Small Mining Operations Research Articles

Mortality from silicosis in Brazil: Temporal trends in the period 1980-2017.

Silicosis is the most prevalent pneumoconiosis in Brazil. We aimed to estimate mortality rates and temporal trends for silicosis, and to identify areas of highest mortality. Records of silicosis as the underlying (1980-2017) or contributory (2000-2017) cause of death in adults aged 20 years and older were retrieved from the Brazilian Mortality Database. Age-standardized mortality rates (ASMR) were calculated. The annual trend in ASMR was analyzed by joinpoint regression. Mortality rates per 100,000 person-years were calculated for each municipality. We analyzed temporal trends in municipalities where similar activities with exposure to silica were performed. There were 3164 death records (96.6% men) distributed over 14% of the municipalities. Mean age of death was 59.2 (SD 15.1) and mean ASMR was 0.085/100,000 (confidence interval 0.080-0.091). Joinpoint regression showed a significant increase in ASMR from 1980 to 2006 and a significant decrease after 2006 driven by a decline in deaths of individuals younger than 70 years. The highest mortality rate was 21.83/100,000 person-years, in a municipality with small mining operations for gems. Gold mining municipalities showed the highest composite death rate, 4.0/100,000 person-years. Tuberculosis was the main cause of death when silicosis was a contributing cause. In contrast with developed countries, silicosis mortality in Brazil increased to 2006 and subsequently started to drop, mostly from a plateau or decrease in deaths occurring in municipalities which regulated economic activities. However, this decrease did not occur in the older age group nor in the unregulated sector, the latter being the main challenge for exposure control and surveillance.

Valuation and Prioritization of Early-Stage Exploration Projects: a Case Study of Cu–Ag and Au-Mineralized Systems in the Tiltil Mining District, Chile

A problem for mining districts, for example those with small to medium operations, is the uncertainty with respect to the valuation of exploration targets. In cases where a mining district has been only partially developed, geological uncertainty likely represents a substantial part of resource valuation risk. To address this problem, we developed a method for valuing exploration targets in the early stage of exploration based on four variables: (1) risks associated with exploration; (2) geological uncertainty; (3) economic potential; and (4) exploration costs. The new method presented offers a simple and replicable means to value mineralized bodies and prioritize mining activities based on quantitative geoscientific information and can additionally be adapted to analyze other exploration projects, such as those located in areas without mining activity. In this work, we studied a series of Cu–Ag and Au veins located in the Tiltil Mining District in the Coastal Cordillera of the Chilean Central Andes. We performed four steps in order to characterize the level of uncertainty in the resource exploration and valuation: (1) we acquired district-level data on the geology in and around Tiltil and the activity of 39 small mining operations; (2) we designed a preliminary conceptual exploration campaign; (3) we applied and adapted a new method for the valuation of mineral resources; and (4) we estimated the economic value of the studied mineral targets. The valuation method uses the product of three mutually independent variables: potential value, exploration risk, and geological uncertainty. The estimated value of minerals, at Tiltil, without discounting cash flows is 50.2 billion CLP, while a discount rate of 15.62% returns an estimate of 26.7 billion CLP. When adjusting these values for the level of geological uncertainty discerned in our method, the resulting values are approximately 56% less. We additionally applied the valuation method to seven potential mining targets, considering both potential exploration resources and inferred resources, and found values ranging from 21.8 billion and 11.8 billion CLP (32.3 million and 17.5 million USD with an exchange rate of 675.48 CLP per USD) without discounting cash flows and with a discount rate of 15.62%. We encourage the use of this new method in the early-stage development of small mining operations in order to characterize correctly potential profitability.

