Variations In Trace Element Contents Research Articles

Trace element geochemistry of ilmenite megacrysts from the Monastery kimberlite, South Africa

Ilmenite megacrysts in the Monastery kimberlite occur both as discrete monomineralic crystals and intergrown with all the other phases of the Cr-poor megacryst suite (cpx, opx, garnet, Fe-rich olivine, phlogopite and zircon). The ilmenites show systematic variations in trace element content which are interpreted in terms of a fractional crystallization model. Covariation of major and trace elements in the ilmenites with respect to their Nb content defines smooth curves, with breaks in the trends corresponding to changes in the inferred cumulate assemblage. Nb apparently behaved as an incompatible element in the megacryst magma throughout its crystallization history, and the Nb content of ilmenite serves as a useful fractionation index. After the appearance of ilmenite, the crystallization sequence of the Monastery megacryst suit is ilmenite+cpx+garnet+opx, followed by ilmenite+phlogopite, then ilmenite+zircon±phlogopite and finally by ilmenite+zircon+olivine+phlogopite. The incompatible behaviour of Nb indicates that ilmenite was overall never a predominant phase in the cumulate assemblage. Elevated Cr contents in late-stage ilmenites cannot be explained by the simple fractional crystallization model, and may require another process such as magma mixing or magma reaction with wall rock. The parent megacryst magma must have been highly magnesian and enriched in incompatible trace elements and in this respect may have been similar to meimechite. The late differentiate of this magma cannot be kimberlite, but must be undersaturated and high in iron, potassium, titanium and incompatible elements.

Trace Element Analysis of Food Spices by Inaa

Abstract Extensive use of food spices in oriental and Latin American cooking, pharmacy, and perfumery entails the evaluation of trace element contents in them. Instrumental neutron activation analysis (INAA) was used to determine the concentration of 18 trace elements (essential, toxic and non-essential) in six different spices consumed in Rawalpindi/Islamabad area. Turmeric powder and ginger powder were found to contain relatively high amounts of essential elements and low amounts of toxic elements. The comparison of our values with Canadian and Egyptian data shows variation in trace element contents of red pepper, turmeric, coriander and ginger. The estimated dietary intake through food spices show that these may be considered appreciable sources of trace element intake due to their extensive use. With the present studies the investigation of trace element contents of 13 food spices has been completed.

Trace Element Analysis of Food Spices by Instrumental Neutron Activation Analysis. I. Trace Elements in Food Spices Belonging to Umbelliferae, Myrtaceae, Piperaceae, Zingiberaceae and Lauraceae Families

Abstract Spices are extensively used in oriental and Latin American cooking and some of these are also used in pharmacy and perfumery. Therefore, concentrations of essential and toxic elements have been measured by instrumental neutron activation analysis (INAA) in seven different spices consumed in the area of Islamabad/Rawalpindi. Cumin and caraway seeds were found to contain relatively high amounts of essential as well as toxic elements. The comparison of our values with Canadian and Egyptian data shows variation in trace element contents of black pepper and cumin seeds. The studies show that these food spices are additional sources of trace element intake.

Crystallographic and chemical variations during pyritization in the upper Barremian and lower Aptian dark claystones from the Lower Saxonian Basin (NW Germany)

ABSTRACTIn the Lower Saxonian Basin, cores from three drill holes provide a cross‐section from the basin centre towards the margin through the upper Barremian/lowermost Aptian pyritic claystones and marls. Microscopic analyses distinguish six types of pyrite (I: ‘cones and tubes’, II: ‘tubes’, III: ‘isometric crystal aggregates’, IV: ‘pseudomorphs of fossils’, V: ‘star‐like concretions’, and VI: ‘filiform pyrite‐marcasite intergrowths’) which are associated with subordinate amounts of Fe carbonate, chalcopyrite, sphalerite and wurtzite. The crystal morphology of these sulphides shows a clear‐cut diagenetic sequence from pyrite crystals dominated by the octahedron to those dominated by the cube.Among these early to late diagenetic pyrites, the conversion of crystal habits is accompanied by a striking variation in trace element contents, some of which have extremely low values (e.g. Au, Se, Te, Tl, Co). In this context, classification of crystal habits and analyses of As and Ni establishes a sequence of pyritization which may help define a basin zonation for these argillaceous sedimentary rocks, categorized as ‘normal facies’—oxygenated bottom waters—interrupted by short episodes of bottom water oxygen depletion (‘bituminous facies’). Substitution of the cube for the octahedron in the Fe bisulphide aggregates led to a continuous removal of As and Ni from the pyrite, attesting to a steady decrease of those elements in the pore fluids with time. By contrast, within each type of pyrite, As and Ni contents increase from the margin towards the centre of the basin, owing to pre‐concentration of both elements in the basinal sediments, which are more abundant in organic matter. Some other elements, however, such as Mn, Cu, Sb and Ag, do not follow this trend and are unrelated to the lattice transformation of the Fe bisulphides. Their sometimes anomalously high quantities in Fe bisulphides are controlled by the host rock chemistry (presence of volcaniclastic material) and accessory minerals intergrown with pyrite (e.g. chalcopyrite).Pyrite I through III formed in tubular hollows of burrowing organisms, and type IV in tests of fossils. Types V and VI did not result from replacement or void filling but were generated by diffusion of sulphate along inhomogeneties, such as bedding planes, shrinkage cracks or water escape structures.

