Conference Papers
Melting Experiments in the PbS-FeS-ZnS-Cu2S-S System: Possibility and Nature of an Anatectic Base Metal Sulfide Melt
SKU:
C-63402
Partial melting of pre-existing sulfide deposits during metamorphism has been shown to be a viable ore genesis process that can enrich rare and precious elements. In this study we have done experiments in evacuated silica tubes to examine the possibility of producing anatectic sulfide melt. Detailed scanning electron microscopy (SEM) and electron probe micro analysis (EPMA) of the experimental run products suggest that in a deposit containing sphalerite, chalcopyrite, pyrite and galena, sulfide melt can be produced at 595?C. This melt, ignoring Fe, contains the metals Cu, Pb and Zn in the approximate weight proportion 37:61:2. At 760 ?C, when pyrite is not stable, the melt becomes richer in Pb with Cu:Pb:Zn = 16:82:2. Partial melting of common sulfide deposits during medium to high grade metamorphism thus can produce anatectic sulfide melts that would essentially be rich in Pb and Cu with higher Pb-contents at higher temperature of melting. The extremely uncommon Pb-Cu deposit of Sargipali, Odisha possibly owes its origin to the segregation and emplacement of such melt.
Mesozoic and Tertiary Stratigraphy of Kutch* (Kachchh) ? A Review
SKU:
C-105405
The Kutch rift basin is filled with synrift Middle Jurassic to Early Cretaceous sediments and Post-rift Late Paleocene to Pliocene and Quaternary sediments. The Late Cretaceous-Early Paleocene break in sedimentation is marked by postrift inversion related uplift and Deccan Trap volcanism. The Trap flows separate the two groups Mesozoic and Tertiary. The ammonite rich highly fossiliferous Mesozoic strata attracted attention of the paleontologists and based on the ammonite assemblages the Mesozoic was classified by Waagen (1875) into four age groups. This initial classification was later expanded and modified by subsequent workers like Spath, Rajnath, Biswas, Krishna et al. and Fursich et al. With the development of new stratigraphic concept and recognition of Litho-, Bio- and Chrono-stratigraphy, both Mesozoic and Tertiary stratigraphy were re-studied and revised. Wynne and Fedden were the first to map the entire basin during the period, 1867-69, and described the geology of the basin in great details (1872). They strictly followed the lithologic criteria in selecting the Mesozoic and Tertiary stratigraphic units for mapping. Following the cue from Wynne, Biswas and co-workers worked out a lithostratigraphic classification (Biswas, 1971; 1977) and carried out detailed mapping of the entire basin tracing the precisely defined rock-units. The classification had taken note of the varying litho-facies and association in different sub-basins in the rifted set up. This classification was formally presented following the Inernational Code of stratigraphic classification, terminology and usage (Hedberg, 1972). The classification is undergoing refinement as more detailed researches are carried out by later workers applying new concepts like sequence stratigraphy, sediment dynamics and facies. However, some workers are advocating for retaining the old names of four stratigraphic units given by Waagen in 1875 as 'traditional' names although these names had no relevance to stratoypes and facies variation and do not fit into present concept of lithostratigraphy. These so called traditional units were never defined with description of lithology and the boundaries based on field mapping excepting locally by some later workers (Rajnath, 1932; Agarwal, 1957). In this paper, the views and suggestions of different workers and the current status of the Mesozoic stratigraphy are reviewed and a modified and updated version of rock-stratigraphic classification is presented.The Tertiary stratigraphy was also studied in great details and systematically classified in all the three categories which are well accepted. Many new research works are being carried out presently on different aspects of stratigraphy applying the latest concepts.The main objective of this review is to present the current status of the Mesozoic and Tertiary stratigraphy of Kutch and update the classifications.
