Sodic metasomatism in the Palaeoproterozoic Hotazel iron-formation, Transvaal Supergroup, South Africa: implications for fluid–rock interaction in the Kalahari manganese field

Petrological and geochemical evidence is presented on the occurrence of aegirine in the Palaeoproterozoic Hotazel iron‐formation, which hosts the giant manganese deposits of the Kalahari manganese field, South Africa. The mineral has an essentially pure Na end‐member composition and occurs sporadically in iron‐formation immediately bordering the manganese ore beds. The development of aegirine appears to have taken place due to the action of late‐infiltrating, saline hydrothermal fluids at the expense of a pre‐existing, binary quartz–hematite assemblage. It is proposed that such a process would have overprinted (and therefore post‐dated) a spatially more extensive, low‐temperature alteration event which brought about thorough carbonate leaching, oxidation and residual enrichment of metals in the Hotazel iron–manganese rocks.     

COMPONENTS OF CHANGE IN THE SPATIAL DISTRIBUTION OF THE ELDERLY POPULATION IN ONTARIO, 1976–1986

Although the elderly population is increasing rapidly in all parts of Canada, the pattern of change is far from uniform. A number of properties of the aging process are strongly differentiated at the county and township levels, variations which have considerable significance for the design and implementation of social service and health care systems. Using data from the 1976, 1981, and 1986 Censuses for Ontario, components of change in the elderly population are obtained by cohort survival methods. The significance of rapid metropolitan growth of the elderly compared with the slow growth of the rural elderly is highlighted, while intra-county distributional shifts in the elderly population raise important questions for the next decade.
Quoique l'âge de la population augmente rapidement à travers le Canada, ce changement nes'opèrepas de façon uniforme. Certaines caractéristiques du processus de vieillissement sont vraiment differentes à l'échelle des comtés et des municipalités. Ces différences sont d'une grande importance lors de la création etde l'implantation des services-santé et des services sociaux. À l'aide des statistiques de recensement pour les années 1976, 1981, et 1986 pour l'Ontario, les facteurs de changement des populations de personnes âgées sont obtenus au moyen des paramètres de 'survie des groupes.' La signification du taux d'accroissement rapide des personnes â gés en milieu urbain comparé au taux d'accroissement plus lent de ces mêmes personnes en milieu rural est mise en évidence. Les variations de la distribution de cette population d'un comtéà I'autre soulèvent d'importantes interrogations pour la prochaine décade .     

Romantic Scotland,tragic England,ambiguous Britain: constructions of ‘the Empire’ in post‐devolution national accounting

ABSTRACT. This article compares the ways in which references to ‘the (British) Empire’ were constructed and used in interview accounts of national identity and domestic politics in Scotland and in England. In Scotland, spontaneous accounts of Empire were typically formulated in conjunction with nationalist moral meta‐narratives. Respondents variously inferred heroic national character from Scotland's role in Empire, or cast Scottish history as an enduring struggle between progressive forces of nationalism and atavistic forces of Anglo‐British colonialism. The construct of Britishness was often seen to derive from, and to be synonymous with, the history of Empire. In England, the Empire story tended to be framed within anti‐nationalist meta‐narratives. Imperialism was generally understood to represent a product of excessive nationalism, and tales of Empire were used to draw exemplary moral lessons concerning the deficiencies of Anglo‐British national character and of the catastrophic consequences of the pursuit of national self‐interest more generally. The existence of Britain, and the construct of Britishness, were generally understood to both predate and postdate the history of Empire.     

Mineralogy and fluid inclusion gas chemistry of production well mineral scale deposits at the Dixie Valley geothermal field,USA

At the Dixie Valley geothermal field, Nevada, USA, fluid boiling triggered the precipitation of carbonate scale minerals in concentric bands around tubing inserted into production well 28–33. When the tubing was removed, this mineral scale was sampled at 44 depth intervals between the wellhead and 1227 m depth. These samples provide a unique opportunity to evaluate the effects of fluid boiling on the scale mineralogy and geochemistry of the vapor and liquid phase. In this study, the mineralogy of the scale deposits and the composition of the fluid inclusion gases trapped in the mineral scales were analyzed. The scale consists mainly of calcite from 670–1112 m depth and aragonite from 1125 to 1227 m depth, with traces of quartz and Mg‐smectite. Mineral textures, including hopper growth, twinning, and fibrous growth in the aragonite and banded deposits of fine grained calcite crystals, are the result of progressive boiling. The fluid inclusion noncondensable gas was dominated by CO₂. However, significant variations in He relative to N₂ and Ar provide evidence that the geothermal reservoir consists of mixed source deeply circulating reservoir water and shallow, air saturated meteoric water. Gas analyses for many inclusions also showed higher CH₄ and H₂ relative to CO₂ than measured in gas sampled from this well, other production wells, and fumaroles. These inclusions are interpreted to have trapped CH₄‐ and H₂‐enriched gas resulting from early stages of boiling.     

BULK STABLE LIGHT ISOTOPIC RATIOS IN RECENT AND ARCHAEOLOGICAL RESINS: TOWARDS DETECTING THE TRANSPORT OF RESINS IN ANTIQUITY?*

We have applied and refined methods for the determination of bulk hydrogen, carbon and oxygen isotope ratios in modern and archaeological resins. The modern resins have a wide range of isotopic values and vary within the same tree, between individual trees, with species and location. For all isotopes measured, there is a general trend of increasing depletion of the heavier isotope with increasing altitude. There is also a linear trend between depletion of δD and δ¹³C values with increasing latitude; this trend is less clear for oxygen, but is related to the meteoric water line. Two case studies using archaeological resins known or suspected to have been transported in antiquity have been investigated to determine whether isotopic signatures can assist in pinpointing the geographical origin of the resin: Pistacia sp. resin from Canaanite amphorae imported into Egypt from known geographical locations in the eastern Mediterranean during the Late Bronze Age, and Roman amphorae sherds lined with Pinus sp. resin from sites ranging from Britain to the eastern Mediterranean. These results show separate groupings between the two resin types (pine/pistacia) and between the modern/archaeological resins. Some archaeological samples are distinct from the others and the modern resins show differences between geographical areas. However, there are no clear patterns relating the different Canaanite fabrics or the suggested manufacturing site of the Roman amphorae.