ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad S... more ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin, Cuddapah Basin. Several evidences of hydrothermal activity exist in both basement granite and the cover sediments in Koppunuru and Rallavagu Tanda (R.V. Tanda) uranium prospects of Palnad Sub-basin. Profuse development of fracture filled veins consisting of epidote–quartz, chlorite–quartz and quartz is observed at various depths above and below unconformity. Fluid–rock interaction during the formation of these veins has resulted in the alteration of feldspars and mafic minerals of granite and arkosic quartzite into a mineral assemblage consisting of various proportion of illite, chlorite, muscovite and pyrite, with the intensity of alterations being highest near to the unconformity. Pyrite is often associated with illite dominant alteration zone. We infer that circulation of basinal brine through basement granite and cover sediments was responsible for mobilising uranium from granite and its precipitation at favourable locations in cover sediments. Increase in pH of ore fluid due to illitisation and chloritisation of wallrock together with availability of carbonaceous matter and pyrite as reductant have controlled the localisation of uranium mineralisation in Banganapalle Formation.
In the southwestern part of Palnad sub-basin around Koppunuru–Chenchu colony area, Palnad sedimen... more In the southwestern part of Palnad sub-basin around Koppunuru–Chenchu colony area, Palnad sediments (Kurnool Group) are deposited unconformably over Palaeoproterozoic basement granite. Five major lithofacies have been identified in shallow dipping Banganapalle Formation on the basis of borehole litho-logs viz., a) basal conglomerate, b) quartzite-shale intercalated sequence, c) lower quartz arenite, d) shale-siltstone intercalated sequence, and e) upper quartz arenite. These are also distinguished by contrasting resistivity and self-potential signals. Soft-sedimentary deformational structures (penecontemporaneous deformation) like load structure, convolute bedding/laminations, and slump structures such as micro-slips, gravity faults and folds are prominent in quartzite-grey shale and shale-siltstone intercalated sequences indicate perturbation and submergence of the basin contemporaneous to deposition. Glauconite with traces of carbonaceous matter in different lithofacies indicates marginal marine, mildly alkaline and reducing depositional condition. Integrated field, borehole and petrographic evidences suggest cyclic sedimentation of the Banganapalle Formation in inter- to supra-tidal flat environment. Out of the above five lithofacies, upper quartz arenite and basal conglomerate units have shown high uranium potential.
In the present study, backscatter scanning Electron Microscopy (SEM) technique is applied for qua... more In the present study, backscatter scanning Electron Microscopy (SEM) technique is applied for qualitative analysis and characterisation of the fine clastic sediments of Barakar and Motur formations. These studies revealed that the preservation of large amount of detrital clay minerals implies absence of reworking of the sediments in a turbulent environment. Kaolinite reflects acidic environment and derivation from weathered granite and analogous Ca-poor igneous and metamorphic rocks. Kaolinite forms both in oxidizing and reducing environments, in presence of organic mattersuch as humic complex and organic acid. Montmorillonite is the alteration product of mostly basic rocks, where stable alteration minerals formed in alkaline conditionsdue to availability of Mg and Ca. Illite is relatively stable alteration product of mostly acidic rocks due to intense weathering in humid climate and mostly confined to shale. Chlorite is derived from aggradations of less organized sheet minerals, degradation of pre-existing ferromagnesian minerals and by crystallisation from dilute solutions. In present samples, montmorillonite show high ion base-exchange and lie on the basal plane surface, whereas kaolinite has low ion base-exchange capacity. The morphology of monazite and xenotime suggests short transportation and derivation from nearby granitic source rocks. The clear and uneroded edges of the zirconreveal short transportation and first cycle of weathering and sedimentation.
