Late Cretaceous structural control and Alpine overprint of the high-sulfidation Cu-Au epithermal Chelopech deposit, Srednogorie belt, Bulgaria

The Chelopech epithermal high-sulfidation deposit is located in the Panagyurishte ore district in Bulgaria, which is defined by a NNW alignment of Upper Cretaceous porphyry-Cu and Cu-Au epithermal deposits, and forms part of the Eastern European Banat-Srednogorie belt. Detailed structural mapping and drillcore descriptions have been used to define the structural evolution of the Chelopech deposit from the Late Cretaceous to the present. The Chelopech deposit is characterized by three fault populations including ∼N55, ∼N110, and ∼N155-trending faults, which are also recognized in the entire Panagyurishte district. Mapping and 3-D modeling show that hydrothermal alteration and orebody geometry at Chelopech are controlled by the ∼N55-trending and ∼N110-trending faults. Moreover, the ∼N155-trending faults are parallel to the regional ore deposit alignment of the Panagyurishte ore district. It is concluded that the three fault populations are early features and Late Cretaceous in age, and that they were active during high-sulfidation ore formation at Chelopech. However, the relative fault chronology cannot be deduced anymore due to Late Cretaceous and Tertiary tectonic overprint. Structurally controlled ore formation was followed by Senonian sandstone, limestone, and flysch deposition. The entire Late Cretaceous magmatic and sedimentary rock succession underwent folding, which produced WNW-oriented folds throughout the Panagyurishte district. A subsequent tectonic stage resulted in overthrusting of older rock units along ∼NE-trending reverse faults on the Upper Cretaceous magmatic and sedimentary host rocks of the high-sulfidation epithermal deposit at Chelopech. The three fault populations contemporaneous with ore formation, i.e., the ∼N55-, ∼N110- and ∼N155-trending faults, were reactivated as thrusts or reverse faults, dextral strike-slip faults, and transfer faults, respectively, during this event. Previous studies indicate that the present-day setting is characterized by dextral transtensional strike-slip tectonics. The ∼NE-trending overthrust affecting the Chelopech deposit and the reactivation of the ore-controlling faults are compatible with dextral strike-slip tectonics, but indicate local transpression, thus revealing that the Chelopech deposit might be sited at a transpressive offset within a generally transtensional strike-slip system. The early WNW-trending folds require a roughly NNE-SSW shortening, which is incompatible with the present-day dextral strike-slip tectonic setting and the ∼NE-trending thrust formed during the tectonic overprint of the Chelopech deposit. This reveals a rotation of the principal stress axes after Late Cretaceous high-sulfidation ore formation and post-ore deposition of sedimentary rocks. The nature of the sedimentary rocks interlayered and immediately covering the Upper Cretaceous magmatic rocks hosting the Chelopech deposit indicates sedimentation and associated volcanism in an extensional setting immediately before ore formation. It is concluded that the Chelopech deposit was formed when the tectonic setting changed from extensional during Late Cretaceous basin sedimentation and magmatism, to compressional producing WNW-trending folds under a roughly NNE-SSW compression, possibly in a sinistral strike-slip system. Thus, like other world-class, high-sulfidation epithermal deposits, the Chelopech deposit was formed at the end of an extensional period or during a transient period of stress relaxation, which are particularly favorable tectonic settings for the formation of high-sulfidation epithermal deposits. The exceptional preservation of the Upper Cretaceous Chelopech epithermal deposit is explained by the combined deposition of a thick Senonian sedimentary sequence on top of the Upper Cretaceous magmatic host rocks of the deposit, and the later overthrust of older rock units on top of the deposit. Our study at Chelopech supports previous studies stating that post-ore basin sedimentation and tectonic processes provide the favorable environment to preserve old epithermal deposits from erosion. The tectonic evolution of the Chelopech deposit is similar to that of the entire Panagyurishte ore district. This coherence of the magmatic, hydrothermal, and tectonic events from north to south suggests that the ore deposits of the entire Panagyurishte ore district were formed in a similar tectonic environmen

Origin of the supergiant Olympic Dam Cu-U-Au-Ag deposit, South Australia: Was a sedimentary basin involved?

