Effect of a Sublethal Concentration of Zinc Sulphate on the Growth Rate of Fingerlings of Channa punctatus (Bloch), a Freshwater Murrel

Fingerlings of Channa punctatus are exposed to 12 mg/l zinc sulphate for 31 d at daily feeding. From the 19th day a significant decrease of growth (increase of weight) by 7 … 8 % as compared with the untreated control fishes was found. After exposure for 30 d the RNA- and protein-contents of the muscles are lower by 10 and 13 %, respectively.     

Simulation of strong ground motion for a potential Mw7.3 earthquake in Kopili fault zone,northeast India

Natural Hazards - The occurrence of major natural disasters in recent years has impacted large cities worldwide and boosted the need of assessing urban resilience. As a key factor of resilience,...     

Mantle-derived fluids in the basement of the Deccan Trap: evidence from stable carbon and oxygen isotopes of carbonates from the Killari borehole basement, Maharashtra, India

We report here for the first time geochemical, mineralogical and stable carbon and oxygen isotopic data on the crystalline basement rocks of the 1993 Killari earthquake region of Maharashtra (India), which is covered by a thick suite of Deccan volcanics. Our results revealed the hitherto unknown amphibolite–granulite nature of the 2.5?Ga basement, which contains 2.00–2.28?wt% of CO₂. The stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotopic measurements on carbonates separated from two basement samples KIL-13 (440.5?m depth) and KIL-20 (499.6?m depth) collected from the KLR-1 borehole drilled in the epicentral region showed the respective values of ?6.23 and ?6.22‰ versus PDB for δ¹³C and 7.94 and 8.11‰ versus SMOW for δ¹⁸O. The samples plot in the primary igneous carbonatite field, indicating the mantle origin of the carbonates, derived through the process of mantle metasomatism from the deep mantle carbon reservoir. This would suggest large-scale crust-mantle thermal fluid interaction beneath the Killari seismogenic region, which is characterized by massive upwarping of the high-velocity mafic crust and retrograde metamorphism.     

Rocket borne studies of electron density irregularities in equatorial D and E regions

Electron density irregularities in the equatorialD andE regions have been studied using ground-based and rocket-borne experiments. In this paper this subject is reviewed with an emphasis on the rocket-borne measurements of electron density and electric field structures and other parameters relevant for identifying processes responsible for generation of electron density irregularities. These studies have led to the identification of various causative mechanisms, in terms of plasma and neutral dynamical processes for producing irregularities. Based on these mechanisms, the irregularities are classified and discussed. There are many observations which have eluded explanation and hence call for sustained efforts.     

Petrology and geochemistry of the Mesoproterozoic Vattikod lamproites,Eastern Dharwar Craton,southern India: evidence for multiple enrichment of sub-continental lithospheric mantle and links with amalgamation and break-up of the Columbia supercontinent

Numerous lamproite dykes are hosted by the Eastern Dharwar Craton, southern India, particularly towards the northwestern margin of the Cuddapah Basin. We present here a comprehensive mineralogical and geochemical (including Sr and Nd isotopic) study on the lamproites from the Vattikod Field, exposed in the vicinity of the well-studied Ramadugu lamproite field. The Vattikod lamproites trend WNW–ESE to NW–SE and reveal effects of low-temperature post-magmatic alteration. The studied lamproites show porphyritic texture with carbonated and serpentinized olivine, diopside, fluorine-rich phlogopite, amphibole, apatite, chromite, allanite, and calcite. The trace-element geochemistry (elevated Sr and HFSE) reveals their mixed affinity to orogenic as well as anorogenic lamproites. Higher fluorine content of the hydrous phases coupled with higher whole-rock K₂O highlights the role of metasomatic phlogopite and apatite in the mantle source regions. Trace-element ratios such as Zr/Hf and Ti/Eu reveal carbonate metasomatism of mantle previously enriched by ancient subduction processes. The initial ⁸⁷Sr/⁸⁶Sr-isotopic ratios (calculated for an assumed emplacement age of 1350 Ma) vary from 0.7037 to 0.7087 and ?Nd range from ??10.6 to ??9.3, consistent with data on global lamproites and ultrapotassic rocks. We attribute the mixed orogenic–anorogenic character for the lamproites under study to multi-stage metasomatism. We relate the (1) earlier subduction-related enrichment to the Paleoproterozoic amalgamation of the Columbia supercontinent and the (2) second episode of carbonate metasomatism to the Mesoproterozoic rift-related asthenospheric upwelling associated with the Columbia breakup. This study highlights the association of lamproites with supercontinent amalgamation and fragmentation in the Earth history.     