Using extended Layzer's potential flow model, we investigate the effects of surface tension o... more Using extended Layzer's potential flow model, we investigate the effects of surface tension on the growth of the bubble and spike in combined Rayleigh-Taylor and Kelvin-Helmholtz instability. The nonlinear asymptotic solutions are obtained analytically for the velocity and curvature of the bubble and spike tip. We find that the surface tension decreases the velocity but does not affect the curvature, provided surface tension is greater than a critical value. For a certain condition, we observe that surface tension stabilizes the motion. Any perturbation, whatever its magnitude, results stable with nonlinear oscillations. The nonlinear oscillations depend on surface tension and relative velocity shear of the two fluids. Received: 20 March 2014, Accepted: 7 August 2014; Edited by: A. Marti; DOI:http://dx.doi.org/10.4279/PIP.060006Cite as: R Banerjee, S Kanjilal, Papers in Physics 6, 060006 (2014)
An attempt is made to understand uranium series disequilibrium in unconformity proximal related u... more An attempt is made to understand uranium series disequilibrium in unconformity proximal related uranium mineralisation in Chenchu colony area, Guntur district, Andhra Pradesh, India. The uranium mineralization in Chenchu colony is the western continuity of the Koppunuru uranium deposit and predominantly hosted by gritty quartzite/conglomerate, which occasionally transgresses to underlying basement granite/basic rock. Disequilibrium studies are based on borehole core samples (35 boreholes, No. of samples=634) broadly divided in two groups of cover rocks of Banganapalle formation (above unconformity) and basement granites (below unconformity). Linear regression coefficient between uranium and radium is 0.95, which reflects excellent correlation and significant enrichment of parent uranium. Disequilibrium studies have indicated predominant disequilibrium in favour of parent uranium (35%), which is probably due to the weathering process causing migration of some of the radionuclides while dissolution of minerals due to groundwater action might have also played a significant role. Further, escape of radon might have accentuated the disequilibrium factor resulting in an increase in the grade of the mineralization. This is well corroborated by the presence of fractures and faults in the study area providing channels for radon migration/escape.
CITATIONS 4 READS 45 5 authors, including: Some of the authors of this publication are also worki... more CITATIONS 4 READS 45 5 authors, including: Some of the authors of this publication are also working on these related projects: Deciphering the history of hydrothermal activity and controls on uranium mineralization at Koppunuru: constraints from mineral chemistry, stable isotope and fluid inclusion studies View project Petrography of Radioactive and non-radioactive rocks from Koppunuru Prospect and adjoining areas, Nalgonda District, A.P. View project
The Cuddapah basin in southern India, consisting of the Palnad, Srisailam, Kurnool and Papaghni s... more The Cuddapah basin in southern India, consisting of the Palnad, Srisailam, Kurnool and Papaghni sub-basins, contains unmetamorphosed and undeformed sediments deposited during a long span of time in the Proterozoic. In the absence of robust age constraints, there is considerable confusion regarding the relative timing of sedimentation in these sub-basins. In this study, U-Pb isotopic dating of zircon and U-Th-Pb total dating of monazite and uraninite from the gritty quartzite that supposedly belongs to the formation Banganapalle Quartzite have been used to constrain the beginning of sedimentation in the Palnad sub-basin. Magmatic and detrital zircons recording an age of 2.53 Ga indicate that the sediments were derived from the granitic basement or similar sources and were deposited after 2.53 Ga. Hydrothermally altered zircons both in the basement and the cover provide con-cordant ages of 2.32 and 2.12 Ga and date two major hydrothermal events. Thus, the gritty quartzite must have been deposited sometime between 2.53 and 2.12 Ga and represents the earliest sediments in the Cuddapah basin. Monazite and uraninite give a wide spectrum of ages between 2.5 Ga and 150 Ma, which indicates several pulses of hydrothermal activity over a considerable time span, both in the basement granite and the overlying quartzite. The new age constraints suggest that the gritty quartzite may be stratigraphically equivalent to the Gulcheru Quartzite that is the oldest unit in the Cuddapah basin, and that a sedimentary/erosional hiatus exists above it.