Microbial-Enzymatic Gold Nuggetization Process in Extraction of Gold from Old Mill Tailings of Kolar Gold Fields, Karnataka
SKU:
C-165475
About 100kg of tailing sample containing 0.72g/t of gold was collected from the Kolar Gold Fields, Karnataka and passed the entire quantity through three processes conducted on Lab scale. The first process is Hyper accumulation of Gold from Tailing (HAGT). This process involved the aquatic plant Eichhornia crassipes commonly known as Water Hyacinth which was cultivated and harvested in ponds loaded with the 100kg of gold-bearing tailing sample. In the 2nd process, the harvested Water Hyacinth was introduced into Microbe Incubated Bio Reactor (MIBR) where in the Hydrogen, Carbon, Lignin, Hemicellulose, Cellulose and Glucose contained in Water Hyacinth were converted to natural gas by methane-producing bacteria using a proprietary process called Microbe Incubated Bio-Reaction. In the 3rd stage, which is the final stage, the gold Nuggetization process namely Microbial Enzymatic Gold Nuggetization (MEGN) was introduced to treat the product outcome from MIBR process. The MEGN process was very effective in extraction and concentration of gold. The MEGN process employed certain harmless non-pathogen microorganisms such as Cupriavidus metallidurans and Delftiaacidovorans which were cultivated by the authors in their laboratory. These microorganisms produced an enzyme called Cup A and Cop A which have the ability to convert gold compounds into their non-absorbable forms and accumulate or concentrate them in their exterior. The size of such accumulated gold compounds varied from a few microns to a few millimetres, hence are termed nuggets and the process is named nuggetization. The weight of such accumulated nuggets was a few micrograms to milligram.The net weight of the processed and dried Water Hyacinth from the first process (HAGT) was about 3.2 kg. A 100-gram sample of this was analysed for its efficacy. The concentration of metals especially gold and silver showed significant concentrations in all tissues of the plants. The analysis revealed higher contents of heavy metals such as Cadmium (Cd), Chromium (Cr) in the roots of Water Hyacinth, whereas significant concentration of Nickel (Ni), Lead (Pb), Cobalt (Co), Gold (Au), Silver (Ag), Silicon (Si) and Iron (Fe) were observed in shoots. Interestingly the content of Nickel was the highest. The gold concentration was 78mg/kg. The product of the 2nd process (MIBR) was designated as the Super-Ore which weighed about 2 to 3 % of the net weight of the pre-processed water hyacinth. The Super-Ore was subjected to Nuggetization process (MEGN) when the concentration of gold increased from 78mg/kg to 120mg/kg as analysed by fire assay, whilst the quantity of super-ore got reduced. Thus, the gold present in the 100 kg of tailing was accumulated through water hyacinth, converted to a ?super-ore? and nuggetized.
Micropalaeontological Response To Mid-Late Cretaceous Oceanic Anoxic Events: 50th Anniversary Tribute to the Pioneering Work Of R.P.S. Jefferies
SKU:
C-63290
In the early 1960s, R.P.S. Jefferies conducted an investigation of the microfossils found in the Actinocamax plenus Marls of Southern England. This was the first investigation of its kind, using closely-spaced samples and providing a detailed analysis of a relatively short interval of geological time. The Plenus Marls Member, as it is now known, is the on-shore representation of Oceanic Anoxic Event ll (=Bonarelli Event or Cenomanian/Turonian Boundary Event [CTBE]). Jefferies' detailed analysis of the changes over this major extinction event in Earth history has provided the foundation for much later research. Anoxic events - including the CTBE - characterise the mid-Late Cretaceous interval and all are associated with stable isotope excursions, geochemical changes and distinctive patterns of both extinction and appearance of various taxa. Some of these (e.g., calcareous dinoflagellates, radiolaria) are now regarded as 'disaster taxa' and their appearance, in variable numbers, from a range of locations can be used to inform judgements about the nature of these events.
Micropaleontology in Multi-Disciplinary Research: Applications to OAE2 and KTB
SKU:
C-63279
Today, it is virtually unthinkable to solve almost any geologic problem without microfossils, whether in terms of age control or environmental proxies. Perhaps the turning point came in 1980 with the impact hypothesis as cause for the end- Cretaceous mass extinction. Although this hypothesis initiated one of the longest running and most acrimonious scientific debates, its most lasting and positive effects include the introduction of really high-resolution biostratigraphy at the cm-scale and the beginning of truly interdisciplinary and multi-disciplinary studies. Rarely has there been a topic so popular, albeit contentious, that it attracted interest and attention by disciplines across the spectrum of earth sciences and beyond. This report highlights advances in high-resolution biostratigraphy and environmental studies based on major events in Earth's history, such as the Oceanic Anoxic Event 2 (OAE2) and the Cretaceous-Tertiary boundary (KTB) mass extinction. It illustrates current age control, biostratigraphic resolution, stable isotope records with characteristic ?13C excursions and integration with other disciplines to derive environmental interpretations.
Middle Cenomanian to Middle Turonian Planktic Foraminiferal Assemblages from Scattered Outcrops in the Karai – Kulakkalnattam Area, Uttattur Group, Southern India
SKU:
C-63318
The purpose of the present study is to record the planktic foraminiferal fauna present and to determine the Cenomanian- Turonian boundary based on the planktic foraminifera of the Karai - Kulakkalnattam Traverse of Uttattur Group, East coast of India. For this study one hundred ninety five sediment samples were systematically collected from the Karai - Kulakkalnattam traverse. Foraminifers were separated out by using standard micropaleontological techniques. Five Species of planktic foraminifera were identified and studied. In the present study area the Cenomanian-Turonian boundary (C/T) is placed in the upper most part of the Whiteinella archaeocratacea Partial range zone. The distribution of foraminifera and stratigraphic importance of this species are discussed.
