Gold mining in Ghana's forest reserves: a report on the current debate     

Gavin Hilson  Frank Nyame 《Area》2006,38(2):175-185

This paper examines the debate surrounding a recent decision made by the Ghanaian government to permit gold exploration – and potentially, mining – in 'protected' forest reserves. In 2001, four mining companies were awarded mineral exploration concessions in forested regions of the country, and have since put forward applications to mine for gold. Notwithstanding the sharp divide in opinion on the issue, the continued uncertainty surrounding the implications of the proposed activities makes further research on the ground imperative in the short term. Work aiming to elicit indigenous perspectives on the projects, as well as research that facilitates dialogue between and/or among stakeholder parties, should be prioritized.  相似文献   

Basin-related effects on ground motion for earthquake scenarios in the Lower Rhine Embayment   总被引：1，自引：0，他引：1  

Michael Ewald  Heiner Igel  Klaus-Günter Hinzen  Frank Scherbaum 《Geophysical Journal International》2006,166(1):197-212

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Quantitative determination of stress by inversion of speckle interferometer fringe patterns: experimental laboratory tests     

Douglas R. Schmitt  Mamadou S. Diallo  Frank Weichman 《Geophysical Journal International》2006,167(3):1425-1438

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Inversion for rheological parameters from post-seismic surface deformation associated with the 1960 Valdivia earthquake, Chile   总被引：3，自引：0，他引：3  

Francisco Lorenzo-Martín  Frank Roth  Rongjiang Wang 《Geophysical Journal International》2006,164(1):75-87

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Jurassic strike slip versus subduction in the Eastern Alps     

Wolfgang Frank  Wolfgang Schlager 《International Journal of Earth Sciences》2006,95(3):431-450

Late Jurassic formations of the Northern Calcareous Alps (NCA) contain ample evidence of synsedimentary tectonics in the form of elongate basins filled with turbidites, debris flows and slumps. Clasts are derived from the Mesozoic of the NCA; they commonly measure tens of metres in diameter and occasionally form kilometre-size bodies. These sedimentologic observations and the presumed evidence of Late Jurassic high-pressure metamorphism recently led to the hypothesis of a south-dipping Jurassic subduction zone with accretionary wedge in the southern parts of the NCA. We present new ⁴⁰Ar/³⁹Ar dates from the location of the postulated high-pressure metamorphism that bracket the age of this crystallization not earlier than 114–120 Ma. The event is therefore part of the well-documented mid-Cretaceous metamorphism of the Austro-alpine domain. Thus, there is currently no evidence of Late Jurassic high-pressure metamorphism to support the subduction hypothesis. The sediment record of the Late Jurassic deformation in the NCA, including the formation of local thrust sheets, is no conclusive evidence for subduction. All these phenomena are perfectly compatible with synsedimentary strike-slip tectonics. Large strike-slip fault zones with restraining and releasing bends and associated flower structures and pull-apart basins are a perfectly viable alternative to the subduction model for the Late Jurassic history of the NCA. However, in contrast to the Eastern Alps transect, where arguments for a Jurassic subduction are missing, a glaucophane bearing Jurassic high-pressure metamorphism in the Meliatic realm of the West Carpathians is well documented. There, the high-pressure/low-temperature slices occur between the Gemeric unit and the Silica nappe system (including the Aggtelek-Rudabanya units), which corresponds in facies with the Juvavic units in the southern part of the NCA. To solve the contrasting palaeogeographic reconstructions we propose that the upper Jurassic left lateral strike-slip system proposed here for the Eastern Alps continued eastwards and caused the eastward displacement of the Silica units into the Meliatic accretionary wedge.  相似文献   

Early Cretaceous U–Pb zircon ages for the Copiapó plutonic complex and implications for the IOCG mineralization at Candelaria, Atacama Region, Chile     

Robert Marschik  Frank Söllner 《Mineralium Deposita》2006,41(8):785-801

Four of the major plutons in the vicinity of the Candelaria mine (470 Mt at 0.95% Cu, 0.22 g/t Au, 3.1 g/t Ag) and a dike–sill system exposed in the Candelaria open pit have been dated with the U–Pb zircon method. The new geochronological data indicate that dacite magmatism around 123 Ma preceded the crystallization of hornblende diorite (Khd) at 118 ± 1 Ma, quartz–monzonite porphyry (Kqm) at 116.3 ± 0.4 Ma, monzodiorite (Kmd) at 115.5 ± 0.4 Ma, and tonalite (Kt) at 110.7 ± 0.4 Ma. The new ages of the plutons are consistent with field relationships regarding the relative timing of emplacement. Plutonism temporally overlaps with the iron oxide Cu–Au mineralization (Re–Os molybdenite ages at ∼115 Ma) and silicate alteration (ages mainly from 114 to 116 and 110 to 112 Ma) in the Candelaria–Punta del Cobre district. The dated dacite porphyry and hornblende diorite intrusions preceded the ore formation. A genetic link of the metallic mineralization with the quartz–monzonite porphyry and/or the monzodiorite is likely. Both of these metaluminous, shoshonitic (high-K) intrusions could have provided energy and contributed fluids, metals, and sulfur to the hydrothermal system that caused the iron oxide Cu–Au mineralization. The age of the tonalite at 110.7 Ma falls in the same range as the late alteration at 110 to 112 Ma. Tonalite emplacement may have sustained existing or driven newly developed hydrothermal cells that caused this late alteration or modified ⁴⁰Ar/³⁹Ar and K/Ar systematic in some areas.  相似文献   

