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Hydrothermal Mn-oxide deposits from the Tonga-Kermadec Ridge and the Valu Fa Ridge back-arc spreading center in the Lau Basin have been studied mineralogically and by bulk and partition geochemical techniques. The Mn-oxides are present as three main morphological types; of these, a dense, grey submetallic material is most common. Common lamination of this material suggests an intermittent rate of formation. Mineralogically, the crusts comprise variable proportions of 10Å and 7Å manganite. Concentrations of some trace elements, including Li, Mo, and Zn are generally significantly higher than those observed in Mn-crusts of hydrogenous origin, suggesting that the observed trace element enrichments are due to a hydrothermal source. Both temporal and geographical controls are seen to affect these trace element concentrations. Although most of the hydrothermally enriched elements are associated with the Mn-oxide phases, Li appears to reflect either a surficial adsorption or the presence of a separate Li-rich phase. Observed variations in deposit composition could reflect differences in the geochemistry of the basement rocks from which the elements have been leached, the proximity of high-temperature sulphide deposits and temporal variability in the hydrothermal systems. [ABSTRACT FROM AUTHOR]

Background: Clinical samples were distributed on 10 occasions to six UK laboratories that perform urinary steroid profile analysis. Urine samples were from normal adult men and women, normal children and neonates. Samples from patients with Cushing's syndrome, virilization, adrenarche, obesity and congenital adrenal hyperplasia (21 and 17-hydroxylase defects) were also used for evaluation., Methods: Samples were analysed by capillary column gas chromatography (all laboratories) after hydrolysis of conjugates and derivative formation (five laboratories) or by variation of 17-oxogenic steroid methodology (one laboratory)., Results: For each distribution of samples, the performance of the participants was compared for quantitative analysis, and user comments were summarized. Quantitative results showed variation without necessarily biasing the result. Comments varied considerably in length. The interpretations did not always lead to a clear diagnosis or advise about appropriate further tests., Conclusions: This pilot urine steroid profiling scheme has clearly identified the requirement for external quality assessment. It is now hoped to offer this scheme worldwide in collaboration with the European Research Network for the Evaluation and Improvement of Screening, Diagnosis and Treatment of Inherited Disorders of Metabolism (ERNDIM).