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CaCO3 Content (caco3 + content)
Selected AbstractsSedimentological, modal analysis and geochemical studies of desert and coastal dunes, Altar Desert, NW MexicoEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2007J. J. Kasper-Zubillaga Abstract Sedimentological, compositional and geochemical determinations were carried out on 54 desert and coastal dune sand samples to study the provenance of desert and coastal dunes of the Altar Desert, Sonora, Mexico. Grain size distributions of the desert dune sands are influenced by the Colorado River Delta sediment supply and wind selectiveness. The desert dune sands are derived mainly from the quartz-rich Colorado River Delta sediments and sedimentary lithics. The dune height does not exert a control over the grain size distributions of the desert dune sands. The quartz enrichment of the desert dune sands may be due to wind sorting, which concentrates more quartz grains, and to the aeolian activity, which has depleted the feldspar grains through subaerial collisions. The desert dune sands suffer from little chemical weathering and they are chemically homogeneous, with chemical alteration indices similar to those found in other deserts of the world. The desert sands have been more influenced by sedimentary and granitic sources. This is supported by the fact that Ba and Sr concentration values of the desert sands are within the range of the Ba and Sr concentration values of the Colorado River quartz-rich sediments. The Sr values are also linked to the presence of Ca-bearing minerals. The Zr values are linked to the sedimentary sources and heavy mineral content in the desert dunes. The Golfo de Santa Clara and Puerto Peñasco coastal dune sands are influenced by long shore drift, tidal and aeolian processes. Coarse grains are found on the flanks whereas fine grains are on the crest of the dunes. High tidal regimens, long shore drift and supply from Colorado Delta River sediments produce quartz-rich sands on the beach that are subsequently transported into the coastal dunes. Outcrops of Quaternary sedimentary rocks and granitic sources increase the sedimentary and plutonic lithic content of the coastal dune sands. The chemical index of alteration (CIA) values for the desert and coastal dune sands indicate that both dune types are chemically homogeneous. The trace element values for the coastal dune sands are similar to those found for the desert dune sands. However, an increase in Sr content in the coastal dune sands may be due to more CaCO3 of biogenic origin as compared to the desert dune sands. Correlations between the studied parameters show that the dune sands are controlled by sedimentary sources (e.g. Colorado River Delta sediments), since heavy minerals are present in low percentages in the dune sands, probably due to little heavy mineral content from the source sediment; grain sizes in the dune sands are coarser than those in which heavy minerals are found and/or the wind speed might not exert a potential entrainment effect on the heavy mineral fractions to be transported into the dune. A cluster analysis shows that the El Pinacate group is significantly different from the rest of the dune sands in terms of the grain-size parameters due to longer transport of the sands and the long distance from the source sediment, whereas the Puerto Peñasco coastal dune sands are different from the rest of the groups in terms of their geochemistry, probably caused by their high CaCO3 content and slight decrease in the CIA value. Copyright © 2006 John Wiley & Sons, Ltd. [source] Origin and palaeo-environments of calcareous sediments in the Moshaweng dry valley, southeast BotswanaEARTH SURFACE PROCESSES AND LANDFORMS, Issue 6 2002S. Ringrose Abstract Quaternary sedimentation in the Moshaweng dry valley of southeastern Botswana is evaluated on the basis of geomorphological evolution and sedimentological analyses. Stratigraphic evidence reveals an upper surface (1095 m) containing abundant sil-calcrete, an intermediate surface (1085 m) in which sil-calcrete underlies nodular calcrete and lower (1075 m) surface in which sil-calcrete and nodular calcrete are interbedded. This subdivision is reflected in the geochemical composition of the sediments which show an overall trend of decreasing SiO2 content (and increasing CaCO3 content) with depth from the highest to the lowest surface levels. The calcretes and sil-calcretes represent modifications of pre-existing detrital Kalahari Group sand and basal Kalahari pebbles which thinned over a Karoo bedrock high. Modification took place during wet periods when abundant Ca++ -rich groundwater flowed along the