Mineralogy and Ore Petrography of Vanadiferous Titaniferous Magnetite Ores of Mayurbhanj Basic Igneous Complex, Odisha
SKU:
C-63394
The vanadium bearing titaniferous magnetite ore deposits occur within the gabbro - anorthosite suite of rocks (Mayurbhanj basic igneous complex) extending for about 15 km from Kumhardubi in northwest to Hatichhar in south east, Mayurbhanj district, Odisha. The ore bodies occur as lodes, pockets and float boulders. The ore microscopic studies reveal the presence of primary Ti-magnetite, ilmenite, ulvospinel, spinel, martite, goethite, lepidocrocite and minor and trace amounts of diaspore, apatite, sulphides and silicate gangues. The titanomagnetite and ilmenite grains reveal various micro-intergrowths: (a) discrete coarse granular ilmenite, (b) external and internal granules of ilmenite, (c) trellis intergrowth of coarse and fine ilmenite lamellae, (d) ilmenite showing sandwich intergrowth, (e) magnetite-ulvospinel (?ilmenite) cloth intergrowth, (f) spinel lamellae in magnetite, (g) spinel-ilmenite intergrowth and (h) hematite lamellae in ilmenite. The evolutions of different types of micro-intergrowths are interpreted in terms of exsolution and oxidation above and below the magnetite - ulvospinel solvus. Ti magnetite grains show incipient to extensive alteration to martite due to oxidation during weathering.
Morphometric Characterization and Neotectonic Evolution of Island Belt Uplift of Kachchh, Western India
SKU:
C-105418
Kachchh is a tectonically controlled palaeo-rift basin. Correlation of major structural fabrics with sequential growth of minor geomorphic configuration is well understood by applying morphometric parameters in the northern Island Belt region of Kachchh. The present study is an attempt to correlate morphometric studies with field based geomorphic features to find out the active tectonics of the Island Belt Uplift of Kachchh. Morphometric parameters like long profiles, gradient index, mountain front sinuosity etc suggest tectonically active landscape. Two to three distinct knick points and peaks on the long profiles and gradient indexes of key drainage basins are complement with three bedrock terraces and three scarps indicating three episodes of tectonic pulses along the IBF and associated transverse faults during the Quaternary period.
Multiproxy Evidence of Main Deccan Traps Pulse near the Cretaceous-Tertiary Boundary
SKU:
C-63309
Recent studies indicate that the bulk (80%) of Deccan trap eruptions occurred over a relatively short time interval in magnetic polarity C29r, whereas multiproxy studies from central and southeastern India place the Cretaceous-Tertiary (KT) mass extinction near the end of this main phase of Deccan volcanism suggesting a cause-and-effect relationship. Beyond India multiproxy studies also place the main Deccan phase in the uppermost Maastrichtian C29r below the KTB (planktic foraminiferal zones CF2-CF1), as indicated by a rapid shift in 187Os/188Os ratios in deep-sea sections from the Atlantic, Pacific and Indian Oceans, coincident with rapid climate warming, coeval increase in weathering, a significant decrease in bulk carbonate indicative of acidification due to volcanic SO2, and major biotic stress conditions expressed in species dwarfing and decreased abundance in calcareous microfossils (planktic foraminifera and nannofossils). These observations indicate that Deccan volcanism played a key role in increasing atmospheric CO2 and SO2 levels that resulted in global warming and acidified oceans, respectively, increasing biotic stress that predisposed faunas to eventual extinction at the KTB.
Nanogeoscience in Gold Exploration: Challenges and Opportunities in India
SKU:
C-165474
Minerals behave differently at nanoscale, compared to their bulk properties and significant variations are observed in their physico-mechanical properties at the nanoscale. The other physico-chemical processes such as transportation, precipitation, dissolution, phase changes and microbial interaction are also related to nanoscale mineral phases in different geological environments. The study of all such phenomena at nanoscale has a significant implication at the deposit and province scale ore system of a gold prospect. This work is a review of the existing national scenario in terms of the scope and potential for such kind of investigation, where nanotechnology has a key role in understanding the nanoscale processes during the gold mineralization. Such studies are being carried out in India within the Archean terrains of the Dharwar Craton (DC) and as well as Archean and Paleo to Mesoproterozoic Singhbhum Crustal Province (SCP). The investigations are mostly confined to the metasedimenthosted auriferous sulfides such as pyrites and arsenopyrites. The sub micrometer gold grains within the sulfides are studied to understand the mechanism of the mobilization of gold and its subsequent precipitation within a mineralizing system. The present study includes a review of the such nanoscale characterization of sulfides by conventional petrographic and ore microscopic technique followed by quantitative analysis of major and trace element by Field Emission Scanning Electron Microscopy (FE-SEM), Electron Probe Micro Analyzer (EPMA) and Laser-Ablation Inductively-Coupled Plasma Mass Spectrometry (LA-ICP MS). The FE-SEM and EPMA are used to study the mineral chemistry and the distribution of trace elements. The LA-ICP MS are used to carry out the quantitative analysis of various trace element concentrations associated with auriferous sulfides. The application of nanogeosciences led to the discovery of new deposits of Carlin type gold mineralization in Nevada, USA and Guizhou Province in China. Similar types of studies were also carried out in the Zarshuran gold deposits in northwest Iran and Alshar gold deposits in southern Macedonia. These studies highlight the fact that the application of nanogeoscience techniques have significant implications on exploitation, beneficiation and mining of gold prospects.
