Chhotanagpur Granite Gneiss Complex Research Articles

Mineral Chemistry and IMA Nomenclature of Amphibole Minerals of Amphibolite Sills from Chhotanagpur Granite Gneiss Complex (CGGC), Southern Sonbhadra, Central India

ABSTRACT In southern part of Sonbhadra District, near the Rihand Dam, low to medium grade amphibolites of Paleoproterozoic age are exposed. The outcrops are in the form of sills that occur at places in the Chhotanagpur Granite Gneiss Complex (CGGC). The essential mineralogical constituents of the amphibolite are amphibole-plagioclase-chlorite-biotite-iron oxides. Based on the mineral chemistry and interpretation as per the international mineralogical association (IMA) nomenclature scheme, amphiboles in the analysed amphibolite rock samples have been identified as magnesio-hornblende, magnesio-ferri-hornblende and edenite.

Garnet-Staurolite-Mica Schist from Southern Sonbhadra District, U.P.: Constraints from Geothermobarometry and P-T Pseudosection Modelling

Abstract The area around Renukoot town shows the exposure of garnetstaurolite- mica schist belonging to the Chhotanagpur Granite Gneiss Complex (CGGC). The characteristic mineral assemblage present in the rock are garnet–biotite–staurolite–quartz along with minor opaque minerals like rutile, ilmenite and hematite. For the constituent minerals, the calculated XMg value decreases in the order: chlorite>biotite>staurolite>garnet. The metamorphic conditions of the garnet-staurolite-mica schist were determined using the winTWQ and Perple_X programmes, and the peak pressure-temperature conditions for the rock are estimated to be 5.3 kbar and 570°C. The metamorphic episode in the CGGC during Mesoproterozoic time may be attributed to the global level Columbian Super-continental accretionary orogeny.

Microstructural and compositional variations of allanite in hydrothermal veins: Implications for REE mobilization in Chhotanagpur Granite Gneiss Complex, Purulia district, West Bengal, India

Microstructural and compositional variations of allanite in hydrothermal veins: Implications for REE mobilization in Chhotanagpur Granite Gneiss Complex, Purulia district, West Bengal, India

Groundwater quality enumeration and health risk in the extended part of Chhotanagpur granite gneiss complex of India.

The majority of people on the earth bank largely on groundwater to quench their thirst. In the era of rapid population growth, the over-exploitation of groundwater gives rise to water scarcity, and people find themselves in distress to manage safe drinking water. In this backdrop, the present study is carried out in the terrain of Pre-Cambrian igneous and high- to low-graded metamorphic rocks, to assess the groundwater potential zones (GWPZs) and evaluation of groundwater quality. The map of GWPZ is produced employing the multi-criteria decision-making model and geospatial technology. It unveils that around 29% area of the watershed enjoys good GWPZ, whereas around 43% area experiences low GWPZ. The overall accuracy of the simulated model is 92%. The water quality index indicates that 68% of water samples belong to excellent to good water quality. A significant proportion of water samples (24%) are found to be unsuitable for drinking, which may be due to groundwater contamination by the process of leaching of mineral-rich weathered rocks. The presence of fluoride (F-) beyond the maximum permissible limit (1.5mg L-1) of WHO is recorded among 18% samples of the watershed, where 24,963 souls including 3457 children aged between 0 and 6years lived and might have ingested F- through drinking water. Hence, the health risk of those people is quite high. Children are at a more non-carcinogenic health risk of F- than adults. The study also confirms no statistically significant difference (p ˃ 0.05) is observed between low and high GWPZ with respect to groundwater quality. The study recommends adopting a sustainable outlook to explore GWPZ, and an assessment of drinking water quality must be done before drinking.

