CHARACTERIZATION OF MAJOR,MINOR AND TRACE ELEMENTS IN SIX CCRMP (TDB-1, WGB-1, UMT-1, WPR-1, WMG-1 AND WMS-1) AND ONE IWG (ZW-C) GEOCHEMICAL CANDIDATE REFERENCE MATERIALS*

Elemental compostions of six CCRMP (TDB-1, WGB-1, UMT-1, WPR-1, WMG-1 and WMS-1) and one IWG (ZW-C) geochemical candidate reference materials were determined by XRF, ICP-AES, ICP-MS, GFAAS and other modern instrumental techniques. Inter-method results compared favourably in the case of elements for which multiple data were available.     

Mineralogy and Petrogenesis of the Deccan Trap Lava Flows around Mahabaleshwar, India

Electron microprobe analyses of minerals of thirteen DeccanTrap lava flows at Mahabaleshwar have been carried out in thepresent study. All of these flows have tholeiitic bulk compositionsand all, except one (represented by MB-81-17 of Mahoney et al.,1982) contain olivine, plagioclase, two pyroxenes, and Fe-Tioxide minerals. Olivine and plagioclase appear as distinct phenocrystsin all but one flow, and Ca-rich pyroxene joins as a phenocrystphase in the younger flows. Pigeonite and Fe-Ti oxide minerals(titanomagnetite and ilmenite) occur in the groundmass. Olivineoccurs as both groundmass and phenocryst phase in MB-81-17 (whichis the only flow without low-Ca pyroxene phase); in all otherflows olivine appears only as phenocryst phase. In all but one(MB-81-17) flow olivine is completely altered. MB-81-17 olivinegrains are only partly altered, and in this rock the cores ofphenocrysts are rounded and have a composition of Fo₇₇ whereastheir euhedral rims have a composition around Fo₆₇. The groundmassolivine grains in MB-81-17 are Fo_41–32. Substantial Fe-enrichmentand zoning trends are shown by the pyroxenes in individual rocks.The cores of Ca-rich pyroxene phenocrysts of some of the flowshave as much as 4 wt. per cent A1₂O₃ and may have crystallizedat higher (crustal) pressures. Pigeonite thermometry (Ishii,1975) suggests an average of 1050?C for crystallization of thegroundmass pigeonite (eruption temperature?). Fe-Ti oxide mineralsare mostly altered in the older flows. In the younger flows,coexisting unaltered titanomagnetite and ilmenite yield maximumtemperature estimates for the crystallization of these phaseof about 1025?C and an oxygen fugacity of 10^–11.5 atm.The T-fo₂ path followed by these flows seems to have been consistentlysomewhat lower than that defined by the 1 atm. fayalite-magnetitequartz curve. All of the lavas examined have experienced extensivefractional crystallization of olivine and some clinopyroxeneat relatively higher pressures. These lavas were saturated orclose to being saturated with olivine+plagioclase+clinopyroxeneduring eruption. Plagioclase accumulation, although it appearsto have occurred, has not been significant. It is suggestedthat MB-81-17 magma was contaminated by a calcite-rich rock(limestone?) whereas the lower Group 1 magmas may have beenselectively contaminated by quartz-bearing contaminant. Alternately,parental magma of MB-81-1 (with the highest Mg-number and 8= -16) may have been produced in the upper mantle into whichminor masses of old crust was well mixed. Magma mixing, crystalfractionation, and contamination processes of Mahabaleshwarbasalts and possible genetic relationships with other DeccanTrap lavas are discussed.     

Carbonate-bearing mantle peridotite xenoliths from Spitsbergen: phase relationships,mineral compositions and trace-element residence

 Carbonates of mantle origin have been found in xenoliths from Quaternary basaltic volcanoes in NW Spitsbergen. The carbonates range from dolomite to Mg-bearing calcite and have high Mg-numbers [Mg/(Mg+Fe)=(0.92–0.99)]. In some samples they occur interstitially, e.g. at triple junctions of silicate minerals and appear to be in textural and chemical equilibrium with host lherzolite. Most commonly, however, the carbonates make up fine-grained aggregates together with (Ca,Mg)-rich olivine and (Al,Cr,Ti)-rich clinopyroxene that typically replace spinel, amphibole, and orthopyroxene as well as primary clinopyroxene and olivine. Some lherzolites contain amphibole and apatite that appear to have formed before precipitation of the carbonates. In situ analyses by proton microprobe show very high contents of Sr in the clinopyroxene, carbonates and apatite; the apatite is also very rich in LREE, U, Th, Cl, Br. Disseminated amphibole in carbonate-bearing rocks is very poor in Nb and Zr, in contrast to vein amphibole and mica from carbonate-free rocks that are rich in Nb and Zr. Overall, the Spitsbergen xenoliths provide evidence both for the occurrence of primary carbonate in apparent equilibrium with the spinel lherzolites (regardless of the nature of events that emplaced them) and for the formation of carbonate-bearing pockets consistent with metasomatism by carbonate melts. Calcite and amorphous carbonate-rich materials occur in com- posite carbonate-fluid inclusions, veins and partial melting zones that appear to be related to fluid action in the mantle, heating of the xenoliths during their entrainment in basaltic magma, and to decompression melting of the carbonates. Magnesite is a product of secondary, post-eruption alteration of the xenoliths. Received: 6 October 1995/Accepted: 17 June 1996     

