Gabbro, plagiogranite and associated dykes in the supra-subduction zone Evros Ophiolites, NE Greece

The incomplete Evros ophiolites in NE Greece form a NE-SW-oriented discontinuous belt in the Alpine orogen of the north Aegean. Field data, petrology and geochemistry are presented here for the intrusive section and associated mafic dykes of these ophiolites. Bodies of high-level isotropic gabbro and plagiogranite in the ophiolite suite are cross-cut by NE-SW-trending boninitic and tholeiitic-boninitic affinity dykes, respectively. The dykes fill tensile fractures or faults, which implies dyke emplacement in an extensional tectonic regime. The tholeiitic-transitional boninitic gabbro is REE- and HFS-depleted relative to N-MORB, indicating derivation from melting of a refractory mantle peridotite source. Associated boninitic dykes are slightly LREE-enriched, showing mineral and whole-rock geochemistry similar to the gabbro. The plagiogranite is a strongly REE-enriched high-silica trondhjemite, with textures and composition typical for an oceanic crust differentiate. Plagiogranite-hosted tholeiitic and transitional boninitic dykes are variably REE-enriched. Geochemical modelling indicates origin of the plagiogranite by up to 75 % fractional crystallization of basaltic magma similar to that producing the associated tholeiitic dykes. All mafic rocks have high LILE/HFSE ratios and negative Ta-Nb-Ti and Ce anomalies, typical for subduction zone-related settings. The mafic rocks show a similar trace-element character to the mafic lavas of an extrusive section in Bulgaria, suggesting they both form genetically related intrusive and extrusive suites of the Evros ophiolites. The field occurrence, the structural context, the petrology and geochemical signature of the studied magmatic assemblage provide evidence for its origin in a proto-arc (fore-arc) tectonic setting, thus tracing the early stages of the tectono-magmatic evolution of Jurassic arc-marginal basin system that has generated the supra-subduction type Evros ophiolite

Mesozoic-Tertiary structural evolution of an extensional gneiss dome—the Kesebir-Kardamos dome, eastern Rhodope (Bulgaria-Greece)

The tectonic evolution of the Rhodope massif involves Mid-Cretaceous contractional deformation and protracted Oligocene and Miocene extension. We present structural, kinematic and strain data on the Kesebir-Kardamos dome in eastern Rhodope, which document early Tertiary extension. The dome consists of three superposed crustal units bounded by a low-angle NNE-dipping detachment on its northern flank in Bulgaria. The detachment separates footwall gneiss and migmatite in a lower unit from intermediate metamorphic and overlying upper sedimentary units in the hanging wall. The high-grade metamorphic rocks of the footwall have recorded isothermal decompression. Direct juxtaposition of the sedimentary unit onto footwall rocks is due to local extensional omission of the intermediate unit. Structural analysis and deformational/metamorphic relationships give evidence for several events. The earliest event corresponds to top-to-the SSE ductile shearing within the intermediate unit, interpreted as reflecting Mid-Late Cretaceous crustal thickening and nappe stacking. Late Cretaceous-Palaeocene/Eocene late-tectonic to post-tectonic granitoids that intruded into the intermediate unit between 70 and 53Ma constrain at least pre-latest Late Cretaceous age for the crustal-stacking event. Subsequent extension-related deformation caused pervasive mylonitisation of the footwall, with top-to-the NNE ductile, then brittle shear. Ductile flow was dominated by non-coaxial deformation, indicated by quartz c-axis fabrics, but was nearly coaxial in the dome core. Latest events relate to brittle faulting that accommodated extension at shallow crustal levels on high-angle normal faults and additional movement along strike-slip faults. Radiometric and stratigraphic constraints bracket the ductile, then brittle, extensional events at the Kesebir-Kardamos dome between 55 and 35Ma. Extension began in Paleocene-early Eocene time and displacement on the detachment led to unroofing of the intermediate unit, which supplied material for the syn-detachment deposits in supra-detachment basin. Subsequent cooling and exhumation of the footwall unit from beneath the detachment occurred between 42 and 37Ma as indicated by mica cooling ages in footwall rocks, and extension proceeded at brittle levels with high-angle faulting constrained at 35Ma by the age of hydrothermal adularia crystallized in open spaces created along the faults. This was followed by Late Eocene-Oligocene post-detachment overlap successions and volcanic activity. Crustal extension described herein is contemporaneous with the closure of the Vardar Ocean to the southwest. It has accommodated an earlier hinterland-directed unroofing of the Rhodope nappe complex, and may be pre-cursor of, and/or make a transition to the Aegean back-arc extension that further contributed to its exhumation during the Late Miocene. This study underlines the importance of crustal extension at the scale of the Rhodope massif, in particular, in the eastern Rhodope region, as it recognizes an early Tertiary extension that should be considered in future tectonic models of the Rhodope and north Aegean region

