Evolution of a Porphyry-Cu Mineralized Magma System at Santa Rita, New Mexico (USA)

The magmatic processes leading to porphyry-Cu mineralization at Santa Rita are reconstructed on the basis of petrographic studies, thermobarometry, and laser-ablation inductively-coupled-plasma mass-spectrometry analyses of silicate melt and sulfide inclusions from dikes ranging from basaltic andesite to rhyodacite. Combined results suggest that magma evolution at Santa Rita is similar to that of sulfur-rich volcanoes situated above subduction zones, being characterized by repeated injection of hot, mafic magma into an anhydrite-bearing magma chamber of rhyodacitic composition. The most mafic end-member identified at Santa Rita is a shoshonitic basaltic andesite that crystallized at 1000-1050°C, 1-3 kbar and log fO2 = NNO + 0·7 to NNO + 1·0, whereas the rhyodacite crystallized at 730-760°C and log fO2 = NNO + 1·3 to NNO + 1·9. Mixing between the two magmas caused precipitation of 0·1-0·2 wt % magmatic sulfides and an associated decrease in the Cu content of the silicate melt from 300-500 ppm to less than 20 ppm. Quantitative modeling suggests that temporal storage of ore-metals in magmatic sulfides does not significantly enhance the amount of copper ultimately available to ore-forming hydrothermal fluids. Magmatic sulfides are therefore not vital to the formation of porphyry-Cu deposits, unless a mechanism is required that holds back ore-forming metals until late in the evolution of the volcanic-plutonic syste

Tectono-magmatic controls on decratonic gold deposits

<jats:title>Abstract</jats:title><jats:p>Magmatic-hydrothermal gold–copper deposits in post-subduction settings represent essential targets for mineral exploration, but controls on their formation remain controversial. The early Cretaceous lode Au districts that formed during lithosphere destruction of the North China Craton provide an ideal opportunity to better understand the key tectono-magmatic factors responsible for the genesis of Au-rich deposits in post-subduction settings. Here, we present a LA-ICP-MS study of silicate melt inclusions and sulfide inclusions from ore-related mafic to intermediate rocks in the central Taihangshan Au district in the interior of the North China Craton to constrain the content and evolution of magmatic ore metals ± volatiles. The results, combined with numerical modeling, suggest that the ore-related magmas contained only a few ng/g Au, which is similar to the Au content of non-mineralization-related mafic to intermediate magmas worldwide. The low Au content of the lode Au-related magmas suggest that large volumes of magmas had to accumulate in the middle to lower crust through trans-lithospheric fault systems to produce the lode Au deposits. It is further suggested that the lode Au-related magmas were alkali-rich, hydrous, oxidized and relatively rich in sulfur and chlorine (mafic melt inclusions contain 0.14‒0.24 wt% S and 0.1‒0.2 wt% Cl). These properties are considered critical for the generation of auriferous ore fluids. By comparing the tectono-magmatic setting of the giant Jiaodong Au province (~ 4000 t Au) with the central Taihangshan district (~ 150 t Au), we propose that the much larger total Au tonnage of the Jiaodong district results from the accumulation of a much larger volume of ore-forming magmas at deep crustal levels, induced by a stronger degree of lithosphere modification. In addition, given that the composition of lode Au-related magmas is similar to that of porphyry Cu–Au-related magmas, the lack of giant, early Cretaceous porphyry Cu–Au deposits in the North China Craton suggests that strong extensional settings favor the formation of lode Au deposits instead of porphyry Cu–Au deposits. The present study, therefore, has general implications for the genesis of Au-rich deposits in strongly extensional settings.</jats:p&gt

Le test de concordance de script (TCS) explore-t-il des processus de raisonnement clinique différents de ceux du QCM à contexte riche (basés sur des cas cliniques) ? : et si oui, quels sont-ils ?

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

L’identification et la remédiation des difficultés de raisonnement clinique en médecine (État des pratiques, recherche d’outils et processus pour soutenir les cliniciens enseignants)

