The Kharapeh orogenic gold deposit: geological,structural, and geochemical controls on epizonal ore formation in West Azerbaijan Province,Northwestern Iran

The Kharapeh gold deposit is located along the northwestern margin of the Sanandaj–Sirjan Zone (SSZ) in the West Azerbaijan province, Iran. It is an epizonal orogenic gold deposit formed within the deformed zone between central Iran and the Arabian plate during the Cretaceous–Tertiary Zagros orogeny. The deposit area is underlain by Cretaceous schist and marble, as well as altered andesite and dacite dikes. Structural analysis indicates that the rocks underwent tight to isoclinal recumbent folding and were subsequently co-axially refolded to upright open folds during a second deformation. Late- to post-tectonic Cenozoic granites and granodiorites occur northeast of the deposit area. Mineralization mainly is recognized within NW-trending extensional structures as veins and breccia zones. Normal faults, intermediate dikes, and quartz veins, oriented subparallel to the axial surface of the Kharapeh antiform, indicate synchronous extension perpendicular to the fold axis during the second folding event. The gold-bearing quartz veins are >1 km in length and average about 6 m in width; breccia zones are 10–50 m in length and ≤1 m in width. Hydrothermal alteration mainly consists of silicification, sulfidation, chloritization, sericitization, and carbonatization. Paragenetic relationships indicate three distinct stages—replacement and silicification, brecciation and fracture filling, and cataclastic brecciation—with the latter two being gold-rich. Fluid inclusion data suggest mineral deposition at temperatures of at least 220–255°C and depths of at least 1.4–1.8 km, from a H₂O–CO₂±CH₄ fluid of relatively high salinity (12–14 wt.% NaCl equiv.), which may reflect metamorphism of passive margin carbonate sequences. Ore fluid δ¹⁸O values between about 7‰ and 9‰ suggest no significant meteoric water input, despite gold deposition in a relatively shallow epizonal environment. Similarities to other deposits in the SSZ suggest that the deposit formed as part of a diachronous gold event during the middle to late Tertiary throughout the SSZ and during the final stages of the Zagros orogeny. The proximity of Kharapeh to the main tectonic suture of the orogen, well-developed regional fold systems with superimposed complex fracture geometries, and recognition of nearby volcanogenic massive sulfide systems that suggest a region characterized by sulfur- and metal-rich crustal rocks, collectively indicate an area of the SSZ with high favorability for undiscovered gold resources.     

Evidence of 1.7- to 1.8-Ga Collisional Arc in the Kaoko Belt, NW Namibia

Detailed structural and isotopic analyses in the Hoanib and Ugab River Valleys indicate the existence of an exotic 1.7- to 1.8-Ga terrane in the Pan-African Kaoko Belt. This crustal block, called as Mudorib Complex, is imbricated between autochthonous and para-autochthonous rocks of Congo Craton, Kaoko Basin, and Western Kaoko Batholith units during the main tectono-thermal phase of Kaoko Belt collision around 580?Ma, involving the Rio de La Plata, Congo and Kahalari paleoplates. This terrain is positioned between the 1.9-Ga Pruwes Complex units of SW edge of the Congo Craton and the 0.58- to 0.55-Ga Amspoort Suite granitoids of the Western Kaoko Batholith. It is coincident with a regional positive aeromagnetic anomaly trending from NNW in the Ugab region to the Namibia-Angola border. Internally, Mudorib Complex consists in 1.73- to 1.81-Ga tonalitic?Ctrondhjemitic?Cdioritic?Cgranodioritic sequence of gneisses associated with cogenetic gabbroic and anothositic-gneisses in the core zone of this Pan-African structure. Field relationship and U?CPb zircon and Sm?CNd whole-rock isotope data combined with geochemical information suggest the existence of two rock associations in the Mudorib Complex, namely late Paleoproterozoic tonalitic?Ctrondhjemitic?Cdioritic-gneisses with island-arc affinity and tholeiitic metabasites of juvenile origin, showing Nd model age of 1.73?C2.17?Ga and ??Nd(t) of ?2.05?C+4.3. This 1.8- to 1.7-Ga complex is also intruded by granitic dykes formed at 1.49?C1.50?Ga with Nd model age of 1.75?C2.34?Ga during stable tectonic conditions. In addition to widespread Pan-African tectono-metamorphic events, a secondary metamorphic event of ~1.3?Ga is also recognized in the Mudorib rocks, which may be associated with accretion process of the complex to the Paleoproterozoic to Archean nucleus of the Kaoko Belt in the Hoanib River Valley.     