Petrogenesis and Rb-Sr Isotopic Characteristics of PaleoMesoproterozoic Mirgarani Granite Sonbhadra Uttar Pradesh India: Geodynamics Implication for Supercontinent Cycle

The Rb-Sr whole-rock isochron, age 1636 ± 66 Ma of Mirgarani granite, is the one of the oldest granite dated in the northwestern part of the Chhotanagpur Granite Gneiss Complex (CGGC). The initial Sr ratio is 0.715 ± 0.012 (MSWD = 0.11), showing an S-type affinity. The Mirgarani granite has intruded the migmatite complex of the Dudhi Group and forms the Mirgarani formation comparable to the granites of the Bihar Mica Belt around Hazaribagh (1590 ± 30 Ma). The present studies have established the chronostratigraphy of the Dudhi Group and adjoining areas in CGGC. Petro graphic and geochemical studies revealed that the granite is enriched in Rb (271 ppm), Pb (77 ppm), Th (25 ppm), and U (33 ppm) and depleted in Sr (95 ppm), Nb (16 ppm), Ba (399 ppm) and Zr (143 ppm) contents as compared to the normal granite. The Mirgarani granite is a peraluminous (A/CNK = 1.23), high potassic (K2O 6.42%), Calc-Alkalic to Alkali-Calcic {(Na2O+K2O)-CaO = 6.29} S-Type granite, a feature supported by the presence of modal garnet and normative corundum (2.68%). The Mirgarani granite is considered to have been formed by the anatexis of a crustal sedimentary protolith at a depth of approximately 30 km with temperatures ranging from 685-700 °C during the Co lumbian - Nuna Supercontinent.

Unravelling Source Area Composition for the Paleoproterozoic Basal Conglomerate (Vindhyan Supergroup) around Dalla, Sonbhadra District, Central India

Abstract The present investigation reveals that the Basal Conglomerate is ~ 2-3 m thick forming basal part of the Vindhyan Supergroup in the Sonbhadra district, central India. The Basal Conglomerate consists of fragments of different rock types supported by the sandy matrix. It contains pebble-sized clasts of quartzite, jasper, phyllite and slate dominated by the quartzite clasts.The matrix is composed of sandy material that is rich in quartz, chert and iron oxides. The occurrence of quartzite clasts suggests its derivation from the Chhotanagpur Granite Gneiss Complex (CGGC) and the phyllite, slate and jasper suggest their derivation from the Mahakoshal Group. The presence of polycrystalline and monocrystalline quartz suggests their derivation from Chhotanagpur Granite Gneiss Complex and the presence of chert suggests its derivation from the Mahakoshal Group. The iron oxides were produced as a result of leaching of iron during chemical weathering. The X-ray diffractometry of the matrix suggest ubiquitous presence of quarz, muscovite and kaolinite. The kaolinite has formed due to alteration of feldspars under warm and humid conditions. This is also supported by the presence of ferruginous matter in the matrix.

Phase equilibria modelling and geochemistry of high‐grade gneiss from the Chhotanagpur Granite Gneiss Complex, eastern India: Implications for tectono‐metamorphic evolution

We investigated high-grade gneiss from the Daltonganj region of the Chhotanagpur Granite Gneiss Complex (CGGC) in eastern India. EPMA monazite dating from the Daltonganj region revealed three age domains at ca. 1434, ca. 978, and ca. 850 Ma, which have been interpreted as the protolithic age and two metamorphic stages of high-grade gneisses, respectively. The Grt1 + Chl + Amp1 + Bt assemblages are thought to represent the first metamorphism as a pre-peak stage of high-grade gneiss, which could have occurred after ∼1434 Ma. The peak metamorphic stage is defined by relict porphyroblasts of orthopyroxene and garnet2 formed during ∼978 Ma in a burial process followed by an isothermal decompression or post-peak stage represented by a Crd + Grt3 + Amp3 assemblage at ∼850 Ma. The P-T conditions estimated for the pre-peak, peak, and post-peak stages using the NCKFMASH model system are 6.6-6.8 kbar/635-645°C, 8.65-9.42 kbar/772-788°C, and 5.71-6.18 kbar/745-762°C, respectively. The geochronology and metamorphic conditions define a clockwise P-T-t path for the high-grade gneiss, indicating that rocks experienced high-pressure conditions during burial metamorphism at subduction-related tectonic activity, followed by an isothermal decompression condition after the gneissic unit was exhumed. The geochemical composition of the high-grade gneiss reveals that the protolith is calc-alkaline basaltic magma formed in an island arc setting and that the restitic features of the gneisses developed after granitic melt segregation.

