Co2+ as a chemical analogue for Fe2+ in high-temperature experiments in basaltic systems

High-temperature experiments on ferromagnesian compositions have been hampered by the rapid absorption of up to 95% of the original iron by platinum and 40% by silver-palladium capsules. Molybdenum or iron capsule materials can decrease or alleviate iron loss, but restrict oxygen fugacities to values near the iron-wustite buffer. Because Co²⁺ is stable at f_O2 =HM and because the solubility of Co in platinum in this range of f_O2 is ～0.05% at temperatures to 1350°C, its use as an analogue for Fe²⁺ is possible. In addition, experiments simulating various Fe²⁺ ratios can be easily performed by choosing appropriate Co²⁺/Fe³⁺ ratios. The cobalt phases produced possess brilliant and distinctive colors which are valuable aids in optical identification of minute phases. The cobalt analogue hypothesis was tested with atmospheric pressure experiments in air on the cobalt analogue of the 1921 Kilauea basalt at three simulated Fe²⁺/Fe³⁺ ratios. The results were compared with those of R.E.T. Hill (1969) for the natural 1921 basalt. The phase relations were the same, with the cobalt system stability fields systematically shifted by about +50°C. Microprobe analysis of olivines and the coexisting glasses indicate that the distribution of Co²⁺ between olivine and melt is independent of temperature and liquid composition. Although the analogue liquid composition differs from the equilibrium composition of the natural system, it may be corrected be employing distribution coefficients (K_D = 0.61 for the Co system; K_D = 0.33 for the Fe system) to closely approximate what the natural system would yield if iron loss did not occur.     

Masculinities, femininities and the geographies of public and private drinking landscapes

Geographers have been slow to address issues about abstinence, drinking and drunkenness, but the importance of alcohol on the social and political agenda has underpinned recent growth in this field. Explorations of the gendered geographies of drinking are one important strand in this emerging field, but there is currently a paucity of research on women and gender (as opposed to men), and a dearth of research which looks beyond a rather narrowly specified range of public drinking environments. This paper addressed these short-comings through a quantitative and qualitative examination of different men’s and women’s alcohol consumption in private as well as diverse public drinking environments in 21st Century Britain. The paper emphasises the importance of gendered moralities in shaping gender and intra-gender differences in drinking levels, locations and motivations, and explores the connections between apparently separate public and private drinking environments.     

Job Accessibility and Male Teenage Employment, 1980–1990: The Declining Significance of Space?*

The spatial mismatch hypothesis, which argues that job decentralization has had a major impact on the economic fortunes of inner-city minorities, has been a popular argument in academic and policy circles. It is possible, however, that employment decentralization was a temporary shock to inner-city labor markets and that labor supply has successfully adjusted by residential relocation and alterations in job search patterns. This paper examines this issue with an empirical analysis of the 1980 and 1990 employment probabilities of black and white male teenagers living in the largest metropolitan areas of the United States. Findings indicate that the impact of job accessibility on employment probabilities declined between 1980 and 1990, especially for black male teenagers not enrolled in school. Accessibility had a declining effect for this group because of losing the advantage of accessibility rather than overcoming the disadvantage of inaccessibility. By 1990, black male teens living in job-accessible areas no longer enjoyed as much of an employment advantage relative to teens living in job-inaccessible areas as they did in 1980. We should thus be cautious about ascribing too much theoretical or policy importance to job accessibility factors.     

Ammonium in thermal waters of Yellowstone National Park: Processes affecting speciation and isotope fractionation

Dissolved inorganic nitrogen, largely in reduced form (), has been documented in thermal waters throughout Yellowstone National Park, with concentrations ranging from a few micromolar along the Firehole River to millimolar concentrations at Washburn Hot Springs. Indirect evidence from rock nitrogen analyses and previous work on organic compounds associated with Washburn Hot Springs and the Mirror Plateau indicate multiple sources for thermal water NH₄(T), including Mesozoic marine sedimentary rocks, Eocene lacustrine deposits, and glacial deposits. A positive correlation between NH₄(T) concentration and δ¹⁸O of thermal water indicates that boiling is an important mechanism for increasing concentrations of NH₄(T) and other solutes in some areas. The isotopic composition of dissolved NH₄(T) is highly variable (δ¹⁵N = −6‰ to +30‰) and is positively correlated with pH values. In comparison to likely δ¹⁵N values of nitrogen source materials (+1‰ to +7‰), high δ¹⁵N values in hot springs with pH >5 are attributed to isotope fractionation associated with loss by volatilization. NH₄(T) in springs with low pH typically is relatively unfractionated, except for some acid springs with negative δ¹⁵N values that are attributed to condensation. NH₄(T) concentration and isotopic variations were evident spatially (between springs) and temporally (in individual springs). These variations are likely to be reflected in biomass and sediments associated with the hot springs and outflows. Elevated NH₄(T) concentrations can persist for 10s to 1000s of meters in surface waters draining hot spring areas before being completely assimilated or oxidized.     

Institutional geographies of the New Age movement

This paper is concerned with the production and reproduction of different institutional geographies of the New Age movement. Instead of taking institutional geographies to be given and fixed co-ordinates in the social field, the paper seeks to understand how they are relational outcomes and effects that require constant upkeep. After characterising the New Age movement, in terms of its central cosmology and visions of transformation, the paper takes an actor-network theory (ANT) approach to the understanding of institutional geographies. Through analysing how New Age knowledges and practices travel through time and space, and utilising ANT’s concept of ‘centres of translation’, institutional geographies are taken to be active space-times that are both enrolled into New Age teachers and practitioners programs of action, and space-times that actively enrol teachers and practitioners. It is argued that the intertwining of different engineered actor-networks in and through these space-times maintains the New Age movement itself and thus examining institutional geographies can tell of the movement’s shape or topology. A controversy over the work of David Icke is explored to reveal how institutional geographies are sites for regulation of what counts as New Age knowledge. Finally, this paper seeks, partially at least, to assess in terms of the ANT approach taken, the visions of transformation propounded by the New Age movement.     

