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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

John Oman : Orkney's theologian : a contextual study of John Oman's theology with reference to personal freedom as the unifying principle

McKimmon, Eric George January 2012 (has links)
This thesis is a contextual study of the work of Orkney theologian John Oman (1860- 1939), with reference to personal freedom as the unifying principle. Oman’s early life in Orkney, his philosophical awakening in Edinburgh and his wide reading of European thought are the contexts explored. From these contexts emerges a theology that is eclectic in nature and which finds coherence in the principle of personal freedom. Oman’s concept of freedom is defined theologically, metaphysically and personally; this is followed by discussion of its application to the specific subject areas of Christology and Ecclesiology. The priority that Oman gives to personal freedom results in a distinctive theology of Christ and the Church. Thus, the uniqueness of Christ lies in the freedom which he exemplifies in humanity; and the Church is a community of freedom transcending institutional expression. The thesis concludes that Oman’s sui generis theology is the outcome of the heritage of freedom gifted in various contexts. However, this heritage of freedom was radicalised by Oman, as he developed his own theological vision.
102

Exploring the use of e-government/online social network in the Government of Oman

Al Bulushi, Ali Salim January 2018 (has links)
The rapid development of information and telecommunication technologies (ICTs) in the 21st century has changed society at all levels: individual, group, company and government. As a result, there has been a significant rise in the availability of ICTs and related technologies around the globe, including in developing countries. ICTs include internet infrastructure such as the use of mobile devices, the internet connection and the affiliated platforms of online social networks (OSNs). The provision of online products and services by the government is known as electronic e-government. From a theoretical literature review it was found that research emphasising the use of OSNs in e-government and OSNs in Oman was scarce. Further, studies investigating and explaining the use of OSNs in the public sector and government were few. This motivated the researcher to explore and understand this issue, leading to the formation of the aim of this research: To explore and understand the use of e-government/OSNs in a public sector organisation in a developing country, in this case, government organisations in Oman. To achieve this, a comprehensive and detailed literature review of e-government/OSN research in developed, developing and Gulf countries was completed. Additionally, related theories on ICT diffusion and adoption, institutional theory and culture theory were used as a lens through which a better understanding of e-government/OSNs would be provided and to develop the initial conceptual framework that was then applied in practice. To acquire the data for this research a qualitative research approach involving the use of a case study was employed. The data collection techniques used included observations, interviews and a review of related archival documents. A total of 44 people were interviewed and an additional 37 participants assisted with the observational part of this study. The research results revealed that government organisations adopted OSNs to explore the use of the technology and to cope with the increasing public demands of government. The study revealed many benefits for government organisations after OSNs were adopted, including greater public interaction and participation, increased information transparency, better understanding and increased public awareness of government services, leading to better work efficiency and effectiveness. Further, public interaction and participation was noted to be important for the government as it helped government employees be more responsible and accountable for their work actions. Additionally, due to the application of OSNs, organisational and national cultural changes were identified that led to government work process and procedures being amended such that there was more public participation and interaction. This led to an influence of government policies and decision-making with regards to public services. After the applied part of this study, the initial conceptual framework was revised to reflect the practical aspects of this research. The contributions of this study are: for e-government research, it will add to the increasing body of knowledge in this area. For Omani theoretical literature, it will widen the boundaries of knowledge and OSN use, particularly for the Omani government and other governments in developing countries that seek to use e-government solutions. In countries where cultural aspects are important, this study can provide insights that may not have been considered before. Further, this study has shown that understanding organisational changes and the cultural contexts with respect to e-government and OSN use is important; therefore, more knowledge in this area can be provided by this study. For policymakers, the contribution of this research is the provision of an understanding of a wide range of issues surrounding the adoption of new technologies. In turn, this can assist policymakers with policy-formation such that their institutional purposes and roles can be fulfilled. This study contributes to private sector organisations including internet and OSN providers by explaining and illustrating the benefits of using OSNs in a developing country with an autocratic regime that seeks to provide citizen benefits.
103

The influence of entrepreneurial leadership on factors affecting SME growth in supply chains : the case of Oman