Occurrences of Rare Earth Element (REE) Bearing Minerals in Migmatitic Gneiss and Granitoids of Chhotanagpur Granite Gneissic Complex, Bihar, India

Abstract This paper presents the geochemical characteristics, petrogenetic processes and source characteristics of Rare Earth Elements (REE) bearing migmatitic gneiss and granitoids near Tangeshwar village, Banka district, Bihar, in order to demarcate the potential zone of REE mineralization. These migmatitic gneiss and granitoids belongs to the Chhotanagpur granite gneissic complex (CGGC). The study of migmatitic gneiss and granitoids of CGGC suggest that they have high content of SiO2, low contents of Fe2O3 and MgO and SiO2 vs. Na2O and K2O shows positive correlation which suggest, they are dominated by sodic and alkali rich minerals and were derived from a felsic (granitic) source. Also LREE-LILE enrichment, HFSE depletion and calc-alkaline nature indicates that the magmatism is related to the subduction zone. Petrographic and EPMA studies of these migmatitic gneiss and granitoids confirms the presence of REE bearing mineral phases such as allanite, xenotime, monazite, and basnasite. They are generally present at the rim of biotite, as an inclusion in biotite and also along the grain boundaries and within the cracks of major silicate minerals. This suggest that the REE formation takes place at the deuteric stage of magma crystallisation followed by the formation of granite. Chemical analysis of bed rock samples for rare earth elements using ICPMS shows that the highest concentration is in migmatitic gneiss and granitoids, which varies from 47.85- 925.67 ppm and 47.85- 626.48 ppm respectively.

Reappraisal of 75 Years of Exploration for Atomic Minerals in India and the Way Forward

Abstract In India, Atomic Minerals Directorate for Exploration and Research (AMD), the oldest unit under the Department of Atomic Energy (DAE) is mandated with the exploration and augmentation of atomic mineral(s) resources of the country to support the Nuclear Power Programme (NPP) of India. AMD, till date have established four (04) generations of uranium metallogeny in India, distributed in 46 deposits and several other occurrences, major share of which are contributed by the globally unique, stratabound carbonate hosted, syn-diagenetic Tummalapalle Group of deposit (~59%), metamorphite type deposits along the Singhbhum Shear Zone (~21%), unconformity related deposits in northern part of Cuddapah Basin (~5%) and sandstone type deposits in Cretaceous Mahadek Basin (~6%). Besides these, metasomatite type deposits along the North Delhi Fold Belt (4%) and granite related-structurally controlled, high grade deposits in Bhima Basin (2%) along with some small hydrothermal/metamorphite/migmatite type deposits in Aravalli, Kotri-Dongargarh, Higher Himalaya belts and Chhotanagpur Granite Gneiss Complex contribute to the national inventory which stands at 3,76,000 tonne uranium oxide. AMD have stockpiled substantial quantities of Nb-Ta, Be and Li minerals needed for the NPP of India from prospective pegmatite belts in the country. AMD have established immense potential for REE mineralization in carbonatite complexes of Ambadungar in Gujarat and per-alkaline granite-rhyolite of Siwana Ring Complex, Barmer district, Rajasthan. Exploration along the coastal and riverine placers of the country has established 130 heavy mineral placer deposits with substantial thorium and REE resources. The progressive advancements by AMD through adaptation of integrated multidisciplinary exploration techniques coupled with major thrust in airborne/ground geophysics and expansion of state-of-the-art analytical facilities have facilitated systematic planning for future augmentation of atomic mineral(s) resources. Exploration inputs are envisaged to be intensified in the brownfield target areas for resource augmentation while R&D and phase-wise exploration inputs will be focused for developing the identified greenfield areas following a planned roadmap to ensure selfsufficiency in atomic mineral resources for sustained growth of the NPP to reach the target of net zero carbon emissions by 2070.

