Carbon (delta C-13(PDB)) and oxygen (delta O-18(SMOW)) isotopic compositions of carbonates of auriferous quartz-carbonate veins (QCVs), S-isotope (delta S-34(CDT)) composition of gold bearing sulphide minerals and REE geochemical characteristics of the auriferous QCVs of Ajjanahalli and Gadag Gold Fields in the Neoarchaean Chitradurga-Gadag greenstone belt, Dharwar Craton, southern India have been studied in detail to constrain the source of auriferous vein fluids. The carbonate delta C-13 values of the auriferous QCVs of Ajjanahalli fall in the range -2.09 to -8.59 parts per thousand (average: -4.5 +/- 1.5 parts per thousand); delta O-18 are in the range 11.27-26.12 parts per thousand (average: 15.69 +/- 4.12 parts per thousand). The delta C-13 and delta O-18 values of carbonates of the BIF that host the auriferous QCVs respectively are -1.54 to -2.00 parts per thousand (average: -1.76 +/- 0.19 parts per thousand) and 14.12-26.36 (average: 21.9 +/- 5.6 parts per thousand). The carbonates from the carbonated metabasalts, also host for QCVs show delta C-13 values between -1.39 and -1.92 parts per thousand (average: -1.59 +/- 0.24 parts per thousand) and delta O-18 between 11.44 and 12.91 parts per thousand (average: 11.88 +/- 0.6 parts per thousand). delta C-13 and delta O-18 of QCVs are clearly distinct from those of meta-sedimentary carbonates in BIF and carbonates in carbonated metabasalts. The calculated isotope composition of the original fluid for the auriferous QCVs delta C-13 Sigma c are in the range -2.97 parts per thousand to -9.45 parts per thousand (average: -5.2 +/- 1.4 parts per thousand) and delta O-18(H2O) fall in the range between 6.46 and 20.58 parts per thousand (average: 7.8 +/- 0.95 parts per thousand). The delta C-13 and corresponding delta C-13 Sigma C values of the QCVs are comparable to those of mantle derived fluids or those emanating from juvenile magmas (-6 +/- 2 parts per thousand). Though many of the delta O-18(H2O) values are similar to those of mantle or juvenile magmatogenic fluids (-8 +/- 2 delta), some are heavier. These heavier delta O-18 and delta O-18(H2O) values are shown to have resulted from post-vein emplacement water-rock interaction at lower temperatures. Mantle/juvenile magmatic source for fluids is also indicated by the S-isotope (delta S-34(CDT)) composition of gold bearing sulphide minerals. Pyrite delta S-34(py) of Ajjanahalli and GGF fall in the range -0.21 to 5.8 parts per thousand (average: 3.08 +/- 1.82 parts per thousand) and 0.93 and 3.36 parts per thousand (average: 1.98 +/- 0.82 parts per thousand) respectively. The arsenopyrite delta S-34(asp) values range between 1.09 parts per thousand and 3.8 parts per thousand (average: 2.95 +/- 1.08 parts per thousand) for Ajjanahalli and 2.84 parts per thousand for Gadag. The corresponding sulphur isotope composition of the original fluids delta S-34(H2S) (calculated from delta S-34(CDT) values) for Ajjanahalli gold deposit is in range -0.03 to 4.6 parts per thousand (average of 1.89 +/- 1.82 parts per thousand). For the GGF, the values range from -0.17 to 2.11 parts per thousand (average: 0.88 +/- 0.82%). All these delta S-34(CDT) and their corresponding delta S-34(H2S) are very close to juvenile delta S-34 values (i.e. 0 +/- 2%) confirming the mantle/juvenile magmatic origin of the mineralizing fluids. Mantle/juvenile origin of auriferous fluids for auriferous QCVs from both the areas is also supported by initial Sr isotope ratios as low as 0.702 and positive is an element of(Nd) values up to +10 or higher. LILE, HFSE, REE geochemistry of the auriferous QCVs are also consistent with the above conclusions based on isotope data. The QCVs of both these deposits show +ve Eu anomaly which is typical for hydrothermal fluids of mantle origin. The LILE and HFSE data of the QCVs show that fluids required for them have not been generated by melting of subducted slabs. It is therefore concluded that the new isotope and geochemical data provide convincing evidence for direct involvement of auriferous fluids of mantle origin for these orogenic gold deposits.