Al-Matani, Khalid January 2018 (has links)
This thesis explores in depth the factors influencing growth in small and medium enterprises (SMEs) from a supply chain perspective and examines how entrepreneurship affects them in Omani SMEs. The study is undertaken in order to complement the scarce literature on SMEs related to supply chains and improve the understanding of what factors are crucial in determining growth in them. The research is focused on the role of entrepreneurial qualities and behaviours for the growth of SMEs in developing countries, as their economies are more dependent on smaller companies. The context of this research is within Oman, which represents a typical developing economy containing a large number of active SMEs. The main factors for SMEs growth are identified through a literature review of past and contemporary research studies on supply chain networks, SMEs, growth and entrepreneurship. The factors are divided into areas related to the positions of the company (market position of the firm, negotiating power, Supply chain relationships and firm's image), and to SMEs' value-adding capabilities (cost optimisation, and innovations). The review also reveals that the critical entrepreneurial traits are: managers' culture and motivations, strategic thinking, sense for opportunities, risk-taking, continuous learning, their leadership abilities and networking skills. Based on the literature review findings a conceptual framework is proposed. This research is exploratory and explanatory in nature and relies on a qualitative approach to find out how entrepreneurship relates to growth in SMEs. Primary data is collected from in-depth semi-structured interviews with managers in 25 Omani SMEs from various industrial and service sectors 10 representing different supply chain positions. The data is processed through content analysis using the factors identified from the literature review as initial themes. The findings affirm the importance of SMEs' supply chain positions and their value adding capabilities for growth. Furthermore, all elements of entrepreneurship are found to affect growth factors. Results show positive attitude and growth aspirations lead to more proactive market behaviour, while strategic thinking helps managers choose more sustainable market positions. Results indicate leadership improves company costs by increasing employees' motivation and productivity and also facilitates the implementation of innovations. Learning orientation is stated to be crucial for exploring new ideas for innovations, while a good sense for opportunity helps managers evaluate them and choose the right ones. Finally, risk-taking propensity emerges as instrumental in the actual undertaking of innovation projects as it is needed for initiating them.
104

Transnational higher education and quality : Oman's experience and the concept of policy borrowing

Al Shanfari, Samya Awadh January 2017 (has links)
Globalization has had a well-documented impact on higher education (e.g. Giddens, 1990; Ginkle, 2003; Altbach and Knight, 2007). The attendant massive expansion of higher education both globally and at national level has brought with it increasing concerns regarding quality. One context within which such concerns are evident is that of Transnational Higher Education (TNHE). TNHE, also known as cross-border education, mainly refers to education that is provided to students residing in a country other than the one where the awarding institution is located (UNESCO/Council of Europe, 2001). TNHE takes various forms and serves multiple objectives but the multidimensional phenomenon can be described as an example of Policy Borrowing (Phillips and Ochs, 2003). Oman is a country whose modern educational system was established very recently (1970) and is still expanding rapidly. As elsewhere in the ‘developing world’, the Omani government has met the increasing demand for higher education in large part by encouraging private higher education provision. However, this has been associated with an increasing desire to build capacity and assure quality of provision. In response, the Omani Ministry of Higher Education turned to TNHE for solutions: private sector providers in Oman have been required to enter academic partnerships with internationally recognized universities. In this research, I investigate the rationales, approaches and perceptions of this process from a receiver country perspective and address the implications. Most published research on TNHE focuses on providers’ perspectives and activities, and the impact of TNHE has only been studied in a small number of generally sizeable countries. However, the Gulf States, especially Oman, have not received the same attention, mainly due to the fact that TNHE is a recent phenomenon in this part of the world. Research to date in Oman thus remains very limited (Ameen, Chapman and Al Barawani, 2010; Al Barawani, Ameen and Chapman, 2011). The main objective of the research at the centre of this Thesis was therefore to explore the expectations, experiences and conclusions of a sample of staff of three private sector universities in Oman regarding TNHE, within which their university was/is active. The topic is investigated in the context of national policy and institutional TNHE strategy. Data were generated through documentary analysis and qualitative interviews. In-depth face-to-face interviews were conducted in three stages: Stage one: desk research and pilot study to set the direction for the research (8 participants) Stage two: interviews carried out over multiple visits to the three private universities selected as the cases (29 participants) Stage three: interviews with policy- and decision-makers (6 participants), to help in the process of reviewing and contextualizing the data from Stage 2. Data analysis revealed variation from the existing literature on this topic when it comes to defining the concept of affiliation, which is central to the approach taken in Oman to TNHE, as well as inconsistency across the three case universities, highlighting the complex dynamic that exists, with hugely varied expectations, numerous rationales and motivations and varying experiences being reported. Findings also reveal that, as reported by the majority of interviewees, the key rationales for engagement with TNHE are building capacity and assuring quality, alongside other rationales such as generating revenue and increasing student recruitment, which form the main driving force on the part of receiver institutions. This is consistent with the overall national imperative of increasing the number of HE places available for Oman’s young people, although the focus on volume is seen by the informants in the institutions as falling short in terms of capacity building and the enhancement of quality. Many interviewees voiced concerns that foreign partners’ approaches do not necessarily contribute to capacity building and may remain limited in scope, impacting on the quality of teaching and learning in ways that are not necessarily positive. Indeed, concerns were reported that the original overarching educational rationales of improving quality and capacity building may have been displaced by a more instrumental emphasis, for example on income generation. Some informants were firmly in favour of developing indigenized systems and reducing reliance on foreign partners. This point is taken up in a concluding discussion of the implications of the findings for Omani universities currently dependent on Transnational Higher Education, and the implications of this dependency for the Omani higher education system as a whole.
105

