V. Balaram

Rare-earth elements and Stable Isotope Geochemistry of early Cambrian chert-phosphorite assemblages from the Lower Tal Formation of the Krol Belt (Lesser Himalaya, India)

Abstract The Neoproterozoic–Cambrian transitional sequence in the Mussoorie and Garhwal Hills of the Lesser Himalaya is represented by dolomites of the Upper Krol Formation and chert-phosphorite assemblages of the lowermost Tal Formation. These rocks provide valuable information regarding the assumed existence of a stratified ocean during the terminal Neoproterozoic and beginning of earliest Cambrian (Nemakit-Daldynian). The isotopic compositions of carbonate and organic carbon in the transition profile can be best interpreted as reflecting an oceanic anoxic event (OAE) prior to the phase of early Cambrian phosphate formation. The chert-phosphorite beds record negative Ce and positive Eu anomalies. While Ce is an important paleooceanic redox indicator, Eu is rather immobile under normal diagenetic conditions. The observed Eu anomaly is linked to the high Ba content in these phosphorites and is indicative of an anoxic (or sulfate reducing) diagenetic environment. The suggested stratification of the ocean during the Late Neoproterozoic and Nemakit-Daldynian times would have been linked to the reduction of oxygen supply to the zone below the redoxcline, causing 12 C -and P-rich organic matter previously produced in the photic zone to be trapped in large quantities within the deeper anoxic zone. This would, in turn, increase the 13 C content of the water in the photic zone. Moreover, in the deeper anoxic waters, reduction of Ce4+ to Ce3+ would result in an enrichment of dissolved Ce (as Ce3+). Upwelling of this anoxic bottom stratum would bring the 12 C -and Ce-enriched waters back to the oxic marine realm. However, on entering the highly oxic productive zone, the excess Ce is expected to be removed from the water by oxidation to insoluble Ce4+ followed by precipitation or preferential scavenging. Due to these oxidation reactions, the waters of the shallow oxic zone would tend to become rapidly depleted in Ce. In other words, ocean mixing and upwelling during the early Cambrian were ultimately responsible for the transport of 12 C , P and Ce to the oxic shelves. Sharp drops in both δ 13 C carb and δ 13 C org support the existence of oceanic anoxia followed by oceanic mixing at this juncture of Earth history. The large spread of the δ 34 S values of early diagenetic pyrites within the phosphorite bearing sequence in contrast to the limited spread of δ 13 C carb values suggests that phosphatisation took place under exclusively suboxic diagenetic non-sulfate reducing condition and pyritisation began only when phosphate layers entered the zone of sulfate reduction.

Assessment of the effects of municipal sewage, immersed idols and boating on the heavy metal and other elemental pollution of surface water of the eutrophic Hussainsagar Lake (Hyderabad, India)

The surface water qualities of Hussainsagar, an eutrophic urban lake in the midst of twin cities of Hyderabad and Secunderabad (India) receiving large quantities of external inputs—both untreated municipal sewage containing industrial effluents, and treated sewage, a large number of annually immersed idols of God and Goddess, and intense boating activities were assessed in relation to the concentration of elements including heavy metals of the water along the necklace road of the lake. Elemental analyses of water using ICP-MS revealed 26 elements including heavy metals—As, Cd, Cr, Ni, Pb, Cu, Fe, Mn, Se, Ba, Zn, Mo, V, Co, Ag, Sr, Rb, Mg, K, Ca, Al, Si, Sb, Na, Li, and B, in the surface water of the lake. Of these, the first 15 elements were found in elevated concentrations in the water at the outfall point of the untreated municipal sewage (site 3), which was the main dominating source of contamination of the lake water while Cu and Sb were recorded in higher concentrations at the outfall of treated effluent from Sewage Treatment Plant, and three elements (Ba, Si, and B) were in higher concentration at the sites of outfall of sewage flowing from an oxygenated pond (site 4), Ca, Zn, and Sr, at the site immersed with idols (site 1), and Pb, Ag, and Al at the center of the lake (site 5) with intense boating activities. Concentrations of most of these elements exceeded the maximum permissible limits of national (Indian Council Medical Research) standards for drinking water. The concentrations of most of the elemental contaminants showed significant positive correlations between them.