Natural Disaster Monitoring System ? Karnataka Model
SKU:
C-95964
International Panel on Climate Change Working Group II has suggested that the extreme weather events are likely to increase in both frequency and severity, particularly on regional and local scales (IPCC 2007). Consequently, devastating weather phenomena like successive droughts, torrential rainfall associated with lightning strikes, hailstorms, strong surface winds, and intense vertical wind shear are to increase and cause loss of life and property. It has been recommended to plan and implement monitoring system and sector-oriented early warning systems for the communities at risk.Karnataka State Natural Disaster Monitoring Centre (KSNDMC) has taken up pioneering and path breaking initiatives towards monitoring Natural Disasters. The Disaster monitoring mechanism, with a proactive approach, adopted by KSNDMC is a unique model in the country which has enabled the Executives earmarking areas affected by Disasters and notifying them in time. This has greatly supported the activation of response system in planning and implementing mitigation measures.KSNDMC has installed a network of weather monitoring stations which comprises Solar Powered GPRS enabled Telemetric Weather Stations at 747 Hoblis and Telemetric Rain Gauge Stations at all the 5625 Grampanchayaths. The data on Temperature, Relative Humidity, Wind Speed, Wind Direction, Rainfall Intensity and amount of Rainfall is being collected at every 15 minutes. The near-real time data collected through the network is being analysed, maps and reports generated at real time. The meso-scale weather forecast, at same spatial resolution as that of weather monitoring stations network, has also been developed.The Forecasts Alerts, Early warnings, Reports and Advises are being disseminated through email, SMS to the mobile phones of State level to Grampanchayath level officers of all line departments of GoK. To disseminate weather related information, forecast and related advises directly to the general public a 24x7 interactive Help Desk "VARUNA MITRA" is operational throughout the year.The near-real time data collection, report generation and dissemination have been helping the State Government in planning and executing disaster management and mitigation plans at micro-level.
Neoproterozoic Chert Permineralized Silicified Microbiota from the Carbonate Facies of Raipur Group, Chhattisgarh Basin, India: Their Biostratigraphic Significance
SKU:
C-63321
A diverse assemblage of microorganisms are being discovered in black bedded, nodular and lenticular silicified cherts in the limestone/dolomite sequence of the Saradih Formation, Raipur Group, Baradwar sub-basin - a part of main Chhattisgarh basin, India. The composition of microbiota in the present assemblage includes 33 genera (9 acritarchs and 24 cyanobacteria) of different morphotypes categorized as: Acritarchs - Comasphaeridium, Dictyotidium, Favososphaeridium, Leiosphaeridia, Meghystrichosphaeridium, Navifusa, Tianzhushania, Trachyhystrichosphaera and Trachysphaeridium; Coccoids - Eoentophysalis, Eomicrocystis, Eosynechococcus, Glenobotrydion, Gloeodiniopsis, Myxococcoides, Palaeoanacystis, Scissilisphaera, Sphaerophycus and Tasmanites; Filaments - Archaeotrichion, Biocatenoides, Cephalophytarion, Cyanonema, Eomicrocoleus, Heliconema, Oscillatoriopsis, Palaeolyngbya, Partitiofilum, Polybessurus, Polythrichoides, Siphonophycus, Richnonema, and Veteronostocale. Like equivalent Proterozoic microbiota, the Saradih assemblage includes extensively well preserved morphotypes of both prokaryotic and eukaryotic affinities representing planktic and benthic habitats belonging to different groups and families. The mat forming and mat dwelling forms are abundant in Saradih assemblage. Mat-dwelling microbenthos and possible coastal microplanktons are abundant in subtidal to lower intertidal settings whereas, densely woven mat populations with few associated taxa characterized more restricted parts of tidal flats. The preservation of vertically oriented sheaths and bundles indicates that in these mats carbonate cementation was commonly penecontemporaneous with mat growth. The microbiotic population in present finding are widely recorded from the peritidal to open shelf carbonate facies of the Late Neoproterozoic (Cryogenian) sediments across world.