An Institutional Perspective on Talent Management: Four Case Studies in the Banking and Petroleum Sectors in the Sultanate of Oman

Rashid Saif AL Amri, Raiya January 2016 (has links)
Talent Management (TM) is of growing interest within academia and in the strategic HRM literature in particular. Despite many attempts to study TM from different perspectives, it remains an ambiguous and elusive concept that is difficult to define and hence challenging to explore and address. Studies on TM are based within Western contexts and therefore it is questionable whether TM models and theories are transferable to other nations and contexts. This research examines the nature of TM in the Middle Eastern context of Oman, from the perspective of Institutional Theory. Through a qualitative, multiple case-study approach, data was collected from four banking and petroleum-sector organisations through semi-structured interviews. The findings suggest that the different influences of institutional pressures (e.g. nationalisation, competition, organisational characteristics) have significantly shaped TM in these organisations. The findings show that TM effectiveness and sustainability depends upon a range of factors including: generational differences, employee expectations, the role of expatriates and national culture. Thus, TM and its approach has to be understood and framed within the context of institutions which interact with organisational characteristics; this shapes the way in which the organisations define their TM approach in order to seek legitimacy, business continuity and effectiveness.
106

Etude pétrologique, géochimique et structurale de la zone de transition dunitique dans l'ophiolite d'Oman : identification des processus pétrogénétiques à l'interface manteau/croûte / Complex Monge-Ampère flows on compact Hermitian manifolds