Application of Microwave Plasma Atomic Emission Spectrometry (MP-AES) for environmental monitoring of industrially contaminated sites in Hyderabad City

Recently introduced microwave plasma-atomic emission spectroscopy (MP-AES) represents yet another and very important addition to the existing array of modern instrumental analytical techniques. In this study, an attempt is made to summarize the performance characteristics of MP-AES and its potential as an analytical tool for environmental studies with some practical examples from Patancheru and Uppal industrial sectors of Hyderabad city. A range of soil, sediment, water reference materials, particulate matter, and real-life samples were chosen to evaluate the performance of this new analytical technique. Analytical wavelengths were selected considering the interference effects of other concomitant elements present in different sample solutions. The detection limits for several elements were found to be in the range from 0.05 to 5 ng/g. The trace metals analyzed in both the sectors followed the topography with more pollution in the low-lying sites. The metal contents were found to be more in ground waters than surface waters. Since a decade, the pollutants are transfered from Patancheru industrial area to Musi River. After polluting Nakkavagu and turning huge tracts of agricultural lands barren besides making people residing along the rivulet impotent and sick, industrialists of Patancheru are shifting the effluents to downstream of Musi River through an 18-km pipeline from Patancheru. Since the effluent undergoes primary treatment at Common Effluent Treatment Plant (CETP) at Patanchru and travels through pipeline and mixes with sewage, the organic effluents will be diluted. But the inorganic pollutants such as heavy and toxic metals tend to accumulate in the environmental segments near and downstreams of Musi River. The data generated by MP-AES of toxic metals like Zn, Cu, and Cr in the ground and surface waters can only be attributed to pollution from Patancheru since no other sources are available to Musi River.

Risk assessment of metals from groundwater in northeast Rajasthan

The present study was conducted to investigate trace metal (Li, Be, B, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As Se, Mo, Cd, Sb, Ba and Pb) concentrations of drinking water samples in northeast Rajasthan, India. Furthermore, the study aimed to ascertain carcinogenic and non-carcinogenic health risks of metals by ingestion and dermal absorption pathways to the local residents. Metal concentrations were analyzed by using high resolution inductively coupled plasma mass spectrometry and compared with permissible limits set by the Bureau of Indian Standards, United States Environmental Protection Agency and World Health Organization. The results indicate that the concentrations of Be, B, Al, Cr, Fe, Cu, Zn, As, Mo, Sb and Ba were lower than their respective permissible limits, whereas the concentrations of Mn, Ni, Se, Cd and Pb in some samples were higher than their permissible limits.The total hazard index (summing the hazard index through ingestion and dermal routes) at all the sampling sites exceeded or nearing unity, indicating the presence of non-carcinogenic health effects from ingestion of water and dermal contact with water. The results indicate that the total excess lifetime cancer risk (considering both ingestion and dermal exposure pathways) of metals exposure was in accordance to the acceptable lifetime risks for carcinogens in drinking water (10-6–10-4). Both carcinogenic and non-carcinogenic risks were mainly attributed to the ingestion pathways.

Geochemistry and Tectonic Setting of Tuting Metavolcanic Rocks of Possible Ophiolitic Affinity from Eastern Himalayan Syntaxis

Geochemistry of Tuting metavolcanic rocks is being reported for the first time. Narrow slivers of mafic volcanic rocks, as those at Tuting, also occur in close association with slivers of more complete sections of ophiolites at the Tsangpo river section upstream of Tuting and skirt round the Namche Barwa antiform. These detached slivers of the mafic volcanic rocks and the ophiolites represent the easternmost components of the Yarlung Tsangpo Ophiolite, and also define the arcuate shape of the Eastern Himalayan syntaxis. The metavolcanic rocks exposed at the apex of the Siang river dome at Tuting (Tsangpo River named Siang down stream of Tuting) is the only exposure of such rocks from the Himalayan syntaxial area in India.The Tuting metavolcanic rocks correspond to andesite and basaltic andesite as per TAS diagram. The mobility of major elements possibly has affected their classification. As per Zr/TiO2 — Nb/Y diagram of Winchester and Floyd (1977), proposed for classification of altered igneous rocks, the Tuting samples mainly correspond to ‘sub-akaline basalt’ and one sample plot as ‘andesite/basalt’. These have a flat chrondrite-normalised REE pattern. MORB-normalized multi-elemental plot shows enrichment in large ion lithophile (LIL) and the light rare earth elements (LREE), and depletion in several high field strength elements (HFSE). Based on these trace element patterns and a few discrimination plots, the Tuting metavolcanic rocks are inferred to have generated in supra-subduction zone environment in an intraoceanic arc, back arc setting, or in a mid-ocean ridge process that resembles the Chile Ridge spreading centre.