Fragmented subfossil <Emphasis Type="Italic">Chaoborus</Emphasis> mandibles reveal periods of cyprinid presence in lake histories

Cyprinid fish have pharyngeal teeth that mash ingested food. Here we show that roach (Rutilus rutilus L.), a common cyprinid in Swedish boreal lakes, often break the mandibles of ingested Chaoborus larvae into smaller fragments. The presence/absence of roach in historic fish communities could therefore possibly be determined from the proportion of fragmented Chaoborus mandibles in lake sediments, which we assessed using the following three approaches. (1) Roach that were fed Chaoborus larvae in laboratory aquaria evacuated a significantly higher fraction of fragmented prey mandibles than perch (Perca fluviatilis L.). (2) Surface sediments from lakes in an acidified region in southwestern Sweden showed significantly higher proportions of fragmented mandibles for lakes containing roach compared to lakes devoid of cyprinid fish. (3) A paleo-study in Lake Lysevatten, into which roach were introduced in the 1880s and were extirpated in the 1960s, showed significantly higher proportions of fragmented mandibles in sediment layers from the roach period. We conclude that mandible fragmentation was related to roach presence, and propose that the proportion of fragmented Chaoborus mandibles in lake sediments may provide important information when historical cyprinid alterations are of interest, as in paleo-studies on acidification, eutrophication, or fish introductions.     

The development of the Space Environment Viability of Organics (SEVO) experiment aboard the Organism/Organic Exposure to Orbital Stresses (O/OREOS) satellite

The Space Environment Viability of Organics (SEVO) experiment is one of two scientific payloads aboard the triple-cube satellite Organism/ORganic Exposure to Orbital Stresses (O/OREOS). O/OREOS is the first technology demonstration mission of the NASA Astrobiology Small Payloads Program. The 1-kg, 1000-cm³ SEVO cube is investigating the chemical evolution of organic materials in interstellar space and planetary environments by exposing organic molecules under controlled conditions directly to the low-Earth orbit (LEO) particle and electromagnetic radiation environment. O/OREOS was launched on November 19, 2010 into a 650-km, 72°-inclination orbit and has a nominal operational lifetime of six months. Four classes of organic compounds, namely an amino acid, a quinone, a polycyclic aromatic hydrocarbon (PAH), and a metallo-porphyrin are being studied. Initial reaction conditions were established by hermetically sealing the thin-film organic samples in self-contained micro-environments. Chemical changes in the samples caused by direct exposure to LEO radiation and by interactions with the irradiated microenvironments are monitored in situ by ultraviolet/visible/near-infrared (UV/VIS/NIR) absorption spectroscopy using a novel compact fixed-grating CCD spectrometer with the Sun as its light source. The goals of the O/OREOS mission include: (1) demonstrating key small satellite technologies that can enable future low-cost astrobiology experiments, (2) deploying a miniature UV/VIS/NIR spectrometer suitable for in-situ astrobiology and other scientific investigations, (3) testing the capability to establish a variety of experimental reaction conditions to enable the study of astrobiological processes on small satellites, and (4) measuring the chemical evolution of organic molecules in LEO under conditions that can be extrapolated to interstellar and planetary environments. In this paper, the science and technology development of the SEVO instrument payload and its measurements are described.     

