Data of rock analyses—I. African periodical and serial literature
No abstract available.
Geochimica et Cosmochimica Acta↗
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Comparison of radiogenic helium and lead in zircon
A direct comparison of helium and radiogenic lead in nonmetamict zircon crystals has indicated a 25 per cent discrepancy between these radiogenic constituents. It appears that the amount of helium is only three-quarters of the amount that should be present according to the content of radiogenic lead. Approximately the same proportion was found in zircon having a wide range in age, activity, and total alpha irradiation, and in large pegmatite zircon crystals, as well as in microscopic crystals from igneous rocks.
Geochimica et Cosmochimica Acta↗
Data of rock analyses-III. New Zealand periodical and serial literature. Bibliography and index of rock analyses
No abstract available.
Geochimica et Cosmochimica Acta↗
Minor elements in Keweenawan lavas, Michigan
The distribution of minor elements in three basaltic flows of the Keweenawan series, of Michigan, is related to differentiation in the flows. Thus, nickel is most abundant in the early differentiates; nickel, chromium, and barium are generally deficient in the pegmatites, which formed late; whereas copper, vanadium, yttrium, and other minor elements are concentrated in the pegmatites. The minor-element content of individual minerals in the Greenstone flow varies markedly from one mineral to another and seems to depend primarily on the presence or absence in the minerals of major elements for which the minor elements can substitute. Minor elements have substituted most readily for those major elements with similar ionic radii. Valence and electronegativity also seem to influence the ease of substitution. The distribution of other minor elements in copper-bearing lodes of the Michigan copper district shows no apparent relation to copper mineralization.
Michigan↗
Determination of yttrium, lanthanum, cerium, neodymium, and ytterbium in test samples granite G-1 and diabase W-1 by a combined chemical-spectrochemical technique
No abstract available.
Geochimica et Cosmochimica Acta↗
Semi-quantitative spectrographic analysis and rank correlation in geochemistry
The rank correlation coefficient, r s , which involves less computation than the product-moment correlation coefficient, r , can be used to indicate the degree of relationship between two elements. The method is applicable in situations where the assumptions underlying normal distribution correlation theory may not be satisfied. Semi-quantitative spectrographic analyses which are reported as grouped or partly ranked data can be used to calculate rank correlations between elements.
Geochimica et Cosmochimica Acta↗
Reduction of quinquevalent vanadium solutions by wood and lignite
To determine whether reduced vanadium ores could have been deposited by reduction from supergene quinquevalent vanadium solutions, the reducing capacity of fresh wood, wood degraded by long burial, and lignite was determined experimentally at temperatures of 120° and 150° in closed containers. A precipitate obtained by reduction of quinquevalent vanadium solutions with wood gave an X-ray pattern identical with a recently discovered low-valent vanadium mineral. The evidence indicated that deposition of reduced vanadium minerals by this mechanism is possible.
Geochimica et Cosmochimica Acta↗
Systematic variation of rare-earth elements in cerium-earth minerals
In a continuation of a study reported previously, rare-earth elements and thorium have been determined in monazite, allanite, cerite, bastnaesite, and a number of miscellaneous cerium-earth minerals. A quantity called sigma (∑), which is the sum of the atomic percentages of La, Ce, and Pr, is proposed as an index of composition of all cerium-earth minerals with respect to the rare-earth elements. The value of ∑ for all of the minerals analysed falls between 58 and 92 atomic per cent. Monazites, allanites, and cerites cover the entire observed range, whereas bastnaesites are sharply restricted to the range between 80 and 92 atomic per cent. The minimum value of ∑ for a cerium-earth mineral corresponds to the smallest possible unit-cell size of the mineral. In monazite, this structurally controlled minimum value of ∑ is estimated to be around 30 atomic per cent. Neodymium, because of its abundance, and yttrium, because of its small size, have dominant roles in contraction of the structure. In the other direction, the limit of variation in composition will be reached when lanthanum becomes the sole rare-earth element in a cerium-earth mineral. Cerium-earth minerals from alkalic rocks are all characterized by values of ∑ greater than 80 atomic per cent, indicating that the processes that formed these rocks were unusually efficient in fractionating the rare-earth elements—efficient in the sense that a highly selected assemblage is produced without eliminating the bulk of these elements. Analyses of inner and outer parts of two large crystals of monazite from different deposits show no difference in ∑ in one crystal and a slightly smaller value of ∑ in the outer part of the other crystal compared to the inner part. The ∑ of monazites from pegmatites that intrude genetically related granitic rocks in North Carolina is found to be either higher or lower than the ∑ of monazites in the intruded host rock. These results indicate that the fractionation of the rare-earth elements is not a simple unidirectional process. When a cerium-earth mineral undergoes replacement, its rare-earth elements may be fractionated into two parts, one forming a new mineral with ∑ that is smaller, and the other a second new mineral with ∑ that is larger than that of the original mineral. The complete analysis of a cerium-earth mineral to determine its ∑ is time consuming. The discovery of a direct relationship between ∑ and the Ce/(Nd + Y) atomic ratio in cerium earth minerals allows a rapid determination of ∑ from spectrograms obtained in a previously described method for determining thorium in these minerals.
