Market performance of agricultural commodities in semi-arid South Kordofan, Sudan

Research conducted by the Western Sudan Agricultural Research Project allows examination of the impact of the recent African drought upon agricultural market performance and structure. Price volatility, as well as high prices, was a major destabilizing factor in agricultural commodity markets. Small farmers and petty traders are largely risk avoiders rather than profit maximizers, and tend not to move product when faced with price uncertainty. At the same time, responsibility for marketing functions shifts to these small operators and producers. These are the channel members least able to finance increased functional responsibility. Again, the result is that products may be held off of the market. Policy makers must recognize these marketing factors when devising strategies appropriate to semi-arid regions such as South Kordofan. Policy recommendations can be offered which can facilitate the movement of product, and thus greatly ease the marketing constraints associated with drought.     

A multi-disciplinary framework for the study of private housing schemes: integrating anthropological,psychological and political levels of theory and analysis

This paper examines the theories and methods involved in the study of the impact of private governance on residents in two distinct kinds of middle class housing schemes: gated community residents in New York and Texas living in single family attached and detached houses, and cooperative apartment dwellers in New York City. The studies employed a range of methodologies drawing on the disciplines of anthropology, psychology and political science. An attempt was made to understand residents lived experiences through a number of disciplinary lenses: theories of community and culture; theories of rationalization and psychological resistance, and theories of moral minimalism and representation. Each of these disciplinary layers added to the analysis, while at the same time, creating epistemological disjunctures and concerns that had to be addressed by the research team on an ongoing basis. The paper concludes with an evaluation of the benefits of this approach in terms of the production of new knowledge about private governance, while offering cautionary comments about undertaking interdisciplinary projects of this nature.     

Assessment of Rock Slope Instability of the Proposed Galat Sufar Open Pit Mine,River Nile State,Sudan

Geotechnical and Geological Engineering - In this study, a proposed Galat Sufar open pit mine, river Nile state, Sudan has been approved through mining design processes. However, the area situated...     

高精度磁法在苏丹红海州佛地宛铁矿找矿中的应用

苏丹红海州的佛地宛铁矿产于元古代中性火山岩-次火山岩的断裂带中,属于裂隙充填型铁矿床.文章通过2.5维人机交互反演和磁化率三维反演模型等方法联合解释铁矿区铁矿体地表及其深部矿体特征,通过反演结果显示出铁矿体的赋存状态、规模大小和延展深度,使高精度要磁测工作获得较好的成果.     

Surface mineralogy of degraded agricultural lands affected by natural acid-saline seeps, southwestern Australia

Acid and saline seeps are an increasing problem in the most parts of the world and Australia as well. They are areas of bare soil or reduced crop production. Seasonal surface sampling through topo-sequence of the study area and analytical results of XRD, SEM and VNIR indicate that morphological and mineralogical changes within a natural acid saline seep affected landscape revealed that seasonal differences in surface mineralogy. These dynamic and seasonally influenced changes to surface and near surface mineralogy of an acid saline seep affected landform during the wet months, due to waterlogging, the sulfidization process dominates, while during the drier months, oxidative weathering of pyrite and iron hydrolysis results in precipitation of iron oxyhydroxides at and near the surface with the generation of acidity. During the dry season, the surface mineralogy of the natural seepage zone is dominated by salts （halite）, sulfates （gypsum and barite） and, importantly, iron oxyhydroxides gel precipitates and crusts （ferrihydrite, goethite, schwertmannite）. The study found the iron oxyhydroxide minerals present in the surface crusts and precipitates reflect acid conditions, as opposed to halite and gypsum that reflect only saline conditions. The visible near infra-red （VNIR） reflectance spectra of the surface minerals from unaffected, salt crusted and acid seep areas, showed spectral differences expressed in the VNIR region due to absorption bands of iron oxides and hydroxides. This difference in the surface mineralogy during summer months can be readily identified via multi-spectral and hyper-spectral remote sensing methods mainly during summer,     