Reconstruction of historical riverine sediment production on the goldfields of Victoria, Australia

A significant but previously unquantified factor in anthropogenic change in Australian rivers was the release of large volumes of sediment produced by gold mining in the 19th century. This material, known historically as ‘sludge’, rapidly entered waterways adjacent to mining areas and caused major environmental damage. We interrogate detailed historical records from the colony of Victoria spanning the period 1859 to 1891 to reconstruct the temporal and spatial distribution of sediment volumes released by mining activity. Based on these records, we estimate that at least 650 million m3 of material was released into rivers in the 19th century, exceeding natural sediment yield to rivers by an average 140 times. Although the sediment yield per river is not high when compared with examples around the world, the widespread impacts of sludge distinguishes the case of Victoria. The sludge affected three-quarters of catchments in the state due to the large number of small mining operations spread over hundreds of creeks and gullies across the colony. The impacts of sludge to rivers and farmland filled newspapers for more than 50 years and generated numerous parliamentary inquiries. Today, the impacts are largely forgotten and unrecognised, as are the continuing impacts on aquatic systems. The estimates generated in this study provide a basis for understanding the continuing impact of historical mining on Victorian rivers.

Are cleaner production innovations the solution for small mining operations in poor regions? The case of Padua in Brazil

Abstract Mining in Santo Antonio de Padua, a city located in the underdeveloped northeast area of the Rio de Janeiro state, in Brazil, is currently the most important economic activity in the region. Unfortunately, companies lag behind technologically and use rudimentary production methods, which cause serious environmental problems, social implications and poor competitiveness. In order to seek sustainable solutions for the Padua mining region, local support organizations have created initiatives to develop endogenous cleaner production innovations to enhance the industry's sustainability performance. During this process, some barriers for mining companies to adopt these developed technologies have emerged. This research draws on the cleaner production, sustainability and innovation literature and uses a qualitative research with multiple sources of evidence to understand the dynamics behind the Padua mining region. More specifically, this research explores how initiatives to improve the sustainability performance led by local support organizations took place, analyzes their outcomes (i.e., cleaner production innovations), and identifies some of the barriers to technology adoption. This paper offers three key research contributions. First, we claim that cleaner production approaches alone cannot create sustainable mining regions in emerging and developing countries, but they are definitively a step in the right direction since they provide the base for expanding the scope towards sustainability. Second, we argue that technology cannot be understood as the panacea for sustainability because it will never represent the complete solution for companies' sustainability problems. Third, we claim that companies can face a “managerial trap” if they pursue enhanced sustainability performance solely through the adoption of cleaner production innovations.

Occupational injury among migrant workers in China: a systematic review

ObjectivesThis review considers the state of occupational injury surveillance and prevention among migrant workers in China and suggests areas of focus for future research on the topic.MethodsBibliographic databases were searched...

Petrology of mafic and ultramafic intrusions from the Portneuf–Mauricie Domain, Grenville Province, Canada: Implications for plutonic complexes in a Proterozoic island arc

The Portneuf–Mauricie Domain (PMD), located in the south-central part of the Grenville Province, comprises several mafic and ultramafic intrusions hosting Ni–Cu±platinum-group element (PGE) prospects and a former small mining operation (Lac Édouard mine). These meter- to kilometer-scale, sulfide-bearing intrusions display diverse forms, such as layered and tabular bodies with no particular internal structure, and zoned plutons. They were injected ~1.40Ga into a mature oceanic arc, before and during accretion of the arc to the Laurentian margin. The pressure–temperature conditions of the magmas at the beginning of their emplacement were 3kbar and 1319–1200°C (according to the petrologic modeling results from this study). The PMD mineralized intrusions are interpreted to represent former magma chambers or magma conduits in the roots of the oceanic arc.The parent magmas of the mineralized intrusions resulted mainly from the partial melting of a mantle source composed of spinel-bearing lherzolite. Petrologic modeling and the occurrence of primary amphibole in the plutonic rocks indicate that these parent melts were basaltic and hydrous. In addition, fractional crystallization modeling and Mg/Fe ratios suggest that most of the intrusions may have formed from evolved magmas, with Mg#=60, resulting from the fractionation of more primitive magmas (primary magmas, with Mg#=68). Petrologic modeling demonstrates that 30% fractional crystallization resulted in the primitive to evolved characteristics of the studied intrusive rocks (as indicated by the crystallization sequences and mineral chemistry). Exceptions are the Réservoir Blanc, Boivin, and Rochette West parent magmas, which may have undergone more extensive fractional crystallization, since these intrusions contain pyroxenes that are more iron rich and have lower Mg numbers than pyroxenes in the other PMD intrusions.The PMD mafic and ultramafic intrusions were intruded into an island arc located offshore from the Laurentian continent. Thus, their presence confirms the existence of a well-developed magmatic network (responsible of the fractionation processes) beneath the Proterozoic arc, which resulted in the wide range of compositions observed in the various plutons.

