Aligned olivine in the Springwater pallasite

The mechanism by which olivine grains became embedded within iron‐nickel alloy in pallasite meteorites continues to be a matter of scientific debate. Geochemical and textural observations have failed to fully elucidate the origin and history of the olivine crystals; however, little research attention has been devoted to their crystallographic orientations within the metal matrix. Using electron backscatter diffraction, we have collected crystallographic orientation data for 296 crystals within ～65 cm² sample surface from Springwater. Though no global crystallographic preferred orientation exists, very low misorientations are observed among [100] axes of olivine crystals within specific texturally defined domains. Combined with a thorough characterization of large‐scale Springwater textures, the definitively nonrandom spatial distribution of olivine orientations provides clues regarding the nature of the olivine's initial formation environment as well as the sequence of events subsequent to metal incorporation.     

How Reliable are Citizen‐Derived Scientific Data? Assessing the Quality of Contrail Observations Made by the General Public

Citizen science projects encourage the general public to participate in scientific research. Participants can contribute large volumes of data over broad spatial and temporal frames; however, the challenge is to generate data of sufficient quality to be useable in scientific research. Most observations made by citizen‐scientists can be independently verified by “experts”. However, verification is more problematic when the phenomena being recorded are short‐lived. This article uses a GIS methodology to verify the quality of contrail observations made by the general public as part of the OPAL Climate Survey. We verify observations using datasets derived from a variety of different sources (experts, models and amateur enthusiasts) with different spatial and temporal properties which reflect the complex 3D nature of the atmosphere. Our results suggest that ～70% of citizen observations are plausible, based on favorable atmospheric conditions and the presence or absence of aircraft; a finding which is in keeping with other, more conventional citizen science projects. However, questions remain as to why the quality of the citizen‐based observations was so high. Given the lack of supporting data on observers, it is impossible to determine whether the dataset was generated by the activities of many participants or a small but dedicated number of individual observers.     

Implications of climate change due to the enhanced greenhouse effect on floods and droughts in Australia

Potential impacts of climate change on heavy rainfall events and flooding in the Australian region are explored using the results of a general circulation model (GCM) run in an equilibrium enhanced greenhouse experiment. In the doubled CO₂ simulation, the model simulates an increase in the frequency of high-rainfall events and a decrease in the frequency of low-rainfall events. This result applies over most of Australia, is statistically more significant than simulated changes in total rainfall, and is supported by theoretical considerations. We show that this result implies decreased return periods for heavy rainfall events. The further implication is that flooding could increase, although we discuss here the many difficulties associated with assessing in quantitative terms the significance of the modelling results for the real world.The second part of the paper assesses the implications of climate change for drought occurrence in Australia. This is undertaken using an off-line soil water balance model driven by observed time series of rainfall and potential evaporation to determine the sensitivity of the soil water regime to changes in rainfall and temperature, and hence potential evaporation. Potential impacts are assessed at nine sites, representing a range of climate regimes and possible climate futures, by linking this sensitivity analysis with scenarios of regional climate change, derived from analysis of enhanced greenhouse experiment results from five GCMs. Results indicate that significant drying may be limited to the south of Australia. However, because the direction of change in terms of the soil water regime is uncertain at all sites and for all seasons, there is no basis for statements about how drought potential may change.     

Mixed Caledonian appinite magmas: implications for lamprophyre fractionation and high Ba-Sr granite genesis

Ach'Uaine Hybrid appinites represent a rare example of lamprophyric magmas that were demonstrably exactly contemporaneous with felsic differentiates, preserved within a suite of minor, hypabyssal intrusions emplaced at the end of the Caledonian orogeny in northern Scotland. Numerous small stocks, bosses and dykes show outcrop-scale relationships characteristic of mingling between lamprophyric and syenitic magmas, and are commonly cut by sharp-sided granite veins. The mafic rocks are characterised by Ni and Cr abundances and MgO sufficiently high to signal derivation from a mantle source within which radiogenic ⁸⁷Sr/⁸⁶Sr and nonradiogenic ¹⁴³Nd/¹⁴⁴Nd ratios require significant time-integrated incompatible element enrichment. This is manifest in high Ba, Sr and light REE abundances and incompatible element ratios in the derived magmas directly comparable with those of high Ba-Sr granitoids and related rocks. Quantitative major element, trace element, radiogenic and stable isotope modelling is consistent with early fractionation of clinopyroxene and biotite, accompanied by minor crustal assimilation, having driven the evolving lamprophyric magma to cogenetic syenite. Subsequent derivation of granite required a major change to feldspar-dominated crystal fractionation with continued, still minor contamination. The elemental and isotopic characteristics of the granitic terminus are so similar to high Ba-Sr granitoids both locally and worldwide, that these too may have had large mantle components and represent significant juvenile additions to the crust. Received: 26 September 1995 / Accepted: 5 June 1996     

Distribution of petroleum hydrocarbons and organochlorinated contaminants in marine biota and coastal sediments from the ROPME Sea Area during 2005

The composition and spatial distribution of various petroleum hydrocarbons (PHs), comprising both aliphatic and polycyclic aromatic hydrocarbons (PAHs), and selected chlorinated pesticides and PCBs were measured in biota and coastal sediments from seven countries in the Persian Gulf and the Gulf of Oman (Bahrain, Iran, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates). Evidence of extensive marine contamination with respect to organochlorinated compounds and PHs was not observed. Only one site, namely the BAPCO oil refinery in Bahrain, was considered to be chronically contaminated. Comparison of the results from this survey for Σ DDTs and Σ PCBs in rock oysters from the Gulf of Oman with similar measurements made at the same locations over the past two decades indicates a temporal trend of overall decreasing Σ PCB concentrations in oysters, whereas Σ DDTs levels have little changed during that period.     

Chlorinated hydrocarbons in pelagic organisms from the open Mediterranean Sea

Pelagic organisms from the central and eastern basins of the Mediterranean Sea were surveyed for chlorinated hydrocarbon residues. Levels in selected macrozooplankton and nekton, as well as mixed microplankton, were compared with those in similar species from other oceanic areas. Although data are sparse, PCBs in macrozooplankton and nekton do not appear to differ significantly from concentrations in similar species measured elsewhere. In the case of mixed microplankton, there was a trend towards slightly lower values in the Mediterranean samples. Differences between our results and those reported previously for other oceanic regions are discussed.