Ni-Cu-PGE Mineralization of Heti Prospect, Western Bastar Craton, Central India: An Appraisal Based on Petrographic, SEM and EPMA Study
SKU:
C-63387
The Gondpipri mafic-ultramafic complex consists of several tectonically dismembered gabbro-websterite-troctolite peridotite bodies disposed intermittently in a 10 km long NE-SW trending linear belt within tonalite- trondhjemite-granodiorite (TTG) and charnockite-enderbite, Western Bastar Craton (WBC), Central India. Ni-Co sulphide associated PGE mineralization is recorded in gabbro variants viz. norite gabbro-anorthositic gabbro-gabbro at Heti. The mineralized gabbroic body extends for 500 m strike length with 40 m width and dips 45? to 55? southerly following regional structural trends. The host rocks contain total Cu + Ni up to 5000 ppm with a Cu: Ni ratio <1 and PGE concentration with a maximum of 660 ppb Pd, 506 ppb Pt, 84 ppb Rh, 180 ppb Ir and 75 ppb Ru. Ore microscopic study coupled with Scanning Electronic Microscopy (SEM) and Electron Microprobe Analyzer (EPMA) reveals that Ni-mineralization is mainly hosted in sulphide phases, associated with oxide-silicates. SEM and Ore petrographic studies shows that mineral paragenesis involve pyrrhotite exsolved pentlandite at high temperature followed by chalcopyrite and PGM formed at relatively low temperatures, where Pt and Pd were eventually bonded with Te, Bi in the residual liquid to form moncheite (PtPdTe2). PGM occurs as dispersed grains at the interface of sulphide and silicate as well as inclusions in Cr-magnetite and silicates. Coexisting oxide and sulphides suggest that sulphide-silicate liquid immiscibility was predominantly induced by the precipitation of Fe rich mineral like magnetite and Cr-magnetite, which causes sulphur saturation melt by decreasing in sulphur solubility and helps in concentration of PGE in sulphide melt. Ni-Fe-S Phase diagram of Heti prospect furthermore shows clustering of Ni, Fe and S suggesting steady sulphur saturation condition that prevailed during the crystallization of sulphides, which probably formed the Ni mineralization associated with PGE concentration in sulphide phase.
Origin, Depositional Setting and Stratigraphic Implications of Palaeogene Glauconite of Kutch
SKU:
C-105413
A combined sedimentological, stratigraphical, mineralogical and geochemical investigation on Palaeogene glauconites of Kutch address some of the crucial issues related to origin of glauconite and its depositional and stratigraphic significance. Glauconite occurs within fossiliferous green shale units of Naredi, Harudi and Maniyara Fort Formation. It occurs primarily in two modes, either as an altered form of fecal pellets or as infillings within the bioclasts. The origin of glauconite may be best explained by direct precipitation of Fe-rich glauconitic smectite within the pores of bioclasts and fecal pellets followed by its maturation to glauconitic mica by the addition of K. Fecal pellet is a more favourable substrate than bioclasts for glauconitization because of easy percolation of pore water within and availability of relevant ions in pellets. Strong biostratigraphic control allows us to clearly establish that relatively high rate of sedimentation (>27 m/Ma) discourage glauconite formation in the Fulra limestone while low rate of sedimentation rate (<5m /Ma) allowed its formation. Occurrence of glauconite exclusively within the transgressive systems tracts and its absence within the highstand systems tracts corroborates the requirement of low rate of sedimentation. Formation of mature glauconite in shallow marine open as well as in protected lagoon suggests that glauconite may be a poor indicator of depositional environment, despite the fact that it forms in modern deep marine conditions. However, positive Ce-anomaly in all glauconites suggests that dys-oxic depositional setting encourages glauconite formation. Absence of glauconite within the unfossiliferous and emerged red shales, immediately overlying and underlying the glauconitic green shales suggest that oxic condition discourages glauconite formation.
Palaeocene to Early Eocene Planktonic Foraminifera of the Pondicherry Area, South India
SKU:
C-63308
Planktonic foraminifera from several outcrops and sections in the Pondicherry area, South India, were analyzed to determine their age. Preliminary analysis of the samples collected from various outcrops and sections of Pondicherry area yielded abundant well preserved planktonic foraminifera belonging to Globoanomolina, Parasubbotina, Subbotina Praemurica, Igorina, Acarinina, Morozovella, Pseudohastigerina and Astrorotalia occurring in part of the sequence in association with abundant Discocyclinids. Fifty-two planktonic foraminiferal species of these genera are recorded from and interval spanning from the early Palaeocene zone P1b to the early Eocene zone P9. The stratigraphic distribution of the planktonic foraminifera from these samples do not allow identification of individual biozones, undifferentiated zone intervals can be recognized, including P1b-P2, P3a-P5 and P6-P9. Species are illustrated based on SEM microphotographs. More detailed biostratigraphic work is needed and will be carried out to identify individual zones and determine the completeness of the sections.
