Structural controls on hydrothermal flow in a segmented rift system, Taupo Volcanic Zone, New Zealand

Vigorous hydrothermal convection transfers 10 times the average continental heat flow through the central Taupo Volcanic Zone (TVZ), a region of active extension (approximately 8 mm year^?1) and productive rhyolitic volcanism. Over 20 high‐temperature (>250°C) geothermal fields occur within Quaternary pyroclastic basins, with convective circulation to depths of 7–8 km presumably extending through basement rocks. Parallel‐striking normal faults, fractures and dikes dissect the convective regime, interacting with fluids to either enhance or restrict flow according to the relative permeability of structure and host rock. In the basement, high bulk permeability is maintained by focussed flow through faults and associated fractures well oriented for reactivation in the prevailing stress field. In contrast, distributed flow through fault‐bounded compartments prevails within Quaternary basins, masking any signal of deeper structural control. Exceptions occur where more competent rocks are exposed at the surface. As in narrow magmatic rifts elsewhere, the extensional fabric is partitioned into discrete rift segments linked along strike by accommodation zones. Eighty per cent of TVZ geothermal fields correlate spatially with rift architecture, with 60% located in accommodation zones. We suggest that segmented rift fabrics generate bulk permeability anisotropy that is to some extent predictable, with rift segments characterized by enhanced axial flow, and accommodation zones characterized by locally enhanced vertical permeability that is tectonically maintained. This provides a plausible explanation for the common occurrence of geothermal fields within accommodation zones and their notable absence within densely faulted rift segments. Maintenance of structural permeability in zones of active hydrothermal precipitation necessarily requires repeated brittle failure. Geothermal plumes therefore exploit tectonically maintained permeability within accommodation zones, with rift segments functioning mostly as drawdown regions. The influence of rift architecture on flow paths has important implications for geothermal extraction and epithermal mineral exploration within the TVZ and other structurally segmented hydrothermal systems, both active and extinct.     

Toponymy of the Child Ballads: Problems of Representation in Written and Oral Texts

Foundation myths by definition are politically focused tales, describing the origin of nations, states, ruling dynasties, clans, and other consanguineal groups. The myths of Tan’gun and Chumong are the oldest extant foundation myths of Korea, but only the Myth of Tan’gun has had a continuous influence on the affirmation of Korean polities and nationalism for over a thousand years. This article explores why that has been the case.     

Reviews

THE RELEVANCE of ‘closure theory’ to archaeology is discussed, and it is argued that the role of material culture in shaping medieval group identities was enhanced by taxation on movable property during the 13th century. Emphasis on monetary value led to concepts of ranking expressed in sumptuary laws and the use of symbols in late medieval contractual society.     

REGIONAL POPULATION REDISTRIBUTION IN THE USSR: 1979-84

This paper examines regional redistribution and population growth rate trends in the USSR from 1979 to 1984, and compares them to preceding intercensal trends for 1959-70 and 1970-79. Total and regional rates of population change for 1979-84 were generally lower than in preceding periods. The most pronounced regional shift continues to be toward rapidly growing Central Asia, which has surpassed the Center as the most populous Soviet region. However, Central Asia now has net out-migration, and the degree of shift to Central Asia was less than during 1970-79. Between 1979 and 1984 a noticeable northward and eastward shift occurred. In particular, there appeared to be a resurgence of Siberia. After two decades of decline, the share of the Soviet population residing in Siberia increased between 1979 and 1984. Another notable development was the slowing of the rate of rural population decline, especially in the Non-Chernozem Zone of European USSR and in Siberia. It is possible that policies to promote migration to Siberia and to stem rural depopulation may be having some effect. The shift to cities in general and large cities in particular, however, continues. (The author would like to thank Robert Lewis for his useful comments and Jane Rowland for her excellent typing).     

Declining Towns in Russia, 1989-1993

An article based on data for the last census of the former USSR and population estimates for 1993 for urban places of over 15,000 population in the Russian Federation surveys the regional distribution, economic functions, and size characteristics of urban settlements in Russia with declining population over the period 1989-93. Interesting comparisons are drawn with patterns prevailing during previous periods, revealing recent increases in the number of such towns in major manufacturing regions and the North and an increase in the number of large cities. Towns experiencing the very greatest percentage declines (-10.0 percent or more) also are investigated. 2 tables, 2 figures, 18 references.     

A Picture of the Floating World: Grounding the Secessionary Affluence of the Residential Cruise Liner

Abstract:  A quarter century of financial deregulation, robber-baron corporatism and growing income polarisation has enabled the spatial partitioning of urban space into new and complex arrangements of micro-neighbourhood governance and privatism. These archipelagos of fortress homes and neighbourhoods increasingly lie outside the spaces of conventional state and city government. Yet while residential spaces of urban affluence have been unable to fully remove contact with the social diversity of the public realm, nomadic forms of super-affluence, flowing around a global–national urban system, have generated a form of networked extra-territoriality—a social space decoupled from the perceived risks and general dowdiness of the social world beneath it. This paper examines this space via the curious case of The World , a large residential cruise ship which, as its name suggests, roams the oceans and ports of the globe. Our title is taken from the name given to Japanese paintings of the new affluence and fantasy of life lived by the affluent and artists in late nineteenth century Japanese cities ( O Ukiyo E , or pictures of the floating world). We suggest that The World forms a similarly disconnected realm, not only literally afloat, also detached from the reality of a world that has been strategically left behind.