Geochimica et Cosmochimica Acta↗
Comparison of the isotopic abundance of U235 and U238 and the radium activity ratios in Colorado Plateau uranium ores
The isotopic abundances of uranium and the radium activity ratios of eleven samples of uranium ore from the Colorado Plateau have been measured. No significant variation in the isotopic abundance of the uranium was noted; with'in the experimental error, the average U 235 /U 238 ratio is 137.7. There is a significant variation in the Ra 226 /Ra 223 activity ratios (0.048−0.143), which indicates a relatively recent alteration of the ore samples. The variations do not, however, explain the lead-uranium and lead-lead age discrepancies.
Geochimica et Cosmochimica Acta↗
Data of rock analyses-IV. Icelandic periodical and serial literature Bibliography of rock analyses
No abstract available.
Geochimica et Cosmochimica Acta↗
Isolation and identification of an ester from a crude oil
A dioctylphthalate has been isolated from a crude oil by means of adsorption column chromatography. The ester was identified by means of elemental analysis, refractive index, and its infra-red absorption spectrum. Saponification of the isolate and examination of the resultant alcohol by means of infrared absorption spectra led to the conclusion that the ester is a branched chain dioctylphthalate. This is the first reported occurrence of an ester in crude petroleum.
Geochimica et Cosmochimica Acta↗
Equilibrium distribution of dissolved sulphur species in water at 25°C and 1 atm total pressure
The E h -pH diagrams for the equilibrium concentrations in aqueous solution at 25°C of native sulphur and all the various sulphur-containing ions and acids from which the ions are produced have been constructed for systems having a total sulphur concentration of 0.1 molar. The composite of these diagrams indicates that elemental sulphur, H 2 S, HS − HSO 4 − and SO 4 are the species that predominate in the environments that might be found in nature. This indication is in agreement with the composition of all sulphur-containing minerals.
Geochimica et Cosmochimica Acta↗
Retention of lead during oxidative ashing of selected naturally occurring carbonaceous substances
The amount of lead retained in the ash of lead-bearing carbonaceous material is essentially independent of the method of ashing. Samples containing lead in the range of 0.00X to 0.X per cent were ashed by ignition in a high-oxygen atmosphere and were also wet-ashed. The lead in the ash was determined colorimetrically. Results were the same by both methods, but the time required is 3 to 10 times less for the dry-ashing method.
Geochimica et Cosmochimica Acta↗
G-1-W-1 values-spectrochemical determination using an internal standard
No abstract available.
Geochimica et Cosmochimica Acta↗
Determination of the oxidation state of uranium in apatite and phosphorite deposits
Geological and mineralogical evidence indicate that the uranium present in apatite may proxy for calcium in the mineral structure as U(IV). An experimental investigation was conducted and chemical evidence was obtained that establishes the presence of U(IV) in apatite. The following analytical procedure was developed for the determination of U(IV). Carbonatefluorapatite is dissolved in 1.5 M orthophosphoric acid at a temperature of 5°C or slightly below and fluorapatite is dissolved in cold 1.2 M hydrochloric acid (approximately 5°C) containing 1.5 g of hydroxylamine hydrochloride per 100 ml. Uranium(IV) is precipitated by cupferron using titanium as a carrier. The uranium in the precipitate is separated by use of the ethyl acetate extraction procedure and determined fluorimetrically. The validity and the limitations of the method have been established by spike experiments.
Geochimica et Cosmochimica Acta↗
The solid solubility of MgCO3 in CaCO3: A revision
No abstract available.
Geochimica et Cosmochimica Acta↗
Some natural variations in the relative abundance of copper isotopes
The relative isotopic abundance of copper has been measured in a number of minerals and a few plant materials. Suites of samples from Michigan and the Colorado Plateau have been examined in more detail to determine if local variations due to isotopic exchange or diffusion could be found. The relative isotopic abundance of copper in specimens from several other localities was also determined. The variations noted were small but in some cases were felt to be significant because they were larger than the experimental error (0·1 per cent in the ratio). A total spread of −1 to +8 parts per mil compared to the standard was found in the specimens tested.
Geochimica et Cosmochimica Acta↗