INTRODUCTION : Le raisonnement clinique est au coeur de l’exercice professionnel. Cependant, nous manquons d'instruments pour identifier et objectiver les difficultés de raisonnement clinique, et il existe relativement peu de descriptions de méthodes de remédiation définies. Un important travail reste donc à faire, pour mieux comprendre comment les difficultés se manifestent dans le raisonnement clinique des étudiants en formation, mais également pour rendre ces concepts plus accessibles aux enseignants; ceci permettra alors d’améliorer la qualité de la démarche d’identification des difficultés, et d’envisager des remédiations ciblées et efficaces. OBJECTIFS : Cette recherche s’articule d’une part, autour de l’objectivation et la compréhension des pratiques actuelles des cliniciens enseignants en médecine, d’autre part, autour de la construction et l’implantation d’outils et de processus susceptibles de faciliter la démarche de diagnostic et de remédiation des difficultés de raisonnement clinique. MÉTHODOLOGIE : Une recherche de type qualitative, utilisant les méthodes de la recherche action participative s’est révélée pertinente pour atteindre nos objectifs. La recherche est composée de quatre étapes : 1. Une étude exploratoire. 2. La construction et de l’implantation d’un premier outil dans trois milieux cliniques en médecine familiale. 3. L’élaboration d’une taxonomie des difficultés de raisonnement clinique ainsi que la construction d’un nouvel outil. 4. Le développement d’une approche globale pour soutenir et former les cliniciens enseignants. RÉSULTATS : Les enseignants ont une perception rapide, mais qui demeure globale et intuitive, des potentielles difficultés de raisonnement clinique des résidents. Cette perception ne se traduit pas forcément en termes pédagogiques. Nous avons pu observer l’absence de processus pédagogiques organisés et structurés pour la gestion de ces difficultés. Ceci semble projeter les cliniciens enseignants dans une zone d’inconfort, en les confrontant à un manque de maîtrise et à l’incertitude au sujet de leurs actions pédagogiques. La catégorisation des difficultés de raisonnement clinique que nous avons construite permet d’identifier les difficultés telles qu’elles se manifestent dans le quotidien des supervisions cliniques. Cet outil a cependant besoin d’être intégré dans un processus plus global. CONCLUSION : Une approche globale qui comprenne le développement de processus implantés par le Département, l’implantation d’outils, la vulgarisation de la théorie, et la formation des enseignants est déterminante.CONTEXT: Clinical reasoning is central to medical practice. However, we lack tools to identify and objectify the difficulties of clinical reasoning, and there are relatively few descriptions of remediation methods defined. Much work remains to be done to better understand how the problems manifest themselves in the clinical reasoning of students in training, but also to make these concepts more accessible to teachers.Then this will improve the quality of the identification process difficulties, and allow considering targeted and effective remediations.PURPOSE: This research is based on the one hand, around the objectification and understanding of current practices of clinical teachers, on the other hand, around the construction and implementation of tools and processes to facilitate the process of diagnosis and remediation of difficulties in clinical reasoning. METHODOLOGY: A qualitative research, mainly using the methods of participatory action research has been relevant to achieving our goals. The research consists of four steps: 1. An exploratory study 2. The construction and implementation of a first tool in three clinical settings 3. The development of a taxonomy of difficulties in clinical reasoning and the construction of a new tool. 4. The development of a comprehensive approach to support and train clinical teachers RESULTS: Teachers have a quick perception, but still global and intuitive, of the potential difficulties of clinical reasoning residents. This perception does not necessarily move into pedagogical terms. We observed the absence of organized and structured pedagogical processes to manage these difficulties. This seems to project the clinical teachers in a zone of discomfort, by confronting them with a lack of control and uncertainty about their educational activities. The categorization of clinical reasoning difficulties that we have built allows identifying the problems as they occur in everyday clinical supervision. This tool, however, needs to be integrated into a larger process. CONCLUSION: It is necessary to develop a comprehensive approach that includes faculty development process, implementation tools, vulgarization of the theory, and teacher training

The international standardisation arena and the civil society participation stakes : results of the INTERTERM project

International standards are playing an increasingly important role in market governance while frequently exerting direct effects on health, safety and the environment. Yet civil society, more often than not, is absent from the standardisation procedures. The recommendation made here is to foster the participation of civil society actors in standardisation by framing standardisation topics in a way that will encourage the mobilisation of these actors in accordance with their repertoire of actions and interests and by organising the plural expertise required for the effective participation that is necessary if they are to exert an influence

Les arènes de la normalisation internationale à l'épreuve de la participation de la société civile : résultats du projet INTERNORM

Les normes internationales occupent une place de plus en plus importante dans la gouvernance des marchés et ont souvent une incidence directe sur la santé, la sécurité et l'environnement. Mais la société civile est le plus souvent absente des procédures de normalisation. Il est recommandé de favoriser la participation des acteurs de la société civile dans la normalisation par une mise en forme des travaux de normalisation à même d'encourager leur mobilisation selon les thèmes et enjeux abordés et par l'organisation de l'expertise plurielle requise pour une participation effective à même de leur conférer une certaine influence

Les arènes de la normalisation internationale à l'épreuve de la participation : le projet INTERNORM

This paper presents the results of the INTERNORM action-research designed to support the involvement of not-for-profit organisations in international standard setting bodies such as the ISO. It analyses how a participatory mechanism can influence the institutional environment of technical diplomacy, and reflects on the democratisation of the field of international standardisation. This reflection draws upon international relations literature on new forms of global governance and social studies of science and technology

Using script theory to cultivate illness script formation and clinical reasoning in health professions education

Background: Script theory proposes an explanation for how information is stored in and retrieved from the human mind to influence individuals’ interpretation of events in the world. Applied to medicine, script theory focuses on knowledge organization as the foundation of clinical reasoning during patient encounters. According to script theory, medical knowledge is bundled into networks called ‘illness scripts’ that allow physicians to integrate new incoming information with existing knowledge, recognize patterns and irregularities in symptom complexes, identify similarities and differences between disease states, and make predictions about how diseases are likely to unfold. These knowledge networks become updated and refined through experience and learning. The implications of script theory on medical education are profound. Since clinician-teachers cannot simply transfer their customized collections of illness scripts into the minds of learners, they must create opportunities to help learners develop and fine-tune their own sets of scripts. In this essay, we provide a basic sketch of script theory, outline the role that illness scripts play in guiding reasoning during clinical encounters, and propose strategies for aligning teaching practices in the classroom and the clinical setting with the basic principles of script theory