Soil-Landform Relationship to Understand Quantitative Pedogenesis under Varying Physiographic Catena of Chhotanagpur Plateau Regions of India

Pedogenic indices were considered to understand maturity of soils in different geomorphic units in quantitative terms. High redness rating and low sand/silt and silt/clay ratio at higher elevations of Rajmahal trap, Hazaribagh plateau and Ranchi plateau indicates rapid pedogenic processes and formation of Paleo-Alfisols (Rhodustalfs and Paleustalfs). High CEC/Clay in lower elevations of Rajmahal trap and Hazaribagh plateau indicates formation of more 2: 1 type of interstratified minerals. Predominant occurrence of amorphous iron (Fe) in soils of Rajmahal basalts was indicated by high ammonium oxalate extractable Fe. Higher proportions of dithionite extractable Fe of clay in gullied lands, uplands of Hazaribagh plateau and hillocks of Ranchi plateau indicate the prevalence of crystalline Fe in Chhotanagpur granite gneissic complex. More crystalline nature of soil clays at higher elevation of Ranchi and Hazaribagh plateaus are noted as indicator of laterization processes. Soils on pediments, uplands and plateaus comprise well matured profiles with formation of paleosols of relict types, whereas that of gullied lands and hillock were least weathered. Undulating plains, old alluvial plains and low-lying plains consists of soils under intermediate stages of weathering with intermediate stages of soil forming processes. These soils (P3, P4, P11 and P12) appear to support agricultural land use comparatively better than other soils despite topographic undulation and soil physicochemical constraints in the region. Presence of considerable amount of interstratified type of 2:1 minerals at lower elevations may attribute to restore better organic carbon sequestering capacity supporting long-term agricultural practices in the region. The present endeavour deals with study of quantitative pedogenesis as a tool to understand soil-landform relationship in varying physiographic catena of Chhotanagpur plateau regions of India.

Metamorphic evolution of the pelitic and mafic granulites from Daltonganj, Chhotanagpur Granite Gneiss Complex, India: Constraints from zircon U–Pb age and phase equilibria modelling

The Daltonganj region is located on the northwestern extension of the Chhotanagpur Granite Gneiss Complex in the eastern Indian Peninsula, which is characterized by pelitic and mafic assemblages of granulite facies rock. The pelitic granulites contain garnet, cordierite, biotite, plagioclase, K‐feldspar, sillimanite, and quartz. Petrographical interpretations divulge prograde and retrograde metamorphic events within mafic granulites, which consist of clinopyroxene, orthopyroxene, amphibole, plagioclase, biotite, and quartz. Field observation, petrography, phase equilibrium modelling, and U–Pb zircon geochronology of the pelitic granulites reveal two stages of metamorphic events along the clockwise P–T path. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) zircon U–Pb age dating of pelitic granulites shows the detrital zircon ages from ~1,734 Ma to 1,677 Ma, and the possible metamorphic domains show the weighted mean age of 1,638 ± 22 Ma, which represents the timing of metamorphism. Subsequently, the magmatic emplacement of mafic granulites was recorded at 1,629 ± 6 Ma age by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) zircon U–Pb dating which coincide with the timing of metamorphism of the pelitic granulite. Phase equilibrium modelling in the NCKFMASHTO system divulges the pre‐peak metamorphic stage at ~3.2 kbar and ~620°C and the first stage which is characterized by a peak metamorphic condition that ranges from 7.40 to 9.10 kbar and from 815 to 835°C during ~1,638 Ma with the mineral assemblage of garnet + sillimanite + biotite + plagioclase + K‐feldspar + melt + quartz + ilmenite. Sequentially, the retrograde metamorphism is observed by a nearly isothermal decompression stage at ~4.0 kbar/~790°C after 1,638 Ma, due to the appearance of garnet + cordierite + biotite + plagioclase + K‐feldspar + melt + quartz + ilmenite + magnetite. The formation of cordierite is due to the decompression and dehydration melting phases. The Nb, Sr, and Ti negative anomalies suggest their generation from crustal sources. The geochemical analyses constrain that the sedimentation of pelitic sediments was recorded along the convergent margin and encountered by a subduction‐related tectonic setting. The geochemical interpretation provides significant evidence that the protoliths of pelitic granulites were derived from the Singhbhum Mobile Belt, Mahakoshal Supracrustal Belt, and Bundelkhand Craton, while their metamorphism was processed by the continent–continent collision and followed by exhumation.