Rospabé, Mathieu 19 January 2018 (has links)
L'origine de la zone de transition dunitique (DTZ) à l'interface manteau-croûte est mal connue, ainsi que les processus physico-chimiques impliqués dans sa genèse. Pour aborder cette question, ce travail a porté sur l'étude pétrologique, géochimique et structurale de 20 coupes (600 échantillons) levées dans la DTZ du massif de Sumail (ophiolite d'Oman), épaisse de plus de 400 mètres à l'aplomb d'un paléo-diapir mantellique. Au-delà des données in situ sur minéraux (microsonde, LA-ICP-MS) et des compositions en éléments majeurs des roches totales, le développement d'une procédure analytique a permis l'acquisition des compositions en éléments en traces des dunites dont les teneurs sont de l'ordre du ng.g-1. La DTZ est faite de dunites pures (olivine et chromite) et de dunites imprégnées, contenant une quantité variable de minéraux interstitiels ayant cristallisé à partir d'un magma percolant. Ces faciès renferment des minéraux d'une variété insoupçonnée incluant, en plus de ceux clairement issus d'un MORB (clinopyroxène et plagioclase), de l'orthopyroxène, amphibole, grenat, et des diopsides témoignant d'un processus d'hybridation entre le MORB et des fluides hydratés. Les forts rapports Mg# et teneurs en TiO2 des orthopyroxènes et amphiboles ainsi que la composition des clinopyroxènes, intermédiaire entre clinopyroxènes magmatiques et diopsides hydrothermaux, a permis de contraindre la composition du magma hybride qui résulterait du mélange entre un magma d'affinité tholéiitique et un fluide supercritique riche en silice, voire trondhjémitique issu de la fusion incongruente hydratée des orthopyroxènes mantelliques, similaire au produit de fusion hydratée des roches environnantes (péridotites serpentinisées, troctolites, gabbros). Ces minéraux sont observés en position interstitielle et en inclusion dans les chromites, témoignant de leur origine précoce et du fait que les magmas hybrides ont participé à la formation de la DTZ. La combinaison des interprétations des données in situ et des données roches totales a permis la déconvolution du message polyphasé enregistré par les dunites : la signature du protolithe, celles de la dunitisation et du rééquilibrage de la matrice d'olivine avec un MORB percolant (métasomatisme cryptique), la signature de refertilisation par la cristallisation des minéraux interstitiels (métasomatisme modal), ainsi que les effets de la serpentinisation. Il apparaît que les dunites pures, caractérisées par un spectres de terres rares en forme de U ou de V, semblent avoir acquis cette signature très précocement, probablement lors de la phase initiale de leur genèse sous l'effet de rééquilibrages avec des liquides très riches en éléments incompatibles (REE, Th, U, HFSE) et pouvant correspondre au magma hybride. L'étude structurale de la DTZ dans le massif de Sumail a montré l'influence de la tectonique synmagmatique sur la structuration de la DTZ, se traduisant par l'alternance d'horizons imprégnés ou non ainsi que par l'évolution verticale sur plusieurs dizaines de mètres des compositions chimiques à l'approche des zones de failles. On l'observe notamment pour les teneurs en éléments immobiles dans les fluides tels que le Ti, les REE ou le Th. La DTZ semble s'être développée dans un environnement transtensif dont les deux systèmes de failles principaux N130 et N165-180 ont accommodé la percolation des magmas et fluides responsables de la dunitisation ainsi que l'introduction des fluides hydrothermaux pouvant conditionner les échanges globaux avec les enveloppes externes.La comparaison avec les DTZ d'autres massifs en Oman ou à Trinity (Californie), ayant évolué dans un contexte magmatique différent, montre également l'importance des failles synmagmatiques dans la structuration de la DTZ. Les liquides qui ont percolé dans ces DTZ apparaissent systématiquement sous-saturés en Al et saturés en H2O, amenant à interpréter le caractère hydraté comme une condition critique pour la genèse des dunites. / The origin of the dunitic transition zone (DTZ) between the mantle and the crust is still largely unknown, as well as the physical and chemical processes involved in its genesis. To address this topic, this thesis focused on the petrological, geochemical and structural study of 20 cross-sections (600 samples) collected along the DTZ from the Sumail massif, Oman ophiolite, 400 meters thick and located above a former paleo-mantle diapir. In addition to mineral compositions acquired using in situ methods (microprobe, LA-ICP-MS) and to whole rock major elements, the development of an analytical procedure permitted to determine trace element contents in dunites that display low concentrations (regularly about one ng.g-1). The DTZ is made of pure dunites (olivine and minor chromites), and of impregnated ones, containing a variable amount of interstitial minerals that crystallized from a percolating melt. These latter rocks contain an unexpected mineralogical variety with, in addition to clinopyroxene and plagioclase showing a MORB affinity, the presence of orthopyroxene, amphibole, garnet and diopsides that highlights a hybridization process between the MORB and hydrated fluids. The high Mg# ratio and TiO2 content in orthopyroxene and amphibole together with the clinopyroxene composition, intermediate between igneous clinopyroxene and pure hydrothermal diopside, allow deciphering the nature of the parent melt as the result of the mixing between tholeiitic melt and a supercritical water enriched in silica, or trondhjemitic fluid issued from the hydrated incongruent melting of mantle orthopyroxene, similar to melts produced by the hydrated melting of country rocks (serpentinized peridotites, troctolites, gabbros). All these minerals are observed both in interstitial position and as inclusions in chromite, showing that they crystallized early and that hybrid melts participated to the genesis of the DTZ. The comparison between mineral and whole rock compositions permitted to highlight the different processes that led to the observed chemical signatures of dunites: the protolithe signature, the dunitization process, chemical reequilibration between the olivine matrix and the percolating MORB, refertilization following the crystallization of interstitial minerals, as well as the effects of later serpentinization. Pure dunites, characterized by U or V-shaped REE patterns, seem to have acquired early the LREE-enriched signature that probably results from the reequilibration with silica- and incompatible trace elements-rich fluids (REE, Th, U, HFSE) generated through the harzburgite orthopyroxenes incongruent melting and probably reflecting the hybrid melt that crystallized interstitial hydrous minerals. The structural study of the DTZ in Sumail highlights the effect of synmagmatic faults on the DTZ development, resulting in the alternation between pure and impregnated horizons as well as in the vertical chemical structuration with compositions evolving on few tens of meters until fault zones. This is particularly true for chemical species expected as immobile during weathering as Ti, REE or Th. The DTZ seems to have been developed in a transtensional environment structured by two main faults systems, oriented N130 and N165-180. These faults spatially constrained both the melt flow, thus the dunitization, and the introduction of hydrothermal fluids probably oceanic in origin. This meeting zone between igneous and hydrothermal fluids can strongly influence the chemical exchanges and distribution between the deep lithosphere and the surface. The comparison between the Sumail DTZ and other ones from Oman or Trinity (California) ophiolites, which evolved in a different magmatic setting, shows the systematic role of synmagmatic faults. Melts that percolated these other DTZ were under-saturated in Al and saturated in water, allowing to interpret the hydrated component as an essential condition for dunites genesis at the mantle-crust transition.
107

