Characterization of the Geophagic Materials and Their Associated Rocks and Soils from Anfoega, Ghana

This study was conducted to examine the physico-chemical and mineralogical properties of geophagic materials and their associated rocks and soils from Anfoega, Ghana. The geophagic materials were sampled from pits >10 m deep overlain by massive sandstones and shallow soils which were also sampled. The pH of the geophagic materials was strongly acid. The pH of the soils from the three sites was slightly to moderately acid, that of the fourth site was moderately acid in the surface but strongly acid in the lower layers. While the geophagic materials were enriched with clay, the soil samples contained high amounts of sand. The CEC of the geophagic materials (18.0 to 23.2 cmolc kg-1) was higher than that of the soils (5.3 to 22.6 cmolc kg-1). Thin sections of the rocks showed high amounts of quartz and accessory feldspars and sericite. The geophagic materials contained high amounts of clay (with >79% SiO2), quartz, feldspars and sericite. X-ray diffractograms of the geophagic materials, rocks and soils were dominated by quartz, kaolinite, muscovite and feldspars. The sialic minerals in the geophagic materials (shales) were probably leached from the overlying sandstones. The mineralogy of the soils indicated that they were formed in-situ from the underlying sandstones

Arsenic Intensity Risk Assessment at AngloGold Obuasi Goldmine, Ghana, West Africa: Using Sorption and Geotechnical Factors

This research evaluated arsenic (As) intensity risk using sorption and geotechnical factors in the AngloGold Obuasi mine environment in Ghana. Water samples from tailings dam boreholes and surface stream were analysed for As contents over a time period of 24 months and over a distance of about 9 km respectively, under closed conditions, where there are no more discharges of waste. The porosity and bulk density of the subsurface material were also determined. Data generated from the mass-time and mass-distance analysis were used to establish As intensity risk assessment model based on documented global As impact data. From the model, a period of about 4 years is required in monitoring boreholes and a distance of about 12 km is required along the stream profile for As concentration to reduce from the maximum value of about 2.50 mg/l to 0.01 mg/l. Using the porosity, bulk density and combined degradation properties of the monitored media of the mobile As, the estimated retardation factor was 1.96 and the solute velocity estimated to be 1.53 × 10-7 ms-1 in the borehole environment, and 1.074 and 9.25 × 10-1 ms-1 along the streambed, respectively. This study shows that the pollution risk assessment model can be used to spatially estimate exposure to As contamination in the environment, while the transport characteristics can be used to determine clean-up criteria for effective As remediation in drainage

The Bepkong gold deposit, Northwestern Ghana

The Bepkong gold deposit is located in the Wa-Lawra belt of the Paleoproterozoic Baoule-Mossi domain of the West African Craton, in NW Ghana. It occurs in pelitic and volcano-sedimentary rocks, metamorphosed to greenschist facies, in genetic association with zones of shear interpreted to form during the regional D-3 deformational event, denominated D-B1 at the deposit scale. The ore zone forms a corridor-like body composed of multiple quartz +/- carbonate veins surrounded by an alteration envelope, characterized by the presence of chlorite, calcite, sericite, quartz and disseminated pyrite, arsenopyrite plus subordinate pyrrhotite and chalcopyrite. The veins contain only small proportions of pyrite, whereas most of the sulphides, particularly arsenopyrite, occur in the altered host rock, next to the veins. Pyrite is also common outside of the ore zone. Gold is found in arsenopyrite, where it occurs as invisible gold and as visible - albeit micron-size - grains in its rims, and as free gold within fractures cross -cutting this sulphide. More rarely, free gold also occurs in the veins, in fractured quartz. In the ore zone, pyrite formseuhedral crystals surrounding arsenopyrite, but does not contain gold, suggesting that it formed at a late stage, from a gold-free hydrothermal fluid

Sulfur isotope signatures in the lower crust: A SIMS study on S-rich scapolite of granulites

© 2017 Elsevier B.V. Scapolite is an important reservoir for volatiles in the deep crust and provides unique insights into the S isotope signatures at the mantle/crust interface. Here we document the first scapolite reference material (herein referred to as CB1) for in situ S isotope analysis. The chemical and isotopic composition of this euhedral, S-rich scapolite megacryst was characterized via LA-ICP-MS, EPMA, SIMS, and bulk fluorination gas source isotope ratio mass spectrometry. The CB1 scapolite is isotopically homogeneous and our results show that crystal orientation does not affect in situ S isotope SIMS analysis. This makes CB1 an ideal primary calibration standard for in situ analysis of S isotope ratios (36S/32S,34S/32S and33S/32S) in scapolite. With this reference material in hand, we then applied in situ SIMS analysis of S isotopes for the first time on scapolite in granulite samples from the lower crust/upper mantle. The analysed sample suite comprises rocks from classic granulite xenolith locations in southeastern Australia, as well as a sample from the high-grade suture zone of the Dahomeyides in south-eastern Ghana. The results show that scapolites in the lower crust have d34S values between ~- 0.5 and + 4 (‰ VCDT). These values fall within the range of S isotope signatures present in mantle rocks and provide no evidence for the recycling of seawater-derived S into the lower crust. We propose that scapolite formed during granulite facies metamorphism of igneous cumulates, where S was sourced from precursor igneous sulfides. Sulfur isotope heterogeneities between individual scapolite grains in some of the studied samples may reflect non-uniform S-isotope compositions of igneous S-phases, which precipitated from mantle-derived melt

Occupational image, organisational image and identity in dirty work: Intersections of organisational efforts and media accounts

This article proposes that media representations of an occupational category may intersect with organizations’ efforts to construct a positive organizational identity and image. We fuse three streams of literature namely, organizational identity and image, media and the social construction of reality, and dirty work to extend extant literature on organizational identity and image. Attention is drawn to occupational image as the position of an occupational category in society. We contend that occupational image is likely to influence the decisions and actions taken by organizations and its members, in particular when the occupation is central to the organization’s mission. Occupational image is partly informed by the media. We analyse one year of media coverage of a dirty work occupation, specifically exotic dancing, and identify various ways in which the media portrays the exotic dancing occupation and the organizations providing these services. We focus upon two of these categories, namely Public (dis) Order and Art and Entertainment. We also draw upon a variety of data from one organization, For Your Eyes Only, to explore how organizational efforts to construct a positive organizational identity (based upon professionalism and legitimacy) and image (based upon fantasy, exclusivity and high quality service) intersect these media representations