Variations of trace element contents within single tree rings

X-ray fluorescence was used to measure variations in relative and absolute trace-element concentrations within single tree rings taken from a 32-year-old pine tree near a coalburning power plant. The Zn/Cu ratio was found to have a constant value, both along individual rings and between different rings. The Fe, Ca and 8 concentrations varied in a single tree ring and depended on the age of the tree. The results indicate that the variations in concentrations of elements along a single ring are caused by heterogeneous tree tissue structure.

Determination of trace elements of Egyptian cane sugar (Naga Hammady factories) by neutron activation, atomic absorption spectrophotometric and inductively coupled plasma-atomic emission spectrometric analyses.

INAA, AAS and ICP-AES techniques are applied to the determination of trace amounts of Ag, Al, As, Au, Ba, Br, Ca, Cd, Ce, Cl, Co, Cr, Cs, Cu, Dy, Eu, Fe, Ga, Hf, K, La, Li, Lu, Mg, Mn, Na, Nb, Ni, Pb, Sb, Sc, Se, Sm, Sn, Sr, Ta, Th, Ti, U, V, W and Zn in the stalks of sugar cane plant after extracting juice, raw juice principal (mixed) juice, juice withdrawn from the successive stages of sugar industry, sirup, deposits from evaporators, molasse, A-? and B-sugar and in the soil samples (collected from the field supplying the factories by cane plants) taken from the immediate vicinity of the plant roots at surface, 30 and 60 cm depth. The results obtained are in a good agreement of the safety baselines of using juice as beverage, molasse derivatives (honey, sweets, ...) as diet for common people in the developed countries and in industry (methanol, ethanol, acetone & acetic acid, ...) and sugar sweeting for many purposes (in beverages, desserts, ...). Differences of trace elements concentrations in soil samples may be reasoned to geochemical and biogeochemical fractionation while those in juice may be due to the changes in the environmental conditions, chemical composition and botanic structures. Variations in trace element contents in the products formed during the successive stages of sugar industry may be a result of evaporation, filtration processes, chemical treatments or corrosion of vessels, containers or engines. Trace elements are very important where they are responsible for enzymatic and biochemical reactions, matabolism, health and diseases.

Electron microprobe studies of Iceland Research Drilling Project high‐temperature hydrothermal mineral geochemistry

The geochemistry of epidote‐ and chlorite‐dominated hydrothermal assemblages in the Iceland Research Drilling Project drill core has been studied by electron microprobe. The association of epidote, andradite, and Cu‐Fe sulphides suggests maximum basalt alteration temperatures of 350°–300°C. Near‐pure andradite implies a fluid XCO2 <0.05. The sequence of successively lower temperature minerals (epidote, prehnite, laumontite) in veins and vesicles suggests precipitation during rapid cooling from >300°C to <200°C and together with zonation in garnet and epidote implies fluid depletion in Fe3+ with time. The eradication of probable early zeolite facies assemblages and this cooling sequence suggest that temperatures rose to >300°C during burial of the lower part of the IRDP sequence before vigorous fluid circulation, producing rapid cooling and intense alteration, was established. Transition metals (Fe, Mn, Cu) were released from primary assemblages but were incorporated in epidote, chlorite, and sulphide. Epidote contains average SrO = 0.23%, but intersample variations in trace element contents of secondary minerals are complex, and there are no correlations with depth. It is concluded that the effects on whole rock chemistry (including Sr) and secondary mineral chemistry were largely controlled by kinetic factors such as (1) differing responses to alteration by primary assemblages and (2) permeability variations.

Geochemical investigations of basalts and associated rocks from the ocean floor and their implications

Variations in trace element contents and inter-element ratios of deep-sea basalts are much more marked than variations in major element contents. This paper explores possible reasons for the variations which have been discovered. Inadequacy of sampling techniques may be responsible for some reported differences, but variations due to this cause are unlikely to approach the magnitude of reported variations. Some variation in samples from restricted areas of the ocean floor can be correlated with variation in the degree of silica saturation of the basalts. Submarine alteration of lavas by reaction with sea water is another possible cause of variation. Studies of metamorphosed deep-sea basalts suggest that very low-grade metamorphism may cause some, though slight, elemental migration. Studies on ultrabasic rocks show variations in trace element contents which, to some degree, appear to complement the variations encountered in basalts, suggesting that the extent of partial melting in the mantle during basaltic genesis influences the trace element contents of the products of melting. However, when such possible explanations have been considered, there remain variations in trace element contents of otherwise comparable basalts from different parts of the ocean floor, which appear to represent real variations in the trace element contents of the erupted basaltic magmas. In view of the difficulty of explaining such differences by contamination of magmas on their way to the surface, it is suggested that variations exist in the trace element contents of mantle material at the levels of basaltic genesis. Geochemical provinces exist in oceanic areas just as they do in continental regions.

Activation Analysis of Human Head Hair. IV. : Variation in Trace Element Contents in Hair with the Lapse of Time

Activation Analysis of Human Head Hair. IV. : Variation in Trace Element Contents in Hair with the Lapse of Time