Jean-Pierre Brun

Université de Rennes 1 | UR1 · Observatoire des Sciences de l'Univers de Rennes (OSUR)

rogeny results from crustal thickening at active margins, and much progress has been made on understanding the associated kinematics. However, the ultimate cause of orogeny is still debated, especially for the case of extreme crustal thickening. Inspired by the seminal work of Holmes (1931), we explore the connections between the style of orogeny a...

We study slab breakoff of subducting plates with variable orientations of passive margins (ocean-continent transition: OCT) using three-dimensional laboratory experiments. Our results show that the initial obliquity of the OCT with the trench determines the depth and timing of slab breakoff. The reference model involves a straight OCT parallel to t...

Whereas, salt margins are rather common, the growth of continental shelves on top of salt margins is a topic that has seldom been considered. In such settings, the sediments coming from the nearby continental areas are deposited on a viscous substratum and therefore a continental shelf can form and stabilize only if the salt layer underlying sedime...

The core complexes of the North Aegean result from the gravity spreading of a thrust wedge, driven by the Hellenic slab rollback, since middle Eocene. The development of the Southern Rhodope Core Complex occurred in two stages: (i) core complex exhumation accommodated by the Kerdylion detachment and (ii) steep normal faulting controlling the deposi...

Based on a review of the surface and deep structure of the Eastern Alps, we link the timing and the inferred displacement fields to exhumation of upper and lower crustal units of the orogenic nappe stack during collision. The discussion focuses mainly on the Tauern Window and its country rocks, the only area of the Eastern Alps where the orogenic w...

Deep crustal and mantle rocks are exhumed in core complex mode of extension in three types of structures: metamorphic core complexes, oceanic core complexes and magma poor passive margins. Using available analogue and numerical models and their comparison with natural examples, the present paper reviews the mechanical processes involved in these di...

Aegean extension is a process driven by slab rollback that, since 45 Ma, shows a twostage evolution. From Middle Eocene to Middle Miocene it is accommodated by localized deformation leading to i) the exhumation of high-pressure metamorphic rocks from mantle to crustal depths, ii) the exhumation of high-temperature rocks in core complexes and iii) t...

The Alboran Domain, situated at the western end of the Mediterranean subduction system, is characterized by the Ronda Peridotites, one of the world largest exposures of sub continental mantle. Using U-Pb (LA-ICP-MS) and Ar-Ar dating, we precisely dated two tectonic events associated with the Tertiary exhumation of the Ronda Peridotites. First, shea...

When deeply buried in subduction zones, rocks undergo mineral transformations that record the increase of pressure and temperature. The fact that high-pressure metamorphic parageneses are found at the Earth’s surface proves that rock burial is followed by exhumation. Here we use analysis of available data sets from high-pressure metamorphic rocks w...

The Chalkidiki block is a major domain in the North Aegean that, contrary to other domains in the region, largely escaped thermal perturbations during Tertiary extension. As a result, the Chalkidiki block is an ideal candidate to glean information related to the timing of Mesozoic thermal events using appropriate geochronological techniques. We hav...

The identification of the structures and deformation patterns in magma-poor continental rifted margins is essential to characterize the processes of continental lithosphere necking. Brittle faults, often termed mantle detachments, are believed to play an essential role in the rifting processes that lead to mantle exhumation. However, ductile shear...

Back-arc extension in the Aegean, which was driven by slab rollback since 45 Ma, is described here for the first time in two stages. From Middle Eocene to Middle Miocene, deformation was localized leading to i) the exhumation of high-pressure metamorphic rocks to crustal depths, ii) the exhumation of high-temperature metamorphic rocks in core compl...

In the Chalkidiki Peninsula of northern Greece a thrust complex made of a basement (Vertiskos Unit), a cover (Circum–Rhodope belt) and arc/back-arc units (Chortiatis Magmatic Suite and eastern Vardar Ophiolites) is exposed in the Chalkidiki Peninsula of northern Greece. The complex forms the western part of the Rhodope Metamorphic Province and lies...

Since the discovery of calcareous nannofossils, dinoflagellate cysts and planktonic foraminifers in deposits from the Dacic Basin, intensive research has been performed in order to evidence which gateway this microplankton used to connect Paratethys and the Mediterranean prior and after the Messinian Salinity Crisis (MSC). Such a gateway is also to...

In the framework of the Africa-Europe convergence, the Mediterranean system presents a complex interaction between subduction rollback and upper-plate deformation during the Tertiary. The western end of the system shows a narrow arcuate geometry across the Gibraltar arc, the Betic-Rif belt, in which the relationship between slab dynamics and surfac...