Type 2 Diabetes Mellitus and Colorectal Cancer Risk and Survival in Oman

Mafiana, Rose Ngozi 01 January 2017 (has links)
Type 2 diabetes mellitus (T2DM) and colorectal cancer (CRC) are 2 chronic diseases with common risk factors related to physical inactivity, obesity, and diet. Literature on T2DM as a risk factor for CRC development and survival in Oman is scarce. Using de-identified archival data provided by Sultan Qaboos University Hospital (SQUH) Oman, a retrospective, case-control, and time-to-event study designs were used to compare odds of developing CRC, and survival rates among adults with and without T2DM. The ecosocial theory provided the theoretical base for this research. Logistic regression was used to examine the odds of developing CRC among 114 cases versus 170 hospital controls. The Cox proportional hazards regression was used to compare survival rates among 228 CRC cases by T2DM status and survival rates by T2DM status across strata of gender, age group, and tumor location and cancer stage. According to the study findings, after having adjusted for potential confounding variables, there was no association between T2DM and odds of developing CRC (OR = 1.49, 95% CI: 0.29-7.68, p = 0.64) or between T2DM and CRC survival rates (HR = 1.07, 95% CI: 0.65 -1.75, p = 0.80). There was also no association between T2DM and CRC survival rates across the strata of potential effect modifiers examined. This research could contribute to positive social change by creating awareness among policy makers that will provide them with information on CRC risk-reduction strategies in the Omani population.
108

Cystic fibrosis in children of the Eastern Arabian Peninsula : A clinical, spatial and genetic study.

