Evidence for a magmatic origin for Carlin-type gold deposits: isotopic composition of sulfur in the Betze-Post-Screamer Deposit, Nevada, USA

We report here new sulfur isotope analyses from the Betze-Post-Screamer deposit, the largest Carlin-type gold deposit in the world. Carlin-type deposits contain high concentrations of arsenic, antimony, mercury, tellurium and other elements of environmental interest, and are surrounded by large volumes of crust in which these elements are also enriched. Uncertainty about the source of sulfur and metals in and around Carlin-type deposits has hampered formulation of models for their origin, which are needed for improved mineral exploration and environmental assessment. Previous studies have concluded that most Carlin-type deposits formed from sulfide sulfur that is largely of sedimentary origin. Most of these studies are based on analyses of mineral separates consisting of pre-ore diagenetic pyrite with thin overgrowths of ore-related arsenian pyrite rather than pure, ore-related pyrite. Our SIMS spot analyses of ore-related pyrite overgrowths in the Screamer zone of the Betze-Post-Screamer deposit yield δ 34 S values of about −1 to 4‰ with one value of about 7‰. Conventional analyses of realgar and orpiment separates from throughout the deposit yield δ 34 S values of about 5–7‰ with one value of 10‰ in the Screamer zone. These results, along with results from an earlier SIMS study in the Post zone of the deposit and phase equilibrium constraints, indicate that early arsenian pyrite were formed from fluids of magmatic origin with variable contamination from sulfur in Paleozoic sedimentary rocks. Later arsenic sulfides were formed from solutions to which sulfur of sedimentary origin had been added. The presence of Paleozoic sedimentary sulfur in Carlin-type deposits does not require direct involvement of hydrothermal solutions of sedimentary origin. Instead, it could have been added by magmatic assimilation of Paleozoic sedimentary rocks or by hydrothermal leaching of sulfur from wall rocks to the deposit. Thus, the dominant process delivering sulfur, arsenic, gold and mineralizing fluids to Carlin-type systems and their surrounding country rocks was probably separation of fluids from a magmatic source.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46046/1/126_2005_Article_477.pd

Depression among physicians working in public healthcare in Belo Horizonte, Brazil.

Purpose Prevalence of depressive disorders has been reported among physicians in a number of different settings. The aim of the present study is to assess the prevalence of self-reported depression and its associated factors among physicians working in the public healthcare system of Belo Horizonte, Minas Gerais state, Brazil. Methods A cross-sectional survey was carried out in 2009 to investigate individual and occupational dimensions of depressive disorders in a group of physicians working at several municipal healthcare units. The percentage of physicians that self-reported a confirmed diagnosis of depression by another physician was used as the prevalence proportion; the Poisson regression univariate and multivariate models were applied to study factors associated with depression. Results The response rate was 81.2 %, of which 12.0 % reported depression confirmed by another physician. Reports of RSI/WMSD (p\0.001) and passive work (p\0.05) were positively and independently associated with the outcome. Conclusions Our data bring valuable information that may help guide interventions and health-promoting activities for physicians by indicating concrete measures to change working conditions that affect mental health