structurally aligned valley system. With the onset of drier conditions, water table fluctuations led to the precipitation of nodular calcretes in the phreatic layer to a depth of about 20 m. A major geochemical change resulted in the preferential silicification of the nodular calcrete deposits. Conditions for silica mobilization may be related to drying-induced salinity and in situ geochemical differentiation brought about by pebble dissociation towards the top of the sediment pile. As calcretization and valley formation progressed to lower levels, silica release took place on a diminishing scale. Thermoluminescence dating infers a mid-Pleistocene age for sil-calcrete formation suggesting that valley evolution and original calcrete precipitation are much older. Late stage dissolution of CaCO3 from pre-existing surface calcretes or sil-calcretes led to the formation of pedogenic case-hardened deposits during a time of reduced flow through the Moshaweng system possibly during the upper or late Pleistocene. Copyright © 2002 John Wiley & Sons, Ltd. [source] Dynamic mechanical properties and morphology of high-density polyethylene/CaCO3 blends with and without an impact modifierJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Yu-Lin Yang Abstract Dynamic mechanical analysis and differential scanning calorimetry were used to investigate the relaxations and crystallization of high-density polyethylene (HDPE) reinforced with calcium carbonate (CaCO3) particles and an elastomer. Five series of blends were designed and manufactured, including one series of binary blends composed of HDPE and amino acid treated CaCO3 and four series of ternary blends composed of HDPE, treated or untreated CaCO3, and a polyolefin elastomer [poly(ethylene- co -octene) (POE)] grafted with maleic anhydride. The analysis of the tan , diagrams indicated that the ternary blends exhibited phase separation. The modulus increased significantly with the CaCO3 content, and the glass-transition temperature of POE was the leading parameter that controlled the mechanical properties of the ternary blends. The dynamic mechanical properties and crystallization of the blends were controlled by the synergistic effect of CaCO3 and maleic anhydride grafted POE, which was favored by the core,shell structure of the inclusions. The treatment of the CaCO3 filler had little influence on the mechanical properties and morphology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3907,3914, 2007 [source] Soil organic matter composition and soil lightnessJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2004Sandra Spielvogel Abstract Relationships between soil lightness, soil organic matter (SOM) composition, content of organic C, CaCO3, and texture were studied using 42 top-soil horizons from different soil types located in southern Germany. SOM composition was determined by CPMAS 13C NMR spectroscopy, soil color was measured by diffuse-reflectance spectrophotometry and given in the CIE L*a*b* color coordination system (Commission Internationale de l'Eclairage, 1978). Multiple-regression analysis showed, that soil lightness of top-soil horizons is principally determined by OC concentration, but CaCO3 and soil texture are also major variables. Soil lightness decreased with increasing OC content. Carbonate content had an important effect on soil lightness even at low concentrations due to its lightening property. Regressions between soil lightness and organic C content were strongly linear, when the soils were differentiated according to texture and CaCO3 content. The aryl-C content was the only SOM component which correlated significantly with soil lightness (rS = ,0.87). In the linear regressions carried out on the different soil groups, soil aryl-C content was a more significant predictor for soil lightness than total OC content. Zusammensetzung der organischen Bodensubstanz und Bodenhelligkeit Der Zusammenhang zwischen Bodenhelligkeit, Zusammensetzung der organischen Substanz und Gehalt an Corg., CaCO3 und Textur wurde in 42 Oberböden aus verschiedenen Bodentypen Süddeutschlands untersucht. Die Zusammensetzung der organischen Substanz wurde mittels CPMAS- 13C-NMR-Spektroskopie bestimmt, die Bodenfarbe mittels Spektralphotometer und als Bodenhelligkeitswert im CIE L*a*b*-Farbkoordinatensystem (Commission Internationale de l'Eclairage, 1978) angegeben. Die Auswertung über multiple Regression zeigte, dass die Bodenhelligkeit hauptsächlich vom OC-Gehalt bestimmt wird; CaCO3 -Gehalt und Textur erwiesen sich als weitere relevante Variablen. Die Bodenhelligkeit nimmt mit zunehmendem OC-Gehalt ab. Aufgrund seiner stark aufhellenden Wirkung hat der Carbonatgehalt auch bei niedrigen