Kyanite-eclogite xenoliths from Wajrakarur are considered as remnants of subducted ocean-floor crust [1]. Here trace element concentration and isotopic data are presented in garnet (Grt) and kyanite (Ky) from xenoliths KL-2 E1-E4, characterized by [2]). We use the precise Sr/Sr host kimberlite groundmass perovskite ratio (0.70312-0.70333, [3]) as a proxy for the extent of kimberlitic magma infiltration at 1.1 Ga. The xenolithic Grt and Cr-rich (upto 1506 ppm) Ky have more radiogenic Sr/Sr values than kimberlite, at 1.1 Ga, of 0.703829-0.705203 and 0.703811-0.704502, respectively. Furthermore, the Grt and Ky Nd/Nd ratios, at 1.1 Ga, are 0.509321-0.511372 and 0.510951-0.511156, respectively, and are distinctly lower than those of the host kimberlite (0.511870-0.512290, [4]). This indicates that the infiltration of kimberlitic fluid has not altered the Sr/Sr and Nd/Nd ratios in the Grt and Ky, and therefore their isotope compositions must be inherited and predate the kimberlite magma generation event at 1.1 Ga. Trace elements in Grt and Ky indicate extreme metasomatism (Sr in Grt 104-296 ppm, in Ky 672-8713 ppm [limit Sr<2ppm] and Nb in Grt 0.64-1.78 ppm, in Ky 1.7-4.54 ppm [limit Nb<0.5ppm]). The xenoliths underwent at least one major melting event inferred from extreme depletions in Re, Os and Os/Os ratios [5]. Their mantle-like δ18O values (Grt 5.3-5.4‰, Ky 5.3-5.9‰), positive Eu anomalies in both Grt and Ky (similar to Group 1 HREE-depleted garnets of [1]) suggests that the protolith likely was a chromite-bearing leucogabbro, emplaced as a high-pressure cumulate at the crust-mantle boundary, which was later eclogitized due to deep-seated subduction and underwent episodes of extreme melting and metasomatism before 1.1 Ga and at least before 1.7 Ga, as inferred from their youngest Re depletion dates [5].

This paper examines the potential of oxygen stable isotope composition of Sparidae (sea-bream) tooth enamel phosphate (delta(18)Op) as an indicator of the habitat in which the fish were captured. The isotopic compositions of Sparidae molariform teeth recovered from the coastal site of Tel Dor (northern coast of Israel), from a sequence dated to the 12th-7th centuries BCE and from modern samples were studied. The delta(18)Op values of the archaeological specimens exhibited a wide range of values, varying between 21.3 and 25.2 +/- 0.2 parts per thousand.While delta(18)Op values from the teeth dated to the 12th-9th centuries BCE resembled typical East Mediterranean coastal water, some of the later teeth, dated to the 9th-7th centuries BCE, exhibited higher values. The later values indicate tooth enamel deposition in a hyper-saline environment similar to delta(18)Op values of Sparidae observed at Bardawil Lagoon (Southeastern Mediterranean coast, east of the Suez Canal, Egypt). Prior to this study all Sparidae fish recovered at Tel Dor were regarded as evidence of local fishing activity. The current results exhibit, for the first time, that some of the Sparids may have been exported from the Bardawil Lagoon. We discuss, however, an alternative scenario, namely, the possible existence of saline lagoons near Tel Dor in antiquity. (C) 2015 Elsevier Ltd. All rights reserved.

The discussion on our paper on Paleoproterozoic glaciation arises out of the failure of previous geological mapping in the Sausar belt to identify many features, which were reported earlier, and to examine the outcrops critically for evidence of volcanism and glaciation in Central India. The details of these are given in this reply.

Carbon isotope (δ13C) compositions of total organic carbon (TOC) as well as several extracted higher plant derived lignin biomarkers, along with the recovery of grass phytoliths, provide the first direct evidence of existence of extensive grass land (C4) vegetation over the Ganges deltaic plain during the Last Glacial Maximum (LGM). The earliest Holocene (∼9ka) is marked by pronounced 13C depletion in the lignin phenols coinciding with rapid sea level rise, intensified monsoon, and replacement of grassland vegetation by mangroves. Another C4 invasion phase is identified during the late Holocene (∼6–2ka). Both the LGM and late Holocene C4 phases coincide with the well known monsoon minima. The study suggests that change in pCO2 might not be the singular driver of vegetation change as proposed recently and the climate models must take the monsoon like mega-climate processes into account for reconstructing the glacial biomes.