Gondwana Geological Magazine., Spl.vol. 12, Oct 2010
In the southwestern part of Palnad sub-basin around Koppunuru–Chenchu colony area, Palnad sedimen... more In the southwestern part of Palnad sub-basin around Koppunuru–Chenchu colony area, Palnad sediments (Kurnool Group) are deposited unconformably over Palaeoproterozoic basement granite. Five major lithofacies have been identified in shallow dipping Banganapalle Formation on the basis of borehole litho-logs viz., a) basal conglomerate, b) quartzite-shale intercalated sequence, c) lower quartz arenite, d) shale-siltstone intercalated sequence, and e) upper quartz arenite. These are also distinguished by contrasting resistivity and self-potential signals. Soft-sedimentary deformational structures (penecontemporaneous deformation) like load structure, convolute bedding/laminations, and slump structures such as micro-slips, gravity faults and folds are prominent in quartzite-grey shale and shale-siltstone intercalated sequences indicate perturbation and submergence of the basin contemporaneous to deposition. Glauconite with traces of carbonaceous matter in different lithofacies indicates marginal marine, mildly alkaline and reducing depositional condition. Integrated field, borehole and petrographic evidences suggest cyclic sedimentation of the Banganapalle Formation in inter- to supra-tidal flat environment. Out of the above five lithofacies, upper quartz arenite and basal conglomerate units have shown high uranium potential.
There is a paucity of suitable geothermometers for low temparature geological processes. Water-ro... more There is a paucity of suitable geothermometers for low temparature geological processes. Water-rock interactions at lower temperatures relavant to diagenesis, low-T hydrothermal process and low-T metamorphism can be studied if chlorite is present as a stable phase. However, this requires meticulous analytical data acquisition and complecated formula calculation protocols. For a quick assessment of low-T events in sedimentary and metasedimentary rocks, Raman spectroscopic study of associated carbonaceous matter provides a convinient alternative. Here we show the efficacy of this method (Kouketsu et al., 2014) and provide chlorite thermometric estimates (Bourdelle et al., 2013) for comparison from the Proterozoic Banganapalle Quartzite. While Raman Spectroscopic study of carbonaceous matter, probably of organic nature, yielded the temperatures of 327, 357, 370, 400 and 413°C, the corresponding thermometers obtained from chlorite thermometry were 228, 322, 339 and 347°C. Although the temperatures of 327 to 357°C overlap with the chlorite temperatures from 322 to 347°C, the carbonaceous matter record still higher temperatures while the chlorites record still lower temperatures indicating the irreversible change that occurs in the carbonaceous matter and the capability of the chlorites to re-equilibrate to lower temperatures, at least partially.
Disequilibrium studies were attempted on mineralised core samples (n=870) from Koppunuru uranium ... more Disequilibrium studies were attempted on mineralised core samples (n=870) from Koppunuru uranium deposit located in south-western part of Palnad sub-basin, Guntur district, Andhra Pradesh, India. The area exposes Banganapalle quartzites unconformably deposited over altered biotite granite (basement). Uranium mineralisation in Koppunuru deposit is hosted by Banganapalle quartzites well above the unconformity, and grit/basement granite close to the unconformity contact. For disequilibrium studies, the core samples were broadly divided in two groups, (a)quartzite hosted (above unconformity) and (b) basement granite hosted mineralisation (below unconformity). Average disequilibrium factor of 41% has been recorded in favour of parent uranium in both types of core samples. It shows significant enrichment of uranium in the system as evident from 41% of disequilibrium in favour of parent uranium. This is probably due to significant migration of some of the daughter radio nuclides due to dissolution of minerals by groundwater action. Besides, the escape of radioactive radon might have accentuated the disequilibrium factor thus increasing the grade of uranium mineralization. The presence of fractures and faults in the study area are the probable conduits for radon migration/escape. Linear regression coefficient between uranium and radium is 0.98 indicates invariability of disequilibrium irrespective of grade.
Granitoids including granite pegmatites that are predominantly exposed in the southeastern part o... more Granitoids including granite pegmatites that are predominantly exposed in the southeastern part of Nanded district, Maharashtra, comprising granodiorite-adamellite suite of rocks belong to the younger phase of the Peninsular Gneiss. They are mostly peraluminous in nature (high A1 2O3/ CaO+Na2O+K2O i.e. A/CNK (0.9-1.3) with low agpaitic index (0.6-0.9). Negative correlation of CaO, MgO and FeO(T) with differentiation index, and low initial ratio of 87Sr/86Sr (0.7009±0.0005) point to fractional crystallisation of sub-crustal to mantle melt. Both I-and S-type characteristics are shown by these granitoids. Radioactivity is mainly associated with adsorbed uranium on iron oxide nodules and also due to beta-uranophane encrustations.
