty accounts for the randomness in pebbleorientation. Accumulation of huge coarse clastics is, however, attributed to gravity mass flow. The general lack of turbidite structures in these litho-units can be attributed to flow inhomogeneity, flow velocity, nature of depositional substrate, relative significance of head-versus-body spilling from turbidity current. Presence of primary structures in arenaceous rocks and occurrence of these rocks as isolated bodies point to vigorous reworking and redeposition of the bottom sediments after cessation of the main flow. The huge pile of the rnicaceous phyllites probably represents relatively rapid deposition of silt grains from a highly concentrated mud-dominated turbidity current or very fluid silty debris flow deposited during the waning phase of turbidity flow. The entire load was deposited possibly over a shallow shelf edge. Retention of the original grain fabrics and the sedimentary structures in these metasediments, even though they are very close to a regionally developed shear zone, points to the existence of focally developed, sheltered low stress regimes provided by the Granite basement.
Establishment of Gravity Stations and Inference of Crustal Thickness around Mormugao Harbour and NIO
Authors: Subba Raju L. V. , Krishna K. S.
Published: November 2024

Complete descriptions and basic facts of nine gravity stations of Marmugao harbour are presented. They exhibit a maximum Bouguer difference of 2.12 mGal in an overall distance of about 2 km. Keeping in view the limited amount of data, certain broad and tentative conclusions regarding crustal structure are drawn.
Campanian - Maastrichtian Nannoplankton biostratigraphy of the Narsapur claystone Formation, Krishna-Godavari Basin, India
Authors: Saxena R. K. , Misra C. M.
Published: November 2024

Nannoplankton biostratigraphy of the Campanian - Maastrichtian 870 metre thick argillaceous subsurface sediments below the Lowest trap of Narsapur area, Krishna-Godavari Basin has been presented in the paper. These infratrappean sediments are assigned to Micula nurus and Arkhangelskiella cymbifomis zones of Late Maasbichtian age and undifferentiated CC 19-CC 23 nannoplankton zones of the Campanian age. Occurrence of global Late Maastrichtian marker Micula murus just below the lowest trap is significant and considered to be important short lived nanno-event in Late Maastrichtian times. The initiation of oldest volcanic eruption in the Narsapur area is around 67.0 Ma. (middle of Micula mums zone) and it is correlated with the lowest limit of the Deccan volcanism in Razole area.
The Role of Telluric (TE) and Magnetotelluric (MT) Methods in the Exploration of deep Sedimentary Basins
Authors: Adam A. , Nemesi L. , Arora B. R.
Published: November 2024

After, a methodical overview of the magnetotelluric and telluric methods, the paper with the help of test example from the Pannonian basin (Hungary) illustrates the effectiveness of a combined telluric and magnetotelluric methods in the study of basement structures of deep basins. It is strongly emphasized that in the case of such adeep basin me relation between the gravity map and basin structure may be totally distorted by the crustal-mantle anomalies, first of all by the intrusion of mantle material of high density. Recognising the merits of combined telluric-magnetotelluric method in the exploration of sedimentary basins for hydrocarbon traps, the significance of the application of these methods to Indian sedimentary basins is highlighted. Usefulness of electrical conductance map, derived from these investigations, in demarcating thermally favourable zones of hydrocarbon maturation is envisaged.
Uraniferous Organic Matter in the Sandstone-Type Uranium Ore from Domiasiat, Meghalaya, India
Authors: Krishna Rao N. , Sunilkumar T. S. , Narasimhan D.
Published: November 2024

Uranium in the sandstone-hosted uranium deposit at Domiasiat, Meghalaya is mainly associated with organic matter (OM), which is also enriched in several trace elements, viz. Zn, Pb, Ni, V, Co, Ba, Sn, Mo, Cr, Ag, P etc. This paper is an attempt to characterize and discuss the origin of the OM and the associated uranium.