Carbon (delta C-13(PDB)) and oxygen (delta O-13(SMOW)) isotopic compositions of auriferous quartz-carbonate veins (QCVs) of gold deposits from Sangli, Kabuliyatkatti, Nagavi, Nabapur and Mysore mining areas developed on the Central Lode system of the Gadag Gold Field (GGF) in the Neoarchaean Gadag schist belt of the Dharwar Craton, southern India have been examined for the first time to understand the origin of the mineralising fluids. In majority of the samples (46 out of 49), delta C-13(PDB) of carbonates of the QCVs fall in the range from -2.2 parts per thousand to -9.7 parts per thousand and the delta O-18 values range from 12.0 parts per thousand to 30.5 parts per thousand SMOW. The calculated fluid delta C-13(Sigma C) compositions for these deposits range from -2.1 parts per thousand to -9.6 parts per thousand and delta O-18(H2O) from 6.8 parts per thousand to 25.9 parts per thousand, respectively. Carbonate delta C-13 and fluid delta C-13(Sigma C) compositions of the carbonates of the QCVs of the GGF are not only distinct from the carbon isotope range of marine carbonates or meta-sedimentary carbonates of the Chitradurga schist belt, but are consistent with C-isotope values of magmatic (-5 +/- 3 parts per thousand, Burrows et al., 1986) and/or mantle (-6 +/- 2 parts per thousand, Ohmoto, 1986) carbonates. As dissolution/decarbonation reactions during metamorphism of pre-existing carbonate/carbonated rocks produce CO2 with delta C-13 values similar to or more enriched than parent rock, the carbonate or fluid delta C-13 ratios of the QCVs (which fall in the compositional range of mantle/magmatic derived CO2 or carbonates) obtained in this work cannot be the result of metamorphism. The present study corroborates our previous reports from Ajjanahalli and G.R. Halli gold deposits (Sarangi et al., 2012) occurring in the vicinity of the southern extension of the same crustal scale shear zone on which all the GGF deposits are located.The age of gold mineralisation in this area has been reported to be 2522 +/- 6 Ma by Sarma et al., 2011. Chardon et al. (2011) have proposed large-scale remobilization of the older gneissic basement, as well as, emplacement of juvenile granites between 2559 Ma and 2507 Ma, dose to the crustal scale shear zone along the eastern margin of the Chitradurga schist belt. Based on these observations and our isotope studies, it is proposed that gold mineralising fluids were derived from mantle/juvenile magmatic melts and were channelled through crustal scale shear zones to give rise to the gold deposits in the GGF. (C) 2015 Elsevier B.V. All rights reserved.

Results of experiments carried out to study the kinetic fractionation during liquid condensation of water vapor in supersaturated environment are reported. The ground level ambient atmospheric water vapor was condensed on an ice-cooled (similar to 0 degrees C) metallic surface to obtain the liquid condensate. The ambient vapor was also sampled simultaneously by complete cryogenic (-78 degrees C) trapping to obtain unfractionated liquefied vapor.Unlike equilibrium fractionation, the liquid condensate at 0 degrees C was found to be depleted in O-18 and moderately enriched in (II)-I-2 compared to vapor. Consequently, the liquid had unusually high d-excess. This observation signifies kinetic fractionation, similar to that reported for ice condensation (Jouzel and Merlivat, 1984).The observed kinetic effect can be explained by diffusion of water isotopologues across super- saturated boundary layer formed when condensation temperature is lower than the dew point. The magnitude of kinetic fractionation depends on degree of super- saturation determined by temperature and relative humidity (Rh) in ambient air and the temperature of condensation. Limited observations indicate possibility of similar kinetic fractionation during natural condensation of dew. This suggests that kinetic fractionation may also be involved in various other natural condensation processes when super- saturated conditions are generated. (c) 2012 Elsevier Ltd. All rights reserved.