Abstr act Var ious geochemical processes within the aquifer and anthropogenic activities in the a... more Abstr act Var ious geochemical processes within the aquifer and anthropogenic activities in the area influence the spatial and tempor al var iations of sur face and groundwater quality. The pr esent study on seasonal var iati on and i nfluence of ur ani um mi ner al i sed zones i n gr oundwater quality ar ound K oppunur u based on monthly sampling fr om Febr uar y 2010 to Januar y 2011 indicates pr esence of 2–3388 ppb U and show or der of abundance of maj or cations as Na + >Ca 2+ >K + >M g 2+ while that of anions as HCO 3 – >Cl – >SO 4 2– >CO 3 2–. M ixed Ca–M g–Cl and Ca–HCO 3 ar e the dominant gr oundwater types in this ar ea. M ar ginal decr ease in Eh and cor r esponding incr ease in pH is quite appar ent dur ing post-M onsoon season. Na and SO 4 exhibit pr ogr essively decr easing tr end fr om pr e-to post-M onsoon season whi le r el ativel y hi gher content of CO 3 dur i ng post-M onsoon season suggests dissolution of calcar eous lithounits of Nar j i For mation by gr oundwater. High TDS, its linear ity with conductivity and str ong positive cor r elation among Na, K , Cl, SO 4 and TDS for all seasons ar e mainly due to low annual r ainfall/gr oundwater r echar ge and dominance of evapotr anspir ation process. Pr incipal Component Analysis (PCA) and Gibbs r atio plot suggest r ock–water inter action as maj or contr ibutor to the salinity and var iation in water chemistr y. M aj or ity of groundwater samples indicate negative Chloroalkaline indices (CAI) suggesting cation–anion exchange r eactions, wher ein M g and Ca fr om water ar e exchanged with Na and K available in silt/clay layer s of Banganapalle For mation. Based on BI S and WHO pr escr ibed limits, studied gr oundwater has limited suitability for human consumption on the grounds of moder ate to high har dness, salinity and TDS. However, the concentr ation of toxic element such as F is well within the desir ed limits, except one sample (upto 2.1ppm), while four samples show higher U content thr oughout the year as compar ed to the per missible limits of 30 ppb. Similar ly, pr edominance of low to medium SAR with medium to high conductivity categor izes the studied gr oundwater as suitable for ir r igation pur pose. K eywor ds: Groundwater geochemistr y, Ur anium, Pr incipal Component Analysis (PCA), Sodium Absor ption Ratio (SAR), Chloroalkaline I ndex (CAI), Water potability, Guntur. Groundwater geochemistry is primarily controlled by the aquifer lithology, rock–water chemical interacti on processes and cl imati c factors l i ke evaporati on, preci pi tati on, and evapotranspiration, which vary with changing seasons. Secondary controls, like interaction with disintegrated products of rock weathering, presence of sulphide species, tailings and mine dumps may l ead to the acidi fi cati on of the
ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad S... more ABSTRACT Unconformity related uranium mineralisation occurs in Banganapalle Formation of Palnad Sub-basin, Cuddapah Basin. Several evidences of hydrothermal activity exist in both basement granite and the cover sediments in Koppunuru and Rallavagu Tanda (R.V. Tanda) uranium prospects of Palnad Sub-basin. Profuse development of fracture filled veins consisting of epidote–quartz, chlorite–quartz and quartz is observed at various depths above and below unconformity. Fluid–rock interaction during the formation of these veins has resulted in the alteration of feldspars and mafic minerals of granite and arkosic quartzite into a mineral assemblage consisting of various proportion of illite, chlorite, muscovite and pyrite, with the intensity of alterations being highest near to the unconformity. Pyrite is often associated with illite dominant alteration zone. We infer that circulation of basinal brine through basement granite and cover sediments was responsible for mobilising uranium from granite and its precipitation at favourable locations in cover sediments. Increase in pH of ore fluid due to illitisation and chloritisation of wallrock together with availability of carbonaceous matter and pyrite as reductant have controlled the localisation of uranium mineralisation in Banganapalle Formation.