The OM occurs in several forms - lumps, layers, veins, dispersions, fracture fillings, coatings and impregnations. Based on structural features and optical properties, seven types of OM are identified. The structural and compositional features indicate that the OM is type II kerogen with macerals mainly belonging to liptinite group. Some of the primary structures have acted as loci of deposition of uraninite and other inorganic minerals like pyrite, marcasite, sphaleri'te and apatite, thereby giving rise to certain interesting textural features. Development of asecondary granular structure and bIades of secondary OM are features related to maturation. Uranium occurs in the form of uraninite of three generations, minor coffinite and a distinct organo-uranyl complex.

Both the South Khasi granite batholith and the tuffaceous matter related to Sylhet Trap episode appear to be the source for various inorganic elements enriched in the OM. From structures and association it appears that uranium fixation in the OM has taken pIace both due to anaerobic reduction by bacterial H2S and complexation to form organo-uranyl complexes. The latter, on maturation, was reduced to form fine precipitates of uraninite dispersed in the OM. It is suggested that the maturity of OM, extending up to semi-anthracitic stage, has taken place due to radiolysis and radiogenic heat.
Mineralogy of Panchpatrnali Bauxite Deposit Based on XRD, IR, DTA and SEM Studies
Authors: Som S. K. , Bhattacharya A. K.
Published: November 2024

Mineralogy of bauxite profile, after khondalite parentage, at Panchpatmdi area, Koraput district, Orissa is studied by XRD, JR, DTA and Optical/electron microscopy. XRD shows thedominance of kaolinite in saprolite, whereas IR and DTA results confirm its presence in the entire profile. All the above studies confirm the strongly disordered nature of kaolinite. Gibbsite, geothite, hematite, diaspore and allophane are present in the entire profile with the intermittent occurrence of boehrnite, anatase, and futile. Microscopic investigation reveals poIycyclic crystalisation of gibbsite and ultimately resilicated to kaolinitevia dlophane. Transformation of alurninious parent minerals to gibbsite is direct without the intermediate kaolinite stage. Evidences are presented to show that gibbsites are later transformed to kaolinite due to ground water activities.
Mineral Chemistry and Geochemistry of the Mesocratic Quartz Syenite Intrusions from Vikurthi and Kotappakonda, Guntur District, Andhra Pradesh
Authors: Madhavan V. , Srinivas M. , Mallikharjurna Rao J. , Chalapathi Rao N. V.
Published: November 2024

The paper presents the mineral analyses and the major, trace and rare earth element geochemistry of the subalkaline syenites from Vikurthi and Kotappakonda in the Guntur district of Andhra Pradesh. A comprehensive model is proposed wherein these and other similar rocks from the Cuddapah intrusive province are envisaged as the differentiated products of an intermediate magma of trachybasaltic composition, which, in turn, has been derived by the differentiation of a parental gabbro magma.
Petrochemistry of a Gametiferrous Chlorite Schist Horizon from the Sandur Schist Belt, Karnataka
Authors: Bhat S. S. , Bhattacharya A. , Dasgupta H. C. , Dasgupta D.
Published: November 2024

Petrology and mineral chemistry of garnetiferrous chlorite schists belonging to Deogiri formation in the Sandur schist belt have been studied. Mineral assemblages and chemical data on muscovite, biotite, chlorite, garnet from the Deogiri chlorite schists indicate low grade regional metamorphism under greenschist facies condition. Mineralogy of the metabasics associated with Deogiri chlorite schists and with the overlying Donimalai formation in this region, except near the peripheral contacts, also suggest greenschist facies metamorphism for the schist belt. Mineralogy and chemistry of Deogiri metabasalts indicated ocean floor type of alteration/metamorphisrn for the Deogiri metabasalts. Rocks close to the granite contact have seemingly undergone an episode of thermal metamorphism which is distinct from the regional metamorphism of the entire schist belt and possibly isolated both in space and time.
Detrital Origin of Fuchsite-Bearing Quartzites in the Western Dharwar Craton, Karnataka, India
Authors: Argast Scott
Published: November 2024