Biomarker assemblage of some Miocene-aged Bulgarian lignite lithotypes

Two homogeneous (humovitrain and xylain) and one heterogeneous (humoclarain) lithotype macerals, separated from a lignite, were subjected to mild reductive treatment by NaH. The extensive chromatographic separation of the decalin-soluble fraction revealed some structural peculiarities. A strong predominance of α-phyllocladane was characteristic for all macerals. Series of n-, iso-, and anteiso-alkanes, regular isoprenoids, alkylbenzenes and 1-methyl-4-n-alkylcyclohexanes were identified by mass spectrometry. An angiosperm source input was represented by friedelane, lupane and seco-hopane structures. Products of des-A and des-E-ring cleavages and C-10 demethylation were registered by mass spectrometry. The main difference was in the hopane distribution pattern. A strong prevalence of extended ββ-hopanes was found in the humoclarain sample. The mass spectral data revealed the existence of a basic difference in hopane precursors—diploptent or diplopterol for the homogeneous lithotypes and bacteriohopanetetrol for the heterogeneous lithotype.     

Polar aromatic biomarkers of Miocene-aged Chukurovo resinite and correlation with a progenitor macrofossil

Functionalised aromatic constituents of Chukurovo resinite are compared here with the chemical composition of a macrofossil assigned paleobotanically as Taxodium dubium (Sternb.) Heer. Terpenoids and lipids of fossil wood tissue embedded in a clay sediment were extracted and analyzed for comparison. The information was interpreted in relation to the biomarker compositions of different conifer families, as well as to the effects of contamination by inward migration of organic matter from the adjacent sediments.Many of identified geolipids, i.e., alkanes, alkanols, alkan-2-ones, and steranes/triterpanes have no chemosystematic value because they are ubiquitous in the plant kingdom. Ferruginol, sugiol, and products of their diagenetic transformations were identified as the dominant specific biomarkers in the resinite. Ferruginol and its analogues were the most abundant diterpenoids in Taxodium dubium sample. Thus, the biomarker composition of the extractable matter of the resinite strongly suggests that species of Cupressaceae contributed significantly to the Chukurovo paleoenvironment.     

Oblique wave scattering by submerged thin wall with gap in finite-depth water

The problem of oblique wave scattering by a submerged thin vertical wall with a gap in finite-depth water and its modification when another identical wall is introduced, are investigated in this paper. The techniques of both one-term and multiterm Galerkin approximations have been utilized in the mathematical analysis. The multi-term approximations in terms of appropriate Chebyshev polynomials provide extremely accurate numerical estimates for the reflection coefficient. The reflection coefficient is depicted graphically for a number of geometries. It is found that by the introduction of another identical wall, there occurs zero reflection for certain wave numbers. This may have some bearings on the modelling of a breakwater.     

The Coastal Springs of Southern Kerala,SW India – Hydrology and Water Quality Assessment

Spring water is a reliable source of potable water in many parts of the world. Uplifted coasts of the Southern Kerala host many high yielding cold water springs which emerge from the sand - clay interface of the Neogene outcrops. Lack of adequate studies on the hydrological and water quality aspects of these springs is challenging the wise use and management of these springs. Therefore, an attempt has been made to map the locations and study the water quality of the free-falling type of springs emerging from the Neogene outcrops exposed on the cliffed coasts of Southern Kerala, especially falling within the jurisdiction of Kollam and Thiruvananthapuram districts. A total of 31 springs from four distinct geomorphic settings has been located in our survey conducted in 2008–2009 period. But, our recent survey carried out in March 2017 revealed that about 10 % of the springs were dried out due to various reasons. The total spring water discharge during 2017 was about 450 liters/minute against the total discharge of 800 liters/minute in 2007–08 period. In general, the hydrochemistry of spring waters is dominated by alkali and strong acids, i.e. alkali-chloride type. Most of the hydrochemical parameters exhibit a great degree of seasonal and spatial variations and are well within the permissible limits (with the exception of pH) for all four groups of springs. The low mineral contents may be attributed to minimal weathering from silicate-rich rocks and insignificant leaching from soil due to infiltration from anthropogenic activities. The spring water quality in all the four groups of the study area is bacteriologically contaminated and therefore proper disinfection is required before human consumption. Most of the spring water samples are classified to be “excellent to good” for irrigation and is not expected to cause any salinity hazard.     

