Atomic Minerals Directorate for Exploration and Research

ABSTRACTThe Saidiwasan (also known as Siriwasan) carbonatite‐sill is located approximately 10 km to the north of the well‐known Ambadungar carbonatite–alkaline complex within the Chhota Udaipur carbonatite‐alkaline province. This complex comprises prominent sövite plugs within carbonatitic breccias, each exhibiting diverse and variable mineralogical assemblages that include pyroxene, amphibole, apatite, pyrochlore, perovskite and titanite. The enrichment of rare earth elements (REEs) in the Saidiwasan sövites is closely associated with the presence of pyrochlore, perovskite, apatite and monazite. This study employs detailed mineral chemistry to elucidate the secondary processes affecting pyrochlore and apatite grains. Primary magmatic pyrochlore in Saidiwasan sövites are characterised by elevated concentrations of calcium, niobium, fluorine and sodium, which are subsequently replaced by secondary cation‐deficient grains due to supergene weathering. These alterations primarily occur at the A site and occasionally at the B site, involving the substitution of fluorine by hydroxide (OH–) groups. During alteration, calcium and sodium are leached from the pyrochlore structure, with charge balance maintained by the substitution of REE, Th, U, Ba or Sr. In the later supergene stages, marginal and fractured zones of pyrochlore grains experience metamictization, resulting in Pb‐rich and cation‐deficient hydrated varieties. Fluoro‐apatites within the sövites display significant REE concentrations and are relatively unaltered. LREE constitute the dominant proportion of the total REE content in Saidiwasan apatite. Based on mineral chemistry and bulk rock analyses, this study aims to provide a comprehensive understanding of the Saidiwasan sövites. Despite its promising characteristics, the Saidiwasan carbonatite complex remains underexplored and largely overlooked within the Chhota Udaipur Province, although it possesses significant potential for hosting economically viable mineral deposits, thus warranting further investigation and exploration.

ABSTRACT The mining and beneficiation of low-grade phosphate ores has become inevitable due to its increasing consumption for fertilizers. Controlling of ore grade through blending and beneficiation of low-grade ore requires extensive chemical analysis in each step for optimizing process parameters. To facilitate rapid analysis of phosphate ore a new analytical procedure has been developed using sequential WDXRF spectrometer. A set of international certified reference materials (CRMs) and well-characterized in-house standards of phosphatic siliceous dolostone of the Vempalle Formation, Cuddapah basin were utilized for calibration of the analytical signals. The newly developed analytical procedure has been tested by analyzing major oxides in four natural samples of phosphate ore from the Proterozoic Jhamarkotra rock phosphate deposit, Udaipur, Rajasthan. The analytical results indicate wide tolerance ranges of the calibration lines especially for CaO, P2O5, SiO2 and MgO. The results were subsequently validated with the data obtained on the same set of samples by Inductively Coupled Plasma-Optical Emission Spectrometric (ICP-OES) technique. The comparison shows that the precision and accuracy of WDXRFS data for CaO, P2O5, and SiO2 in phosphate ore are well within the statistically acceptable range i.e., <1% and 5–10% respectively, except for other major oxides at low (<1 wt.%) concentrations. This study reveals that WDXRFS can be used as a cost effective, rapid and eco-friendly technique for routine analysis of phosphate ore, containing significantly wide ranges of CaO, P2O5 as well as SiO2 and MgO impurities, for grade controlling during mining and optimizing process parameters during beneficiation and extraction.

In this study, biomass fly ash was investigated and determined by XRD to be predominantly langbeinite, aphthitalite, sylvine, apatite and hydroxyapatite. An alkaline leaching study was carried out on the material in a glass reactor at l/s ratio 4 temperature 600C at pH 12.85 and after drying was analyzed by ICP. The crystal structure composition of K2SO4 72.28% and potassium content of 33.47%(w/w) was recovered. The elemental transformations in this leaching process were: K 74.16%, Mg 0.55% was found to be 0.8%. It was found that a minimum of 4.84 g H2SO4 per 100 g fly ash was required to precipitate the Ca(OH)2 migrated into the liquid solution and the overall leaching efficiency was found to be 29.85%. In the alkaline leaching process, potassium was found to be easily recovered from each biomass ash. By adding 40 g H2SO4/100 g biomass waste remaining after leaching, a phosphorus recovery of 74.9% was observed. In this preliminary study, unsatisfactory results were obtained in obtaining the industry standard H3PO4. The reason for this is that the Al, Mg and K in the fly ash are subject to selective dissolution as a result of working at high pH in the alkaline leaching process.

Abstract The Malawi Rift is localized within Precambrian amphibolite‐granulite facies metamorphic belts, bounded by up to 150 km long border faults, and generates earthquakes throughout ∼40 km thick crust. Rift‐related faults are inferred to exploit pre‐existing weaknesses that allow rifting of otherwise dry and strong crust. It is unclear what these weaknesses are, and how localization into weak zones can be reconciled with strength required for lower crustal seismicity. We present results of mineral equilibria modeling, which indicate that Proterozoic metamorphism generated dry crust dominated by a quartz‐feldspar assemblage that is metastable at current conditions. For rift propagation to be possible at current cool thermal gradients and in mechanically strong, dry quartzofeldspathic rocks, mid‐ to lower‐crustal strain must be localized into relatively weak, inherited shear zones that deform primarily by aseismic, viscous creep. These shear zones are embedded within high‐strength crust, and interaction between creeping shear zones and enveloped or surrounding rocks may locally increase stress and trigger frictional, seismic slip at mid‐ to lower‐crustal depths. Over time, this interaction may produce a fracture network that allows infiltration of fluids. We therefore suggest that during rifting of previously deformed and metamorphosed crust, major faults are most likely to grow from below, with their location and orientation prescribed by underlying inherited viscous shear zones. In this case, fluids may infiltrate and locally weaken metastable lower crust, including allowing time‐dependent fluid‐driven seismicity and local partial melting, but length‐scales of this weakening is limited by the scale of the permeability network.

The guest of honour, Shri N. Kutumba Rao, highlighted the importance of new mineral discoveries from Vindhyan Supergroup (VSG) and opined that new mineral exploration blocks will come up soon.The guest of honour Dr D.K. Sinha, mentioned the importance of the western Vindhyan Basin (VB) exposed in Rajasthan and its correlation with the eastern VB of the Son Valley area.Shri N.V. Nitnaware, Chairman VISACOP expressed his hope that the seminar will provide a guiding direction

There is large variations in diverse water samples due to time interval between sample collection and analysis in the presence of fluoride and humic substances in hot arid regions.