Raman confirmation of microdiamond in the Svartberget Fe‐Ti type garnet peridotite,Western Gneiss Region,Western Norway

Ultra‐high pressure metamorphic rocks have been found worldwide. The volume and areal extent of an exhumed UHPM domain are important for understanding the geodynamic mechanisms responsible for the high pressure and relatively medium temperature conditions needed for their creation. We report here Raman microspectroscopical data that prove the existence of microdiamonds at the Svartberget Fe‐Ti type peridotite locality in the Western Gneiss Region of Norway. Raman microscopy of two carbon microinclusions belonging to polyphase inclusion assemblages included in garnets from a garnet‐phlogopite websterite vein yielded a sharp, narrow, intense peak at 1332 cm^?1, characteristic of diamond. The diamond is associated with polyphase solid inclusions possibly originating from supercritical, dense, H‐C‐N‐O‐F‐P‐S‐Cl fluids. Lithological, textural and geochronological evidence points towards a Caledonian origin of the trapped fluid and subsequent diamond formation.     

Toxicity and compositional analysis of aromatic hydrocarbon fractions of two pairs of undegraded and biodegraded crude oils from the Santa Maria (California) and Vienna basins

The monoaromatic and total aromatic hydrocarbon fractions of two pairs of undegraded and moderately biodegraded crude oils from the Santa Maria basin (California) and the Vienna basin (Austria), all dominated by unresolved complex mixtures, were studied regarding their composition and toxicity towards the feeding rate of the marine mussel Mytilus edulis. Total aromatic and monoaromatic hydrocarbon fractions from sulphur-rich Monterey Formation crude oils were slightly more toxic than the fractions isolated from sulphur-lean Vienna basin oils. The ecotoxicity tests did not show any significant differences in toxicity of aromatic compounds from undegraded or in-reservoir biodegraded crude oils from the same oilfield although some differences in composition were observed. Organic sulphur compounds are suspected to cause the slightly higher toxicity of the aromatic hydrocarbon fractions from the Monterey oils.     

Nitrous oxide emission from Gulf Coast wetlands

Nitrous oxide evolution may contribute to partial destruction of the ozone layer in the stratosphere. A two year study of the release of N₂O from adjoining salt, brackish, and fresh marsh sediment indicates that the annual emission was 31, 48, and 55 mg N m^?2 respectively. Emission from open water area was less than the corresponding emission from the marsh sediment. In vitro experiments indicate that the N₂O emission was increased when the sediment was drained for extended periods of time. The addition of NO₃^? significantly increased the rate of N₂O evolution, indicating that a large potential for denitrification exists in the anoxic sediment. Appreciable losses of N₂O would only be expected when the marshes receive an extraneous source of nitrate such as sewage and/or wastewater.The contribution of the Gulf Coast wetlands to the atmospheric N₂O balance is estimated to be 3.3 × 10⁹ g N₂O. The maximum average daily emission was equivalent to 1.5 g N₂O-N ha^?1, which is less than the measured emission from uncultivated soils (Mosieret al., 1981) but greater than the estimates from noncropped land (CAST, 1976).     

Simulation of structural phase transition in NaNO3 and CaCO3

 The order-disorder phase transitions in NaNO₃ and CaCO₃ are simulated by molecular dynamics. The simulations are based on the potentials calculated from the Gordon–Kim modified electron gas formalism extended to molecular ions. We successfully reproduced the transition temperature T _c and the abnormally large c axis thermal expansion observed in experiment. The phase transitions in NaNO₃ and CaCO₃ were found to be initiated by ±60 and ±180° reorientation of the NO₃ and CO₃ ions about the c axis. The orientations of NO₃ and CO₃ ions are continuous with six preferred calcite-type orientations above the phase-transition temperature. Received: 30 January 2001 / Accepted: 11 May 2001     

Geochemistry of Ordovician Keli Group basalts associated with Besshi-type Cu-Zn deposits from the southern Trondheim and Sulitjelma mining districts of Norway

Besshi-type volcanogenic Cu-Zn deposits in the Scandinavian Caledonides are hosted by Ordovician metabasalts and clastic sediments of the Storen, Fundsjo and Sulitjelma groups. The basalts are transitional between T-MORB and marginal basin tholeiites in composition and are characterised by Nd and Pb isotopic compositions which overlap the more radiogenic values of Lower Palaeozoic MORB. These features, along with the intercalation of the basalts with tuffs and continentally derived sediments, indicate an epicontinental rift or marginal basin origin, possibly analogous to the present Red Sea and Gulf of Aden rifts. This implies the development of a restricted ocean basin in the north of Iapetus between the Laurentian and Baltoscandian microcontinents during the Cambrian and Early Ordovician.     

Evaluation of Geochemical Reference Standards by X-Ray Fluorescence Analysis

Twenty five elements in twenty six geochemical reference standards analyzed by X-ray fluorescence spectrometry yield major and trace element concentrations close to consensus values. Ninety percent of our analyses agree with consensus values for standards to within pm 0.5 to 1.5 relative percent for major elements and pm 3 to 5 relative percent or pm 1-3 ppm, whichever is higher, for trace elements. Consistent divergences from consensus values of trace elements are noted.