In the southwestern part of Palnad sub-basin around Koppunuru–Chenchu colony area, Palnad sedimen... more In the southwestern part of Palnad sub-basin around Koppunuru–Chenchu colony area, Palnad sediments (Kurnool Group) are deposited unconformably over Palaeoproterozoic basement granite. Five major lithofacies have been identified in shallow dipping Banganapalle Formation on the basis of borehole litho-logs viz., a) basal conglomerate, b) quartzite-shale intercalated sequence, c) lower quartz arenite, d) shale-siltstone intercalated sequence, and e) upper quartz arenite. These are also distinguished by contrasting resistivity and self-potential signals. Soft-sedimentary deformational structures (penecontemporaneous deformation) like load structure, convolute bedding/laminations, and slump structures such as micro-slips, gravity faults and folds are prominent in quartzite-grey shale and shale-siltstone intercalated sequences indicate perturbation and submergence of the basin contemporaneous to deposition. Glauconite with traces of carbonaceous matter in different lithofacies indicates marginal marine, mildly alkaline and reducing depositional condition. Integrated field, borehole and petrographic evidences suggest cyclic sedimentation of the Banganapalle Formation in inter- to supra-tidal flat environment. Out of the above five lithofacies, upper quartz arenite and basal conglomerate units have shown high uranium potential.
In the present study, backscatter scanning Electron Microscopy (SEM) technique is applied for qua... more In the present study, backscatter scanning Electron Microscopy (SEM) technique is applied for qualitative analysis and characterisation of the fine clastic sediments of Barakar and Motur formations. These studies revealed that the preservation of large amount of detrital clay minerals implies absence of reworking of the sediments in a turbulent environment. Kaolinite reflects acidic environment and derivation from weathered granite and analogous Ca-poor igneous and metamorphic rocks. Kaolinite forms both in oxidizing and reducing environments, in presence of organic mattersuch as humic complex and organic acid. Montmorillonite is the alteration product of mostly basic rocks, where stable alteration minerals formed in alkaline conditionsdue to availability of Mg and Ca. Illite is relatively stable alteration product of mostly acidic rocks due to intense weathering in humid climate and mostly confined to shale. Chlorite is derived from aggradations of less organized sheet minerals, degradation of pre-existing ferromagnesian minerals and by crystallisation from dilute solutions. In present samples, montmorillonite show high ion base-exchange and lie on the basal plane surface, whereas kaolinite has low ion base-exchange capacity. The morphology of monazite and xenotime suggests short transportation and derivation from nearby granitic source rocks. The clear and uneroded edges of the zirconreveal short transportation and first cycle of weathering and sedimentation.
Using extended Layzer's potential flow model, we investigate the effects of surface tension o... more Using extended Layzer's potential flow model, we investigate the effects of surface tension on the growth of the bubble and spike in combined Rayleigh-Taylor and Kelvin-Helmholtz instability. The nonlinear asymptotic solutions are obtained analytically for the velocity and curvature of the bubble and spike tip. We find that the surface tension decreases the velocity but does not affect the curvature, provided surface tension is greater than a critical value. For a certain condition, we observe that surface tension stabilizes the motion. Any perturbation, whatever its magnitude, results stable with nonlinear oscillations. The nonlinear oscillations depend on surface tension and relative velocity shear of the two fluids. Received: 20 March 2014, Accepted: 7 August 2014; Edited by: A. Marti; DOI:http://dx.doi.org/10.4279/PIP.060006Cite as: R Banerjee, S Kanjilal, Papers in Physics 6, 060006 (2014)
An attempt is made to understand uranium series disequilibrium in unconformity proximal related u... more An attempt is made to understand uranium series disequilibrium in unconformity proximal related uranium mineralisation in Chenchu colony area, Guntur district, Andhra Pradesh, India. The uranium mineralization in Chenchu colony is the western continuity of the Koppunuru uranium deposit and predominantly hosted by gritty quartzite/conglomerate, which occasionally transgresses to underlying basement granite/basic rock. Disequilibrium studies are based on borehole core samples (35 boreholes, No. of samples=634) broadly divided in two groups of cover rocks of Banganapalle formation (above unconformity) and basement granites (below unconformity). Linear regression coefficient between uranium and radium is 0.95, which reflects excellent correlation and significant enrichment of parent uranium. Disequilibrium studies have indicated predominant disequilibrium in favour of parent uranium (35%), which is probably due to the weathering process causing migration of some of the radionuclides while dissolution of minerals due to groundwater action might have also played a significant role. Further, escape of radon might have accentuated the disequilibrium factor resulting in an increase in the grade of the mineralization. This is well corroborated by the presence of fractures and faults in the study area providing channels for radon migration/escape.