The supergiant Olympic Dam Cu-U-Au-Ag ore deposit of South Australia occurs in a tectonic-hydrothermal breccia complex that is surrounded by Mesoproterozoic granite. The breccia is composed mainly of granite clasts and minor amounts of Mesoproterozoic volcanic clasts. Very thick (>350 m) sections of bedded sedimentary facies that occur in the breccia complex include laminated to very thin planar mudstone beds, thin to medium internally graded sandstone beds, and thick conglomerate beds. The bedded sedimentary facies extend continuously across a 1.5 km × 0.9 km area and are not limited to small separate maar craters, as previously thought. Detrital chromite and volcanic quartz in the bedded sedimentary facies cannot be matched with local sources, and imply that the provenance extended beyond the area of Olympic Dam. The lateral continuity, provenance characteristics, great thickness, below-wave-base lithofacies, and intracontinental setting suggest that the bedded sedimentary facies are remnants of a sedimentary basin that was present at Olympic Dam prior to formation of the breccia complex. We conclude that the Olympic Dam hydrothermal system operated beneath and partly within an active sedimentary basin, was not confi ned to maar craters, and did not vent. This new view of the setting raises the possibility that sedimentary processes were involved in ore genesis

Petrology, geochemistry and U-Pb geochronology of magmatic rocks from the high-sulfidation epithermal Au-Cu Chelopech deposit, Srednogorie zone, Bulgaria

The Chelopech deposit is one of the largest European gold deposits and is located 60km east of Sofia, within the northern part of the Panagyurishte mineral district. It lies within the Banat-Srednegorie metallogenic belt, which extends from Romania through Serbia to Bulgaria. The magmatic rocks define a typical calc-alkaline suite. The magmatic rocks surrounding the Chelopech deposit have been affected by propylitic, quartz-sericite, and advanced argillic alteration, but the igneous textures have been preserved. Alteration processes have resulted in leaching of Na2O, CaO, P2O5, and Sr and enrichment in K2O and Rb. Trace element variation diagrams are typical of subduction-related volcanism, with negative anomalies in high field strength elements (HFSE) and light element, lithophile elements. HFSE and rare earth elements were relatively immobile during the hydrothermal alteration related to ore formation. Based on immobile element classification diagrams, the magmatic rocks are andesitic to dacitic in compositions. Single zircon grains, from three different magmatic rocks spanning the time of the Chelopech magmatism, were dated by high-precision U-Pb geochronology. Zircons of an altered andesitic body, which has been thrust over the deposit, yield a concordant 206Pb/238U age of 92.21 ± 0.21Ma. This age is interpreted as the crystallization age and the maximum age for magmatism at Chelopech. Zircon analyses of a dacitic dome-like body, which crops out to the north of the Chelopech deposit, give a mean 206Pb/238U age of 91.95 ± 0.28Ma. Zircons of the andesitic hypabyssal body hosting the high-sulfidation mineralization and overprinted by hydrothermal alteration give a concordant 206Pb/238U age of 91.45 ± 0.15Ma. This age is interpreted as the intrusion age of the andesite and as the maximum age of the Chelopech epithermal high-sulfidation deposit. 176Hf/177Hf isotope ratios of zircons from the Chelopech magmatic rocks, together with published data on the Chelopech area and the about 92-Ma-old Elatsite porphyry-Cu deposit, suggest two different magma sources in the Chelopech-Elatsite magmatic area. Magmatic rocks associated with the Elatsite porphyry-Cu deposit and the dacitic dome-like body north of Chelopech are characterized by zircons with ɛHfT90 values of ∼5, which suggest an important input of mantle-derived magma. Some zircons display lower ɛHfT90 values, as low as −6, and correlate with increasing 206Pb/238U ages up to about 350Ma, suggesting assimilation of basement rocks during magmatism. In contrast, zircon grains in andesitic rocks from Chelopech are characterized by homogeneous 176Hf/177Hf isotope ratios with ɛHfT90 values of ∼1 and suggest a homogeneous mixed crust-mantle magma source. We conclude that the Elatsite porphyry-Cu and the Chelopech high-sulfidation epithermal deposits were formed within a very short time span and could be partly contemporaneous. However, they are related to two distinct upper crustal magmatic reservoirs, and they cannot be considered as a genetically paired porphyry-Cu and high-sulfidation epithermal related to a single magmatic-hydrothermal system centered on the same intrusio