Five distinct transient warming (hyperthermal) events (Paleocene–Eocene Thermal Maximum [PETM], H1/ETM2/ELMO, H2, I1, and I2), marked by negative carbon isotope excursions (CIEs) occurred between Late Paleocene and Early Eocene (~56 to 52Ma) interval. However, not many records of either the PETM or definitive Early Eocene Hyperthermals (EEHs) are yet available from terrestrial realm in the tropics except two neo-tropical sections of Colombia and Venezuela (Jaramillo et al., 2010). Therefore, response of the tropical biosphere to these warming events is not very well known. Here we report high resolution carbon isotope (δ13C) chemostratigraphy, biomarker, calcareous nannofossils, and pollen data from the Cambay shale Formation of Western India (paleolatitude~5°S), which show complete preservation of all the above CIE events including the PETM, hitherto unknown from tropical terrestrial record. Comparatively larger magnitudes of CIEs for all the hyperthermal events (the PETM and EEHs) point towards a possible intensification of precipitation during the PETM and all the early Eocene hyperthermal/CIE events. This inference is supported by data of lignin phenols and presence of tropical rain forest elements spanning the entire time period ~56–52Ma and suggest that higher organic burial and soil erosion favored deposition of thick lignitic seams as a consequence of high tropical precipitation.

A heterogeneous anisotropic steady-state groundwater flow model for the multi-aquifer system of a part of southern Bengal Basin shows that human intervention has changed the natural groundwater flow system. At present, the shallow groundwater flow is restricted within the aquifer, with very short travel time of tens of years and vertical path length. The deep aquifer is fed by surface water or rainwater from distant locations with travel time of thousands of years and has no hydraulic connection with the arsenic-rich shallow aquifer. Numerical simulations indicate that the future pumping of deep groundwater is not likely to drive in arsenic from the shallow aquifer. Therefore, new wells may be installed in the deep aquifer. High pumping of shallow unpolluted aquifer consisting of brown sand will drive in groundwater containing organic matter from the post-Last Glacial Maximum aquifer-aquitard system. The organic matter drives reduction of manganese oxides at strip interfaces between palaeo-channel and palaeo-interfluve. After the completion of manganese reduction, FeOOH reduction may take place in the marginal palaeo-interfluvial aquifer and release sorbed arsenic. Arsenic then moves into the interior of palaeo-interfluvial aquifer polluting its fresh groundwater. Arsenic migration rates ranges between 0.21 and 6.3 and 1.3 × 10−2 and 0.4 m/year in horizontal and vertical directions, respectively. Therefore, palaeo-interfluvial aquifer will remain arsenic-free for hundreds to thousands of years to supply safe drinking water.

Late Paleocene to early Eocene (~56 to 51 Ma) interval is characterized by five distinct transient warming (hyperthermal) events (Paleocene–Eocene thermal maximum (PETM), H1/ETM2/ELMO, H2, I1 and I2) in a super greenhouse globe associated with negative carbon isotope excursions (CIEs). Although well-documented marine records exist at different latitudes, terrestrial PETM sections are rare. In particular, almost no terrestrial records of either the PETM or early Eocene hyperthermals (EEHs) are yet available from the tropics. Further, evolution of modern order of mammals near the PETM has been recorded in many northern continents; however, the response of mammals in the tropics to these warming events is unknown. A tropical terrestrial record of these hyperthermal/CIE events, encompassing the earliest modern order mammal bearing horizon from India, can therefore be vital in understanding climatic and biotic evolution during the earliest Cenozoic time. Here, for the first time, we report high resolution carbon isotope ( δ 13 C) stratigraphy, nannofossil, and Sr isotope ratio of marine fossil carbonate from the Cambay Shale Formation of Western India. The record shows complete preservation of all the above CIE events, including the PETM, hitherto unknown from the equatorial terrestrial records. δ 13 C chemostratigraphy further suggests that at least the present early Eocene mammal-bearing horizon, recently discovered at Vastan, does not support the ‘out of India’ hypothesis of earliest appearance of modern mammals and subsequent dispersal to the Holarctic continents.

