[en] The primary goal of the U.S. Geological Survey-Bureau of Indian Affairs drilling project in the Upper Jurassic Morrison Formation in McKinley County, New Mexico, was to better understand the relationship between host-rock stratigraphy and uranium mineralization. As part of this project, geochemical studies of approximately 280 samples from 8 cores and 1 outcrop were undertaken; samples from 4 cores show uranium enrichment. Geochemical relationships between samples of weathered outcrop, oxidized core, reduced (unmineralized) core, and ore-bearing core were contrasted by comparison of element abundances. Special comparative studies of sandstone and clay chemistry were made using results from x-ray diffraction, optical petrography, and chemical analysis. Results of these studies are discussed

[en] Inductively coupled argon plasma/optical emission spectrometry (ICAP/OES) is useful as a simultaneous, multielement analytical technique for the determination of trace elements in geological materials. A method for the determination of trace-level rare earth elements (REE) in geological materials using an ICAP 63-channel emission spectrometer is described. Separation and preconcentration of the REE and yttrium from a sample digest are achieved by a nitric acid gradient cation exchange and hydrochloric acid anion exchange. Precision of 1-4% relative standard deviation and comparable accuracy are demonstrated by the triplicate analysis of three spills of BCR-1 and BHVO-1. Analyses of other geological materials including coals, soils, and rocks show comparable precision and accuracy

[en] A method of analysis of geological materials for the determination of the rare-earth elements using the inductively coupled plasma mass spectrometric technique (ICP-MS) has been developed. Instrumental parameters and factors affecting analytical results have been first studied and then optimized. Samples are analyzed directly following an acid digestion, without the need for separation or preconcentration with limits of detection of 2-11 ng/g, precision of +/-2.5% relative standard deviation, and accuracy comparable to inductively coupled plasma emission spectrometry and instrumental neutron activation analysis. A commercially available ICP-MS instrument is used with modifications to the sample introduction system, torch, and sampler orifice to reduce the effects of high salt content of sample solutions prepared from geologic materials. Corrections for isobaric interferences from oxide ions and other diatomic and triatomic ions are made mathematically. Special internal standard procedures are used to compensate for drift in metal:metal oxide ratios and sensitivity. Reference standard values are used to verify the accuracy and utility of the method

[en] The abundance of rare-earth elements (REE) and yttrium in geological materials is generally low, and most samples contain elements that interfere in the determination of the REE and Y, so a separation and/or preconcentration step is often necessary. This is often achieved by ion-exchange chromatography with either nitric or hydrochloric acid. It is advantageous, however, to use both acids sequentially. The final solution thus obtained contains only the REE and Y, with minor amounts of Al, Ba, Ca, Sc, Sr and Ti. Elements that potentially interfere, such as Be, Co, Cr, Fe, Mn, Th, U, V and Zr, are virtually eliminated. Inductively-coupled argon plasma atomic-emission spectroscopy can then be used for a final precise and accurate measurement. The method can also be used with other instrumental methods of analysis. (author)

[en] A study of the chemical evolution and paragenesis of the uranium minerals at the Palermo No. 1 and Ruggles granitic pegmatites, Grafton County, New Hampshire, revealed four stages of secondary mineralization. A total of eight uranium minerals were identified in the four stages. The first stage is a mixture of uranyl oxide hydroxide-hydrates represented by mineral A, which surrounds and replaces a uraninite core. The second stage is a carbonate stage found only at the Palermo No. pegmatite, and is represented by rutherfordine. The third stage is represented by uranyl silicates. At the Palermo No. 1 pegmatite, this stage consists of β-uranophane, and at the Ruggles pegmatite, it consists of soddyite and β-uranophane. A final fourth stage is a phosphate stage represented by phosphuranylite and meta-autunite I. The first three stages of mineralization developed from hydrothermal and meteoric processes. With dropping temperatures, hydrothermal fluids reached meteoric temperatures and acquired the characteristics of meteoric water. The pH shifted from acidic (pH less than about 6 at 100^oC) to alkaline (pH > 7 at 25^oC). Since mineral A contains hydroxyl and a low amount of molecular water, it probably formed at a temperature greater than 100^oC in the acidic environment. After the first stage, the hydrothermal fluids likely reached the temperatures of meteoric water. The initial pH of the meteoric water was acidic (pH less than about 6 at 25^oC) and then slowly shifted to alkaline. The mineralizing fluids became oversaturated in CO₃, Ca, K, and Si. Uraninite and mineral A became unstable and were replaced by rutherfordine and uranyl silicates. The fourth or phosphate stage developed from the introduction of groundwater. The uranyl phosphate minerals precipitated from an acidic fluid (pH < 7 at 25^oC) that was oversaturated with Ca, K, U, and P. (author). 22 refs., 1 tab., 2 figs

No abstract available

[en] Additional studies on an incompletely characterized secondary uranium mineral from the Ruggles and Palermo granitic pegmatites, New Hampshire, referred to as mineral A by Frondel (1956), reveal a mixture of schoepite-group minerals and related uranyl oxide-hydroxide hydrated compounds. A composite chemical analysis yielded (in wt.%): PbO 4.85 (EMP), UO₃ 83.5 (EMP), BaO 0.675 (av. of EMP and ICP), CaO 0.167 (av. of EMP and ICP), K₂O 2.455 (av. of EMP and ICP), SrO 0.21 (ICP), ThO₂ 0.85 (ICP), H₂O 6.9 Σ99.61. Powder-diffraction X-ray studies indicate a close resemblance in patterns between mineral A and several uranyl oxide-hydroxide hydrated minerals, including the schoepite family of minerals and UO₂(OH)₂. The powder-diffraction data for mineral A are most similar to those for synthetic UO_2.86·1.5H₂O and UO₂(OH)₂, but other phases are likely present as well. TA analysis of both mineral A and metaschoepite show similar weight-loss and first derivative curves. The dominant losses are at 100^oC, with secondary events at 400^o and 600^oC. IR spectra show the presence of (OH) and H₂O. Uraninite from both pegmatites, analyzed by LAM-ICP-MS, shows the presence of Th, Pb, K and Ca. (author). 9 refs., 3 tabs., 3 figs

[en] Highly sensitive procedures for the determination of chromium in bio-environmental samples using neutron activation analysis, atomic absorption and gas chromatography have been developed in this laboratory. In the neutron activation procedure, dried samples are irradiated for up to 100 hours at a neutron flux in excess of 10¹⁴ neutrons cm^-2s^-1 for determinations at the parts per 10⁹ level. Following irradiation, chromium is separated by distillation as chromylchloride and precipitated and counted as BaCrO₄. Samples to be analysed by atomic absorption were digested using concentrated nitric acid followed by hydrogen peroxide, and injected into a Perkin Elmer model 2100 graphite furnace. For the gas chromatography determinations an EC detector in pulse mode with linearizer was used to detect chromium trifluoroacetylacetonate following separation on 3% OV-17. Analysis of a round-robin, freeze-dried urine sample by all three methods gave excellent agreement. (author)