Konzentrationen einen deutlichen Einfluss auf die Bodenhelligkeit. Bei Berücksichtigung der Textur und des Carbonatgehalts ergaben sich lineare Beziehungen zwischen Bodenhelligkeit und OC-Gehalt. Der Aryl-C-Gehalt des Bodens war als einzige Humuskomponente signifikant mit der Bodenhelligkeit korreliert (rS = ,0.87). Der Aryl-C-Gehalt des Bodens bestimmt die Bodenhelligkeit schärfer als der OC-Gehalt. [source] An investigation on the mechanical and dynamic rheological properties of single and hybrid filler/polypropylene composites based on talc and calcium carbonatePOLYMER COMPOSITES, Issue 12 2009Hamed Azizi Some results of experiments on the mechanical and rheological properties of mineral filled polypropylene were presented. Single filler and hybrid filler composites of talc and calcium carbonate (CaCO3) were prepared in a co-rotating twin-screw extruder. The effect of filler type, filler content, and coupling agent on the mechanical and rheological properties of the polypropylene were studied. The coupling agent was maleic anhydride-grafted polypropylene (PP- g -MA). It was found that the mechanical properties are affected by filler type, filler concentration, and the interaction between filler and matrix. The tensile strength of the composite is more affected by the talc while the impact strength is influenced mostly by CaCO3 content. The elongation at break of PP/CaCO3 composites was higher than that of PP/talc composites. The incorporation of coupling agent into PP/mineral filler composites increased the mechanical properties. Rheological properties indicated that the complex viscosity and storage modulus of talc filled samples were higher than those of calcium carbonate filled samples while the tan , was lower. The rheological properties of hybrid-filler filled sample were more affected by the talc than calcium carbonate. The PP- g -MA increased the complex viscosity and storage modulus of both single and hybrid composites. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers [source] Mechanical properties and volume dilatation of HDPE/CaCO3 blends with and without impact modifierPOLYMER ENGINEERING & SCIENCE, Issue 11 2006Yu-Lin Yang Different blends of high-density polyethylene (HDPE) with calcium carbonate (CaCO3) were mechanically tested under uniaxial tension with or without poly(ethylene- co -octene) elastomer grafted with maleic anhydride (POEg), as an impact modifier. In some materials, the surface of the CaCO3 was treated with an amino acid and in others the mineral particles were left untreated. The stress,strain behavior were determined at constant true strain rate by using the VidéoTraction© system. Also, the volume changes upon stretching was assessed by means of the video extensometer and correlated with X-ray densitometry measurements. The dependence of modulus, yield stress, and cavitation is shown to depend on the relative percentage of the three constituents. In particular, the cavitation rate increases markedly with the CaCO3 content and decreases with the POEg content. By contrast, the surface pretreatment of the CaCO3 particles appear to be of much lesser importance. POLYM. ENG. SCI., 46:1512,1522, 2006. © 2006 Society of Plastics Engineers [source] Interpretation of the Thermogravimetric Curves of Ancient Pozzolanic ConcretesARCHAEOMETRY, Issue 4 2001F. Branda Pozzolanic concretes submitted to thermogravimetric (TG) analysis show a continuous weight loss starting from about 400 °C. In order to reconcile these observations with those from other analytical methods, it is necessary to attribute this weight loss to CO2 removal. It has been proposed, in the literature, that silicates and CaCO3 react at lower temperatures, producing calcium silicates and CO2. In this paper, the FTIR spectra collected on samples submitted to TG analysis, stopped at conveniently selected temperatures, provide direct evidence that the continuous weight loss recorded with thermogravimetric analysis of the pozzolanic concrete in the temperature range 400,900 °C is to be attributed to the reaction between the silicates and calcite, with the formation of CO2 and of a silicate that is richer in CaO. Therefore it is justifiable that the whole weight loss, in the temperature range 400,900 °C, should be taken into account in the calculation of the CaCO3 content of the concrete. Moreover, the described procedure,of recovering small samples (2 mg) from the sample-holder of the TG apparatus at various steps of the heating rate and comparing the FTIR spectra,can help in identifying the pozzolanic nature of a concrete that, in general, is not easily recognizable from the trend of the thermoanalytical curve. [source] | |||||||||||||