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This work presents Sm‐Nd and Sr isotopic ratios of the BRP‐1 ("Basalt Ribeirão Preto") reference material (RM) based on repeated TIMS measurements over twelve years carried out by the LAGIR laboratory, Brazil. The BRP‐1 RM was produced by the Brazilian Geological Survey from a ca. 130 Ma within‐plate basalt, collected from a quarry near Ribeirão Preto city in the Paraná basin. Isotope ratios were measured using a TRITON mass spectrometer. Instrumental bias and fractionation corrections were performed based on repeated measurements of the certified RMs JNdi‐1 and NIST SRM 987. The measured Nd and Sr isotopic ratios of BRP‐1 are: 143Nd/144Nd = 0.512408 ± 0.000010 (2s), and 87Sr/86Sr = 0.706011 ± 0.000017 (2s). The mass fractions of Sm and Nd are 11.0 ± 0.2 and 51.9 ± 0.6 μg g‐1, respectively, showing no significant differences compared with the accepted values from the literature. No significant difference between measurements was observed, whether digesting samples in single or batch mode, using metal‐jacketed PTFE bombs or PFA vials, or with or without the addition of a spike. The accuracy of these results was evaluated through the measurement of well‐characterised USGS RMs, such as AGV‐1, BCR‐1, BHVO‐1, G‐2 and GSP‐1. [ABSTRACT FROM AUTHOR]

Goethite ([alpha]-FeOOH) is abundant at the Earth's surface and has the unusual capacity to adsorb and fix ions from migrating solutions. Understanding the mechanisms by which foreign elements are incorporated into natural goethite has implications for environmental and mining problems. X-ray absorption spectroscopy (XAS) was used to obtain structural information on the local environment around Ni in natural Ni-containing goethite (1.8-4.1 mol% Ni) from Vermelho lateritic deposit of Serra dos Carajas (Brazil) and in synthetic analogues. The data were collected at the LNLS XAS beam line at the Ni and Fe K-edges, at room temperature, and at the Ni K-edge at 8 K. Nickel was found in essentially the same environment in all natural and synthetic samples, with negligible thermal disorder. The coordination polyhedron is a tetragonal dipyramid of oxygen atoms showing that Ni preserves its usual local symmetry. This finding is compatible with a model in which substitution of Ni for Fe is accompanied by a proton capture resulting in [Ni[O.sub.2](OH).sub.4] octahedra. The polyhedral linkages are similar to that of pure a-FeOOH, consisting of four shared edges at about the same metal-metal distances, as in the pure mineral. The third and longest metal-metal distance is about 6% larger than the expected corner-sharing distance in the [alpha]-FeOOH structure, showing that incorporation of Ni locally distorts and opens the structure.

The complete dissolution of representative test portions of powdered rock samples for the determination of the mass fractions of trace elements by ICP‐MS relies either on aggressive and time‐consuming acid digestions or fusion/sintering with appropriate fluxes. Here, we evaluate a microwave oven dissolution method that employs a solution of NH4HF2 and HNO3. The entire procedure occurs in a closed vessel system and takes up to 4 h. In hundreds of digestions, the precipitation of fluorides was never observed. Replicate decomposition of 100 mg of twenty‐one international reference materials (RMs) of igneous rocks, and also one of a shale presented mostly satisfactory recoveries of forty‐one trace elements. Important exceptions were Zr and Hf in G‐2 and GSP‐2 (mean recoveries of ca. 70%), although for four other felsic rock RMs, the digestion was complete. For ultramafic rock RMs, we present Cr results that indicate quantitative dissolution of Cr‐bearing phases. We discuss the findings and conclude that advances in sample preparation of geological materials for instrumental analysis would benefit from a better understanding of how specific characteristics, such as composition and crystallinity of certain minerals, may affect their reactivity. Key Points: A microwave oven method achieved solubilization of silicate rock powders in up to 4 h. The digestion conditions inhibit the precipitation of fluorides. Recoveries of investigated trace elements were mostly satisfactory, but a few specific exceptions require further investigation. [ABSTRACT FROM AUTHOR]