The nature and provenance of Golestan loess deposits in northeast Iran

Mineralogical, textural, geochemical, and weathering characteristics of loess deposits in Golestan province of Iran suggest that they are mostly derived from felsic igneous rocks and are related to Quaternary palaeoclimate. Whole‐rock analyses indicate heavy minerals such as zircon, tourmaline and phyllosillicate minerals (e.g. muscovite, chlorite, illite) exert a significant control on the chemical composition. The loess samples display uniform chemical composition, indicative of similar alteration history. Chemical index of alteration suggests a weak to moderate degree of weathering in a felsic source area. Scanning electron micrographs of quartz grains reveal abundant silt‐sized quartz particles, a result of glacial grinding during the Late Pleistocene in Central Asia. Subsequently, these silt particles were transported from Central Asia to their depositional site by wind and paraglacial processes. Local topography of northeast Iran (Alborz Mountains) acted as a major barrier, entrapping the airborne particles on the plains of Golestan province. Copyright © 2012 John Wiley & Sons, Ltd.     

Qualitative and Quantitative Characterization of Mangrove Vegetation Structure and Dynamics in a Peri-urban Setting of Douala (Cameroon): An Approach Using Air-Borne Imagery

Qualitative and quantitative characterization of mangrove vegetation structure and dynamics is required for assessment of coastal habitat vulnerability. Changes in mangrove forests around Douala, Cameroon, have been documented using aerial photography between 1974 and 2009. The distribution pattern of tree species was also assessed in 2009 following the point-centered quarter method (PCQM+) protocol. Pristine mangroves observed in 1974 had been disturbed markedly in 2003 and 2009. Some of the pre-existing mangroves were entirely replaced by settlements, road, and crops (maize, bean, banana, oil palm, green vegetables, and sugar cane plantations). From 1974 to 2003, 39.86 % of mangrove forests have disappeared; the net loss of 22.10 % occurred between 2003 and 2009 alone. Mangrove forest area had decreased 53.16 % around Douala over a 35-year period from 1974 to 2009 concurrent with a substantial increase of settlements (60 %), roads (233.33 %), agriculture areas (16 %), non-mangrove areas (193.33 %), and open water (152.94 %). Field survey showed that almost one third of the quadrants in the remaining mangrove forest were empty. The disrupted mangrove forest has an overall mean height, absolute density, and basal area of 19.80 m, 158 trees ha^?1, and 110.44 m² ha^?1, respectively. In comparison with scientific literature on mangrove degradation, this puts the mangroves around Douala at the top of the “peri-urban mangrove degradation” list. In addition, beyond listing of mangrove plants on the Red List of Threatened Species which will seldom lead to widely distributed species being listed, we call for the creation of a Red List of Locally Threatened Ecosystems, which in contrast is likely to list mangroves as an ecosystem under critical risk of (local) extinction in many countries around the globe, in particular, peri-urban sites.     

Hydrogeochemical processes affecting groundwater in an irrigated land in Central Tunisia

Detailed hydrogeochemical investigation has provided new information concerning the major factors and mechanisms controlling the groundwater chemistry of Chougafiya basin. The hydrogeochemical characteristics of groundwaters comprise three main types: Cl–SO₄–Ca, Cl–SO₄–Na and Cl–Na. Hydrochemical characteristics based on the bivariate diagrams of major (Cl^?, SO₄ ^2?, NO₃ ^?, HCO₃ ^?, Na⁺, Mg²⁺, K⁺ and Ca²⁺) and some trace (Br^? and Sr²⁺) ions, mineral saturation indices and hierarchical cluster analysis indicate different origins of groundwater mineralization. The water–rock interaction (dissolution of evaporitic minerals), followed by cation exchange reactions with clay minerals, constitute the main processes that control groundwater salinization. However, the chemical composition of brackish groundwater in the central and southern parts of the study area is influenced by a mixing process with Sabkhas salt groundwater. The mixing proportions inferred from chloride mass balance prove that the contribution of Sabkhas groundwater to Quaternary aquifer ranges between 2.7 and 9.1 %. These intrusion rates reflect the progress of the saltwater–freshwater interface, which is mainly controlled by the piezometric level variation and the distance to the Sabkhas.     