Methods to reduce mercury pollution in small gold mining operations

The use of mercury for gold beneficiation is still a current practice in small mining operations, mainly in underdeveloped countries, due to the low investment required and necessity of easy to operate systems. But the lack of basic protections makes unavoidable the high pollution of water streams, soils, and in fact, human bodies. Some improvements have been done at site like that related to the removal of the mercury from the amalgam, that usually was done in the open air and now have been changed to the utilization of artisan iron retorts which considerably reduce the emissions of mercury vapors to the atmosphere, but there are still high losses of mercury into the waste solids or tailings coming from the amalgamation process (nearly most of the total weight of the ore treated). In order to reduce the mercury losses into the tailings from the process, this research work has been based in the use of cheap systems, available to the isolated miners, to proof that it is feasible to get an important reduction of the losses and the pollution. The procedure has been accomplished by means of washing the ores with alkaline or detergent agents, together with the use of activated mercury purified by electrowinning in a simple device, easily manufactured in site by the own workers. It is also proven herewith that controlling the time of amalgamation and the total amount of mercury used could reduce the total pollution, and in addition, the gold recovery would be improved. This investigation reports the possibility of a reduction of mercury losses down to 2.4 g per 100 g of gold produced (case of rich ores like La Bruja), with gold recovery up to 94 %; and 8,6 g per 100 g of gold produced (from ores with average grades like La Gruesa), and gold recoveries in the range of 92 %. All that is about 20 to 100 times lower than data reported in current bibliography. The introduction of a previous step of the ore concentration in shaking tables, decreases the total amount of solids for the process of amalgamation in the range of 70 %, then reducing the contaminated solid waste. By doing so the recovery of gold is improved in the case of rich ore, but not with the ore of lower grade when comparing with direct amalgamation. In that case it would be required a combination of shaking tables and flotation of the gravity tailings, but that process is more expensive and complicated for the small miners. The described method involves a low capital investment in equipment, and the training to operate the system is not difficult.

Policy and strategy options for small‐scale mining development in Zambia

Abstract Increasing populations compounded by limited formal sector employment have made small‐scale mining an important economic livelihood option for thousands of people in developing countries. Low barriers to entry, the principal economic characteristic of the sub‐sector, will ensure that small mining operations will continue to provide a livelihood for numerous unskilled workers in rural areas, where few alternative job opportunities exist. In addition, with correct policies and strategies in place, the sector has the potential to generate more employment and foreign exchange earnings. The successful evolution of small‐scale mining requires an enabling policy environment that recognizes its specific needs. In this paper small‐scale mining in Zambia is discussed by tracing the impact of changing policies on this sector.

Economic environment of coal mining operations in Appalachia, United States

Appalachia is a mountainous coal region, in the United States, where the small mining operation dominates. The large number of small coal operations makes the coal industry in that area very competitive, the industry concentration ratio being low. The vast majority of the small coal operations are contractors and nonunionized. There are various circumstances under which a large company will elect to supplement their coal production from their, usually larger, coal mines. The size of the coal mine is generally dictated by the size and location of the coal reserves. The optimum rate of coal extraction, and hence the life of the mine, is a factor of the size of the coal reserves and the contribution margin (coal price less variable cost). Large companies tend to have better safety records than smaller companies due to greater numbers of professional engineers and better management. Small mines have the advantage of closer supervision.