Geomorphic assessment of longitudinal profile of the Kanchi river basin, India: Recognition of dynamic equilibrium condition

ABSTRACT The Kanchi, an eastward flowing river, traverses through the Ranchi plateau of the Proterozoic Chhotanagpur granite gneissic complex to meet its trunk stream, the Subarnarekha River. The present study analyzed longitudinal profiles and associated geomorphic indices of the Kanchi River and its tributaries to identify spatial variation in profile form and fluvial response to prevailing controls. This work was carried out using a digital dataset and maps, which were processed in a GIS environment to obtain longitudinal profiles, and different data required in best-fit modelling and geomorphic investigation of longitudinal profiles. The analyses indicate that the rivers are in dynamic equilibrium condition. Spatial distribution of geomorphic indices values reveals that longitudinal profile forms vary from one segment to another along river channels, and these irregularities in the form of prominent and minor knickpoints are highly concentrated in middle river basin areas. The absence of lithological variation and active tectonics, and close association of anomalously steep river segments with structural lineaments and landforms demonstrates structural control on river channel development. PCA denotes strong similarities between geomorphic indices. This understanding of longitudinal variation in river nature may help to formulate strategies for the sustainable development and management of river related resources.

Exsolution intergrowth of cpx-opx and pseudosection modelling of two-pyroxene mafic granulite from Daltonganj of Chhotanagpur Granite Gneiss Complex, Eastern India

In this study, we reconstruct for the first time the evolution of a two-pyroxene mafic granulite from the Daltonganj of Chhotanagpur Granite Gneiss Complex (CGGC). Transmission electron microscopy (TEM) revealed that some of the clinopyroxene have exsolution texture, where orthopyroxene occurs as thin lamellae within the porphyroblast of clinopyroxene. To tightly constrain the P-T conditions at which exsolution lamellae developed after the metamorphic peak, we have applied both conventional and multi-equilibrium thermobarometry, as well as forward thermodynamic modelling. Results from multi-equilibrium thermobarometry, using the software THERMOCALC, suggest peak conditions of the mafic granulite at average pressure-temperature (PTav) conditions of 6.7 ± 1.19 kbar/814 ± 60 °C. In contrast, exsolution bearing opx-cpx minerals crystallised at relatively lower temperature (772 ± 14 °C), determined by the conventional geothermometers. The peak to retrograde evolution of these mafic granulites is constrained through phase equilibrium modelling in the NCKFMASHTO (Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O) model system using the software Perple_X. Phase equilibria results of peak conditions (i.e. 6.0–6.78 kbar and 775–808 °C) are consistent with respect to those obtained through multi-equilibrium and conventional thermobarometry, while the retrograde path is defined down to ~4.5 kbar and ~540 °C. Our results have twofold implications: (i) they show how the integrating of different geothermobarometric methods is the best proxy to tightly constrain the evolution of high-grade metamorphic rocks, and (ii) they pavement to new constraints on the Paleoproterozoic to Neoproterozoic evolution of the CGGC.

Assessment of geoheritage and prospects of geotourism: An approach to geoconservation of important geological and geomorphological sites of Puruliya district, West Bengal, India

Exploration of geoheritage sites is a new venture in tourism studies. The objective of the study is centred around the Geoheritage site conservation for geological and geomorphological interpretation and introduction of Geotourism involving the local people in Puruliya district. The main litho-unit of Puruliya district belongs to Chhotanagpur Granite Gneissic Complex of Archean era. Nine geological/geomorphological important sites are chosen for assessing their geoheritage values and analysing the Geotourism potential. A modified model of Kubalikova (2013) is adopted for the evaluation of the selected nine important sites, where five important criteria i.e. scientific (intrinsic) values, educational values, economical values, conservation values and added (cultural, ecological and aesthetic) values are considered. The result reveals that sites like Durgabera dam, Bhanratongri hill, Garpanchakot and Jaychandi hill can be assumed as top potential Geotourism site occupying highest geoheritage values, whereas Jabar hill, Poradih hill and Tamakhun old mine are quite low in the context of Geoheritage values. Based on the result, few strategies are suggested which can help to develop Geotourism in the study area and raise awareness about the geoheritage values among the students, general visitors and the local residents of the area.