Water solubility in aluminosilicate melts

We have compiled water solubility data for a wide range of natural and synthetic aluminosilicate melts in a search for correlations between melt composition and solubility. The published data reveal some interesting systematics. For example, molar water solubility increases with decreasing silica content in binary and pseudobinary silicates, and much higher solubilities are associated with alkali systems compared to alkaline earth silicate melts. Water solubility increases regularly with decreasing silica content along the silica-nepheline join. From the limited data available for potassium and calcium aluminosilicate melts, these systems appear to behave differently to sodium aluminosilicates. The compiled data are not nearly extensive enough to begin to understand the effects of melt composition on solubility. We suggest that many more systematic studies for a wide range of aluminosilicate melts will be necessary before we can systematize and understand the compositional dependence of water solubility. We have also examined results of experiments designed to probe the details of the water dissolution mechanism, and discuss the present state of interpretation of these data. We conclude that although considerable progress has been made, the water dissolution process is still not well understood at the molecular level, and remains an important research problem.     

Grid transformation for incorporating the Arctic in a global ocean model

A grid transformation is described which isolates the Arctic and North Atlantic, rotates the spherical grid to pass an equator up the Atlantic through the north pole and remaps the Coriolis parameter. Boundary condition information is exchanged along the equatorial Atlantic so that the Arctic-Atlantic model is dynamically coupled to a model of the rest of the global ocean (which remains on the geographic spherical grid). The transform produces a more regular grid over the Arctic and eliminates the need for filtering or special treatment at the pole. The transform has been implemented in the GFDL Modular Ocean Model. After testing with idealized geometry, a 300 y global integration is compared to an integration using the geographic spherical grid and Fourier filtering. Results are similar, with differences in the Arctic and western North Atlantic regions leading to smaller air-sea heat flux near the Gulf Stream separation latitude for the transform case. Use of the transform also leads to a reduction in computation time.     

Neutral gas and dust in the central region of the ultraluminous infrared galaxy Mrk 273

We have used MERLIN to observe neutral hydrogen absorption against the central region of the ultraluminous infrared galaxy (ULIRG) galaxy Mrk 273 with an angular resolution of 0.2 arcsec. This represents a factor of 5 increase in resolution compared with previous work. Absorption has been resolved against two of three radio continuum components. A Hubble Space Telescope ( HST ) image reveals a complex central region composed of clumpy emission obscured by dust lanes. We find that the northern and south-eastern radio components are associated with two optical components. The alignment supports the idea that Mrk 273 has a double nucleus due to a recent galactic merger event.
Broad, strong and spatially varying absorption is seen against the northern radio component with a velocity gradient of 1990±50 km s⁻¹ kpc⁻¹. The absorption resolves into six discrete components with an average column density of 1.7×10²² atom cm⁻². We propose that the absorption is due to a clumpy ring or disc of neutral gas of radius ∼250 pc rotating around a central starburst. In addition to the broad component, narrow absorption (<100 km s⁻¹) is detected against the northern and south-eastern components. Absorption is not detected against the weak (2 mJy) south-western component. We propose that the narrow absorption is due to quiescent gas in a large-scale dust lane that coincides with these regions of narrow absorption.     

A regional-scale study of chromium and nickel in soils of northern California, USA

A soil geochemical survey was conducted in a 27,000-km² study area of northern California that includes the Sierra Nevada Mountains, the Sacramento Valley, and the northern Coast Range. The results show that soil geochemistry in the Sacramento Valley is controlled primarily by the transport and weathering of parent material from the Coast Range to the west and the Sierra Nevada to the east. Chemically and mineralogically distinctive ultramafic (UM) rocks (e.g. serpentinite) outcrop extensively in the Coast Range and Sierra Nevada. These rocks and the soils derived from them have elevated concentrations of Cr and Ni. Surface soil samples derived from UM rocks of the Sierra Nevada and Coast Range contain 1700–10,000 mg/kg Cr and 1300–3900 mg/kg Ni. Valley soils west of the Sacramento River contain 80–1420 mg/kg Cr and 65–224 mg/kg Ni, reflecting significant contributions from UM sources in the Coast Range. Valley soils on the east side contain 30–370 mg/kg Cr and 16–110 mg/kg Ni. Lower Cr and Ni concentrations on the east side of the valley are the result of greater dilution by granitic sources of the Sierra Nevada.Chromium occurs naturally in the Cr(III) and Cr(VI) oxidation states. Trivalent Cr is a non-toxic micronutrient, but Cr(VI) is a highly soluble toxin and carcinogen. X-ray diffraction and scanning electron microscopy of soils with an UM parent show Cr primarily occurs within chromite and other mixed-composition spinels (Al, Mg, Fe, Cr). Chromite contains Cr(III) and is highly refractory with respect to weathering. Comparison of a 4-acid digestion (HNO₃, HCl, HF, HClO₄), which only partially dissolves chromite, and total digestion by lithium metaborate (LiBO₃) fusion, indicates a lower proportion of chromite-bound Cr in valley soils relative to UM source soils. Groundwater on the west side of the Sacramento Valley has particularly high concentrations of dissolved Cr ranging up to 50 μg L⁻¹ and averaging 16.4 μg L⁻¹. This suggests redistribution of Cr during weathering and oxidation of Cr(III)-bearing minerals. It is concluded that regional-scale transport and weathering of ultramafic-derived constituents have resulted in enrichment of Cr and Ni in the Sacramento Valley and a partial change in the residence of Cr.