Carbon and oxygen isotopic compositions of carbonates from auriferous quartz carbonate veins (QCVs) of two orogenic gold deposits - Aijanahalli and Guddadarangavvana Halli (G.R. Halli) - from the Neoarchean Chitradurga schist belt of the Dharwar craton, southern India are examined to understand the origin of the mineralizing fluids. The average carbonate carbon (delta C-13(pdb)) and oxygen (delta O-18(smow)) isotope compositions of QCVs of Ajjanahalli are -5.5 +/- 1.3 parts per thousand and 14.1 +/- 2.7 parts per thousand, respectively. The same ratios for the QCVs of G.R. Halli are -6.2 +/- 1.9 parts per thousand and 14.1 +/- 0.5 parts per thousand. The corresponding average fluid delta C-13 and delta O-18 compositions are -5.81 +/- 1.14 parts per thousand, 13.78 +/- 5.1 parts per thousand. for Ajjanahalli and -4.64 +/- 0.7 parts per thousand, -6.50 +/- 0.6 parts per thousand for G.R. Halli. The delta C-13(pdb) of syn-sedimentary carbonates of BIF of Ajjanahalli (-1.8 +/- 0.1 parts per thousand), carbonated metabasalts of Ajjanahalli (-1.4 parts per thousand) and G.R. Halli (-1.3 parts per thousand) fall in the compositional range of marine carbonates (0 +/- 2 parts per thousand). As dissolution/decarbonation reactions during metamorphism of pre-existing carbonate/carbonated rocks produce CO2 with delta C-13 values similar to or more enriched than parent rock, the carbonate or fluid delta C-13 ratios of the QCVs (which fall in the compositional range of mantle/magmatic derived CO2 or carbonates) obtained in this work cannot be the result of metamorphism. It is proposed that gold mineralizing fluids were derived from juvenile magmatic melts and were channeled through crustal scale shear zones to give rise to the gold deposits. (C) 2012 Elsevier Ltd. All rights reserved.

Hydrochemical and isotopic studies in groundwater was attempted in a basin to gain knowledge on geochemical evolution and water quality status. The results of the chemical analysis indicate the sources of ions into the groundwater are from dissolution and leaching from source rocks, cation exchange and anthropogenic activities. The saturation index calculated indicate oversaturation of carbonate species and undersaturation of amorphous silica indicating groundwater chemical evolution is controlled by water rock interactions. Water type alters from Ca-HCO3 to Na-Cl indicating their hydrochemical evolution and flow path. The water type's classification indicates 5 distinct groups ranging from low EC and highly depleted isotopes to very high EC with enriched stable isotopic composition indicating longer residence time of groundwater.

From 2002 to 2010 inclusive we monitored concentrations of arsenic (As) and major ions (Ca, Mg, Sr, Na, K, Fe, Mn, Cl, and SO(4)) in groundwater from 14 domestic wells and three piezometer nests in a shallow aquifer (<60 m depth), and 3 wells in a deep aquifer (>70 m depth), in southern West Bengal, India. In the deep aquifer, concentrations of As did not change over time despite increases in the concentration of Fe in two wells. The shallow aquifer occurs in two sedimentological settings: palaeo-channel and palaeo-interfluve. At the top of the shallow aquifer of the palaeo-channel, decreases in all constituent concentrations with time, and an (3)H/(3)He age of 1.4 years, proves that the aquifer is beginning to be flushed of pollutants. In As-polluted groundwater (>50 microg/L As) tapped from deeper grey sands of the shallow, palaeo-channel, aquifer, concentrations of As were mostly stable over time, but both increases and decreases occurred with time in response to downward migration of the chemically-stratified water column. In groundwater tapped from Pleistocene brown sands, the concentration of As remained either low and stable (<2 microg/L As), or increased at rates up to 34 microg/L per year. The increases were caused by the flow of As-rich groundwater either downward into brown sand at the base of palaeo-channels, or laterally into a confined, unpolluted, palaeo-interfluvial, aquifer of brown sand that lies regionally beneath a palaeosol. Under the present pumping regime, the prognosis for As-pollution in the shallow aquifer is complex. Wells in brown sand may become polluted over timescales of as little as 2 years, whilst some wells tapping As-polluted groundwater from grey sand will become fit for potable use (<50 microg/L) within a few decades. The evidence of flushing, and of declining As in some of the groundwater from palaeo-channels, which are conduits for recharge of the confined, As-free, palaeo-interfluve aquifer, and probably also the deeper aquifer, offers hopes that the spread of As-pollution will be limited.

