Fluid-induced disturbance of the monazite Th–Pb chronometer: In situ dating and element mapping in pegmatites from the Rhodope (Greece, Bulgaria)

Bosse, Valérie; Boulvais, Philippe; Gautier, Pierre; Tiepolo, Massimo; Ruffet, Gilles; Devidal, Jean‐Luc; Cherneva, Zlatka; Gerdjikov, Ianko; Paquette, Jean‐Louis

doi:10.1016/j.chemgeo.2008.10.025

Cited by 90 publications

(74 citation statements)

References 57 publications

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“…As suggested in Section 1, the existence of a large time gap (≥ 45 Myr) in the geochronological record seems to support the hypothesis of a polycyclic orogenic evolution for the largest part of the RMC. Using the age data of Liati (2005) and Bosse et al (2009), Mposkos et al (2010 have followed this line of reasoning and additionally argued that some of the garnetkyanite metapelites found along the NSZ keep the record of a polycyclic P-T evolution. A first P-T loop, of presumed midMesozoic age, reached UHP conditions followed by granulite facies retrogression while a second P-T loop, of presumed a mid-Cenozoic age, would have reached P-T conditions of ∼12 kbar and ∼650°C (Mposkos et al, 2010).…”

Section: Continuous Versus Discontinuous Metamorphic Evolution and Gementioning

confidence: 99%

“…The second argument stems from the observation that the RMC contains rocks, or rock assemblages, that display two sets of "Alpine" ages related to high-temperature metamorphic conditions (U-Pb zircon and U-Th-Pb monazite ages), the two sets being separated by a time laps of at least 60 Myr, between ≥ 115 and 55 Ma (Liati, 2005;Bosse et al, 2009;Didier et al, 2014;Wawrzenitz et al, 2015). More generally, except in the Eastern Rhodope (Fig.…”

Section: Continuous Versus Discontinuous Metamorphic Evolution and Gementioning

confidence: 99%

“…Contrasting opinions exist as for the origin of top-to-SW shearing along the NSZ, which could reflect either thrusting (e.g., Kilias and Mountrakis, 1990;Barr et al, 1999;Krohe and Mposkos, 2002) or extensional shearing (Nagel et al, 2011). Determining the origin and age of shearing along the NSZ is important considering the apparent conflict that exists between scenarios favoring crustal-scale extension across the RMC since 40 Ma or more (e.g., Kilias et al, 1999;Brun and Sokoutis, 2007;Jolivet and Brun, 2010;Burg, 2011;van Hinsbergen and Schmid, 2012) and studies suggesting ongoing thrusting along the NSZ as late as 37 Ma (Dinter, 1998;Krohe and Mposkos, 2002) or 33 Ma (Bosse et al, 2009;Gautier et al, 2010) and/or eclogite facies metamorphism in the RMC as late as 42-45 Ma (Liati and Gebauer, 1999;Liati et al, 2011;Kirchenbaur et al, 2012). A full analysis of the NSZ is beyond the scope of this paper, nevertheless the results obtained in this study provide critical information for determining the significance of this major shear zone and the tectonic evolution of the RMC.…”

Section: Introductionmentioning

confidence: 99%

“…The two shear zones were initially regarded as distinct, synthetic thrust zones (Ricou et al, 1998). Because they display roughly the same petro-geochronological record (e.g., Bosse et al, 2009;Didier et al, 2014), the NSZ and CSZ have been reinterpreted as two occurrences of the same shear zone (Turpaud and Reischmann, 2010;Nagel et al, 2011;Burg, 2011). With respect to the NSZ, Papanikolaou and Panagopoulos (1981) initially defined a lower unit and an upper unit, later named the Pangaeon Unit (PU) and Sidironero Unit (SU).…”

Section: Introductionmentioning

confidence: 99%

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Polycyclic alpine orogeny in the Rhodope metamorphic complex: the record in migmatites from the Nestos shear zone (N. Greece)

Gautier

Bosse

Cherneva

et al. 2017

Bull. Soc. géol. Fr.