Evolution of the Neoproterozoic Delgo suture zone and crustal growth in Northern Sudan: geochemical and radiogenic isotope constraints

In the Delgo basement area of northern Sudan, low to medium grade metamorphosed volcanic, sedimentary and plutonic rocks are surrounded by high grade gneisses. A NNE-SSW trending suture zone can be defined by the lithological, chemical and structural characteristics of several distinct units. The early Proterozoic gneiss terrain is overlain by metasedimentary units, the metamorphism of which has been dated by the Sm-Nd whole rock-mineral technique (702 ± 27 Ma in the west, 592 ± 16 Ma in the east). In the central part, the Abu Sari volcanic rocks show geochemical signatures of formation at an arc, with a protracted tholeiitic, calc-alkaline and shoshonitic evolution. The overlying El Hamri ophiolite contains chemical features of a back-arc tectonic environments. The ophiolite was dated by the Sm-Nd whole rock method on metagabbros at 752 ± 48 Ma. The further extension of this oceanic basin into the Jebel Rahib in the south-west was dated at 707 ± 54 Ma (Sm-Nd whole rock and minerals).Widespread suite of syn-tectonic granitoid intrusives displays subduction-related characteristics. They where emplaced between 650 to 760 Ma (Pb-zircon evaporation method). Their Nd and Sr isotopic compositions indicate a changing pattern of island arc to active continental margin character along an east-west transect and suggest a west to north-west dipping subduction zone. All units were juxtaposed at the minimum age of 600 Ma and rearranged during an extensional event, which was dated by the Rb-Sr thin slab technique (546 ± 19 Ma) on a migmatite. The Delgo suture provides evidence of a complex terrane pattern in north-east Africa and crustal growth during the Pan-African event by the addition of oceanic material to pre-existing continental crust.     

The transfer of agricultural technology and the development of small-scale farming in rural Africa: Case studies from Ghana, Sudan, Uganda, Zambia and South Africa

In many developing countries, research institutions or centres have been established to develop and/or adapt technologies that would help agricultural development. This is particularly true in Africa where national efforts have been supplemented with international research institutes. Although some modest progress has been achieved in improving agricultural technology, on the whole, the improvement record is not quite encouraging among the small-scale farmers. In many areas, either there are no improved technologies, or where they exist, are unacceptable by farmers. However, where useful technologies exist, their spread has been very limited and where they have been adapted, the benefits only accrue to a small segment of the community. The logical question posed is: why and how do we find ourselves in the current situation? This paper considers the view that to understand fully why the available technologies have remained largely at the research centres, there is need to examine the whole process of research, development, dissemination and utilization of agricultural technology. It is significant to investigate the structural constraints and prospects under which those involved in the process work, their motivations and the interactions between different groups. The traditional ‘top-down’ of development strategy should be supplemented with farmers' indigenous knowledge, and programmes encouraging transfer of agricultural technology should include institutional support. Only by the identification of farmers' environmental and resource utilisation, preferences, socio-economic circumstances and constraints can a development programme of optimum meaning to farmers be devised and implemented with success.     

Groundwater recharge in natural dune systems and agricultural ecosystems in the Thar Desert region, Rajasthan, India

Water and nutrient availability for crop production are critical issues in (semi)arid regions. Unsaturated-zone Cl tracer data and nutrient (NO₃ and PO₄) concentrations were used to quantify recharge rates using the Cl mass balance approach and nutrient availability in the Thar Desert, Rajasthan, India. Soil cores were collected in dune/interdune settings in the arid Thar Desert (near Jaisalmer) and in rain-fed (nonirrigated) and irrigated cropland in the semiarid desert margin (near Jaipur). Recharge rates were also simulated using unsaturated zone modeling. Recharge rates in sparsely vegetated dune/interdune settings in the Jaisalmer study area are 2.7–5.6 mm/year (2–3% of precipitation, 165 mm/year). In contrast, recharge rates in rain-fed agriculture in the Jaipur study area are 61–94 mm/year (10–16% of precipitation, 600 mm/year). Minimum recharge rates under current freshwater irrigated sites are 50–120 mm/year (8–20% of precipitation). Nitrate concentrations are low at most sites. Similarity in recharge rates based on SO₄ with those based on Cl is attributed to a meteoric origin of SO₄ and generally conservative chemical behavior in these sandy soils. Modeling results increased confidence in tracer-based recharge estimates. Recharge rates under rain-fed agriculture indicate that irrigation of 20–40% of cultivated land with 300 mm/year should be sustainable.     