Geology of the Renard 65 kimberlite pipe,Québec,Canada

Renard 65, a diamondiferous pipe in the Neoproterozoic Renard kimberlite cluster (Québec, Canada), is a steeply-dipping and downward-tapering diatreme comprised of three pipe-filling units: kimb65a, kimb65b, and kimb65d. The pipe is surrounded by a marginal and variably-brecciated country rock aureole and is crosscut by numerous hypabyssal dykes: kimb65c. Extensive petrographic and mineralogical characterization of over 700 m of drill core from four separate drill holes, suggests that Renard 65 is a Group I kimberlite, mineralogically classified as phlogopite kimberlite and serpentine-phlogopite kimberlite. Kimb65a is a massive volcaniclastic kimberlite dominated by lithic clasts, magmaclasts, and discrete olivine macrocrysts, hosted within a fine-grained diopside and serpentine-rich matrix. Kimb65b is massive, macrocrystic, coherent kimberlite with a groundmass assemblage of phlogopite, spinel, perovskite, apatite, calcite, serpentine and rare monticellite. Kimb65c is a massive, macrocrystic, hypabyssal kimberlite with a groundmass assemblage of phlogopite, serpentine, calcite, perovskite, spinel, and apatite. Kimb65d is massive volcaniclastic kimberlite with localized textures that are intermediate between volcaniclastic and coherent, with tightly packed magmaclasts separated by a diopside- and serpentine-rich matrix. Lithic clasts of granite-gneiss in kimb65a are weakly reacted, with partial melting of feldspars and crystallization of richterite and actinolite. Lithic clasts in kimb65b and kimb65d are entirely recrystallized to calcite + serpentine/chlorite + pectolite and display inner coronas of diopside-aegirine and an outer corona of phlogopite. Compositions are reported for all minerals in the groundmass of coherent kimberlites, magmaclasts, interclast matrices, and reacted lithic clasts. The Renard 65 rocks are texturally classified as Kimberley-type pyroclastic kimberlites and display transitional textures. The kimberlite units are interpreted to have formed in three melt batches based on their distinct spinel chemistry: kimb65a, kimb65b and kimb65d. We note a strong correlation between the modal abundances of lithic clasts and the textures of the kimberlites, where increasing modal abundances of granite/gneiss are observed in kimberlites with increasingly fragmental textures.

     

On the Influence of a Simple Microphysics Parametrization on Radiation Fog Modelling: A Case Study During ParisFog

A detailed numerical simulation of a radiation fog event with a single column model is presented, which takes into account recent developments in microphysical parametrizations. One-dimensional simulations are performed using the computational fluid dynamics model Code_Saturne and the results are compared to a very detailed in situ dataset collected during the ParisFog campaign, which took place near Paris, France, during the winter 2006–2007. Special attention is given to the detailed and complete diurnal simulations and to the role of microphysics in the fog life cycle. The comparison between the simulated and the observed visibility, in the single-column model case study, shows that the evolution of radiation fog is correctly simulated. Sensitivity simulations show that fog development and dissipation are sensitive to the droplet-size distribution through sedimentation/deposition processes but the aerosol number concentration in the coarse mode has a low impact on the time of fog formation.     

Atmospheric River Signatures in Radiosonde Profiles and Reanalyses at the Dronning Maud Land Coast,East Antarctica

Atmospheric rivers(ARs)are an important component of the hydrological cycle linking moisture sources in lower latitudes to the Antarctic surface mass balance.We investigate AR signatures in the atmospheric vertical profiles at the Dronning Maud Land coast,East Antarctica,using regular and extra radiosonde measurements conducted during the Year of Polar Prediction Special Observing Period November 2018 to February 2019.Prominent AR events affecting the locations of Neumayer and Syowa cause a strong increase in specific humidity extending through the mid-troposphere and a strong low-level jet(LLJ).At Neumayer,the peak in the moisture inversion(up to 4 g kg^?1)is observed between 800 and 900 hPa,while the LLJ(up to 32 m s^?1)is concentrated below 900 hPa.At Syowa the increase in humidity is less pronounced and peaks near the surface,while there is a substantial increase in wind speed(up to 40 m s?1)between 825 and 925 hPa.Moisture transport(MT)within the vertical profile during the ARs attains a maximum of 100 g kg?1 m s?1 at both locations,and is captured by both ERA-Interim and ERA5 reanalysis data at Neumayer,but is strongly underestimated at Syowa.Composites of the enhanced MT events during 2009?19 show that these events represent an extreme state of the lower-tropospheric profile compared to its median values with respect to temperature,humidity,wind speed and,consequently,MT.High temporal-and vertical-resolution radiosonde observations are important for understanding the contribution of these rare events to the total MT towards Antarctica and improving their representation in models.