CITATIONS 4 READS 45 5 authors, including: Some of the authors of this publication are also worki... more CITATIONS 4 READS 45 5 authors, including: Some of the authors of this publication are also working on these related projects: Deciphering the history of hydrothermal activity and controls on uranium mineralization at Koppunuru: constraints from mineral chemistry, stable isotope and fluid inclusion studies View project Petrography of Radioactive and non-radioactive rocks from Koppunuru Prospect and adjoining areas, Nalgonda District, A.P. View project
The Cuddapah basin in southern India, consisting of the Palnad, Srisailam, Kurnool and Papaghni s... more The Cuddapah basin in southern India, consisting of the Palnad, Srisailam, Kurnool and Papaghni sub-basins, contains unmetamorphosed and undeformed sediments deposited during a long span of time in the Proterozoic. In the absence of robust age constraints, there is considerable confusion regarding the relative timing of sedimentation in these sub-basins. In this study, U-Pb isotopic dating of zircon and U-Th-Pb total dating of monazite and uraninite from the gritty quartzite that supposedly belongs to the formation Banganapalle Quartzite have been used to constrain the beginning of sedimentation in the Palnad sub-basin. Magmatic and detrital zircons recording an age of 2.53 Ga indicate that the sediments were derived from the granitic basement or similar sources and were deposited after 2.53 Ga. Hydrothermally altered zircons both in the basement and the cover provide con-cordant ages of 2.32 and 2.12 Ga and date two major hydrothermal events. Thus, the gritty quartzite must have been deposited sometime between 2.53 and 2.12 Ga and represents the earliest sediments in the Cuddapah basin. Monazite and uraninite give a wide spectrum of ages between 2.5 Ga and 150 Ma, which indicates several pulses of hydrothermal activity over a considerable time span, both in the basement granite and the overlying quartzite. The new age constraints suggest that the gritty quartzite may be stratigraphically equivalent to the Gulcheru Quartzite that is the oldest unit in the Cuddapah basin, and that a sedimentary/erosional hiatus exists above it.
Gondwana Geological Magazine., Spl.vol. 12, Oct 2010
In the southwestern part of Palnad sub-basin around Koppunuru–Chenchu colony area, Palnad sedimen... more In the southwestern part of Palnad sub-basin around Koppunuru–Chenchu colony area, Palnad sediments (Kurnool Group) are deposited unconformably over Palaeoproterozoic basement granite. Five major lithofacies have been identified in shallow dipping Banganapalle Formation on the basis of borehole litho-logs viz., a) basal conglomerate, b) quartzite-shale intercalated sequence, c) lower quartz arenite, d) shale-siltstone intercalated sequence, and e) upper quartz arenite. These are also distinguished by contrasting resistivity and self-potential signals. Soft-sedimentary deformational structures (penecontemporaneous deformation) like load structure, convolute bedding/laminations, and slump structures such as micro-slips, gravity faults and folds are prominent in quartzite-grey shale and shale-siltstone intercalated sequences indicate perturbation and submergence of the basin contemporaneous to deposition. Glauconite with traces of carbonaceous matter in different lithofacies indicates marginal marine, mildly alkaline and reducing depositional condition. Integrated field, borehole and petrographic evidences suggest cyclic sedimentation of the Banganapalle Formation in inter- to supra-tidal flat environment. Out of the above five lithofacies, upper quartz arenite and basal conglomerate units have shown high uranium potential.