Analysis of the D/H ratio of pedogenic clay and the 18O/16O ratio of carbonate nodules collected from Siwalik sediments in India indicates three episodes of monsoon intensification at ~11Ma, 6Ma and 3Ma. These episodes coincide with major pulses of tectonic uplift in the Himalayas suggesting causal link between monsoon intensity and uplift. In addition, variation in the carbon isotope ratio of carbonate nodules and residual organic matter indicates a change in vegetation regime from pure C3 type to a mix of C3–C4 type during this time span. Isotopic analysis of samples collected from different locations of the Himalayan Siwalik shows that the late Miocene C4 appearance was locally asynchronous (by ~3Ma), similar to what is seen on a global scale. The lack of synchronous emergence of C4 plants in various parts of Siwalik probably indicates a combined effect of microclimate (e.g. varying monsoon intensity) and habitat disturbance (e.g. forest fire). In contrast, subsequent expansion of C4 plants during the late Miocene–Pliocene time could be entirely due to monsoon intensification that favoured C4 respiration in a warm and seasonally variable rainfall regime.

Sedimentology and sequence stratigraphic analysis of the ∼ 31 Ma old marker White sandstone unit from the Subathu Sub-basin, NW Himalayan foreland, suggest it to be a forced regressive wedge (FRW) formed during the transition from the marine Subathu Formation to the continental Dagshai Formation. The FRW is bounded between the “Surf diastem” below and type 1 unconformity at the top and differs from RSME (regressive surface of marine erosion, occurring below) bounded FRWs described from other classical coastal/foreland settings. Correct identification of bounding surfaces of a FRW has an important implication to the estimation of rate of relative sea-level (RSL) fall. A faster rate of RSL fall, higher than the sedimentation rate, has been postulated for the erosion of the lower shoreface and RSME. Using the logged thickness of the Subathu/Dagshai transition zone including the White sandstone (bounded between the “Surf diastem” and unconformity), available chronology and eustatic sea-level fall (0.023 mm/year at 31 Ma), a higher RSL fall than the sedimentation rate (0.07 mm/year) has been inferred during the deposition of the White sandstone. Petrography of sandstones and their Sr and Nd isotopic compositions indicate a major provenance switch-over from dominant mafic/ultramafic to metamorphic source from White sandstone (∼ 31 Ma) onwards attesting the link between hinterland tectonics, provenance and forced regression. The provenance switch-over at 31 Ma was earlier inferred to be driven by proto-Himalayan thrust propagation in the foreland. Using a simple isostatic model, on the contrary, a mechanism of accelerated surface uplift (at a rate of > 0.10–0.15 mm/year) is suggested for both provenance change and forced regression.

AbstractAnalyses of sulphur isotope compositions in sedimentary pyrites from the Vindhyan, Chattisgarh and Cuddapah basins show heavy δ34S (> +25 ‰) values during the Mesoproterozoic. The data provide evidence in support of a hypothesized global Proterozoic sulphidic anoxic ocean where very low concentrations of marine sulphate, bacterially reduced in closed systems, produced δ34S values in pyrites similar to or even heavier than marine sulphate. The extreme environmental conditions induced by these anoxic oceans could have been responsible for the delayed oxygenation of the biosphere and retarded evolution of multicellular life.

Oxygen isotope composition (δ18O) of fossil bone and tooth enamel phosphate (bioapatite) is an important tool for estimating the isotopic composition of past environmental water. Lack of analytical facility was a hindrance for studying such bioapatites in spite of large number of fossil materials reported from various geological ages in India. We have established in our laboratory, based on available methods, the chemical procedure for extraction of very small amount (<1000 µg) PO4 −3 from bioapatite and on-line mass spectrometric measurement of its δ18O composition by high temperature (∼1450°C) pyrolysis. The achieved precision is ∼± 0.3 ‰ similar to obtained elsewhere, with interlaboratory calibration showing excellent agreement of standard phosphates. Inferred δ18O values of environmental water, based on the analysis of teeth and bones of sharks, fish and terrestrial mammals from the Paleogene successions of the northwest sub-Himalayan and the Peninsular India show strong correspondence with animal habitats. The freshwater δ18O values are much depleted having range similar to modern monsoon precipitation. However, owing to our small dataset it is not possible at this stage to infer about the existence of monsoon over the Indian sub-continent during the Eocene-Oligocene time.