Nd–Sr–Pb isotopes systematics of the Jurassic Evros ophiolite, eastern Circum-Rhodope Belt, NE Greece

We report on the isotopic compositions of the Jurassic supra-subduction zone Evros ophiolite mafic rocks exposed in the eastern Circum-Rhodope Belt of northeastern Greece. These mafic units consist of low-Ti gabbroic and basaltic rocks, whose Nd–Sr–Pb isotopes are compatible with dominant mantle-derived MORB component mixed with a detectable amount of crustal material and/or sediment invoved in their melt source in the subduction zone. These isotopic features are consistent with an intra-oceanic arc origin of the mafic ophiolite rocks, and the Evros ophiolite Nd and Pb isotopes are comparable to those of the counterpart mafic rocks from the Mandritsa unit in Bulgaria.</p

Transvenous lead extraction – summary of the experience of a single Bulgarian center – a retrospective study

Броят на имплантациите на електронни устройства за кардиостимулация постоянно се повишава в световен мащаб. С това респективно се увеличава и броят на пациентите, които имат абсолютни индикации за екстракция на електроди (пейсмейкърни и ICD). Целта на настоящото проучване е да се представят непосредствените и дългосрочните резултати при пациенти след трансвенозна екстракция на електроди, проведена в Клиниката по кардиология на УМБАЛ „Света Анна“ – София. Материали и методи: Проведено е ретроспективно проучване при пациенти с имплантирано устройство за електрокардиостимулация с давност повече от 1 година, при които е направена екстракция на трансвенозните електроди. Проучени са клиничните и процедурните характеристики, успеваемостта и усложненията с проследяване честотата на реинфекция след процедурата. Резултати: В периода август 2016–май 2021 г. при нас са постъпили 54 пациенти с абсолютна индикация за екстракция на системата за електрокардиостимулация. При проведените 54 процедури са екстрахирани 114 пейсмейкърни и ICD електрода. При 47 процедури (87%) е постигнат пълен технически успех с премахване на всички електроди, а при 53 (98,1%) – клиничен успех на процедурата. Регистрирани са 2 големи перипроцедурни усложнения (3,7%), изискващи спешна кардиохирургична интервенция. При направеното проследяване се установява много ниска честота на повторна инфекция – само при 1 пациент (1.9%). Изводи: Екстракцията на трансвенозни електроди е ефективна и безопасна процедура. Изграждането на специализиран център с организирана програма за екстракция на електроди е от ключово значение за постигането на добри непосредствени и дългосрочни резултати.  There has been increased rate of cardiac implantable electronic devices (CIED) implanted worldwide. Respectively the numbers of patients with absolute indications for lead extraction (pacemaker and ICD) grow up exponentially. The aim of our study is to present the initial experience and long-term results of pacemaker and ICD lead extraction in patients treated in Cardiology department of University hospital “Sveta Anna” Sofi a. Material and Methods: Retrospective study was performed of patients with CIED implanted greater than 1 year and indications for lead extraction. Clinical and procedural characteristics, success rate, complications rate, and reinfection rate data were collected and analyzed. Results: In the period August 2016 to May 2021, a total of 54 patients were admitted to our department with an absolute indication for lead extraction. A total of 114 pacemakers and ICD electrodes were extracted during 54 procedures. In 47 patients (87%) was shown complete technical success with removal of all hardware and in 53 patients (98.1%) clinical success of the procedure was found. The incidence of major periprocedural complications requiring urgent cardiac surgery in our series was 2 (3.7%). Follow-up revealed a very low recurrence infection rate – only 1 patient (1.9%). Conclusion: Lead extraction is a safe and effective procedure. The establishment of a specialized center with an organized system for lead extraction is key in achieving excellent short- and long-term results