Palaeoecology and Affinity of Ostracod Fauna from the Classic Localities of Lameta Formation of Jabalpur, Madhya Pradesh, India
SKU:
C-63313
Contrasting opinions have been expressed by different workers about the palaeo-environments of the Lameta Formation of Jabalpur. Some workers have ascribed a shallow marine/estuarine environment of depositions for its sediments, while others have favoured a non-marine interpretation. The present authors have recently recorded 26 ostracod species from the basal beds of Lameta Formation from three classic localities (i.e., Chui Hill, Bara Simla Hill and Chhota Simla Hill). These are univocally freshwater fauna. Khosla and Sahni (2000) earlier proposed Late Cretaceous Mongolian and Chinese affinities for the ostracod fauna of the Lameta Formation of Jabalpur. Whatley and Bajpai (2006) considered them strongly endemic to India. Our study revealed an African and/or South American zoogeographic affinity. The genera common to these continents are Altanicypris, Neuquenocypris, Paracypretta, Stenocypris and Wolburgiopsis.
Palaeoenvironmental Significance of Rectilinear Benthic Foraminifera in the Middle Eocene Section of Matanomadh Sub-Basin, Kutch
SKU:
C-63306
A lignite-bearing section at Matanomadh (N23?30'; E68?55') in Kutch was examined for its foraminiferal assemblage. The section consists of lignite and carbonaceous shale in the lower part and mudstone in the upper part. The mudstone is characterized by a low diversity and moderate abundance of dwarf foraminifera. The presence of Halkyardia minima, Linderina kutchensis and Lockhartia alveolata suggests its correlation with Fulra Limestone exposed in the adjoining regions of Kutch. The smaller benthic foraminifera mainly include the species of Brizalina, Bulimina, Trifarina, Cibicides, Discorbis and Guttulina. The Rectilinear Benthic Foraminifera morphogroup (RBF) constituting up to 60% of the foraminiferal assemblage are characterized by large pores. These are typical characteristics of foraminiferal assemblages from low oxygen environment. The peak abundance of RBF occurs consistently at co-eval levels in several sections of Kutch. It is suggestive of dysoxic conditions in late Middle Eocene, corresponding to planktonic foraminiferal zone P13.
Paleoclimate and Paleoenvironment of the Naredi Formation (Early Eocene), Kutch, Gujarat, India
SKU:
C-63302
The Naredi Formation of Kutch, Gujarat, India, is early Eocene in age and marks the first marine transgression above the last Deccan traps. Sediment deposition occurred in a shallow inner shelf environment that varied from a brackish lagoon to brackish, normal inner shelf and to marginal marine environments. The section can be divided into 2 main transgressive cycles interrupted by a regression phase that is marked by a well-defined sequence boundary marked by a root-bearing paleosoil. Three intervals yielded common to abundant benthic foraminiferal assemblages. Planktic foraminifera are few to rare and restricted to the top of the section, except for Chiloguembelina trinitatensis. An early Eocene age can be attributed to the Naredi section based primarily on larger benthic foraminifera (SBZ8 to SBZ11, equivalent to planktic foraminiferal biozones E4 to E6), rare planktic foraminifera, the stable isotope curve and its correlation with marine sections and sequence stratigraphy. Sediments of the transgression/regression cycles were derived from physical and chemical-weathering processes of basaltic rocks as indicated by the different geochemical proxies. Carbon isotope analyses of bivalve shells and organic matter reveal a negative excursion that is correlative with the global Early Eocene excursion. The presence of fish bones, fish teeth and organic matter can be related to the Early Eocene climatic optimum. Clay mineral data from the Naredi Formation indicate variably hot humid to arid climate conditions.
PGE Geochemistry of Komatiites from Neoarchean Sigegudda Greenstone Terrane, Western Dharwar Craton, India
SKU:
C-63398
The Neoarchaean Sigegudda greenstone terrane is a small (ca. 30 km2) greenstone belt, situated to the north of the Holenarsipur belt in the western Dharwar craton. Two compositionally distinct units of ultramafic rocks are recognized in the Sigegudda greenstone belt and have been interpreted as metamorphosed komatiites and komatiitic basalts. These komatiites have been analyzed for Platinum Group Elements (PGE) concentrations which provide significant petrogentic implications on the mantle melting conditions and sulphide saturation history of the parent magma. The PGE abundances of Sigegudda komatiites are characterized by 0.2-3.6 ppb Os, 0.02-1.2 ppb Ir, 0.4-1 ppb Ru among IPGE; and 0.4-4.8 ppb Pd, 0.4-7.6 ppb Pt, 0.2-1.2 ppb Rh among PPGE. These komatiites have lower concentrations of SPGE in the range of 1.02-15ppb. The chondrite normalized PGE patterns show variable PGE fractionation. The overall PPGE and IPGE variations are marked by both lower ΣPPGE/ΣIPGE (<1) and higher ΣPPGE/ΣIPGE (>1); Pd/Pt ratios lower (0.3-0.5) and higher (0.6-2.0) than the primitive mantle average of 0.55; Pd/Ir > Pt/Pd and Pt/Pd > Pd/Ir. Pd/Ir vs. ΣPGE and Pd vs. Cu variations suggest a sulphur saturated to undersaturated character of the parent magma which indicates variable degrees of mantle melting. PGE distributions of Sigegudda komatiites are consistent with olivine and sulphide fractionation trends of parent magma. Relative enrichment of PPGE over IPGE and pronounced enhancements of Pd relative to Pt in some komatiite samples reflect a multi-stage petrogenetic process marked by melt percolation and contributions from sub-continental lithospheric mantle (SCLM).