EPMA monazite geochronology of the granulites from Daltonganj, eastern India and its correlation with the Rodinia supercontinent

We report the monazite dates of the granulites from Daltonganj (Palamau), Chhotanagpur granite–gneiss complex (CGGC) which covers the significant part of the granulite blocks in central India by using an electron micro probe analyser dating. The monazite grain varies between 70 and 80 μm and shows the distribution of U, Th and Pb in all monazite grains of both samples. Two different dates were obtained from different monazite grains; the first age suggests that the granulite from CGGC preserves the first remnant of the protolith of the Mesoproterozoic era at ~1424 Ma and second one at ~972 Ma which provides evidence of metamorphism of the protolith. The CGGC rocks preserve four regional metamorphic events, namely M1, M2, M3 and M4. But in this work, two different ages from the Daltonganj granulites were obtained which are similar to the M2 (<1500 Ma, i.e., the age of protolith of the granulitic gneiss) and M3 (1200–930 Ma) metamorphic events as reported in the CGGC. The M3 metamorphism attained its average P–T condition at ~7.35 kbar/792°C, and it represents the prograde metamorphic event. The M3 metamorphic event supported the Grenville-orogeny, and it was responsible for the metamorphism of the magmatic protolith of granulitic gneiss from the CGGC at the time of amalgamation of the Rodinia supercontinent. The Rodinia assembly had occurred through the global Grenville-orogenic events between 1100 and 900 Ma, with continental blocks which exist at that time.

A New Find of Uraniferous Migmatites in Singrauli District, Madhya Pradesh, India

ABSTRACT Presence of uranium mineralisation associated with migmatites is reported from Chhotanagpur granite gneiss complex (CGGC) along Baran and Gabala river section in parts of Singrauli district of Madhya Pradesh. Nine radioactive bands along the Baran river and three radioactive bands along Gabala river section near Jhanji hosted by migmatites leucosomes with variable dimensions have been located. The trend of migmatite is E-W to WNW-ESE and dips of 50°-60° N. Grab samples of radioactive migmatite leucosomes from Baran river assay from 93.28 ppm to 534 ppm U and 21.97 ppm to 254 ppm Th, whereas Gabala river migmatites analysed 127.19 ppm to 8564.4 ppm U and 21.97 ppm to 105.48 ppm thorium. Uraninite is the main uranium mineral identified in the leucosome from both the localities. Chemical age of single uraninite grain from Gabala river migmatite is 792Ma age which suggest that uranium mineralisation/uraninite crystallisation in migmatite took place during Neoproterozoic. Euhedral shape of uraninite grain, their high U/Th ratio, high REE content and high unit cell dimension(a0) suggest that uranium mineralisation in migmatite took place at moderate to high temperature hydrothermal fluid. In view of uraniferous nature and their dimension, migmatites of the area warrant detailed exploration to establish migmatite hosted U-mineralisation.

Multistage gedrite in gedrite–hypersthene-bearing high-grade granulites from Daltonganj, Chhotanagpur granite–gneissic complex, Jharkhand, as evident from TEM and textural relations