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-The Rhodope Metamorphic Complex (RMC) is a high-grade crystalline massif located at the northern margin of the Aegean region. Numerous scenarios have been proposed for the evolution of the RMC during Alpine times. A debated issue is whether there has been a single protracted orogenic cycle since around the mid-Mesozoic or whether Alpine orogeny involved distinct episodes of subduction and crustal accretion. We describe a key outcrop located on the Nestos Shear Zone (NSZ), a major NNE-dipping top-to-SW shear zone characterized by an inverted metamorphic sequence. Structural and petrological data document the existence of two anatectic events. The first event, best preserved in decametric structural lenses, is pre-kinematic with respect to top-to-SW shearing and involved high-temperature "dry" melting. Zircon and monazite LA-ICPMS U-Th-Pb data indicate that this event occurred at ∼140 Ma. The second event is syn-kinematic with respect to top-to-SW shearing and involved lower-temperature water-assisted melting. Zircon and rutile LA-ICPMS U-Pb data indicate that this second event occurred at ∼40 Ma. During ongoing top-to-SW shearing and as late as ∼36 Ma, the rocks from the outcrop were at higher temperatures than the peak temperatures experienced by lower levels of the NSZ. This confirms the existence of the inverted metamorphic sequence and demonstrates that the NSZ was a major thrust at 36-40 Ma. The ∼100 Myr time laps between the two anatectic events encompasses the period from ∼115 to ∼70 Ma characterized by a gap in the geochronological record on the scale of the RMC (the Eastern Rhodope excluded). This ∼45 Myr gap likely reflects a period of tectonic quiescence between the mid-Mesozoic orogen and the Cenozoic one, attesting for polycyclic Alpine orogeny in the RMC. Unlike assumed in several geodynamic scenarios, the Alpine evolution of the RMC did not consist of a single orogenic cycle of Mesozoic age followed by Cenozoic crustal-scale extension triggered by mantle delamination. Polycyclic orogeny has resulted in a two-loop P-T-t path for the hangingwall unit of the NSZ. The Cenozoic P-T paths of this unit and the footwall unit merged while both units were being exhumed, a feature attributed to synthrusting extensional spreading of the main mass of the hangingwall unit above the NSZ.Keywords: Aegean / syn-deformation migmatization / U-Pb dating / LA-ICPMS / inverted metamorphism / synmetamorphic thrusting Résumé -Orogenèse alpine polycyclique dans le complexe métamorphique du Rhodope : enregistrement dans les migmatites de la zone de cisaillement du Nestos (Grèce). Le Rhodope est un complexe métamorphique de haut grade situé à la frange Nord de la région égéenne. De nombreux scénarios ont été proposés pour son évolution durant la période alpine. Une question débattue est de déterminer s'il n'y a eu qu'un seul cycle orogénique de longue durée depuis le milieu du Mésozoïque ou bien si l'orogenèse alpine a impliqué des épisodes distincts de subduction-accrétion crustale. Nous décrivons un affleurement-...

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Section: Continuous Versus Discontinuous Metamorphic Evolution and Gementioning

confidence: 99%

Section: Continuous Versus Discontinuous Metamorphic Evolution and Gementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Polycyclic alpine orogeny in the Rhodope metamorphic complex: the record in migmatites from the Nestos shear zone (N. Greece)

Gautier

Bosse

Cherneva

et al. 2017

Bull. Soc. géol. Fr.

