Appareil ignimbritique et minéralisation cuprifère: Alous (Anti-Atlas,Maroc)

Résumé Le gisement d'Alous (4 à 6 Mt à 0,8% Cu) est un exemple apparemment fort rare, de dépôt de cuivre dans un appareil ignimbritique. Celui dans lequel il est installé appartient à une formation volcanique post-orogénique de la fin du Précambrien. Les sulfures de cuivre (chalcocite, bornite avec accessoirement chalcopyrite et pyrite) et les minéraux accompagnateurs (chlorites, séricite, albite, épidote, quartz) ont cristallisé dans des pyromérides au cours du refroidissement de l'ignimbrite. La minéralisation cuprifère est localisée le long de failles radiales et l'on observe une diminution centrifuge des rapports Cu/Fe des sulfures et Mg/Fe des chlorites. Un modèle de circulations hydrothermales associées au volcanisme ignimbritique est proposé: le cuivre aurait été lessivé à partir des laves basiques sous-jacentes puis redéposé sous forme de sulfures le long des failles radiales au cours du refroidissement des ignimbrites.

---

The Alous deposit (from 4 to 6 Mt at 0.8% Cu) is apparently a rare example of copper deposit in ignimbrite volcanos. The volcano from which it comes belongs to a post-orogenic volcanic formation of late Proterozoic age (Anti-Atlas, Morocco). The copper sulphides (chalcocite, bornite with accessory chalcopyrite and pyrite) and associated minerals (chlorites, sericite, albite, epidote, quartz) crystallized during the cooling of the ignimbrite and were included in pyromeride textures. The mineralization is distributed along radial faults and displays, outwards from the volcano center, a decrease of sulphides Cu/Fe ratio and chlorites Mg/Fe ratio. A model of small-scale hydrothermal circulations linked to the volcanic activity is proposed: copper was leached from the underlaying basic lavas then redeposited along radial faults during the ignimbrite cooling.

     

Austerity urbanism and the promise of immigrant- and refugee-centered urban revitalization in the US Rust Belt

Recent urban studies research emphasizes the unevenness of local responses to immigration in the United States and the emergence of economic development-focused inclusionary initiatives as a response to neoliberal downscaling in the Rust Belt. Scholars also highlight the impact of austerity urbanism – the deepening of neoliberal urbanism – in Rust Belt cities following the 2007–2008 financial crisis, noting its potential to produce progressive activism. This article considers the relationship between downscaling, austerity urbanism, and immigration activism in the Rust Belt by analyzing economic revitalization narratives within a regional consortium of inclusionary initiatives. My findings underscore the incongruities and compromises encompassed by welcoming coalitions operating in the age of austerity. Some local actors are motivated by growth agendas but affirm inclusionary values toward immigrants and refugees to substantiate them. Other actors are motivated by social justice agendas but cite the economic benefits of immigration to garner support from other factions.