Climatic changes,desertification and the Republic of Sudan

Meteorological data for a period of 30 to 50 years was analysed to ascertain the climatic changes in the Republic of Sudan. The study confirms that the temperatures are rising and rainfall declining. Rigorous analysis of relative humidity, clouds, rediation and evaporation also confirms the changing pattern, a trend which may accelerate environmental degradation and desertification in Sudan.The author acknowledges the assistance of Nadir Ahmad El-Agib in completing this study. He is also thankful to Dr. Ahmad El-Agib for his help in getting the Meteorological data from Sudan.     

Diffusion of agricultural innovations among traditional farmers of Western Sudan — The case of East Kordofan and El Fasher districts

The innovative behaviour of traditional farmers in a marginal tropical environment is discussed. It is found that personal economic and proper channels of information are important. It is also found that the innovation which does not deviate drastically from the established systems of farming and ways of life will be easily accepted if suitably presented.     

Age constraints on felsic intrusions, metamorphism and gold mineralisation in the Palaeoproterozoic Rio Itapicuru greenstone belt, NE Bahia State, Brazil

U–Pb sensitive high resolution ion microprobe mass spectrometer (SHRIMP) ages of zircon, monazite and xenotime crystals from felsic intrusive rocks from the Rio Itapicuru greenstone belt show two development stages between 2,152 and 2,130 Ma, and between 2,130 and 2,080 Ma. The older intrusions yielded ages of 2,152±6 Ma in monazite crystals and 2,155±9 Ma in zircon crystals derived from the Trilhado granodiorite, and ages of 2,130±7 Ma and 2,128±8 Ma in zircon crystals derived from the Teofilândia tonalite. The emplacement age of the syntectonic Ambrósio dome as indicated by a 2,080±2-Ma xenotime age for a granite dyke probably marks the end of the felsic magmatism. This age shows good agreement with the Ar–Ar plateau age of 2,080±5 Ma obtained in hornblendes from an amphibolite and with a U–Pb SHRIMP age of 2,076±10 Ma in detrital zircon crystals from a quartzite, interpreted as the age of the peak of the metamorphism. The predominance of inherited zircons in the syntectonic Ambrósio dome suggests that the basement of the supracrustal rocks was composed of Archaean continental crust with components of 2,937±16, 3,111±13 and 3,162±13 Ma. Ar–Ar plateau ages of 2,050±4 Ma and 2,054±2 Ma on hydrothermal muscovite samples from the Fazenda Brasileiro gold deposit are interpreted as minimum ages for gold mineralisation and close to the true age of gold deposition. The Ar–Ar data indicate that the mineralisation must have occurred less than 30 million years after the peak of the metamorphism, or episodically between 2,080 Ma and 2,050 Ma, during uplift and exhumation of the orogen.Electronic supplementary material Supplementary material is available for this article at     

银额盆地哈日凹陷Y井天然气产层时代厘定及其意义

银额盆地哈日凹陷Y井钻遇多层天然气显示层,并对井深2946.0~2951.0m井段射孔压裂,获天然气9.15×104m3/d(无阻流量)。对浅层天然气显示层确定为白垩系银根组无异议,但获得工业气流的产层时代归属尚存争议。通过镜质体反射率(Ro)随深度的变化规律的研究,以及利用钻井岩心实验分析获得泥岩地球化学特征对沉积物源区沉积环境的判别,约束了二叠系与白垩系巴音戈壁组的不整合界面位于第9次取心(岩心底深2593.80m)与第10次取心(岩心顶深2909.60m)之间;地球物理测井自然伽马、电阻率等曲线在2792.0m出现突变,确定二叠系与白垩系巴音戈壁组的不整合界面为2792.0m。明确了Y井天然气产层为二叠系,指示了二叠系良好的油气资源前景,区内今后油气勘探应以二叠系为主要目的层。     