Extraction, Storage and Eruption of Multiple Isolated Magma Batches in the Paired Mamaku and Ohakuri Eruption, Taupo Volcanic Zone, New Zealand

The Taupo Volcanic Zone (TVZ) is well known for its extraordinary rate of rhyolitic magma generation and caldera-forming eruptions. Less is known about how large volumes of rhyolitic magma are extracted and stored prior to eruption, and the role tectonics might play in the process of melt extraction and control of caldera eruption(s). Here we present a new model for the extraction, storage and simultaneous eruption of the >245 km3 paired Mamaku and Ohakuri magmas sourced from calderas centred ∼30 km apart (the Rotorua and Ohakuri calderas, respectively) in the central TVZ. The Mamaku and Ohakuri ignimbrites share a similar bulk pumice composition and the same phenocryst assemblage; however, bulk-rock compositions suggest several poorly mixed magma types in each erupted volume, which are randomly distributed throughout the eruptive deposits. To refine models of the pre-eruptive geometry of the magmatic system and discuss a possible origin for triggering of each eruption, we present an expanded database of matrix glass and quartz-hosted melt inclusion compositions along with the existing bulk-rock and mineral compositions. Major and trace element compositions show that the region produced five different magma batches, extracted from the same source region, and a continuous intermediate mush zone beneath the Mamaku-Ohakuri region is suggested here. These magma batches were most probably juxtaposed but isolated from each other in the upper crust, and evolved separately until eruption. The observed geochemical differences between the batches are likely to be generated by different extraction conditions of the rhyolitic melt from a slightly heterogeneous mush. The lack of evidence for more mafic recharge prior to eruption (for example, there are no bright cathodoluminescence rims on quartz crystals) suggests that a magmatic input is unlikely to be an eruption trigger. However, tectonic activity could be an efficient way to trigger the eruption of isolated magma batches, with the evacuation of one magma batch causing a disturbance to the local stress field and activating regionally linked faults, which then lead to the eruption of additional magma batches and associated caldera subsidence. In addition, the extensional tectonic regime coupled with a high heat flux could be the controlling factor in the emplacement of some of the shallowest and most SiO2-rich magmas on Eart

Humeurs au sortir du spectacle

1. Il y a un style Brozzoni « Je ne m'attendais pas à ça, je m'attendais à un truc morbide à cause du thème de la pièce et en fait c'était très enlevé, très joyeux. » « C'est une pièce courageuse : trois heures et demie de spectacle sur le thème du chômage, même si cela m'intéresse et que je me sens concernée, ce n'était pas évident. » « Le spectacle est très homogène. Alors que la première partie s'essouffle parfois (notamment à cause du jeu de Shakespeare) les scènes violentes de la deuxièm..

Impact of volcanism on the sedimentary record of the Neuquén rift basin, Argentina: towards a cause and effect model

The analysis of volcano-sedimentary infill in sedimentary basins constitutes a challenge for basin analysis and hydrocarbon exploration worldwide. In order to understand the contribution of volcanism to the sedimentary record in rift basins, we study the Jurassic effusive-explosive volcanic infill of an inverted extensional depocentre at the Neuquén Basin, Argentina. A cause and effect model that evaluates the relationship between volcanism and sedimentation was devised to develop a conceptual model for the tectono-stratigraphic evolution of this volcanic rift basin. We show how the variations in the volcanism, coupled with the activity of extensional faults, determined the types of volcanic edifices (i.e., composite volcanoes, graben-calderas, and lava fields). Volcanic edifices controlled the stacking patterns of the volcanic units as well as sedimentary systems. The landform of the volcanic edifices, as well as the styles and scales of the eruptions governed the sedimentary input to the basin, setting the main variables of the sedimentary systems, such as provenance, grain size, transport and deposition and geometry. As a result, the contrasting volcaniclastic input, from higher volcaniclastic input to lower volcaniclastic input, associated with different subsidence patterns, determined the high-resolution syn-rift infill patterns of the extensional depocentre. The cause and effect model presented in this study isolates the variables of the volcanic environments that control the sedimentary scenarios. We suggest that, by adjusting the first order input parameters of the model, these cause and effect scenarios could be adapted to similar rift basins, in order to establish predictive facies models with stratigraphic controls, and the impact of volcanism on their stratigraphic records.Fil: D'Elia, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; ArgentinaFil: Martí, Joan. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias de la Tierra Jaume Almera; EspañaFil: Muravchik, Martin. University Of Bergen; Noruega. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bilmes, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología.; ArgentinaFil: Franzese, Juan Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentin

Ecritures photographiques des identités collectives : classe, ethnicité, nation dans la photographie en Grande-Bretagne entre 1990 et 2010

This thesis is based on a corpus of photography books and exhibitions dealing with social, ethnic, and national identities in Britain. It adopts a historicizing perspective by analysing the political and social contexts for the production and circulation of photographs, with special attention to cultural policies. Photographs and exhibitions are studied as narratives and practices that contribute to the formation of collective identities. The genre of photographs, and especially the notion of documentary, is discussed throughout the work, as a corollary to the question of identification. With a focus on representations, collective identities, culture and politics, this study lies in the field of cultural studies and regularly summons some of its prominent figures like Stuart Hall or Paul Gilroy. It shows that photography both documented and helped the dissolution of collective identities at the end of the 1990s, by questioning national identity and its representations, and by advocating greater cultural pluralism. As the social question became less prominent, photography departed from traditional social documentary forms and from the figure of the committed photographer. Parallel to this, in the wake of Black Arts, Black Photography was institutionalized with the creation of Autograph-ABP. It is also argued that when the New Labour party promoted a New Britain, some photographs acted as a magic mirror, revealing dissonances in the brand new narrative of a young, creative, multi-ethnic Britain. However, as photography entered the realm of contemporary art, it also became subject to the multiculturalist policies of the period and sometimes turned into a source of ethnicisation and essentialization. After 2001, as multiculturalism was questioned, photography kept documenting the diversity of British society and helped debunk stereotypes, especially those associated with Muslims and refugees in Britain. Finally, the late 2000s are analysed as a period when new modes of social cohesion are explored through photographic practices. Collaborative documentary projects are experimented to re-engage citizens. New photographs documenting the relation between people and territory in Britain seem to suggest that collective identification may rather be found in shared everyday experience.Cette thèse étudie un corpus de livres et d’expositions de photographies qui abordent les questions d’identité sociale, ethnique et nationale [en Grande-Bretagne]. Elle procède à une historicisation du champ photographique en s’intéressant au contexte social et politique de production et de diffusion des images, et en particulier aux politiques culturelles. Elle considère photographies et expositions comme des discours et pratiques qui contribuent à la formation des identités collectives. Le genre des photographies, et notamment le documentaire, est discuté au fil de l’étude, en lien avec la problématique de l’identification. En s’attachant aux rapports entre représentations, identités collectives, culture et pouvoir, l’analyse s’inscrit dans la lignée des cultural studies, dont quelques auteurs, comme Stuart Hall ou Paul Gilroy sont régulièrement évoqués. Il ressort que la photographie se fait le témoin et l’agent d’une dissolution des identités collectives dans les années 1990, en interrogeant l’identité nationale et ses vecteurs et en revendiquant un plus grand pluralisme culturel. Pour aborder la question sociale, devenue moins centrale, elle rompt avec le documentaire classique et la figure du photographe engagé. Par ailleurs, une photographie noire se structure autour d’Autograph-ABP. Lorsqu’une New Britain (jeune, créative et multiethnique) est promue par les travaillistes, la photographie en révèle les dissonances. Néanmoins, en entrant dans le domaine de l’art contemporain, le médium devient aussi l’objet des politiques culturelles multiculturalistes et se fait parfois source d’ethnicisation et d’essentialisation des identités. Après 2001, lorsque le multiculturalisme est critiqué, la photographie enregistre la diversité de la société britannique et démonte les stéréotypes qui visent particulièrement musulmans et réfugiés. Elle est aussi force de proposition dans la recherche de nouvelles formes de cohésion. Des pratiques documentaires collaboratives sont expérimentées pour un renouveau de la citoyenneté. La capacité de la photographie à explorer le rapport entre territoire et citoyens lui permet aussi d’inventer d’autres modes d’identification collective ancrés dans l’expérience quotidienne