There is a paucity of suitable geothermometers for low temparature geological processes. Water-ro... more There is a paucity of suitable geothermometers for low temparature geological processes. Water-rock interactions at lower temperatures relavant to diagenesis, low-T hydrothermal process and low-T metamorphism can be studied if chlorite is present as a stable phase. However, this requires meticulous analytical data acquisition and complecated formula calculation protocols. For a quick assessment of low-T events in sedimentary and metasedimentary rocks, Raman spectroscopic study of associated carbonaceous matter provides a convinient alternative. Here we show the efficacy of this method (Kouketsu et al., 2014) and provide chlorite thermometric estimates (Bourdelle et al., 2013) for comparison from the Proterozoic Banganapalle Quartzite. While Raman Spectroscopic study of carbonaceous matter, probably of organic nature, yielded the temperatures of 327, 357, 370, 400 and 413°C, the corresponding thermometers obtained from chlorite thermometry were 228, 322, 339 and 347°C. Although the temperatures of 327 to 357°C overlap with the chlorite temperatures from 322 to 347°C, the carbonaceous matter record still higher temperatures while the chlorites record still lower temperatures indicating the irreversible change that occurs in the carbonaceous matter and the capability of the chlorites to re-equilibrate to lower temperatures, at least partially.
Disequilibrium studies were attempted on mineralised core samples (n=870) from Koppunuru uranium ... more Disequilibrium studies were attempted on mineralised core samples (n=870) from Koppunuru uranium deposit located in south-western part of Palnad sub-basin, Guntur district, Andhra Pradesh, India. The area exposes Banganapalle quartzites unconformably deposited over altered biotite granite (basement). Uranium mineralisation in Koppunuru deposit is hosted by Banganapalle quartzites well above the unconformity, and grit/basement granite close to the unconformity contact. For disequilibrium studies, the core samples were broadly divided in two groups, (a)quartzite hosted (above unconformity) and (b) basement granite hosted mineralisation (below unconformity). Average disequilibrium factor of 41% has been recorded in favour of parent uranium in both types of core samples. It shows significant enrichment of uranium in the system as evident from 41% of disequilibrium in favour of parent uranium. This is probably due to significant migration of some of the daughter radio nuclides due to dissolution of minerals by groundwater action. Besides, the escape of radioactive radon might have accentuated the disequilibrium factor thus increasing the grade of uranium mineralization. The presence of fractures and faults in the study area are the probable conduits for radon migration/escape. Linear regression coefficient between uranium and radium is 0.98 indicates invariability of disequilibrium irrespective of grade.
Granitoids including granite pegmatites that are predominantly exposed in the southeastern part o... more Granitoids including granite pegmatites that are predominantly exposed in the southeastern part of Nanded district, Maharashtra, comprising granodiorite-adamellite suite of rocks belong to the younger phase of the Peninsular Gneiss. They are mostly peraluminous in nature (high A1 2O3/ CaO+Na2O+K2O i.e. A/CNK (0.9-1.3) with low agpaitic index (0.6-0.9). Negative correlation of CaO, MgO and FeO(T) with differentiation index, and low initial ratio of 87Sr/86Sr (0.7009±0.0005) point to fractional crystallisation of sub-crustal to mantle melt. Both I-and S-type characteristics are shown by these granitoids. Radioactivity is mainly associated with adsorbed uranium on iron oxide nodules and also due to beta-uranophane encrustations.