A synthesis of existing geological, structural and geophysical data shows that the south Armorican Hercynian belt was marked by syn-convergence crustal thinning and dextral wrenching that were in part coeval in late Carboniferous times. Our kinematic model is further supported by new structural data and 40Ar/39Ar ages on synkinematic leucogranites....

The tertonic interpretation of the Montagne Noire Gneiss Dome (southern French II Massif (Central) has been controversial for a long time. Several models have been proposed : diapirie uplift, wreneching and diapirism, compressive anticline, and metamorphie core complex. Evidence for extensional tectonics in the French Varisean Belt favours the latt...

The Chalkidiki block in Northern Greece represents the southwesternmost piece of the ultrahigh-pressure Rhodope and has played an important role in the evolution of the North Aegean. The eastern part of the Chalkidiki block is a basement complex (Vertiskos Unit) that is made largely of Palaeozoic granitoids and clastic sediments metamorphosed durin...

Since the discovery of calcareous nannofossils, dinoflagellate cysts and planktonic foraminifers in deposits from the Dacic Basin, intensive research has been performed in order to evidence which gateway this microplankton used to connect Paratethys and the Mediterranean prior and after the Messinian Salinity Crisis (MSC). Such a gateway is also to...

The North Aegean core complexes developed in middle Eocene soon after the end of continental block convergence and piling-up of the Hellenic Thrust Wedge. They formed during back-arc extension, driven by the Hellenic slab rollback, at the back of the thrust wedge. A series of scaled laboratory experiments were performed to test whether the gravity...

The Mediterranean offers a unique opportunity to study the driving forces of tectonic deformation within a complex mobile belt. Lithospheric dynamics are affected by slab rollback and collision of two large, slowly moving plates, forcing fragments of continental and oceanic lithosphere to interact. This paper reviews the rich and growing set of con...

While subduction of crustal rocks is increasingly accepted as a common scenario inherent to convergent processes involving continental plates and micro-continents, its occurrence in each particular context, as well as its specific mechanisms and conditions are still debated. The presence of UHP terranes is often interpreted as a strong evidence for...

The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape of Anatolia. Lithosphere-scale analogue models were employed to display that the overall pattern of Ae...

The Vertiskos Unit of northern Greece is an elongated basement belt with a complex poly-metamorphic history. It extends from Greece (Chalkidiki peninsula), to the south, up to Serbia, in the north, and arguably represents the westernmost part of the Rhodope Metamorphic Province (northern Greece – southern Bulgaria). The Vertiskos Unit experienced a...

The interaction between Aegean back-arc extension and Anatolia escape since Middle Miocene. Abstract. The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape...

The Aegean domain is a key area for understanding the processes of back-arc extension. Observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the Hellenic trench and the westward escape of Anatolia. Lithosphere-scale analogue models were employed to display that the overall pattern of Ae...

We report here new LA-ICPMS detrital zircon U-Pb ages of a quartzite from the autochthon of Peloponnesus (Feneos locality), southern Greece. The rock classifies as a mature quartz arenite and belongs to an original shale-sandstone succession now metamorphosed into a phyllite-quartzite unit. Zircon age clusters at 0.52-0.75, 0.85, 0.95-1.1, 1.75-2 a...

Low-angle extensional shear is frequently observed in the Aegean metamorphic rocks. This deformation is commonly interpreted as being related to detachment at crustal scale, yet it often corresponds to ramp-flat extensional systems that, at many places, control the deposition of Neogene sedimentary basins. From a mechanical point of view, the devel...

The Mediterranean offers a unique opportunity to study the driving forces of tectonic deformation within a complex mobile belt. Lithospheric dynamics are affected by slab rollback and collision of two large, slowly moving plates, forcing fragments of continental and oceanic lithosphere to interact. This paper reviews the rich and growing set of con...

A series of analogue experiments was used to explore how lateral variations in lithosphere rheology may result in a subduction polarity reversal. Lithosphere models made of sand and silicone putty were designed to represent a plate convergence setting varying laterally from continent–continent to ocean–continent. Several experiments were performed...

Lawsonite pseudomorphs are used to identify and distinguish the kinematic records of subduction and exhumation in blueschist-facies rocks from Syros (Cyclades; Greece). Lawsonite is a hydrous mineral that crystallizes at high-pressure and low-temperature conditions. During decompression, lawsonite is typically pseudomorphed by an aggregate dominate...