Geological and geotechnical constraints for urban planning and natural environment protection: a case study from Mekelle City, Northern Ethiopia

The study was conducted in the rapidly expanding city of Mekelle located in the northern part of Ethiopia, East Africa. An integrated approach including geomorphological, geological and engineering geological, geotechnical and hydrogeological methods were used to characterize the natural urban environment to be used as a baseline for protection and rational planning of development. Conventional field observation, test pits and drilled boreholes were used to collect soil, rock and water samples and standard laboratory procedures were applied. The results revealed that the main geologic constraints to sustainable development of the city are active erosion, instability of slopes, flood hazard, cyclic/alternating hard and weak rock layers, high swelling–shrinkage soils, shallow and unconfined groundwater with variable composition and high susceptibility to corrosion and pollution. It is recommended to avoid development and expansion of the city in areas of steep land forms, at the foot of steep slopes and in areas covered by black alluvial soil deposits. Development of a systematic multidisciplinary database aided by GIS, with continuous monitoring and updating is also highly recommended and will be useful for further refined geotechnical microzonation. It is the authors’ belief that this study highlights the basic constraints and hazards the city is facing, and provides baseline information and awareness to the city planners, decision makers, geo-environmentalists, engineers and the community for future expansion and rehabilitation plans and to tackle the existing hazards.     

苏丹北部红海州16区块地质特征及找矿方法探讨

16区块位于苏丹北部红海州,区内已发现金矿点11处,铜矿点6处,优选出了4个成矿远景区,评价了小型金矿床1处。该文介绍了16区的成矿地质条件、矿化特征及矿化类型,以已评价的小型金矿床为例讨论了该区金矿成矿作用及控矿因素,指出该区具备良好的金铜矿成矿远景。针对该区实际情况提出遥感解译配合化探测量、物探测量是选勘查靶区的有效方法,地表槽探揭露配合中深部钻探控制是必要的勘查手段。     

Hydrochemical and isotopic behaviour of a Saharan phreatic aquifer suffering severe natural and anthropic constraints (case of Oued-Souf region, Algeria)

An approach combining the use of water dissolved chemical species and isotopic fingerprints has been used to understand the behavior of a phreatic aquifer and to determine the origin of its different water components. This aquifer is located in the large sedimentary basin of the Great Oriental Erg (Algeria) and overlies two deeper aquifers: the Complexe Terminal (CT) and the Continental Intercalaire (CI). Besides the deterioration of its groundwater quality, its water table has risen during the last 20 years. A water budget surplus between 950 and 2500 l s^?1 was estimated. Down-gradient groundwater evolution (south-north) has shown that the mineralisation increases from 1.23 to 5.20 g l^?1 due to evaporite minerals dissolution. Chemical and isotopic data demonstrated that in addition to rainfall there is a contribution from the CT and CI aquifers. The latter are tritium-free and less mineralized than the phreatic aquifer. Their radiocarbon contents are very low (<10 pmC, percent modern Carbon) (Pleistocene recharge) whereas quite the contrary is observed for the superficial aquifer which exhibits fairly high and variable C-14 activities (50–100 pmC), evidence of recent recharge. On the basis of tritium contents, two groundwater groups were identified for the phreatic aquifer.     