Planning and Management of Water Resources in North East India
SKU:
C-165860
The topographical and geographical locations of North-Eastern region of India, consisting of eight states is unique with the hydro- meteorological situations making it one of the highest rainfall zones of the world. The region is characterized by low population density, difficult topography, different habitation pattern and social culture, rich forestry and biodiversity with changing climatic conditions . Rainfall of the region being high, varies with space and time in the scale 1000-11000mm. The major river basins of the region are Brahmaputra basin, Barak basin, Gumti basin and Imphal basin. Thus, the variability in rainfall causes some parts of the region water deficient affecting the people?s lives in general and agriculture in particular. Whereas the excess rainfall in some other regions, especially in the Brahmaputra valley causes the floods ,drainage congestion, sedimentation and soil erosion problems. The region accounts for about 35% of total water resources of the country though its geographical area (26.23 Mha) is only 8% of the country. Ultimate Irrigation Potential (UIP) of the region is 43.16 Mha. Irrigation Potential Created (IPC) through major, medium and minor irrigation schemes of NE are less than one fifth of UIP. Percentage of net irrigated area (NIA) over net sown area of the region is 18.89 as compared to the national average of 44.88 %. Hydropower potential of this region is 63257 MW, of which only 1911 MW has been harnessed so far (3.02%). Per capita availability of water in the region is highest in the country. However, its harnessing is very limited, which is even less than 5% of the existing potential. In spite of such huge water resources potential of the region, harnessing and development of the water resources potential for irrigation and hydropower is very nominal. Thus, to assist the optimal and sustainable use of water resources in the North Eastern Region, there is a need to plan effectively by applying the management tools, and through institutional collaborations, and accordingly initiate actions for control, conservation and utilization of water throughout the region. This paper is a review on the status of development of water resources in NER. Some views and suggestions are also presented in terms of proper planning and management of water resources in the region.
Plant-Microbe-Rock Association in Exploration for Gold
SKU:
C-165476
The paper presents a detailed record of certain types of lichens, microbes and Spinifex grass that have colonized Banded Magnetite Quartzite outcrops exposed over a 60 km long NNW-trending tract within Peninsular Gneiss in parts of Mandya, Ramanagara and Tumkur districts, Karnataka. The study discusses hyper-accumulation of noble metals and trace elements in Spinifex grass. The most common lichens identified are crustose and foliose that produce organic acids. The rhizosphere zone of the soil immediately around the Spinifex root is a hotspot for microbes. They produce the most complex chelating agents that are capable of removing metallic cations from minerals. The bacterial species Bacillus cereus which releases gold is isolated and identified by using biochemical methods. The Spinifex grass finally accumulates gold in its leaves, from the substratum. In this study, assay of ash of the Spinifex grass has indicated presence of gold and PGE and other metals. A few magnetite ore samples that possibly are source of gold have been analysed by destructive and non-destructive analytical methods. The analyses results have indicated their presence in significant quantity. The reasons why the Spinifex grass accumulates gold, Platinum Group Metals and other metals are presented. This work is still in its infancy and warrants a detailed study.
Platinum Group Element Mineralization in the Mothinamakki-Birolli-Suryakalyanigudda Ultramafic-Mafic Complex in Uttara Kannada District, Karnataka
SKU:
C-63386
Significant abundances of Platinum-group elements (PGE) along with gold have been recorded for the first time from pyroxenite and gabbro in the Mothinamakki-Birolli Suryakalyanigudda layered mafic-ultramafic complex in Uttara Kannada district, Karnataka. The associated path finder elements enrichment such as Cr (45-5000 ppm), Ni (49-3002 ppm), Co (21-434 ppm), Cu (55-10701ppm), V (78-3716 ppm) and Zn (41-1156 ppm) in this layered complex suggest a favorable locale for PGE mineralization. Groove samples from sulphide rich pyroxenite and gabbro have analysed Pt content ranging from 5-405 ppb, Pd 5-593 ppb, Rh 5-106 ppb, Ir 5-18 ppb, Ru 5-20 ppb and Au content <25 ppb to 3.8 ppm. The PGE mineralization in Mothinamakki-Birolli area is akin to other PGE hosted complexes reported from the Dharwar schist belt in the southern part of Karnataka.
