Volcano-stratigraphy and geochemistry of collision-related volcanism on the Erzurum–Kars Plateau, northeastern Turkey

The Eastern Anatolia Region exhibits one of the world's best exposed and most complete transects across a volcanic province related to a continental collision zone. Within this region, the Erzurum–Kars Plateau is of special importance since it contains the full record of collision-related volcanism from Middle Miocene to Pliocene. This paper presents a detailed study of the volcanic stratigraphy of the plateau, together with new K–Ar ages and several hundred new major- and trace-element analyses in order to evaluate the magmatic evolution of the plateau and its links to collision-related tectonic processes. The data show that the volcanic units of the Erzurum–Kars Plateau cover a broad compositional range from basalts to rhyolites. Correlations between six logged, volcano-stratigraphic sections suggest that the volcanic activity may be divided into three consecutive Stages, and that activity begins slightly earlier in the west of the plateau than in the east. The Early Stage (mostly from 11 to 6 Ma) is characterised by bimodal volcanism, made up of mafic-intermediate lavas and acid pyroclastic rocks. Their petrography and high-Y fractionation trend suggest that they result from crystallization of anhydrous assemblages at relatively shallow crustal levels. Their stratigraphy and geochemistry suggest that the basic rocks erupted from small transient chambers while the acid rocks erupted from large, zoned magma chambers. The Middle Stage (mostly from 6–5 Ma) is characterised by unimodal volcanism made up predominantly of andesitic–dacitic lavas. Their petrography and low-Y fractionation trend indicate that they resulted from crystallization of hydrous (amphibole-bearing) assemblages in deeper magma chambers. The Late Stage (mostly 5–2.7 Ma) is again characterised by bimodal volcanism, made up mainly of plateau basalts and basaltic andesite lavas and felsic domes. Their petrography and high-Y fractionation trend indicate that they resulted from crystallization of anhydrous assemblages at relatively shallow crustal levels. AFC modelling shows that crustal assimilation was most important in the deeper magma chambers of the Middle Stage. The geochemical data indicate that the parental magma changed little throughout the evolution of the plateau. This parental magma exhibits a distinctive subduction signature represented by selective enrichment in LILE and LREE thought to have been inherited from a lithosphere modified by pre-collision subduction events. The relationships between magmatism and tectonics support models in which delamination of thickened subcontinental lithosphere cause uplift accompanied by melting of this enriched lithosphere. Magma ascent, and possibly magma generation, is then strongly controlled by strike-slip faulting and associated pull-apart extensional tectonics.     

Inverse modeling of groundwater flow in the semiarid evaporitic closed basin of Los Monegros, Spain

 Only minor attention has been given in the past to the study of closed-basin hydrogeology in evaporitic environments, because these basins usually contain poor-quality groundwater. The motivation for hydrogeological research in the Los Monegros area in northeastern Spain was the approval in 1986 of a large irrigation project in the Ebre River basin. The irrigation of 60,000 ha is planned, partly in an evaporitic closed basin containing playa lakes. The project has given rise to environmental concerns. The evaluation of the hydrologic impacts of irrigation requires quantifying properly the hydrogeology of the area. With the available information, a conceptual hydrogeological model was formulated that identifies two main aquifers connected through a leaky aquitard. On the basis of the conceptual model, a numerical model was calibrated under steady-state conditions using the method of maximum-likelihood automatic parameter estimation (Carrera and Neuman, 1986a). The calibrated model reproduces the measured hydraulic heads fairly well and is consistent with independent information on groundwater discharge. By the solution of the inverse problem, reliable parameter estimates were obtained. It is concluded that anisotropy plays a major role in some parts of the lower aquifer. The geometric average of model conductivity is almost two orders of magnitude larger than the average conductivity derived from small-scale field tests. This scale effect in hydraulic conductivity is consistent with the findings of Neuman (1994) and Sánchez-Vila et al. (1996). Received, December 1997 · Revised, December 1997 · Accepted, January 1998     

The role of the Spanish Committee of the International Association of Hydrogeologists in the management and protection of Spain's groundwater resources

 Spain is a relatively large European country (ca. 500,000 km²) with extensive semiarid areas in which there exists a large number of good aquifers. In some areas, these aquifers are intensively developed and are the most important sources of fresh water. Nevertheless, groundwater development and protection has rarely been duly considered by the Spanish Water Administration, despite the pressure to remedy this situation by various groups of experts, some of them members of the Water Administration. The Spanish Committee of the International Association of Hydrogeologists (IAH) has been very active during the last decade in promoting activities to spread groundwater science, technology, and management in Spain and outside, mostly in Latin America, and in trying to orient water policy toward issues of groundwater. These activities include mainly the organization of technical and scientific meetings on current topics such as groundwater in the new Water Act, overexploitation, groundwater in water-resources planning, groundwater pollution, natural-recharge estimation and others. The impact of these activities on the recent water policy of Spain seems significant, and the experience gained may be applicable to other countries. Received, February 1997 · Revised, July 1997 · Accepted, July 1997     

Longitudinal and temporal patterns of benthic coarse particulate organic matter in the Agüera stream (northern Spain)

Benthic coarse particulate organic matter (CPOM) was studied between November 92 and December 93 at four sites along the longitudinal gradient of the Agüera stream system (Northern Spain). CPOM was sorted in four main categories: leaves (several species), fruits and seeds, twigs and debris. Headwater site showed higher densities of total CPOM, leaves and twigs than downstream reaches, but no regular longitudinal pattern of change was noticed. The ranges of mean CPOM standing stock at the sampling sites were 20.5–74.1 g AFDW m^–2 (site B), 9.9–47.7 g AFDW m^–2 (site 5), 4.3–21.4g AFDW m^–2 (site 7) and 9.8–37.9 g AFDW m^–2 (site 9). The particulate matter at downstream sites was in a more advanced stage of breakdown probably as a result of processing and transport from upstream reaches. Leaves species composition of benthic CPOM clearly reflected the type of riparian vegetation at each site. The timing of inputs and the hydrologic regime appeared to act together influencing temporal dynamics of benthic CPOM. A gradual temporal change in species composition of benthic leaf litter was observed under natural mature deciduous forest: first alder, later chestnut and finally oak.     

