Clinopyroxene composition as a method of identification of the magmatic affinities of paleo-volcanic series

Uranium contents and²³⁴U/²³⁸U activity ratios have been determined for groundwaters from the Lincolnshire Limestone artesian aquifer in eastern England. Changes in the quantitative and isotopic chemistry of the dissolved uranium are explained in terms of a mixing model involving the rapidly moving fissure water and much older water stored in the pore system of this oolitic limestone. The western part of the aquifer, closest to recharge, is dominated by oxidising groundwaters which then enter a reducing zone towards the east, where there is an abrupt decrease in Eh and the chlorinity of the groundwaters begins to increase. Uranium contents in the oxidising zone range from 0.7 to 3.4 μg kg^?1 and²³⁴U/²³⁸U activity ratio of this dissolved uranium is close to unity, the equilibrium value. The uranium content decreases abruptly when the grounwaaters enter the reducing zone, averaging 0.04 μg kg^?1 east of the oxidation/reduction barrier. Simultaneously with the decrease in uranium content, there is an increase in²³⁴U/²³⁸U activity ratio and this ratio increases to a maximum within 7 km of the oxidation/reduction barrier. This increase in activity ratio is attributed to enhanced²³⁴U solution due to²³⁴Th recoil from uraniferous fissure surfaces east of the oxidising zone. The activity ratio of dissolved uranium in the ancient pore waters could in principle reach high values due to²³⁴Th recoil from the oolith surfaces. However, the activity ratio actually declines further east and this can only be explained as a consequence of mixing with pore waters in which the uranium activity ratio is closer to equilibrium.²³⁴Th recoil from the oolith surfaces has probably been inhibited by sealing of the uranium-bearing surfaces in the process of oolith cementation.     

CHe in volatile fluxes from the solid Earth: implications for carbon geodynamics

In order to picture C geodynamics past and present, theC³He ratios of the relevant reservoirs are considered. Evaluation of publishedC³He ratio in conjunction with new results for MORB glasses worldwide, suggests that this ratio is unfractionated during magma outgassing, a best estimate being 2 × 10⁹.C³He ratios from other volcanic emissions (hot spots and arcs) do not appear significantly different when the subducted component is omitted.This result permits scaling of the CO₂ degassing flux to that of³He and yields a value of 2 × 10¹² mol/yr which corresponds to a model degassing duration of 3.9 Gyr when recycling to the mantle is disregarded.A bulk Earth chondritic ratio of about 2 × 10⁹ is calculated, very close to the MORB value. On the other hand the reconstructed exospheric (“Rubey inventory”) value of4 ± 1 × 10⁷ is very different from both basaltic and chondritic values.Among the possible interpretations of these results the following two are retained: (1) CO₂ was not released in the early age of the Earth because of the reducing conditions prevailing at that time in the mantle. Formation of the core changed this picture and permitted subsequent degassing of CO₂. (2) Carbonates need a continental crust of significant size to become stabilized in the exosphere. Therefore accumulation in the exosphere was delayed until crustal formation.Alternatively, a similar degassing behaviour for both He and CO₂ requires a massive recycling of carbonates throughout time. This possibility is in contradiction with the present-day maximum recycling rate and the severe imbalance with the observed outgassing flux on one hand and with the small fraction of carbon now present in the exosphere on the other.We conclude that carbon has never been severely degassed. The mantle acts as a buffer for C and most carbon is still retained there, possibly as graphite (or diamond?) or dissolved in minerals.     

Données cytologiques sur deux Cyanophycées:Spirulina platensis (Gom.) Geitler etSpirulina geitleri J. de Toni

The interest of many research specialists is, at present, focused on twoSpirulina, which can be cultivated for alimentary purposes. Optimum conditions for industrial cultivation are known, but far more must be found out about the systematic position of the two microorganisms as well as their structural and metabolic biochemistry, since these facts are essential for more rational industrial use. This paper marks the beginning of a cytological and cytochemical research program.     

Social Applications of Geographical Information Systems: technical tools for social innovation

ABSTRACT

The establishment of the National Key Centre for Social Applications of Geographical Information Systems (GIS) in 1995, under the directorship of Professor Graeme Hugo, was a turning point in the use of GIS in Australia. The field of GIS, previously dominated by environmental applications, now broadened its focus to include populations, services and the interactions between people and the environment. Social applications of GIS offered a unique opportunity to make service planning, reporting, funding allocations and research both smarter and fairer. Geography and geographic relationships as implemented in GIS became the integrating platform for social spatial information, invigorating social research, planning and policy. A key strength of this approach, recognised by Professor Hugo, was the ability to ‘put people back into the planning process’. Further to being an integrating platform, GIS also offered the ability to generate new information and knowledge, which could facilitate evidence-based decision making. This paper focuses in particular on providing a written record of the development of the Accessibility/Remoteness Index of Australia (ARIA) suite of spatial accessibility indices. The lasting legacy and continued relevance of this work in social applications of GIS is also reviewed in this paper, with reference to key examples of how social research and planning in Australia have been made both smarter and fairer through the contributions of Professor Hugo and his team.     