Plausible Offshore Freshwater Aquifer System off the Kerala Coast: A Case Study from the Kuttanad Area of Kerala
SKU:
C-165443
Offshore freshwater aquifer systems exist in many parts of the globe as seaward extension of coastal aquifers. The coastal aquifer systems are often very heterogeneous, combining numerous high permeability aquifers interlaid with low permeability aquitards with varying total thickness.This heterogeneity plays a major role in the fresh groundwater storage, movement, and groundwater salinity distribution within such systems. The Kuttanad is a low lying coastal tract in the western coast of Kerala underlain mainly by the Recent alluvium and thick Tertiary sediments unconformably resting over the Archaeancrystallines.The isopach maps of stratigraphic formations indicate offshore extension of the aquifer systems. The hydraulic gradient and its response to groundwater draft over the decade in these confined aquifers indicate offshore freshwaterseawater interface.The marine transgressions and regressions in the Pleistocene period influenced the evolutionary history of groundwater in the aquifer systems in this sedimentary formation. Offshore groundwater resources could act as an important additional freshwater resource in times of rising water stress.
Pre-Deccan and Deccan Magmatism in Kutch, India: Implications of New 40Ar/39Ar Ages of Intrusions
SKU:
C-105422
The Deccan Traps are of global interest for their possible links to Cretaceous-Tertiary (K-T) mass extinction event and global climate change. Radiometric dating of Deccan Trap lavas and intrusions have shown that bulk of the magmatic activities occurred 65 (?1) Ma. Isotopic similarity between Deccan and Reunion lavas have been used as an evidence to suggest that Deccan magmas were supplied by the Deccan-Reunion plume-head. Kutch is located in northwest India where, based on the trajectory that Indian plate took while crossing over the Deccan-Reunion plume, the earliest Deccan lavas would be expected to erupt. Contrary to this expectation, published 40Ar/39Ar dates of igneous activities suggested that Kutch volcanics are as old as the rest of the Deccan province, even with a small "tail" eruption occurring as late as ca. 61 Ma.Kutch's geology is complicated by the fact that it is marked by old rifting events and significant neotectonic activities. Here we present four new 40Ar/39Ar ages of igneous intrusions from Kutch. Three such intrusions occur in the so-called 'Island Belt' that juts out of the great salt flats (Great Rann of Kutch) in northern Kutch. The fourth intrusion is a gabbroic body that occurs at Dhar Dongar in southern Kutch. Two of the Island Belt intrusions (Sadara Sill and Nir Wandh gabbro) give ages of ca. 75 Ma. A lamprophyre dike from the Island Belt gave an age of ca. 67 Ma. The fourth intrusion from Kutch Mainland yielded the youngest age found in Kutch of ca. 61 Ma. These ages, combined with those determined in previous studies (65-67?1 Ma), suggest the following: Earliest rift-related magmatism occurred 75 Ma, and is clearly of pre-Deccan age. The rest of the igneous activities occurred in two episodes - the most voluminous episode coincided with Deccan age (65-67 Ma) whereas a small volume igneous activity took place at ca. 61 Ma, following a 6 m.y. long hiatus. The 61 Ma episode appears to occur in many different locations within the Deccan. We suggest that the 75 Ma pre-Deccan rifting-magmatic event is a relict of magmatism that occurred during separation of Madagascar from India, which was caused by the Marion plume.
Precepts for Groundwater Drought Index in Kerala: A Case Study from Chaliyar River Basin
SKU:
C-165452
Groundwater Drought Index (GWDI) is recognized as one of the key Hydrological Indices of drought. But the evolution of drought from meteorological to hydrologic drought is not instantaneous and is dominated by several physical mechanisms. In Kerala due to heterogeneity of terrain, the occurrences of drought at different temporal and spatial scales do not fit into the broad indices of standard GWDI. Hence drought prediction has become a major challenge to decision and policy makers as it fails to address multiple causative factors to recognize the actual ground realities. This paper is an effort to bring out the meteorological, hydrogeological and hydrological factors based on which an attempt has been made to review the groundwater drought index to suggest an improved groundwater deficit class by studying the extreme climate eventualities during 2016 (drought) and 2018 (flood). The progression of drought and its corresponding effect on groundwater regime in Chaliyar river basin has been studied in detail. Based on the typical response of drought conditions in different physiographic zones, a modified GWDI from the case study is proposed.