Evidence for two stages of mineralization in West Africa's largest gold deposit: Obuasi, Ghana

The supergiant Obuasi gold deposit is the largest deposit in the Paleoproterozoic Birimian terranes of West Africa with 62 Moz of gold (past production + resources). The deposit is hosted in the Paleoproterozoic Kumasi Group sedimentary rocks composed of carbonaceous phyllites, slates, psammites, and volcaniclastic rocks intruded by different generations of felsic dikes and granites. A three-stage deformation history is defined for the district. The D1Ob stage is weakly recorded in the sedimentary rocks as a layer-parallel fabric and indicates that bedding parallel shearing occurred during the early stage of deformation at Obuasi. The D2Ob is the main deformation stage affecting the Obuasi district and corresponds to a NW-SE shortening. Tight to isoclinal folding, as well as intense subhorizontal stretching, occurred during D2Ob, parallel with the plane of a pervasive NE-striking subvertical foliation (S2Ob). Finally, a N-S shortening event (D3Ob) refolded previously formed structures and formed a distinct ENE-striking, variably dipping S3Ob cleavage that is domainal in nature throughout the deposit. Two economic styles of mineralization occur at Obuasi and contribute equally to the gold budget. These are (1) gold-bearing sulfides, dominantly arsenopyrite, mainly disseminated in metasedimentary rocks and (2) native gold hosted in quartz veins that are as much as 25 m wide. Microstructural evidence, such as strain shadows surrounding gold-bearing arsenopyrite parallel with S2Ob, but folded by S3Ob, indicates that the sulfides were formed during D2Ob. Concentrations of as much as 700 ppm Au are present in the epitaxial growth zones of the arsenopyrite grains. Although the large mineralized quartz veins are boudinaged and refolded (indicating their formation during D2Ob), field and microanalytical observations demonstrate that the gold in the veins is hosted in microcracks controlled by D3Ob, where the S3Ob cleavage crosscuts the quartz veins in the main ore zones. Thus, these observations constitute the first evidence for multiple stages of gold deposition at the Obuasi deposit. Futhermore, three-dimensional modeling of stratigraphy, structure, and gold orebodies highlights three major controls on oreshoot location, which are (1) contacts between volcaniclastic units and pre-D1 felsic dikes, (2) fault intersections, and (3) F3Ob fold hinges. The maximum age for the older disseminated gold event is given by the age of the granites at 2105 ± 2 Ma, which is within error of hydrothermal rutile in the granites of 2098 ± 7 Ma; the absolute age of the younger gold event is not known

Strike-Slip Fault Terminations at Seismogenic Depths: The Structure and Kinematics of the Glacier Lakes Fault, Sierra Nevada United States

[1] Structural complexity is common at the terminations of earthquake surface ruptures; similar deformation may therefore be expected at the end zones of earthquake ruptures at depth. The 8.2 km long Glacier Lakes fault (GLF) in the Sierra Nevada is a left-lateral strike-slip fault with a maximum observed displacement of 125 m. Within the fault, pseudotachylytes crosscut cataclasites, showing that displacement on the GLF was accommodated at least partly by seismic slip. The western termination of the GLF is defined by a gradual decrease in the displacement on the main fault, accompanied by a 1.4 km wide zone of secondary faulting in the dilational quadrant of the GLF. The secondary faults splay counterclockwise from the main fault trace forming average angles of 39° with the main fault. Slip vectors defined by slickenlines plunge more steeply west for these splay faults than for the GLF. Static stress transfer modeling shows that the orientations of the splays, and the plunge of displacement on those splays, are consistent with displacement on the main fault. The GLF termination structure shows that structural complexity is present at the terminations of faults at seismogenic depths and therefore ruptures that propagate beyond fault terminations, or through step overs between two faults, will likely interact with complex secondary fault structures. Models of dynamic rupture propagation must account for the effect of preexisting structures on the elastic properties of the host rock. Additionally, aftershock distributions and focal mechanisms may be controlled by the geometry and kinematics of structures present at fault terminations

Exploring backscattered imaging in low voltage FE-SEM

Contrast levels in backscattered SEM images were investigated, utilising stage deceleration for low voltage imaging and also electron energy filtering. Image contrast variations are explained via use of Monte Carlo simulations which can predict the optimum accelerating and filter voltages for imaging complex sample mixtures

Improving the assessment of risk factors relevant to potential carcinogenicity of gene therapies: a consensus article