Outdoor Leisure Activities in Simon Roberts’s We English Photographic Project: Re-writing landscape and nation

Simon Roberts’s We English series of photographs produced in 2008 has encountered unprecedented success in Britain and abroad. Recording scenes of outdoor leisure activities in various places in England, it has become in a few years the most exhibited series in the history of British photography. It was also published by Chris Boot as a book of fifty-six photographs. The photos show groups of people involved in a variety of activities like hiking, paragliding, angling, hunting, bird watching, horseracing, tobogganing, “mud-racing”, picnicking, or just strolling and relaxing. As the title of the series invites the viewer to consider the Englishness of the activities represented, We English is first analysed as an update on previous representations of English customs, by looking at the rich intertext in Simon Roberts’s pictures, through centuries of English visual culture from 18th century paintings to contemporary photography. Yet this article aims to establish that there is more to Simon Roberts’s project than merely a cultural theatre where English traditions are re-enacted. It is shown that the photographer has considerably broadened the scope through key aesthetic choices. By exploring the relationship between people and public places, We English turns outdoor leisure and landscape into a social theatre. The sense of community and belonging emerges out of shared environment and space rather than from cultural practices that are reproduced and re-presented over time. This paper argues that this approach allows the photographer to reformulate the question of Englishness and national identity altogether and to offer new perspectives on rural England, with outdoor leisure activities creating a sense of openness and conviviality contrasting with previous notions of a closed, stratified, ethnocentric society.La série de photographies de Simon Roberts intitulée We English (2008) connaît un succès sans précédent en Grande-Bretagne et dans le monde, sous la forme à la fois d’expositions et d’un livre de cinquante-six photographies. Ces images réalisées avec un appareil à chambre grand format représentent des scènes d’extérieurs dans différents lieux d’Angleterre, où des groupes de personnes s’adonnent à tous genres d’activités de loisirs comme la randonnée, le piquenique, la chasse, le parapente, la promenade ou le farniente à la plage. Le titre We English semble inviter les spectateurs à déceler des caractéristiques typiquement anglaises dans les pratiques et les paysages représentés. Cet article interroge donc en premier lieu la notion d’anglicité à travers les loisirs et les paysages photographiés par Simon Roberts. Ceux-ci constituent-ils un simple théâtre culturel où se jouent et se re-jouent les traditions anglaises ? Les images de Simon Roberts présentent certes un très riche intertexte avec toute la culture visuelle anglaise que nous retraçons brièvement de la peinture à la photographie contemporaine. Elles peuvent en cela être considérées comme une contribution de plus à la longue histoire de la représentation des loisirs anglais. Néanmoins, cet article montre comment les choix esthétiques de Simon Roberts tendent à transformer ce théâtre culturel en théâtre social. En effet, au fil des photographies, le sentiment d’appartenance et de communauté semble émerger avant tout du partage de l’espace public et de l’expérience collective, et d’une forme de convivialité. L’anglicité ainsi définie s’avère donc beaucoup plus ouverte et moins ethnocentrique qu’il n’y paraît. Au-delà, la série livre une véritable réflexion sur la notion même d’identité nationale

Éléments moins performants

Peter TurriniCie Brozzoni, théâtre de Montbéliard 24-28 avril 1996 Une aventure La mise en scène de la pièce de Turrini a été l'occasion d'une aventure exceptionnelle, qui est évoquée plus que racontée dans sa Chronique, mais dont la presse locale a largement rendu compte. C'est l'histoire d'une compagnie qui dans sa passion du théâtre a trouvé dans le Théâtre de l'unité un compagnon de route. Reconnue au festival d'Avignon off 1994, elle a été invitée par le C.A.P. en janvier 1995 pour prése..

Baptême du feu pour les nouveaux du TUFC à Montbéliard

Les participants à l'atelier du Théâtre Universitaire de Franche-Comté à Montbéliard, pour la plupart des novices dans l'art de l'intervention surprise, ont choisi de participer à leur manière aux journées consacrées à la lutte contre le SIDA. Dès 8 heures du matin, mercredi 29 Novembre, un préservatif géant traversait tranquillement la cour du campus à six mètres au-dessus du sol. Dépannage express pour une étudiante pressée qui réclamait à grand cri qu'on lui prête une « capote ». Le coup d..