Job title:
PhD position
Company:
Job description
Offer DescriptionThe western Mediterranean opened up at the expense of the Tethys from the Oligocene onwards. During this opening, the Tethys margins were partly inverted, lost to subduction and incorporated into the alpine Tell and Rif belts (Leprêtre et al., 2018; Gimeno-Vives et al., 2019, 2020). There, the proximal portions of the margin are still accessible, but the distal parts and the nature of the Tethys crust remain virtually unknown, with the exception of the Algerian Eastern Tell where at least one example of an ophiolitic succession representing the Tethyan crust has been described, here clearly of an oceanic nature (Boukaoud et al., 2021). The Western Tell, between Oran and the Moroccan border, is therefore a key area.
In this underexplored area (2 PhDs in 50 years: Guardia, 1975; Ciszak, 1993), a particular feature is what are known as « external metamorphic massifs ». Here, metamorphism affects rocks that belong to the extrenal part of the mountain range. In addition, these massifs are thought to be linked to subduction processes (e.g. Rif: Negro et al., 2007, 2008) of Oligocene or older age. In the Rif, these massifs only contain rocks of continental origin, but in the Western Tell in the Oran region, they can be associated to ultramafic rocks, which are probably pieces of oceanic crust, but which have never been studied in detail. Secondly, the Oran region also offers a natural sample of basement rocks that outcrop in Triassic salt diapirs, revealing rocks of a very high metamorphic grade, even mantle rocks. Midoun & Perthuisot (1992) have interpreted these rocks as remnants of the Tethyan margin, brought up to the surface by the salt. The Oran region is therefore a key area, as it offers two complementary sampling possibilities for understanding and reconstructing the
evolution of the southern Tethyan margin, from its formation to its disappearance during the opening of the Mediterranean.
The aim of this PhD is therefore to make the best possible use of these two types of outcrop. The study area and key outcrops have been located since the theses by Guardia (1975) and Midoun (1989). They have recently been the subject of a field campaign (May 2023) to specify their locations and potential, with a limited sampling. In the light of the bibliography and these outcrops, the work of deciphering the evolution of the Tethys will focus on :– a renewed and modern characterisation of the basement samples outcropping in the saliferous Triassic (petrography, geochemistry, absolute dating of the protolith and deformations), in order to follow the evolution of the margin over time from its emplacement to its Cenozoic deformation.– a tectonic-metamorphic study of the metamorphic massifs, and more particularly the ‘Rifian affinity’ units of Guardia (1975), whose geological map precisely locates the outcrops, often associated with unstudied ultramafic and metamorphic rocks. Deformation in these massifs needs to be thoroughly re-examined, with modern metamorphic characterisation. The (P, T) conditions of this metamorphism will be assessed using classic (field, petrography) and modern tools (Raman spectroscopy, chlorite thermometry, metamorphic pseudosections), combined with absolute dating tools (U/Pb on zircon/monazite; Ar/Ar on micas) to constrain the timing of events.– a reconsideration of the geometry and nature of this Tethysian margin, which remains poorly understood. The PhD student will thus be proposing an essential update to fill a significant gap in our understanding of the evolution of peri-Mediterranean orogenic systems.RequirementsResearch Field Geosciences » Geology Education Level Master Degree or equivalentSkills/QualificationsStudents interested in this subject should detail in their application a profile that matches their interest in metamorphic petrography and fieldwork. A Master’s degree with a geodynamics/petrography/field orientation will be an advantage. Candidates should have a significant background in petrography, as this expertise will be an important part of their work.Specific RequirementsSince the planned fieldwork will take place in Algeria, it is up to the applicants to check that their country of origin allows its nationals to travel between France and Algeria without any difficulty. This condition is essential.Languages ENGLISH Level GoodResearch Field Geosciences » Geology Years of Research Experience NoneAdditional InformationEligibility criteriaIn their letter of application, students interested in this subject should demonstrate a profile that
matches their interest in metamorphic petrography and fieldwork. Students should have a strong
background in petrography, as this expertise will be an important part of their work.
Since the planned fieldwork will take place in Algeria, it is up to the applicants to check that their
country of origin allows its nationals to travel between France and Algeria without any difficulty. This
condition is essentialSelection processA pre-selection of the candidates applications will lead to a personal interview for the few students selected, before recruitment for the PhD position.Work Location(s)Number of offers available 1 Company/Institute CY Cergy Paris Université Country France GeofieldWhere to apply E-mail[email protected]Contact State/ProvinceIle de france CityNeuville sur Oise WebsiteStreet1 rue Descartes Postal Code95000 Phone+33134257352 Mobile Phone+33670962402STATUS: EXPIRED
Expected salary
Location
Neuville-sur-Oise, Val-d’Oise
Job date
Wed, 01 May 2024 01:21:04 GMT
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