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“…On the other hand, diffusion rates in the monazite structure are extremely low, corresponding to very high blocking temperatures (Cherniak et al, 2004). Resetting of the original monazite composition may occur, however, during subsequent fluid-driven corrosion, infiltration and dissolution-reprecipitation (Bosse et al, 2009). In these cases, Williams et al (2011) notice that fluid-aided alteration of monazite results in complete resetting of the isotopic system, with total removal of Pb from the monazite lattice.…”

Section: Introductory Remarksmentioning

confidence: 99%

Chemical U-Th-Pb geochronology: A precise explicit approximation of the age equation and associated errors

Săbău

2012

Geochronometria

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In a single decaying system, the age determined from the exponential decay law is directly related to its linear Maclaurin approximation. This relationship can be additively extended to several decaying systems resulting in the same daughter element, by using proportionality functions, thus allowing an explicit formulation of the age as a function of element concentrations. The values of the binary proportionality function for the 238 U-235 U-Pb system and the ternary proportionality function for the 232 Th-238U-235 U-Pb system were determined by iterations of the exponential decay formula up to 4 Ga, with a step of 10 Ma, for a set of 24 different U/Th ratios. From the iteration data, the expressions of the two functions and the associated coefficients were determined by polynomial regression and mathematical programing on conveniently separated time and compositional intervals. Additional time-and composition-dependent age corrections optimized by mathematical programming of the residuals lead to an accuracy of 0.005 Ma of the resulting age. The error propagation can be traced through all the operations defined by explicit formulas according to simple error propagation rules, finally allowing the calculation of the standard error of the result. The formulas and parameters derived can be used in a calculation spreadsheet.

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Age and composition of meta‐ophiolite from the Rhodope Middle Allochthon (Satovcha, Bulgaria): A test for the maximum‐allochthony hypothesis of the Hellenides

et al. 2014

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The metamorphosed thrust stack of the Rhodopes comprises a level with ophiolites (Middle Allochthon) underlain and overlain by continent-derived allochthons. The Upper Allochthon represents the European margin, but the origin of the Lower Allochthon remains controversial, with suggestions that it may be derived from an inferred microcontinent (Drama) or from the margin of Adria. Trace element compositions and Sr and Nd isotope ratios of metagabbroic amphibolites and enclosed meta-plagiogranites from the Satovcha Ophiolite, Middle Allochthon, show that they are cogenetic and represent suprasubduction zone ophiolites. U-Pb dating using laser ablation sector field inductively coupled plasma mass spectrometry of zircons from two meta-plagiogranites and a metagabbro yielded identical Jurassic ages (160 ± 1 Ma, 160.6 ± 1.8 Ma, and 160 ± 1 Ma, respectively), similar to ophiolites in the eastern Vardar Zone bordering the Rhodopes to the SW. The trace element patterns also closely resemble those of the Vardar ophiolites. The association with Late Jurassic arc-type granitoids is another feature that applies both to eastern Vardar and Satovcha. This strongly suggests that the Middle Allochthon comprises the metamorphosed northeastward continuation of the Vardar Zone. The Jurassic age of the Satovcha Ophiolite contradicts the hypothesis of Early Jurassic suturing between Europe (Upper Allochthon) and the assumed Drama microcontinent (Lower Allochthon) but is in line with the "maximum allochthony hypothesis," i.e., the assumption that the Lower Allochthon represents Adria and that the "root" of the Vardar-derived thrust sheets is at the NE boundary of the Rhodopes.

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Fluid-induced disturbance of the monazite Th–Pb chronometer: In situ dating and element mapping in pegmatites from the Rhodope (Greece, Bulgaria)

Cited by 90 publications

References 57 publications

Polycyclic alpine orogeny in the Rhodope metamorphic complex: the record in migmatites from the Nestos shear zone (N. Greece)

Polycyclic alpine orogeny in the Rhodope metamorphic complex: the record in migmatites from the Nestos shear zone (N. Greece)

Chemical U-Th-Pb geochronology: A precise explicit approximation of the age equation and associated errors

Age and composition of meta‐ophiolite from the Rhodope Middle Allochthon (Satovcha, Bulgaria): A test for the maximum‐allochthony hypothesis of the Hellenides

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