Geotechnical assessment of ground conditions around a tilted building in Cairo, Egypt using geophysical approaches

The flood plain of the Nile River has been a safe dwelling throughout history. Recently with a growing population and vast growing urbanization, some buildings have started to experience structural damages, which are not related to their construction design, but rather to the ground conditions around the buildings' foundations. Variations in properties of the soil supporting the buildings' foundations such as soil-bearing capacity, moisture content, and scouring may eventually lead to the failure of these buildings. This study is attempting to characterize the variations in the soil properties around the City Star shopping mall, in eastern Cairo, where a large building has tilted over the past few years. This tilting may lead to the collapse of the whole building if it continues at the same rate. An integrated geophysical investigation including multi-channel analysis of surface wave (MASW), ground-penetrating radar (GPR), and 2-D electrical resistivity tomography (ERT) was used around the affected building to help detect possible causes of deterioration. The GPR data showed a soil-filled layer overlaying a thick bottom layer of higher moisture content. The MASW data revealed a middle layer of relatively low shear wave velocity sandwiched between two relatively high shear wave velocity layers. The ERT data showed an upper low resistivity layer overlying a high resistivity layer. Integrating the interpretations of the three geophysical methods provides a combined model that reflects lateral and vertical variation in the soil properties. This variation becomes dramatic near the tilted corner of the building.     

Chlorophyll concentration and surface temperature changes associated with earthquakes

The preparation process of an impending earthquake may leave fingerprints on the earth??s surface. Elastic strain in rocks, formation of micro-cracks, gas releases and other chemical or physical activities in the earth??s crust before and during earthquakes has been reported to cause rises in temperature, surface latent heat flux (SLHF), upwelling index and chlorophyll-a (Chl-a) concentration on the ground or sea surface. Changes in surface temperature can be monitored with thermal infrared sensors such as NOAA-AVHRR and microwave radiometers like AMSR-E/Aqua. SLHF data and upwelling indices are provided by National Centers for Environmental Prediction (NCEP) Reanalysis Project and Pacific Fisheries Environmental Laboratory, respectively. This study examines behaviors of the above four factors prior to the past three oceanic and coastal earthquakes occurred at the Pacific Ocean (Northern California of June 15, 2005, Central California of September 28, 2004, and December 22, 2003). We were successful in detecting pre-earthquake anomalies prior to all three earthquakes. Our detailed analysis revealed 1?C5?°C rises in surface temperature in epicentral areas. Considerable anomalies in Chl-a concentration, 1?C2?weeks before the day of the main earthquakes, were spotted, which are attributed to the rise in upwelling index. Time series of SLHF showed meaningful rises from 1?month to a fortnight before the earthquake events. One problem in our research was the low resolution of the data which makes the graphs that are generated from NCEP database affected by all sources of anomalies, other than seismic activities, within an about 1.8°?C2.5° (200?km) area.     

Hydrogeochemical assessment of groundwater in Isfahan province, Iran

Groundwater quality in five catchment areas in Isfahan province of Iran is assessed by measuring physicochemical parameters including major cation and anion compositions, pH, total dissolved solid, electrical conductivity and total hardness. For this purpose, 567 piezometric well samples were collected in October 2007. The abundance of major ions in four of the catchment areas including Gavkhuni, Ardestan, Salt lake and Central Iran desert basins is similar and follows Cl^??>?SO₄ ^2??>?Na⁺?>?HCO₃ ^??>?Ca²⁺?>?Mg²⁺?>?K⁺?>?CO₃ ^2? trend, while in the fifth basin (Karoon), the trend changes into HCO₃ ^??>?Ca²⁺?>?Cl^??>?SO₄ ^2??>?Mg²⁺?>?Na⁺?>?K⁺?>CO₃ ^2?. In general, four water facies are determined and it is shown that alkali elements and strong acids are dominating over alkaline earth and weak acids. Statistical analysis including Mann?CWhitney U test indicate that physicochemical parameters in three of the five investigated basins [Gavkhuni, Ardestan and Central Iran desert (CID)] are similar, while Karoon and salt lake basins display different characteristics. The result indicate that groundwater west of the province is suitable for irrigation, while in the central and eastern parts of the province the groundwater loses its quality for this purpose. It is concluded that mineral dissolution and evapotranspiration are the main processes that determine major ion compositions.