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Geratiyon-ki-Dhani (GKD) area is located in Khetri sub-basin of North Delhi Fold Belt and exposes metasediments of Ajabgarh Group. The Ajabgarh Group comprises quartz-biotite schist which is intruded by albitite and granite. The primary uranium phases viz. davidite and brannerite occurring with calcite and /or quartz veins are common in albitite. Quartz and calcite from mineralised albitite have been selected for characterization of the ore-forming fluid, which makes a promising uranium deposit. Fluid inclusion petrography indicated presence of three (03) types of fluid inclusions (FIs) based on phases present at room temperature and mode of occurrence; polyphase (type 1a & 1b) and biphase (type 2) inclusions. Type 1a FIs are primary in nature and are composed of vapour bubble, salt crystals with <50% liquid phase and are irregular or negative crystal in shape varying in size between 12–23µm and occasionally contain hematite grain. The type 1a inclusions homogenised mostly by dissolution of salt crystal between 243–382°C (mode=340°C, n=30) corresponding to salinity of 34.32–46.13 wt% NaCl-eq (mode=42wt% NaCl-eq, n=30). Type 1b FIs have vapour bubble, salt crystal with >50% liquid phase, occur as trans-granular trails and in clusters, having irregular shapes with size varying from <5–12µm. The inclusions homogenised by disappearance of salt crystals at 209 to 294°C (mode= 280°C, n=35) corresponding to salinity range from 29.03–38.59 wt% NaCl-eq (mode=36wt% NaCl-eq, n=35). A wide range of overlap is noted in salinity (34.32–38.59 wt% NaCl-eq) and homogenization temperature (243–294°C), histograms of type 1a & 1b inclusions suggest them to be part of a common fluid activity. Polyphase inclusions show simple cooling and follow halite saturation curve in salinity-temperature diagram. Biphase inclusions are invariably associated with type 1b and also show a cooling trend. On the basis of fluid characteristics, it is concluded that magmatic albitite has provided single mineralising solution resulting in davidite enriched mineralisation. The gradual cooling of high temperature (243–382°C), high saline (34.32–46.13 wt% NaC-leq) hydrothermal fluids has ensued U-mineralisation in GKD. The evidences presented here are significant as magmatic albitite hosted mineralisation is found for the first time in North Delhi Fold Belt of Khetri sub-basin of northwest india. it has opened a new concept for exploration which will help more resource addition. [ABSTRACT FROM AUTHOR]

Uranium mineralization at Umra, Udaipur district, Rajasthan is hosted by carbon and siliceous phyllite (with minor calcareous components) of the Paleoproterozoic Aravalli Supergroup. The mineralized zone trends NE-SW to N-S, dipping 45–55° towards SE to E. Uraninite, coffinite and brannerite are the main uranium phases observed that occur in association with sulphides (pyrrhotite, pentlandite, gersdorffite, chalcopyrite and pyrite), magnetite and ilmenite. Uraninite is found to occur as veins and disseminated ultrafine grains. Colloform and botryoidal texture with shrinkage/ synaeresis cracks indicate the presence of pitchblende also, formed at relatively low-temperature. Textural features suggest remobilization of disseminated syngenetic and / or diagenetic uranium minerals during low-grade metamorphism and deformation. Textural features suggest multiple phases of sulphide mineralization also. Mineral chemical data indicate that uraninite and pitchblende are compositionally similar containing 80.09–87.17 wt.% UO2 (av. 84.45 wt.%) and 11.37–11.82 wt.% PbO (av. 11.58 wt.%) with negligible SiO2, CaO, TiO2, FeO, ThO2 and RE2O3. High U/Th ratio (>1000) in uraninite/ pitchblende indicates limited cationic substitution and therefore low temperature (<350°C) hydrothermal origin of mineralization. Chemical age, calculated on the basis of UO2, ThO2 and PbO concentration in uraninite, indicates the minimum age of mineralization is 956±12 Ma. S isotopic data of pyrite suggest syn-sedimentary or diagenetic origin by bacterial reduction of seawater or pore water sulphate under anoxic conditions (−24.7‰ to −16.2‰), as well as hydrothermal (−3.7‰ to +8.8‰) origin. Similarity of S isotopic composition of hydrothermal pyrite with that of pyrite (+5.2‰) from meta-basic rock indicates that a component of S has been derived from the associated basic/meta-basic rocks in the area. Signatures of multiple generations of uranium mineralization, and multiple episodes of deformation, metamorphism and hydrothermal alteration reveal a complex metallogenic history in Umra. Compositional details of uraninite and their occurrence in the form of veinlets in association with hydrothermal pyrite suggest dominantly epigenetic hydrothermal mineralization events coeval with deformations of the Aravalli sediments. [ABSTRACT FROM AUTHOR]