The Earthquake Readiness Scale: The Development of a Valid and Reliable Unifactorial Measure     

Matthew J. Spittal  Frank H. Walkey  John McClure  Richard J. Siegert  Kimberley E. Ballantyne 《Natural Hazards》2006,39(1):15-29

Preparedness is a key dependent variable in many studies examining people’s response to disasters such as earthquakes. A feature of many studies on this issue, however, is the lack of attention given to psychometric issues when constructing measures of preparedness. With regard to earthquake preparation, for example, many studies could be greatly improved by the use of a valid and reliable measure of preparedness. This research developed such a measure that assessed both low-level preparedness, such as having an emergency kit, and high-level preparedness, such as altering home structures to mitigate damage. Studies of Wellington (New Zealand) residents using two samples totalling n=652 showed that 23 items measuring these different aspects of earthquake preparation could be combined into a reliable, valid, unifactorial scale. This brief scale should have utility in multivariate studies of earthquake preparation, either as a dependent variable, where preparation is the outcome variable of primary interest, or as one of several independent variables, where preparation and other measures predict another outcome variable.  相似文献   

Zr-in-rutile thermometry in blueschists from Sifnos, Greece   总被引：1，自引：0，他引：1  

Frank S. Spear  David A. Wark  John T. Cheney  John C. Schumacher  E. Bruce Watson 《Contributions to Mineralogy and Petrology》2006,152(3):375-385

Zr-in-rutile thermometry on samples of blueschist from Sifnos, Greece, yields temperatures that reflect progressive crystallization of rutile from ca. 445 to 505°C with an analytical precision of + 18/−27 and ± 10°C using the electron microprobe and ± 1.5–3.5°C using the ion microprobe. Individual grains are generally homogeneous within analytical uncertainty. Different grains within a single sample record temperature differences as large 55°, although in most samples the range of temperatures is on the order of 25°. In several samples, Zr-in-rutile temperatures from grains within garnet are lower than temperatures from matrix grains, reflecting growth of rutile with increasing temperature of metamorphism. Although the specific rutile-producing reactions have not been identified, it is inferred that rutile grows from either continuous reaction involving the breakdown of lower grade phases (possibly ilmenite), or from pseudomorph reactions involving the breakdown of relic igneous precursors at blueschist-facies conditions. No systematic variation in rutile temperatures was observed across the blueschist belt of northern Sifnos, consistent with the belt having behaved as a coherent block during subduction.  相似文献   

The fall and rise of metropolitan government in Copenhagen     

Hans Thor Andersen  Frank Hansen  John Jørgensen 《GeoJournal》2002,58(1):43-52

In this paper it is argued that the re-establishment of a metropolitan government in the Greater Copenhagen Area in 2000 (Greater Copenhagen Authority) is not to be seen as a return to the kind of regional, coordinative authority (Greater Copenhagen Council) that was abolished in the Thatcherite climate of the 1980s. Throughout the 1980s and 1990s new forms of urban governance, entrepreneurialism and a higher national priority to the capital region were introduced, which changed the conditions under which the new metropolitan government is operating. This `contextualization' of the analysis of the two generations of metropolitan government points to the fact that typologies of metropolitan government, such as the one put forward by Sharpe (1995), often lacks analytical cogency. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Elemental and isotopic fractionation of Type B calcium-, aluminum-rich inclusions: experiments, theoretical considerations, and constraints on their thermal evolution     

Frank M. Richter  Andrew M. Davis  Denton S. EbelAkihiko Hashimoto 《Geochimica et cosmochimica acta》2002,66(3):521-540

Experiments exposing Type B calcium-, aluminum-rich inclusion (CAI)-like melts at high temperatures to high vacuum or reducing hydrogen-rich gas mixtures were used to determine the rates and consequences of elemental and isotopic fractionation by evaporation. Silicon and magnesium were found to evaporate much faster than calcium and aluminum, and the resulting residual liquid trajectories in composition space are reproduced via a thermodynamic model for the saturation vapor pressure of the evaporating species. Isotopic fractionations associated with evaporation were measured for magnesium. The resulting relationship between fraction of magnesium lost and enrichment of the residue in the heavy isotopes of magnesium follows a Rayleigh fractionation curve with a fractionation factor that is close to, but not exactly, the theoretically expected value. The rate of evaporation is found to be a strong function of temperature, oxygen fugacity, and melt composition, which can be understood and modeled in terms of the dependence of the saturation vapor pressures on these variables. The relationship between evaporation rate, which we measure, and calculated saturation vapor involves empirical evaporation coefficients that we find to be significantly less than one (∼0.1). Analytical and numerical models are used to characterize how diffusion in both the melt and in the surrounding gas affects evaporation rates and the degree of chemical and isotopic fractionation. The experimental data and theoretical considerations are combined to give a parameterization of the rates and consequences of evaporation of Type B CAI-like liquids, which is then used to translate the measured isotopic fractionation of Type B CAIs into constraints on their thermal history. Cooling rates of the order of 10°C per hour are indicated.  相似文献