Structure,petrology and geochemistry of the Abu Dom alkaline ring-complex,Bayuda Desert,Sudan

The Abu Dom complex is one of a cluster of Younger Granite ring-complexes piercing the Proterozoic gneisses of the Bayuda Desert of Sudan. Intrusive rocks predominate and range from early metaluminous syenites to later peralkaline syenites and granites. They are disposed as ring-dykes, nested intrusions, and cone-sheet swarms. Field evidence and geochemical variation indicate that the peralkaline rocks evolved from a metaluminous syenitic parent magma as a result of high-level fractionation. The suite carries a clear within-plate signature exemplified by marked enrichments in HFS elements such as Zr and Nb.     

Geochemistry of natural chromium occurrence in a sandstone aquifer in Bauru Basin, São Paulo State, Brazil

Anomalous concentrations of Cr(VI) occur in groundwaters of the Adamantina Aquifer, in a large region in the western state of São Paulo, sometimes exceeding the potability limit (0.05 mg L⁻¹). To identify the possible geochemical reactions responsible for the occurrence of Cr in groundwater in Urânia, borehole rock samples were collected in order to carry out mineralogical and chemical analyses. In addition, multilevel monitoring wells were installed and groundwater samples were analyzed. Analyses of the borehole rock samples show the occurrence of a geochemical anomaly of Cr in the quartzose sandstones (average concentrations of 221 ppm). Chrome-diopside is one of the main minerals contributing to this anomaly, having an average Cr content of 1505 ppm. Sequential extraction experiments indicated weakly adsorbed Cr in the order of 0.54 ppm, and this quantity is enough to provide the Cr concentrations observed in groundwater. Groundwaters from the monitoring wells proved to be stratified, with the highest concentrations of Cr(VI) (0.13 mg L⁻¹) being associated with high redox and pH values (over 10) and high concentrations of Na. Geochemical reactions that may explain the release of Cr from the solid phase to groundwater involve the release of Cr(III) from minerals (like chrome-diopside and Cr-Fe hydroxide), followed by oxidation of Cr(III) to Cr(VI), probably related to the reduction of Mn oxides present in the aquifer. Then cation exchange occurs and dissolution of carbonates which increases the pH of groundwater, resulting in the desorption and mobilization of Cr(VI) into groundwater.     

Origin of natural sulfur-metal chimney in the Tangyin hydrothermal field,Okinawa Trough: constraints from rare earth element and sulfur isotopic compositions

For the first time, we present the rare earth element (REE) and sulfur isotopic composition of hydrothermal precipitates recovered from the Tangyin hydrothermal field (THF), Okinawa Trough at a water depth of 1206 m. The natural sulfur samples exhibit the lowest ΣREE concentrations (ΣREE= 0.65×10^–6–4.580×10^–6) followed by metal sulfides (ΣREE=1.71×10^–6–11.63×10^–6). By contrast, the natural sulfur-sediment samples have maximum ΣREE concentrations (ΣREE=11.54×10^–6–33.06×10^–6), significantly lower than those of the volcanic and sediment samples. Nevertheless, the δEu, δCe, (La/Yb)_N, La/Sm, (Gd/Yb)_N and normalized patterns of the natural sulfur and metal sulfide show the most similarity to the sediment. Most hydrothermal precipitate samples are characterized by enrichments of LREE (LREE/HREE=10.09–24.53) and slightly negative Eu anomalies or no anomaly (δEu=0.48–0.99), which are different from the hydrothermal fluid from sediment-free mid-oceanic ridges and back-arc basins, but identical to the sulfides from the Jade hydrothermal field. The lower temperature and more oxidizing conditions produced by the mixing between seawater and hydrothermal fluids further attenuate the leaching ability of hydrothermal fluid, inducing lower REE concentrations for natural sulfur compared with metal sulfide; meanwhile, the negative Eu anomaly is also weakened or almost absent. The sulfur isotopic compositions of the natural sulfur (δ³⁴S=3.20‰–5.01‰, mean 4.23‰) and metal sulfide samples (δ³⁴S=0.82‰–0.89‰, mean 0.85‰) reveal that the sulfur of the chimney is sourced from magmatic degassing.