Regulators and industry are actively seeking improvements and alternatives to current models and approaches to evaluate potential carcinogenicity of gene therapies (GTs). A meeting of invited experts was organized by NC3Rs/UKEMS (London, March 2023) to discuss this topic. This article describes the consensus reached among delegates on the definition of vector genotoxicity, sources of uncertainty, suitable toxicological endpoints for genotoxic assessment of GTs, and future research needs. The collected recommendations should inform the further development of regulatory guidelines for the nonclinical toxicological assessment of GT products

Colonização e neocolonização da gestão de recursos humanos no Brasil (1950-2010)

Human resource management, as a practical field of business administration and as a teaching and research area, has developed vigorously in Brazil. The objective of this critical essay is to present an historical analysis of this evolution over the last 60 years. To do so we characterize and analyze two periods: 1950-1980, which we call colonization; and 1980-2010, which we call neo-colonization. For each period we present the political and economic context, the changes that occurred in human resource management and the corresponding discourse. Our analysis adopts the perspective of post-colonialism, a rising tide in research in organizational studies, and introduces and uses the perspective of tropicalism, a genuinely local approach, which is derived from the cultural movements of the 1960s. We argue that human resource management developed in Brazil from a colonization movement that came from abroad. This movement, which involved both colonizers and colonized, comprised asymmetries in terms of power, but also included interdependence and re-creations.A Gestão de Recursos Humanos (GRH), como campo prático da Administração de Empresas e como área de ensino e pesquisa, desenvolveu-se vigorosamente no Brasil. Este ensaio crítico tem como objetivo apresentar uma análise histórica dessa evolução nos últimos 60 anos. Para isso, caracterizamos e analisamos dois períodos: 19501980, o qual denominamos colonização; e 1980-2010, o qual denominamos neocolonização. Para cada período, apresentamos o contexto político e econômico, as mudanças ocorridas na GRH e o discurso correspondente. Nossa análise adota a perspectiva do pós-colonialismo, uma corrente de pesquisa ascendente em Estudos Organizacionais, e introduz e utiliza a perspectiva do tropicalismo, uma abordagem genuinamente local, derivada dos movimentos culturais dos anos 1960. Nós argumentamos que a GRH desenvolveu-se no Brasil a partir de um movimento de colonização oriundo do estrangeiro. Tal movimento, envolvendo colonizadores e colonizados, compreendeu assimetrias em termos de poder, porém incluiu também interdependências e recriações.La gestión de Recursos Humanos, como campo práctico de la Administración de Empresas, y como área de enseñanza e investigación, se ha desarrollado vigorosamente en el Brasil. Este ensayo crítico tiene como objetivo presentar un análisis histórico de esta evolución en los últimos 60 años. Para eso, caracterizamos y analizamos dos períodos: 1950-1980, el cual denominamos de colonización; y 1980-2010, al que llamamos de neocolonización. Para cada período, nosotros presentamos un contexto político y económico, los cambios ocurridos en la Gestión de los Recursos Humanos, y el discurso correspondiente. Nuestro análisis adopta la perspectiva del Postcolonialismo, una cadena de investigación ascendente en Estudios Organizacionales, e introduce y utiliza la perspectiva del Tropicalismo, un abordaje genuinamente local, derivado de los movimientos culturales de los años 1960. Nosotros argumentamos que la GRH se ha desarrollado en el Brasil a partir de un movimiento de colonización, oriundo del extranjero. Tal movimiento, envolviendo colonizadores y colonizados, comprendió asimetrías en termos de poder, pero incluyó también interdependencias y recreaciones

Success within a UK open prison and surviving the 'pains of freedom'

Category D open prisons mark a critical juncture of a prisoner’s sentence as they near the end of imprisonment and reach the cusp of release. Such establishments aim to support prisoner re-entry by offering greater freedom and autonomy. A greater understanding of the reality of life within an open establishment and exactly how these conditions support prisoner re-entry is needed. This study is made up of interviews with 11 prisoners residing in a UK open prison. Interviews were analysed qualitatively using interpretative phenomenological analysis which revealed two superordinate themes: ‘redemption through active citizenship’ and ‘coping with invisible boundaries’. These themes are unpacked and their relevance to prisoner re-entry are discussed. The study found that greater freedom and autonomy encouraged reciprocal support amongst residents. Participants discuss strategies they utilise to help them to cope with the ‘pains of freedom’. Implications for supporting individuals in their transformation from prisoner to citizen within an open establishment are highlighted and suggestions for future research offered