Petrography and Geochemistry (Trace, Ree and Pge) of Pedda Cherlo Palle Gabbro-Diorite Pluton, Prakasam Igneous Province, Andhra Pradesh, India

Abstract Prakasam Igneous Province (PIP) is an important geological domain in the Eastern Dharwar Craton (EDC), found in the junction zone between the EDC and Eastern Ghat Mobile Belt (EGMB). The Pedda Cherlo Palle (PCP) gabbros are massive, leucocratic-mesocractic, and show cumulus textures with minerals plagioclase, cpx, and amphiboles. Compositionally, plagioclase is a labradorite-bytownite, cpx is diopside to augite, olivines are hyalosiderites and amphiboles are magnesiohornblendes. PCP gabbros have normal SiO2, high Al2O3, moderate to high TiO2, Na2O and medium Fe2O3, so, classified as subalkaline tholeiitic gabbros. Fractionated rare earth element (REE) patterns, high abundance of large ion lithofile elements (LILE) and transitional metals coupled with light REE (LREE) relative enrichment over heavy REE (HREE) and Nb are characteristics of partial melting of depleted mantle and melts that have undergone fractional crystalisation. These partial melts are enriched in LREE and LILE, due to the addition of slab derived sediment and fluids. PCP gabbros contain low abundance (5.1 to 24.6 ng/g) of platinum group elements (PGE), and show an increase in the order Ir>Os>Pt>Ru»Pd>Rh. We propose that the subduction related intraoceanic island arc might have accreted to the southeastern margin of India to the east of Cuddapah basin in a collisional regime that took place during Ur to Rodinia amalgamations.

Petrographic characteristics of the Proterozoic Vempalle carbonates, Cuddapah Basin, India and their implications

The Vempalle Formation of the Proterozoic Cuddapah basin has a well developed sequence of carbonate rocks, which are interbedded with shales, siltstones and chert. The stromatolitic carbonates are conspicuous at many places but the oolitic carbonates are less prominent and are present only in some areas. All the carbonates are pervasively dolomitized. Petrographic examination of these carbonates revealed that they are predominantly made up of fine grained micrite with patchy development of sparite and chert/quartz. The stromatolitic carbonates show distinct banding of alternate carbonate and cherty layers. The latter are rich in organic matter indicating prevalence of profuse biogenic activity. The oolitic carbonates comprise of ooids showing both concentric and radial patterns and made up of carbonate/chert and cemented by micro/mega quartz or carbonate itself. Diagenetic and post depositional features are reflected in cementation, recrystallization, compaction, stylolite formation and silicification processes. Various stages of cementing material are observed. Secondary vein fillings of carbonate or quartz traverse the carbonate/cherty groundmass. Intraclasts present suggest occasional erosional destruction of associated sediments, short lived transport and local redeposition. Accessory silicate minerals represent terrigenous influx during deposition. Dolomitization of the carbonates was fabric retentive and early diagenetic. The environmental conditions were characterised by low energy, within a shallow water zone, in occasional higher energy events and turbulence. The carbonates appear to have been deposited on a shallow water ramp within a tidal regime.