Abstr act Var ious geochemical processes within the aquifer and anthropogenic activities in the a... more Abstr act Var ious geochemical processes within the aquifer and anthropogenic activities in the area influence the spatial and tempor al var iations of sur face and groundwater quality. The pr esent study on seasonal var iati on and i nfluence of ur ani um mi ner al i sed zones i n gr oundwater quality ar ound K oppunur u based on monthly sampling fr om Febr uar y 2010 to Januar y 2011 indicates pr esence of 2–3388 ppb U and show or der of abundance of maj or cations as Na + >Ca 2+ >K + >M g 2+ while that of anions as HCO 3 – >Cl – >SO 4 2– >CO 3 2–. M ixed Ca–M g–Cl and Ca–HCO 3 ar e the dominant gr oundwater types in this ar ea. M ar ginal decr ease in Eh and cor r esponding incr ease in pH is quite appar ent dur ing post-M onsoon season. Na and SO 4 exhibit pr ogr essively decr easing tr end fr om pr e-to post-M onsoon season whi le r el ativel y hi gher content of CO 3 dur i ng post-M onsoon season suggests dissolution of calcar eous lithounits of Nar j i For mation by gr oundwater. High TDS, its linear ity with conductivity and str ong positive cor r elation among Na, K , Cl, SO 4 and TDS for all seasons ar e mainly due to low annual r ainfall/gr oundwater r echar ge and dominance of evapotr anspir ation process. Pr incipal Component Analysis (PCA) and Gibbs r atio plot suggest r ock–water inter action as maj or contr ibutor to the salinity and var iation in water chemistr y. M aj or ity of groundwater samples indicate negative Chloroalkaline indices (CAI) suggesting cation–anion exchange r eactions, wher ein M g and Ca fr om water ar e exchanged with Na and K available in silt/clay layer s of Banganapalle For mation. Based on BI S and WHO pr escr ibed limits, studied gr oundwater has limited suitability for human consumption on the grounds of moder ate to high har dness, salinity and TDS. However, the concentr ation of toxic element such as F is well within the desir ed limits, except one sample (upto 2.1ppm), while four samples show higher U content thr oughout the year as compar ed to the per missible limits of 30 ppb. Similar ly, pr edominance of low to medium SAR with medium to high conductivity categor izes the studied gr oundwater as suitable for ir r igation pur pose. K eywor ds: Groundwater geochemistr y, Ur anium, Pr incipal Component Analysis (PCA), Sodium Absor ption Ratio (SAR), Chloroalkaline I ndex (CAI), Water potability, Guntur. Groundwater geochemistry is primarily controlled by the aquifer lithology, rock–water chemical interacti on processes and cl imati c factors l i ke evaporati on, preci pi tati on, and evapotranspiration, which vary with changing seasons. Secondary controls, like interaction with disintegrated products of rock weathering, presence of sulphide species, tailings and mine dumps may l ead to the acidi fi cati on of the
Uploads
Papers by RAHUL BANERJEE
Keywords: Palnad sub-basin, Banganapalle Formation, lithofacies, uranium mineralization, Guntur district, Andhra Pradesh
disequilibrium factor of 41% has been recorded in favour of parent uranium in both types of core samples. It shows significant enrichment of uranium in the system as evident from 41% of disequilibrium in favour of parent uranium. This is probably due to significant migration of some of the daughter radio nuclides due to dissolution of minerals by
groundwater action. Besides, the escape of radioactive radon might have accentuated the disequilibrium factor thus increasing the grade of uranium mineralization. The presence of fractures and faults in the study area are the probable conduits for radon migration/escape. Linear regression coefficient between uranium and radium is 0.98 indicates
invariability of disequilibrium irrespective of grade.
Keywords: Palnad sub-basin, Banganapalle Formation, lithofacies, uranium mineralization, Guntur district, Andhra Pradesh
disequilibrium factor of 41% has been recorded in favour of parent uranium in both types of core samples. It shows significant enrichment of uranium in the system as evident from 41% of disequilibrium in favour of parent uranium. This is probably due to significant migration of some of the daughter radio nuclides due to dissolution of minerals by
groundwater action. Besides, the escape of radioactive radon might have accentuated the disequilibrium factor thus increasing the grade of uranium mineralization. The presence of fractures and faults in the study area are the probable conduits for radon migration/escape. Linear regression coefficient between uranium and radium is 0.98 indicates
invariability of disequilibrium irrespective of grade.