Since plate tectonics began on Earth, grandiose "subduction factories" have continually shaped the continents, accreting conti-nental blocks and new crust at the convergent plate boundaries. An enigmatic product of subduction factories is the high-pressure to ultrahigh-pressure (HP-UHP) metamorphic crustal rocks, regurgi-tated to Earth's surface, s...

Detrital zircon U-Pb ages of a quartzite from the Feneos locality of Peloponnesus, S. Greece, were determined by LA-ICPMS. The rock classifies as a mature quartz arenite and belongs to an original shale-sandstone succession now metamorphosed into a phyllite-quartzite unit. The latter chiefly represents the External Blueschist Belt of the Hellenides...

The northern Gulf of Mexico (GoM) is likely the most spectacular salt margin worlwide. Whereas salt was deposited in late Jurassic, a massive extrusion of allochthonous salt bodies occurred during the Cenozoic, as much as 8 km thick in some places, on top of which Neogene minibasins are deposited. The presence of minibasins, sometimes very deep, ha...

We review the geodynamic evolution of the Aegean–Anatolia region and discuss strain localisation there over geological times. From Late Eocene to Present, crustal deformation in the Aegean backarc has localised progressively during slab retreat. Extension started with the formation of the Rhodope Metamorphic Core Complex (Eocene) and migrated to th...

The Messinian Salinity Crisis is well known to have resulted from a significant drop of the Mediterranean sea level. Considering both onshore and offshore observations, the subsequent reflooding is generally thought to have been very sudden. We present here offshore seismic evidence from the Gulf of Lions and re-visited onshore data from Italy and...

The kinematics of regional-scale salt flow in the northern Gulf of Mexico is analysed using: (i) a map of shelf-break contours at the termination of successive depositional episodes; (ii) the location and geometry of large-scale structures of the slope domain as imaged by seismics; and (iii) digital slope bathymetry. In the north margin, salt has f...

The Cycladic Blueschist Unit (CBU) represents the northern passive margin of the Adria continental block and ophiolites that are the remnants of the Pindos Ocean, which were affected by high pressure–low temperature metamorphism in the blueschist and eclogite facies during the Eocene. Prior to the Lutetian, the ophiolitic and margin units were thru...

In the Upper Miocene, the Mediterranean - Middle East tectonic setting changed : The Anatolian plate started moving westward along the newly formed North Anatolia Fault, Arabia collided with Eurasia forming the Bitlis -Zagros range during the formation of the Iranian-Anatolian plateau, and the Hellenic trench accelerated its southern motion. Severa...

1] On Syros, high‐pressure metamorphism affects a lithological pile that is composed of, from base to top: (1) the Komito‐Vari granitic basement, (2) a margin sedimentary sequence that is predominantly made of marbles and schists (the Pyrgos and Kastri units), and (3) the Kambos metaophiolitic mélange. The tectonic history occurred in three main st...

HP/UHP and LT metamorphic units that commonly occur in the inner parts of mountain belts result from the subduction of continental and oceanic material, most often exhumed prior to continental collision. The prograde pressure–temperature history of HP–UHP rocks strongly depends on the convergence rate and on the subduction zone geometry. The maximu...

a b s t r a c t Salt tectonics at passive margins is currently interpreted as a gravity-driven process but according to two different types of models: i) pure spreading only driven by differential sedimentary loading and ii) dominant gliding primarily due to margin tilt (slope instability). A comparative analysis of pure spreading and pure spreadin...

A dynamic orogen reveals various tectonic processes brought about by subduction: accretion of oceanic and continental crust, exhumation of UHP-HP rocks, and often, back-arc extension. In the Mediterranean, orogeny is strongly affected by slab retreat, as in the Aegean and Tyrrhenian Seas. In order to examine the different dynamic processes in a sel...

The kinematics records of subduction and exhumation in Blueschists rocks of Syros (Cyclades; Greece) can be deciphered thanks to Lawsonite pseudomorphs. Since Lawsonite is a hydrous HP mineral that crystallizes along prograde rock paths and undergoes breakdown during decompression, Lawsonite pseudomorphs consist in a useful strain-free gauge to ide...

The available seismic anisotropy data in the Aegean shallow mantle and their relationship with crustal deformation are used for deciphering the lithosphere-scale flow pattern driven by rollback of the Hellenic subduction slab. In the north and central Aegean, the directions of mantle seismic anisotropy trend parallel to stretching lineations in cor...

We present results and interpretation of a 72 km long deep seismic reflection profile acquired across the internal zone of the Hercynian belt of South Brittany. The profile is of excellent quality, most of the crust being highly reflective. The "ARMOR 2 South" profile, is correlated with the "ARMOR 2 North" profile that was published in 2003. Corre...