Comparison of Satellite-Only Gravity Field Models Constructed with All and Parts of the GOCE Gravity Gradient Dataset

The impact of GOCE Satellite Gravity Gradiometer data on gravity field models was tested. All models were constructed with the same Laser Geodynamics Satellite (LAGEOS) and Gravity Recovery and Climate Experiment (GRACE) data, which were combined with one or two of the diagonal gravity gradient components for the entire GOCE mission (November 2009 to October 2013). The Stokes coefficients were estimated by solving large normal equation (NE) systems (i.e., the direct numerical approach). The models were evaluated through comparisons with the European Space Agency's (ESA) gravity field model DIR-R5, by GPS/Leveling, GOCE orbit determination, and geostrophic current evaluations. Among the single gradient models, only the model constructed with the vertical ZZ gradients gave good results that were in agreement with the formal errors. The model based only on XX gradients is the least accurate. The orbit results for all models are very close and confirm this finding. All models constructed with two diagonal gradient components are more accurate than the ZZ-only model due to doubling the amount of data and having two complementary observation directions. This translates also to a slower increase of model errors with spatial resolution. The different evaluation methods cannot unambiguously identify the most accurate two-component model. They do not always agree, emphasizing the importance of evaluating models using many different methods. The XZ gravity gradient gives a small positive contribution to model accuracy.     

Barium and strontium uptake into larval protoconchs and statoliths of the marine neogastropod Kelletia kelletii

The trace elemental composition of calcified larval hard parts may serve as useful tags of natal origin for invertebrate population studies. We examine whether the trace metal barium (Ba) deposits into the calcium carbonate matrix of molluscan larval statolith and protoconch in proportion to seawater Ba concentration at two temperatures (11.5 and 17°C). We also examine strontium (Sr) uptake as a function of temperature. Using encapsulated larvae of the marine gastropod, Kelletia kelletii, reared in the laboratory under controlled conditions, we demonstrate a significant inverse effect of temperature and a positive effect of seawater Ba/Ca ratio on Ba incorporation into larval carbonates. Ba/Ca partition coefficients (D_Ba) in protoconch were 1.13 at 11.4°C and 0.88 at 17.1°C, while D_Ba in larval statolith measured 1.58 at 11.4°C and 1.29 at 17.1°C. Strontium incorporation into statoliths is also inversely affected by temperature, but there was a significant positive effect of temperature on Sr incorporation into protoconch. These data suggest larval statoliths and protoconchs can meaningfully record variation in seawater physical and chemical properties, and, hence, have potential as natural tags of natal origin.     

Distribution of sterol and fatty alcohol biomarkers in particulate matter from the frontal structure of the Alboran Sea (S.W. Mediterranean Sea)

Sterol and fatty alcohol biomarkers were analyzed in suspended and sinking particles from the water column (20–300 m) of the Almeria–Oran frontal zone to characterize the biogenic sources and biogeochemical processes. Diatom- and haptophyte-related sterols were predominant at all sites and vertical distributions of sterol, and fatty alcohol biomarkers in sinking particles were markedly different from suspended particles. In contrast to the relatively fresh sinking particles with elevated concentrations of phyto- and zooplanktonic sterols, suspended particles were extensively degraded with increasing depth and exhibited a more terrestrial and zooplanktonic signature with depth.Sterol and alcohol biomarkers distributions and δ¹³C values from the jet core and the associated gyre of Atlantic waters showed a decoupling between the sinking particles of 100- and 300-m depth, demonstrating the influence of lateral advection in the frontal zone. In contrast, vertical transport of the particulate organic matter in Mediterranean waters was interpreted from the similar isotopic and molecular composition at both depths. The high abundance of phytosterols and phytol below the euphotic zone at 100 m signified that downwelling of biomass occurred on the downstream side of the gyre. The high concentrations of phytosterols and POC, in combination with the high phytosterols/phytol ratio, indicated the accumulation of detrital plant material in the oligotrophic Mediterranean waters near the frontal zone.A higher contribution of phytol in the sinking particles collected during the night at the surface of the jet and at the upstream side of the gyre provided evidence of diel vertical zooplankton migration and important grazing by herbivorous zooplankton.Carbon isotope ratios of sterols confirmed that the 24-ethylcholest-5-en-3β-ol, commonly associated with terrestrial sources, was a substantial constituent of the phytoplankton in this area. However, the more δ¹³C depleted values obtained for this compound in suspended particles suggested that there was some terrestrial contribution that only becomes evident after degradation of the more labile marine organic matter.