⁴⁰Ar/³⁹Ar age constraints for an early Alpine metamorphism of the Sakar unit, Sakar–Strandzha zone, Bulgaria

We investigated the Sakar unit metamorphic rocks of the Sakar Strandzha zone in Bulgaria,using 40Ar/39Ar dating of amphibole from the polymetamorphic basement and white mica in the overlying upper Permian metasedimentary rocks of the Paleokastro Formation. The amphibole and white mica revealed plateau ages of 140.50 ± 1.75 Ma and 126.19 ± 1.29 Ma, respectively, indicating an Early Cretaceous cooling history of the regional amphibolite-facies metamorphism to greenschist-facies conditions. Similar metamorphic grades and cooling histories of the Sakar unit share evidence with the nearby Rhodope Massif for the northern Aegean region-wide early Alpine tectonometamorphic event

Comment on Georgiev et al. "Structure and U–Pb zircon geochronology of an Alpine nappe stack telescoped by extensional detachment faulting (Kulidzhik area, Eastern Rhodopes, Bulgaria)

In this discussion, we evaluate the field, chemical, sedimentary, structural and metamorphic data related to the Kulidzhik area tectonic proposal

Mesozoic–Tertiary structural evolution of an extensional gneiss dome: The Kesebir-Kardamos dome, eastern Rhodope (Bulgaria-Greece)

ISSN:1437-3254ISSN:1437-326

Metamorphic and age constraints on the Alakeçi shear zone: Implications for the extensional exhumation history of the northern Kazdağ Massif, NW Turkey

International audienceThe Kazdag Massif exposes an extensional metamorphic dome in the Biga Peninsula of northwest Turkey, bounded on both flanks by detachments and/or shear zones. The northern flank is marked by the extensional Alakeci shear zone (ASZ), with poorly known P-T-t path. We therefore focus on metamorphic conditions and temporal history of the ASZ to determine its tectono-metamorphic evolution. ASZ mylonites were derived from both the footwall Kazdag Massif core metamorphic rocks and the hanging wall Cetmi melange lithologies. The mylonitic fabrics in the ASZ depict a top-to-the NNE shearing, parallel to the NNE-plunging stretching lineation and NNW-dipping mylonitic foliation. This geometry implies normal sense movement i.e. north-side down-dip extensional displacement along this flank of the Kazdag Massif. The northward transition from ductile to brittle-ductile shear regime through the ASZ shows that the non-coaxial deformation occurred at decreasing temperatures and degree of metamorphism. The paragenesis in equilibrium of the mylonitic gneisses and schists contains quartz + feldspar + muscovite + biotite + garnet staurolite, with late retrogressive chlorite after biotite and garnet. Calculated thermo-barometric conditions for ASZ rocks yielded pressures between 6.9 and 5.7 kbar and temperatures between 706 and 587 degrees C, which constrain the peak metamorphism. The mylonitic rocks supplied isochron Ar-39/Ar-40 mica ages between 26.97 and 24.19 Ma, which we interpret to date the cooling of the mylonites following the P-T decrease across the ASZ. The metamorphic data support the structural record and strengthen the extensional character of the ASZ. The transition from sillimanite-bearing footwall Kazdag Massif core gneisses in the deeper structural levels to chlorite schists; towards the shallow structural levels at the top of the ASZ, is consistent with an extensional exhumation of the metamorphic pile. These data allow us to determine the peak P-T conditions and the temporal evolution in the northern flank of the Kazdag Massif, where Late Oligocene extensional exhumation was assisted by NNE-directed ductile-brittle ASZ, which had operated from amphibolite to greenschist facies. The ASZ, together with similar time-constrained ductile-brittle activity of SW-directed detachment along the southern flank of the massif, collectively indicates a bivergent mode of extension in the western Kazdag Massif. The latter is likely influenced by magmatic activity spatially and temporally related to these extensional zones. At the regional scale, the bivergent tectono-metamorphic pattern of the Kazdag Massif is similar to those observed on other places of the north-central Aegean domain