The studied rock consists of mineral phases garnet–cordierite–gedrite–hypersthene–biotite–quartz and lies nearly 14 km southwest of Daltonganj in the western part of Chhotanagpur granite–gneissic complex. Textural relations of mineral phases, mineral chemistry and transmission electron microscopy (TEM) analyses of the rock samples suggest the early (gedrite1), middle (gedrite2) and late stages (gedrite3) formation of gedrite. Hypersthene appears through the metamorphic reaction gedrite $$+$$ quartz $$=$$ orthopyroxene $$+$$ garnet $$+$$ cordierite $$+ \,\hbox {H}_{2}$$ O due to the breakdown of gedrite3 at the thermal peak of 869 $$^{^{\circ }}$$ C/7.79 kbar. The bundles, prismatic and fibrous forms of three gedrites have been observed in the TEM images. TEM images and selected area electron diffraction patterns show the distribution of metallic element position at the different lattice site. The P–T estimates of the rock from garnet–orthopyroxene, garnet–cordierite and garnet–biotite exchange geothermometers and garnet–sillimanite–cordierite–quartz geobarometers vary from 775 $$^{\circ }$$ to 869 $$^{\circ }$$ C, 642 $$^{\circ }$$ to 703 $$^{\circ }$$ C, 480 $$^{\circ }$$ to 617 $$^{\circ }$$ C and 6.76 to 7.79 kbar, respectively.

Geochemistry of Paleo to Mesoproterozoic Metasedimentary Units of Chandil Formation, North Singhbhum Crustal Province: Implications for Provenance and Source Area Weathering

ABSTRACT The Mesoproterozoic metasedimentary units of Chandil Formation belong to the northern part of Singhbhum crustal province, eastern India. The Formation lies north of Dalma volcano-sedimentary belt and is separated from the Meso-Neoproterozoic Chhotanagpur granite gneissic complex (CGGC) by Tamar-Porapahar shear zone (TPSZ), i.e. South Purulia shear zone, (SPSZ) at its northern boundary. The metasedimentary unit comprises of quartz-mica-sericite-schist, quartzite, amphibolites and carbonaceous phyllites, which have not been studied well, so far in terms of their geochemistry, source rock and provenance characterization. In this work, the existing gaps in all those aspects are studied to infer the provenance of these meta-sedimentary sequences. The high silica contents of the Chandil Formation (∼95% for the quartzites and ∼70% for the metapelites) and low trace element concentrations indicate silica-rich source. The REE patterns of the quartzites and the metapelites exhibit LREE enrichment and HREE depletion with moderate negative Eu-anomalies which strongly favor felsic nature of the provenance. The significant enrichment of LREE, flat HREE patterns and negative Eu-anomalies of the metapelites suggest their derivation from an old upper continental crust, which is composed of felsic components and the negative Eu-anomalies indicate intra-crustal differentiation. The higher concentrations of the HFSE i.e. Zr, Hf and Ta, within the Chandil metasediments relative to those of EPC (Early Proterozoic Continental Crust), also suggests a felsic provenance. The geochemical signatures of the Chandil metasediments indicate that the sediments were derived during a prolonged period of weathering due to the slow upliftment and unroofing of the southern evolving Singhbhum granitic complex (SGC).

High Resolution Multispectral Satellite Data Interpretation and Limited Ground Checking: A Proxy for Geological Mapping and Uranium Exploration in Mahakoshal Fold Belt of Son Valley Area, Madhya Pradesh

