Special issue: Environmental, Health and Social legacies of mining activities in Sub-Saharan Africa

Over > 40 years of implementation of the International Geoscience Programme (IGCP), a partnership and flagship programme between UNESCO and the International Union of Geological Sciences (IUGS), UNESCO realized that the involvement of Africa both in terms of projects devoted to the continent and leadership, was marginal. Between 2011 and 2013, UNESCO collaborated with the Swedish International Development Cooperation Agency (Sida) to support capacity-building activities aiming to increase the participation of Africa in IGCP. From this exercise, two projects (UNESCO/Sida IGCP-594 and IGCP-606) emerged as a research networking platform between scientists from Africa and Europe on the environmental and health challenges of mining activities in Africa. At the end of their implementation, the two projects jointly prepared and published a Special Issue on “Impacts of mining and mineral processing on the environment and human health in Africa” in the Journal of Geochemical Exploration in 2014 edited by Kříbek et al. (2014). However, it was obvious that the challenges facing African countries as a result of mining activities go well beyond simple IGCP projects, and need extensive mobilisation in terms of human re- sources, laboratory facilities and fund raising. The success of two major IGCP projects (IGCP-594 and IGCP-606) encouraged UNESCO to enter into a new Programme Cooperation Agreement with Sida for the period 2014–2018 to support an expanded project entitled “Mapping and Assessing the Environmental and Health Impacts of Abandoned Mines in Sub- Saharan African Countries”. The project aimed to reduce the adverse effects of mining activities on the ecosystem and health of adjacent communities while, at the same time, promote a peaceful mining atmosphere among industry, authorities and local communities. An important advancement in the mining sector is the legal ob- ligation for mining companies to rehabilitate former operational mine sites and ensure that they are restored to a safe environmental state after the mine is closed. While this concept is well rooted in mining legislation in many developed countries, this is not always the case in developing countries, especially in Sub-Saharan Africa. Apart from poor environmental governance as highlighted in the Africa Mining Vision, many African countries lack a precise inventory and assessment of abandoned and derelict mines. It is therefore important to make an assessment of the true extent of the detrimental effects of metal and metalloid pollutants and their impact on human and animal health, as well as on ecosystems. This is a pre-requisite for appropriate legislation development and enforcement. This new project intended to provide crucial scientific knowledge that will contribute to understanding of the factors that control cycling of pollutants from abandoned mines in soils, water and vegetation and the impact on the food chain. Development of appropriated technologies to mitigate environmental risk associated with mining activities was also at the heart of the project. Furthermore, influencing policies, training, education and awareness focusing on communities involved or living around mine sites were important aspects of the project. We anticipate that the results of the project will be used to improve the environmental norms in individual countries in Sub-Saharan Africa and the efficiency of governments in addressing the challenges related to the adverse effects of abandoned mines. The new project builds on a strong network of > 100 scientists working on 29 sites in 17 African countries, with focus on field assessment of pollution (soil, water, crops, health of human and animals), rehabilitation of degraded ecosystems, and policy issues for the attention of communities and governments. For the monitoring of the project, UNESCO put in place a scientific board composed of international experts in this field, some of whom have served as Co-Guest Editors of this Special Issue. An important meeting took place in April 2018 in Nairobi, Kenya, where all project leaders met with the members of the scientific board to evaluate the progress of the project. A key resolution by participants of this meeting was the preparation of another Special Issue to avail the new research contributions to the scientific community

Geochronology and correlations in the Central African Fold Belt along the northern edge of the Congo Craton: New insights from U-Pb dating of zircons from Cameroon, Central African Republic, and south-western Chad

International audienceThe Central African Fold Belt (CAFB) is the least well-known of all major Pan African belts. Here, we present new geochronologic work carried out in several critical areas of western Central African Republic, the region standing between northern Cameroon and southwestern Chad, and southern Cameroon. Our results allow us to: (1) clarify the regional extension of the Congo Craton in SE Cameroon and in the SW Central African Republic; (2) demonstrate that the units thrust along the northern edge of the Congo Craton from Cameroon to the Central African Republic are comparable in nature and in age; (3) better constrain the limits and described better the role of the Adamawa-Yadé crustal block during the Pan-African pre-collisional and collisional events in relation to the Congo Craton and the Yaoundé-Yangana nappe units to the South, and to the Poli-Leré magmatic arc to the North and; (4) clarify some of the elements of correlation with NE Brazil. Overall, a model involving two subduction zones is proposed to explain the evolution of the Pan-African belt north of the Congo Craton. The main steps include; (1) break-up and basin development from the early Tonian to at least 620 Ma on the northern edge of the Congo Craton, and on both the southern and the northern edges of the Adamawa-Yadé Block, concomitantly with the development of the Poli-Leré arc in northern Cameroon and Chad; (2) pre-tectonic plutonism in all domains since c. 800 Ma with culmination between 650 and 620 Ma; (3) collisional events starting around 620 Ma with metamorphism reaching the granulite facies at c. 600 Ma in all the domains; (4) nappe tectonics with thrusting of the Yaoundé-Yangana units onto the Congo Craton, accretion of the Poli-Leré arc to Adamawa-Yadé Block, and widespread syntectonic magmatism (600–580 Ma) with emplacement partly controlled by transcurrent regional shear zones, and emplacement of post-tectonic granitoids (c. 550 Ma) in both Adamawa-Yadé block and Poli-Leré magmatic arc. Collisional and post-collisional (620–550 Ma) events were synchronous along the entire belt from Central Africa to Brazil