Dawson, Kenneth P, mikewood@deakin.edu.au January 2003 (has links)
Aim: The aim of this thesis is to describe the process by which the inherited disease, cystic fibrosis, (CF) was recognised as an important clinical entity in the United Arab Emirates (UAE) and the Sultanate of Oman (Oman). It examines the clinical presentation of the first patients and assesses their degree of severity. Further, it describes the first studies carried out to determine the underlying CF mutations associated with the disease in the UAE and Oman. An estimate is offered of the birth frequency of the condition. Overall, the cultural, geographical and historical aspect of the societies in which the disease occurs is stressed. Methods: An initial literature search was carried out using Medline of any literature pertaining to the Arab World and CF. this was read and classified into the relevance to Arabs in general, the Middle East and then specifically the Arab (Persian) Gulf societies. Thereafter, a clinic was established at Tawam Hospital, Al Ain, UAE, for children presenting With chronic respiratory disease that could serve as a national referral centre. It was run by the Author as a service of the Paediatric Department of the UAE University Medical School. I sent a letter to every Paediatrician working in the UAE informing them of our clinic and offering our services for the diagnosis and management of chronic respiratory disease in children. This was based on the author's experience as a respiratory paediatrician in Australia and New Zealand and as the Professor of Paediatrics in the UAE. No such service then existed in the UAE. Funding was sought to establish a research programme and develop a molecular genetics laboratory in the UAE Medical School. A series of successful research applications provided the grants to commence the investigations. Once a small number of children had been identified as having CF from those referred to the respiratory clinic, the initial project was to assess and report their clinical presentation. Following this an early start was made on the identification of the mutations responsible. Once these were established an attempt was made to estimate the frequency of the condition at birth. Additional clinical studies revolved around assessing the severity of the condition that was associated with the main mutations that were identified. A clinical comparison was made with those with the mutation AF508 and the other main mutation, despite the obvious limitation of small numbers then available. Radiological assessment was made to evaluate the progression of the disease. The final aspect of the study was to assess patients from Oman and compare their findings and mutations with the neighbouring UAE. Based on information gained hypotheses are proposed regarding the spread of the gene mutation by population drift. Thesis outline: A literature review is presented in the form of a critique on the disease and a resume of the relevant aspects of the genetics of CF. Additionally, facts about the two countries' geography and history are presented. Finally, knowledge about CF mutations and population origins from other areas is presented. The second main section deals with the clinical features of the disorder as it presents in the UAE. Molecular findings are then presented and details of the common mutation found in Bedouin Arabs. Hypotheses are then presented based on the information gathered. Results: CF is not a rare disease in the Arab children of the UAE and Oman. These findings refute previous reports of CF being a rare or non-existent disease in Arabs. The condition presents with a severe clinical picture, with early colonisation of the respiratory tract with staphylococcus, haemophilus and pseudomonas organisms, even with conventional CF management practices in place. The CF mutation S549R is prevalent in Arabs of Bedouin stock, while AF508 is found in those of Baluch origin. The former may be descendants of Arabs who left southern Arabia and travelled to the Trucial Coast at the time of the destruction of the great dam at Marib. The origins of this mutation may lie in the area that corresponds to the modern Republic of Yemen. The latter groups are descendants of those who came originally from Baluchistan. It is hypothesised also that the ancestral home of the AF508 mutation may be in the geographical area now known as Baluchistan, that spans three separate modern political territories. The evidence presented supports the concept that the S549R mutation may be associated with a severe, if not the severest, clinical pattern recognised. It equates with that seen with the homozygous AF508 genotype. The absence of an additional mutation in the promoter region accounts for the different clinical pattern seen in previously described patients. Conclusions: There needs to be a major awareness of the presence of CF as a severe clinical disease in the children of the Gulf States. The clinical presentation and findings support the concept of under recognition of the disease. Climatic conditions put the children at special risk of hyponatraemia and electrolyte imbalance. The absence of surviving adults with the disease suggests premature deaths have occurred, but the high fertility rates have maintained the gene pool for this recessive disorder.
109

NATURE ET REPARTITION DES FILONS BASIQUES DANS LA SECTION MANTELLAIRE DE L'OPHIOLITE D'OMAN : Implications pour la genèse des MORBs Implications pour la genèse des MORBs