Quartzites in the Nuggihalli (Banavara), Holenarsipur, JavanahaIli, Bababudan and Chitradurga schist Belts were evaluated using petrographic and chemical methods. All the examined quartzites originated as clastic sandstones, none as inorganically precipitated cherts. Chromium is introduced to the oldest quartzites in the form of detrital chromite. Fuchsite is forming in association with this chromite during metamorphism. There is no evidence for significant contributions of hydrothermal Cr. There are secular trends in median Cr/Al2O3, Cr/Fe2O3, Cr/Zn and K2O/AI2O3 ratios. These trends are consistent with the gradual evolution of mafic and sialic sedimentary source tenanes over the interval from approximately 3.5-2.5 Ga ago. The compositions of the quartzites from Javanahalli and Bababudan Belts are sufficiently different to suspect, but not prove, they are from different sources.
Foraminifera from the Nodular Limestone, Bilthana, Gujarat: Stratigraphic Significance
Authors: Rajshekhar C. , Atpalkar Suresh
Published: November 2024

On the basis of field and microfaunal evidences the Nodular Limestone of Bilthana and Man River Sections are considered to be the same lithounit, though different stratigraphic nomenclatures have been used for these two regions. This Limestone is bioclastic in nature and is not of chemical origin as was thought by earlier workers.

The hitherto unreported foraminifera from the Nodular Limestone of Bilthana, consist of planktonic as well as benthic foraminifera. The former is represented by Heterohelix globulosa, while the latter represent the species of Lagenammina, Scherochorella, Ammobaculites, Haplophragmoides, Spiroplectammina, Trochammina, Textularia, Dentalina, Vaginulina and Frondicularia. The presence of simple Lituolid genera such as Ammobaculites, Haplophragmoides and Trochammina indicates prevalence of shallow water (within shelf condition) during the deposition of this limestone at Bilthana.
Graphite Occurrences in Southern Kerala: Characteristics and Genesis
Authors: Radhika U. P. , Santosh M. , Wada H.
Published: November 2024

Graphite is commonly associated with the metapelites of upper amphibolite to granulite grade in the Kerala Khondalite Belt (KKB). A number of distinct associations of graphite are identified in this study such as: (I) strataboundand stratiform disseminations in metapelites, (2) veins, coarse flakes, pods and lenses associated with pegmatites, (3) enrichment along shear zones, (4) flakes and books in calc-silicate-charnockite associations and (5) residual concentrations in weathered rocks and laterites. While graphite disseminations in the metapelites (khondalites) occur as small flakes oriented parallel to the metamorphic fabric, the vein and pegmatite hosted graphites are found as coarse Rakes and books. Graphite which fills mesoscopic shears and faults also form coarse aggregates. X-ray diffraction studies indicate a high degree of crystallographic ordering for all the graphite types. Scanning Electron Microscopy reveals perfect crystal forms for graphites from the vein and pegmatite assemblages. Carbon stable isotope analysis of twenty three graphite samples are presented. The disseminated graphite yielded d13C values in the range of -17.5 to -32.1 per mil, characteristic of biogenic origin. Graphite associated with pegmatites shows d13C in the range of -10 to -15.1%, while those from shear planes have values ranging from -8.2 to -12.4%. Heavier carbon enrichment in these cases is suggestive of precipitation from CO2-rich fluids. The mechanisms which lead to the precipitation of graphite from CO2-rich fluids are evaluated. Thermodynamic considerations indicate that introduction of CO2-rich fluids into country rocks under low fO2, will result in the precipitationof graphite on a quantitative basis. The vein-, pegmatite-, and shear-hosted graphite in Kerala may therefore represent large scale infiltration of CO2,-rich fluids along structurally controlled pathways.