Geochemistry of sedimentary rocks from Permian–Triassic boundary sections of Tethys Himalaya: implications for paleo-weathering, provenance, and tectonic setting

The geochemical characteristics of two sections—the Permian–Triassic boundary (PTB) Guryul Ravine section, Kashmir Valley, Jammu and Kashmir, India; and the Attargoo section, Spiti Valley, Himachal Pradesh, India—have been studied in the context of provenance, paleo-weathering, and plate tectonic setting. These sections represent the siliciclastic sedimentary sequence from the Tethys Himalaya. The PTB siliciclastic sedimentary sequence in these regions primarily consists of sandstones and shales with variable thickness. Present studied sandstones and shales of both sections had chemical index of alteration values between 65 and 74; such values reveal low-to-moderate degree of chemical weathering. The chemical index of weathering in studied samples ranged from 71 to 94, suggesting a minor K-metasomatism effect on these samples. Plagioclase index of alteration in studied sections ranged from 68 to 92, indicating a moderate degree of weathering of plagioclase feldspars. The provenance discriminant function diagram suggests that the detritus involved in the formation of present studied siliciclastic sedimentary rocks fall in quartzose sedimentary and felsic igneous provenances. These sediments were deposited in a passive continental margin plate tectonic setting according to their location on a Si2O versus K2O/Na2O tectonic setting diagram.

Assessment of uranium in correlation with physico-chemical properties of drinking water of Northern Rajasthan

In the present study, analysis of 238U concentration in 40 drinking water samples collected from different locations of Jodhpur, Nagaur, Bikaner and Jhunjhunu districts of Rajasthan, India has been carried out by using high resolution inductively coupled plasma mass spectroscopy (HR-ICP-MS) technique. The water samples were taken from hand pumps and tube wells having depths ranging from 50 to 800 feet. The measured uranium concentration lies in the range from 0.89 to 166.89 μg l-1 with the mean value of 31.72 μg l-1. The measured uranium content in twelve water samples was found to be higher than the safe limit of 30 μg l-1 as recommended by World Health Organization (WHO, 2011) and US Environmental Protection Agency (USEPA, 2011). Radiological risk calculated in the form of annual effective dose estimated from annual uranium intake ranges from 0.66 to 138.63 μSv y-1 with the mean value of 26.28 μSv y-1. The annual effective dose in two drinking water samples was found to be greater than WHO (2004) recommended level of 100 μSv y-1. Chemical risk calculated in the form of lifetime average daily dose (LAAD) estimated from the water samples varies from 0.02 to 4.57 μg kg-1 d-1 with the mean value of 0.87 μg kg-1 d-1. The lifetime average daily dose (LAAD) of ten drinking water samples was found to be greater than WHO (2011) recommended level of 1 μg kg-1 d-1. The corresponding values of hazard quotient of 48% water samples were found to be greater than unity.A good positive correlation of uranium concentration with total dissolved solids (TDS) and conductance has been observed. However no correlation of uranium concentration with pH was observed. The results revels that uranium concentration in drinking water samples of the study area can cause radiological and chemical threat to the inhabitants.

Major, trace and REE characteristics of the high grade gold geochemical reference material from Middle Reef, Hutti gold mines, Karnataka

The geological, petrological, mineralogical and geochemical characteristics of the Hutti high-grade gold reference material representing the composite sample of sheared gold-sulphide bearing smoky-grey quartz vein hosted in felsic volcanics (Middle Reef) and hydrothermal altered wall rocks are investigated in the present work. Petrological studies on these rocks reveal the presence of deformed quartz ribbons, plagioclase, chlorite, biotite, stipnomelane, actinolite and abundant native gold, arsenopyrite, pyrite and minor scheelite, monazite and xenotime. The major, trace and REE geochemistry of the host barren rhyolites are interpreted as low Yb adakitic variety which show high Ba, Cr, V and Ni concentrations. REE patterns of the gold-sulphide bearing quartz reef is characterized by a pronounced positive Eu anomaly, LREE depletion and nearly flat HREE with a low total REE which indicate possible contribution from deep-seated fluids to the ore-forming process. These patterns also suggest a source which is enriched in Eu and depleted in LREE either due to crystal fractionation or the formation of scheelite. The associated hydrothermally altered wall rocks from proximal zone, exhibit flat REE patterns coupled with high concentrations of Cu, Zn, Cr, V, Sc and Ni indicating their derivation from secondary epigenetic fluids responsible for metasomatic alteration. The abundant barren schistose amphibolites from distal zone represent enriched type of island arc basalts (IAB). The trace, REE-HFSE data on the rhyolite (adakite) and IAB of Middle Reef in the Hutti schist belt substantiates the inference that Archaean subduction processes in an island arc/convergent margin setting are responsible for adakitic magmatism.