Ocean Model Simulation of Southern Indian Ocean Surface Currents

The dynamic importance of the Southern Indian Ocean (SIO) lies in the fact that it connects the three major world oceans: the Pacific, Atlantic, and Indian Oceans. Modeling study has been used to understand the circulation pattern of this very important region. Simulation of SIO (10°N–60°S and 30°E–120°E) is performed with z-coordinate Ocean General Circulation Model (OGCM) viz; MOM3.0 and the results have been compared with observed ship drift data. It is found that except near coastal boundaries and in equatorial region, the simulated current reproduce most well known current pattern such as Antarctic Circumpolar Current (ACC), South Equatorial Current (SEC) etc. and bears a resemblance to that of the observed data; however the magnitude of the surface current is weaker in model than the observed data, which may be due to deficiency in the forcing field and boundary condition and problem with observed data. The annual mean wind stress curl computed over the oceanic domain reveals about ACC and its similar importance. The way in which the ocean responds to the windstress and vertically integrated transport using model output is fascinating and rather good.     

A Petrological and Geochemical Account of Subsurface Noritic Intrusion in the Western Part of Bundelkhand Massif,Shivpuri District,M.P.

Subsurface exploration for uranium in the northwestern part of Bundelkhand massif, near Khor area, Shivpuri dist., M.P., resulted in intercepting a substantial thickness of mafic rock within Bundelkhand granitoid. Intercepts of this mafic rock at various levels in the boreholes, indicate that the rock mainly occurs as dykelike intrusion and fracture-fills within Bundelkhand granite. It is essentially composed of hypersthene and plagioclase, with or without olivine, leading to the characterisation as hypersthene microdolerite, noritic dolerite and norite (±olivine), depending on the grainsize and variation from intergranular to ophitic texture. Chemically, the rock is characterised by av. 49.09% SiO₂, 2.46%TiO₂, 2.33 Fe₂O₃, 9.45% FeO, 5.75% MgO, 8.37% CaO and 0.96% K₂O. The normative composition ranges from 3.53% quartz, 46.86% plagioclase, 12.58% diopside, 19.24% hypersthene. The olivine normative samples show av. 5.65% olivine. Geochemical plots indicate an intra-plate affinity along with oceanic signature, while presence of mineralogical and normative olivine, together with the REE pattern, point towards a lower crustal or mantle source. The mineralogical and normative presence of either quartz or olivine in these mafic rocks implies that it has an intermediate character between the tholeiitic dolerite dykes and the komatiite-type ultramafics reported from Bundelkhand craton. The complex geochemical signature of the rocks also reveals that both intra-continental as well as a mixture of oceanic- to upper mantle signatures are evident. The present study is a first time report of the occurrence of this hitherto unknown noritic body at depth within the Bundelkhand granite, which has no visible surface expression. The findings may strengthen the existing concept of a continuum between Rajasthan craton in the west and Bundelkhand craton in the east, as a single protocontinent.     

Seasonal distribution of trace metals in suspended particulate and bottom sediments of four microtidal river estuaries,west coast of India

ABSTRACT

The seasonal distribution of metals (V, Cr, Co, Cu, Ni, Zn, Pb, Mn, Fe, Al and Ti) in suspended and bottom sediments of four minor estuaries (Terekhol, Chapora, Sal and Talpona rivers) of Goa, India was investigated to understand the metal distribution process in the estuarine region. The highest particulate-metal concentrations were found in low-salinity regions of all the estuaries, in the wet season (e.g. in the Terekhol River, the averages in ppm were Co: 53, Ni: 197, Cu: 208, Zn: 212 and Pb: 65) compared to the dry season averages (Co: 27, Ni: 76, Cu: 105, Zn: 164 and Pb: 13 ppm). The estuarine-mixing diagrams showed non-conservative behaviour in both seasons. The Sal River had the highest particulate-metal concentration (Co: 106, Ni: 300 and Zn: 323 ppm), suggesting an anthropogenic input. The enrichment factor for suspended matter was higher than bottom sediments with extremely high enrichment for Mn (>10). The Geo-accumulation index displayed unpolluted to polluted class for all metals. The study highlights the important role played by small estuaries in seasonal metal release and accumulation along the coastal region.     

High-altitude charged aerosols in the atmosphere of Titan

Observations by several instruments onboard the Cassini spacecraft revealed the existence of heavy hydrocarbon and nitrile species with masses of several thousand atomic mass units in the ionosphere of Titan. These very large molecules are in fact aerosols. The goal of this paper is to compute the concentrations of the charged aerosols in the upper atmosphere (950-1200 km) of Titan. The charging of these aerosols has been studied using the charge balance equations, where positive ions, negative ions, electrons, neutral and charged aerosols are included. Number concentrations of charged aerosols are compared with those observed by the Cassini instruments. The present work estimates the aerosol mass density as 1-10 kg/m³, which is within the predicted range. The results show that the aerosols must be smaller than 10 nm in order to have reasonable agreement with observations by the Cassini Plasma Spectrometer.