Python, Marie 06 June 2002 (has links) (PDF)
L'ophiolite d'Oman est un fragment de dorsale océanique téthysienne obducté sur la marge continentale arabe. Sa section mantellaire contient de nombreux filons basiques assimilés à un réseau de drainage magmatique mantellique fossile ayant alimenté la croûte. L'étude pétrographique et microsonde d'un millier de filons conduit à définir une quarantaine de types lithologiques différents montrant une grande variété de conditions pétrogénétiques dans le manteau. Ces lithologies appartiennent à deux séries de différenciation dont les caractères pétrographiques et géochimique sont bien distincts. La première s'apparente à une série tholéiitique de type N-MORBs et affleure dans quelques régions limitées dont une bande parallèle à l'axe de la paléo-dorsale centrée sur la zone diapirique de Maqsad. L'alimentation de la croûte (majoritairement de type "N-MORB") s'est probablement focalisé au niveau de ces quelques zones. La chimie de ces cumulats couvre largement le domaine des MORBs, illustrant la faiblesse du mélange dans un réseau de drainage magmatique au sein du manteau et la précocité de la cristallisation dans l'histoire des magmas. Les caractères pétrographiques montrent que ces magmas ont circulé dans un environnement "asthénosphérique" relativement chaud. La seconde série s'apparente à un magma parent plus siliceux et déprimé de type andésitique. Elle affleure sur la plus large part de la section mantellaire et est quasi absente dans les zones "tholéiitiques". Les modes d'affleurement et les caractères pétrographiques de ces filons impliquent un contraste de température liquide-encaissant qui pourrait provoquer une cristallisation rapide du magma. Ce qui entraînerait une difficulté d'extraction à l'origine de leur rareté dans la section crustale omanaise. Certains caractères chimiques de ces roches et l'existence de lithologies métamorphiques magnésiennes sont compatibles avec la refusion d'un manteau déprimé hydraté lors d'un précédent épisode d'hydrothermalisme.
110

ENREGISTREMENT STRATIGRAPHIQUE DES PHASES D'EMERSION SUR LES PLATES-FORMES CARBONATEES Une étude intégrée à l'affleurement et en sismique de la plate-forme cénomanienne d'Oman (Formation Natih)

Grélaud, Carine 15 December 2005 (has links) (PDF)
L'émersion de plates-formes carbonatées est généralement enregistrée dans les séries sédimentaires par des phénomènes de karstification et de pédogenèse. Les structures d'érosion, telles que des incisions qui se développent le long des surfaces d'émersion, ont quant à elles été très rarement observées et étudiées. La reconnaissance de ces incisions et l'analyse de leur remplissage permet une meilleure caractérisation et une meilleure hiérarchisation des limites de séquence de dépôt, notamment dans le cas où les surfaces d'émersion ne présentent pas ou peu d'évidences pétrographiques d'une émersion. Deux surfaces d'incision successives ont été analysées dans la partie supérieure de la première séquence de dépôt de 3ème ordre de la Formation Natih en Oman (Albien supérieur-Turonien inférieur). L'interprétation de données sismiques régionales a permis de déterminer et quantifier des géométries progradantes au sein de cette séquence de plate-forme et de corréler les surfaces d'incision à des prismes de régression forcée sur les bordures d'un bassin intrashelf. Cette analyse sismique régionale a ainsi permis de mettre en évidence dans le détail la complexité de l'architecture des cycles de 3ème et 4ème ordre dans les systèmes de plate-forme carbonatée. A ce canevas stratigraphique complexe se superposent les hétérogénéités associées aux phases d'émersion : incisions, prismes de bas niveau marin. L'analyse sédimentologique et stratigraphique détaillée de trois zones d'affleurement aboutit à une description précise des géométries et des faciès de remplissage des incisions, et leur comparaison en fonction de leur position paléogéographique. La morphologie, l'orientation et l'étendue de ces structures ont été analysées à partir d'une interprétation sismique détaillée et couplée à une modélisation sismique ciblée. Des chenaux de marée se développent à différents niveaux stratigraphiques de la Formation Natih marquant en général des phases d'inondation de la plate-forme interne. L'analyse comparative de ces chenaux et des incisions a permis d'établir les similitudes et les principaux critères de différenciation de ces deux types de structures chenalisées dans les séries de plate-forme carbonatée. L'intégration de données d'affleurement et de données sismiques à différentes échelles (locale et régionale) permet d'interpréter et de discuter l'origine et les facteurs qui contrôlent le développement de ces incisions et de proposer une amélioration du modèle stratigraphique. Les deux générations d'incisions enregistrent des variations rapides du niveau marin avec des amplitudes de 20 à 30 m pendant le Cénomanien inférieur. Il ne s'agit pas ici d'un cas unique, puisque des incisions et des prismes de régression forcée ont également été observés dans des systèmes terrigènes de la partie ouest du Canada et en Inde, ainsi que dans des systèmes carbonatés sur la plaque arabe, dans le même intervalle stratigraphique.

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