Abstract: This research aims at integrating remote sensing data and field studies to prospect for uranium mineralisation in the Palaeoproterozoic Mahakoshal Group of rocks in the Son valley area, Central India. In present work, a revised geological map of Mahakoshal Fold Belt (MFB) bounded by Son-Narmada north fault (SNNF) and Son-Narmada south fault (SNSF) along Chorhut-Sidhi-Chitrangi sector falling in Sidhi, Rewa and Shahdol districts of Madhya Pradesh has been prepared based on interpretation of digitally enhanced satellite images. The satellite image interpretation is supported by limited field works, radioelemental measurements (eU, eTh and % K) of in-situ rocks by four channel Portable Gamma Ray Spectrometer (PGRS) and existing published geological maps of Geological Survey of India. In search for mineral potential areas, accurate and up-to-date geological maps are essential as it represent the most basic information for carrying out further exploration activities. However, available geological maps of MFB and sedimentary formations of Vindhayan Supergroup along SNNF and Chhotanagpur Granite Gneissic Complex (CGGC) and Gondwana Supergroup along SNSF available in public domain are discontinuous and multi-scaled. Optical bands of Landsat Enhanced Thematic Mapper Plus (ETM+) and Indian Remote Sensing (IRS) PAN of the study area were used in mapping lithological units, structural features and small intrusive bodies. Principal Component Analysis (PCA), Image Fusion, Linear Contrast Stretch, Histogram Equalisation and False Color Composite (FCC) of various band combination and ratio maps were performed in the digital image processing of geo-rectified satellite imageries. In analyzing and interpreting high resolution multi-spectral images, certain standard norms were employed to acquire information about litho-structural features such as topographic, geomorphic and tectonic facets. The main criteria are colour and tones, geomorphology, drainage patterns and vegetation anomalies. The processed Landsat ETM+ images were interpreted and classified to delineate detailed lithological units and structural features in order to update existing geological maps. To validate the prepared litho-structural map, ground survey was carried out along critical geological sections for checking the geological features like rocks, folds, faults, fractures and foliations. While comparing with the ground geological data to that obtained from the satellite imagery, it is observed that remote sensing interpreted litho-structural map is in a class with the ground observations. Various data sets such as unconformable geological contacts, fault breccias zone, lineaments and gamma ray spectrometric data (eU, eTh and % K) based on PGRS study were integrated and modelled using Geographical Information System (GIS) for identifying important prospective horizons for uranium mineralisation in the MFB of Son valley area. It is concluded that the revised large scale geological map is of practical use for not only for mapping of litho-structural architecture, but also in identifying potential areas for ‘vein –type’ uranium mineralisation along the structurally deformed zones of the SNNF, Asmi-Jiawan fault (AJF) and SNSF; and ‘unconformity- type’ of uranium mineralisation in the outliers of Jungel Group. The revised map and radiometric data acquired are useful in formulating exploration strategy for the ongoing uranium exploration in this area

Petrography, Geochemistry and Rb-Sr Geochronology of the Basement Granitoids from Umthongkut Area, West Khasi Hills District, Meghalaya, India: Implications on Petrogenesis and Uranium Mineralization

Abstract The basement granitoids from Umthongkut, West Khasi Hills district, Meghalaya is exposed in a very small area (1.5 km x 0.5 km) and unconformably overlain by Mahadek sandstone of upper Cretaceous age and successively followed by rocks of Tertiary age. Megascopically, granitoids are leucocratic, mesocratic to mild melanocratic and differ in texture and mineral abundance without any definite contact relation in field. The leucocratic granitoid is medium-grained, designated as granite (syenogranite and monzogranite) with appreciable content of biotite and garnet and has peraluminous to mild metaluminous character (mol. Al2O3/mol. CaO+Na2O+K2O= 0.9-1.17). However, mesocratic granitoid is relatively fine-grained, identified as quartz monzonite with abundant biotite, minor hornblende and opaque like magnetite, ilmenite, anatase, pyrite and chalcopyrite and metaluminous to mild peraluminous (mol. A/CNK=0.76-1.02) in nature. The presence of characteristic minerals and textural replacement features point towards S-type signature for granite and I –type for quartz monzonite. On the other hand, mixed S and I-type characters are observed in geochemical plot of SiO2 vs. A/CNK. The coexistence of granite and quartz monzonite with former being more evolved, S-type signature and presence of garnet with biotite suggests that the granite appears to be generated from melting of lower crustal source of monzonitic composition. The Rb-Sr dating is also attempted and the errorchron age of 1130±53 with low initial 87Sr/86Sr ratio of 0.7063±0.0011Ma appears to be the emplacement age for these coexisting phases of granitoid. Considering the Meghalaya plateau being northeastern extension of Chhotanagpur granite-gneiss complex (CGGC), the calculated age for the studied samples corresponds to the 1200-1000 Ma. which is defined as fourth tectono-magmatic thermal event of CGGC. Interestingly, these granitoids are considered as the probable source for uranium in the sandstones of Mahadek Formation of Cretaceous age hosting ore grade uranium mineralization at Umthongkut,