Spain: words that succeed and climate policies that fail

Official figures submitted in 2002 showing the trends of GH gases during the period 1990-2000 indicate that Spain is a long way from in attaining its commitments with the international and national programmes on climate change. Both structural and cultural factors are used to explain the evolution in climate politics and the growth of its emissions with particular emphasis given to the lack of public participation in this respect. It is also argued that Spain will have either to buy emission reductions abroad or/and find new ways to reduce GH in a more decentralised manner in tune with its current Autonomous Communities’ (ACs) political organisation.     

Evaporite Dissolution Subsidence in the Historical City of Calatayud,Spain: Damage Appraisal and Prevention

Calatayud in NE Spain is an historically important city built on recent alluvial deposits underlain by gypsum and other soluble rocks. Since its foundation by the Muslims in 716 A.D., the city development has been strongly influenced by geohazards including flooding, subsidence and slope movements. Most of the flooding problems have been mitigated by diversion of the local drainage. However, dissolution of the evaporite bedrock in the urban areas continually causes subsidence and triggers rock-falls from the gypsum cliffs overlooking the city. Subsidence is also caused by the hydrocollapse of gypsiferous silt in the alluvial fan deposits. Building damage in the city was surveyed using a classification scheme developed originally to record damage in British coal mining areas. The Calatayud damage survey shows that the worst building subsidence is concentrated along the line of a buried channel that runs underneath the gypsiferous silt alluvial fan. Natural subsurface drainage causes the dissolution and subsidence, which is aggravated by leakage from water and sewage pipes. Some building damage has been exacerbated during reconstruction by incomplete piling leaving buildings partially unsupported. Mitigation measures include the control of water leakage by the installation of flexible service pipes. Careful construction techniques are needed for both conservation and new developments, especially when piled and minipiled foundations are used. Geomorphological mapping is cost-effective in helping to locate and avoid the zones of subsidence for future development.     

Evaluation of water quality pollution indices for heavy metal contamination monitoring. A study case from Akpabuyo-Odukpani area, Lower Cross River Basin (southeastern Nigeria)

This article seeks to show the characteristics of homework in the traditional industrial sectors of clothing and footwear in Germany and Spain. We focus, first, on the national contexts in order to grasp how homework is embedded in the economic, political and social environment, and second, on the women's perspective regarding how homework is integrated into their everyday lives and vital expectatives. Finally, we compare the two different national and cultural contexts and draw some conclusions with which we would like to enrich further discussions on homework. The analysis is based mainly on in-depth interviews and participant observation. The study in Germany was carried out in urban and rural areas of Bavaria, and the Spanish study occurred in rural areas of Catalunya, Galicia, Andalusia, and Valencia. This revised version was published online in July 2006 with corrections to the Cover Date.     

苗儿山花岗岩体单元—超单元特征及其定位机制

根据苗儿山花岗岩体单元－超单元新理论将苗儿岩体划分为13个单元，归并为两个超单元，两个独立单元。不同单元、超单元的性质特征揭示了不同构造期古老岩石重熔的岩浆，沿北东向基底断裂上侵在隆起核部冷凝成岩的演化规律。雪峰期形成猫儿界单元线浅成相裂隙喷溢型火山岩；加里东期以NE向基底断裂的中心式扩展定位形成中深成相黄金超单元主体，自中心往外，岩体由新至老分布；印支－燕山期延续 了加里东期岩浆活动特征；因环状裂隙影响，印支期光旺岭单元侵入体总体呈NE向展布，且以加里东期岩浆侵位中心呈半环状排列；燕山期八角亭超单元3个NE向带，是岩浆呈岩墙式扩张定位的具体表现。     

Seismological and SAR signature of unrest at Nisyros caldera, Greece

Nisyros island, a Quaternary volcanic center located at the SE of the Aegean Volcanic Arc, has been in the past characterized by periods of intense seismic activity accompanied sometimes by hydrothermal explosions, the last one being in 1887. The recent long lasting episode of unrest (1995–1998) in the area is the first instrumentally documented providing information on the behavior of the volcano. Evidence from seismicity and SAR interferometry suggests that the presently active part of the Kos–Nisyros volcano-tectonic complex is located at the NW coast of Nisyros island defining an area much smaller than the whole volcano-tectonic area. Seismicity patterns vary both temporally and spatially consistently with different rates of vertical ground deformation inferred from SAR interferometry. These observations help us to discuss the different elements controlling the behavior of the volcanic system such as: the existence, location and timing of magma chamber inflation, the occurrence of tensile failure at the boundaries of the chamber and the possibility of magmatic fluids being expelled to form a shallow magmatic intrusion, the seismic failure and migration of hypocenters indicating shallow magma transport.