Menderes Masifi ndeki Batı Anadolu Türkiye granulit fasiyesi metamorfizmasının yaşı SHRIMP ve LA ICP MS U Pb zirkon yaşlandırması

The Pan-African basement of theMenderes Massif consists of partially migmatized metasediments, i.e.paragneisses and metapelites, which were intruded by numerous poly-metamorphicPrecambrian gabbros and syn-to post-metamorphic Pan-African metagranites /orthogneisses. The relict phases and assemblages attributed to the Pan-Africanmetamorphic evolution at granulite- and eclogite-facies conditions have beenrecognized in the basement. The relicts of granulite facies metamorphism arerepresented by orthopyroxene bearing-orthogneisses, pelitic granulites andmetatonalites. In addition to granulite facies metamorphism, widespreadmigmatization and anatectic granite generation occur in the basement.&nbsp;In this study, SHRIMP and LA-ICP-MS were applied to provide timing constraints on the granulite faciesmetamorphism and overprinting migmatization, which affected thePan-African basement of the Menderes Massif. Cathodoluminescenceimaging of zircons separated frompelitic granulites occurring in the southern part of Ödemiş-Kiraz submassif (SEof Tire) reveals that many of thegrains contain unzoned and/or planar zoned overgrowth texturesrepresenting metamorphic growth on inherited cores. Textural relationshipsclearly reveal that granulite facies unzoned zircon overgrowth must haveoccurred prior to planar zoned overgrowth reflecting crystallization fromanatectic melts. SHRIMP analyses of unzoned overgrowths yield concordia age of 582.0 ± 5.3 Ma. Whereas, planar zoned zircon overgrowthsoccurring in the outermost parts of the crystals gave concordia age of 565.0 ± 5.4 Ma.LA-ICP-MS analyses of unzoned overgrowths yield concordia age of 582.0 ± 5.3 Ma. The zircons separated from metatonalite at the centre of Ödemiş-Kiraz submassif (northeastof Birgi area) show that many of thegrains contain magmatic crystallization texture and unzoned overgrowthsrepresenting the high temperature metamorphism. Oscillatory zoned magmaticzircons yielded a concordia age of 591.0 ± 6.9 Ma and unzoned overgrowths occurring in the outermost parts of the magmatic zircons gave a concordia age of 578.4 ± 8.2Ma by LA-ICP-MS U-Pb analyses. Thus, c. 590 Ma isinterpreted the crystallization age the protolith of metatonalite.&nbsp; A 580-585 Ma is interpreted the age ofgranulite facies metamorphism and 565 Ma can be accepted as the age ofmigmatization affected the basement series. All ages coincide with final amalgamationprocesses resulting in the formation of the Gondwana super continent as aconsequence of the closure of the Mozambique Ocean during the LateNeoproterozoic.</p

Menderes Masifi'ndeki Jeolojik Problemlerin Çözümüne Zirkon U-Pb Yaş Tayini ile Yaklaşımlar

The late Neoproterozoic poly-metamorphic basement of the Menderes Massif can be divided into two units (Bozdeğ Unit and Birgi Unit) with distinct metamorphic and magmatic histories. Birgi Unit consists of high-grade paragneiss - schist intercalation and (meta) acidic – basic intrusions. Granulite facies metamorphism has been preserved only in a few localities and is characterized by the orthopyroxe relics. Pelitic granulites and hypersthene orthogneisses (charnockites) form the main lithologies. The zircons in charnockites contain featureless overgrowth and rim textures representing metamorphic growth on magmatic cores and inherited grains. The protolith of the charnockites, yielded a crystallization age of ~ 590 Ma. U/Pb SHRIMP and LA-ICP-MS zircon and monazite ages from granulitic rocks gave an age of ca. ~580 Ma, which is interpreted as the time of granulite-facies metamorphism in the basement of the Menderes Massif. These data indicate that the Menderes Massif experienced acidic magmatic activity and granulite-facies metamorphism in Ediacaran. Furthermore, the basement rocks have been overprinted by a Barrovian-type Alpine metamorphism in Eocene (~ 42 Ma). The granulite-facies metamorphism in the Menderes Massif can be attributed to the orogenic event (600-500 Ma; Malagasy orogeny) causing the final amalgamation processes for the northern part of the Gondwana.</p

Geochemistry and zircon U–Pb dating of amphibolite in the Menderes Massif (western Türkiye): First record of Late Devonian extension

The timing ofextensional events in northern Gondwana remains elusive. In relations to thisevent, a new zircon U-Pb age and Hf isotopic compositions, and whole-rockgeochemistry provided here for the amphibolites in the basement unit of theMenderes Massif (MM) within the Anatolide-Tauride Block (ATB). LA-ICP-MS U-Pb zircondating of one sample yielded a crystallisation age of 367.0±2.5 Ma, providing thefirst record of Late Devonian (Famennian) mafic magmatism in the MenderesMassif. This sample contains inherited zircon grains with ages spanning from588 Ma to 541 Ma, likely sourced from late Neoproterozoic country rocks. Chondrite-normalizedrare earth element patterns exhibit enrichment in light rare earth elements andflat patterns for heavy rare earth elements, suggesting affinities withtholeiitic EMORB and ocean island basalt. The geochemical data, coupled with the positiveεHf(t) values ranging from 0.5 to 7.8, indicate that the amphibolite likelyoriginated from juvenile melts generated by partial melting of theasthenospheric mantle. This melt was subsequently modified by crustalcontamination and fractional crystallization. Contemporaneous EMORB- andOIB-like mafic rocks are identified in the eastern Taurides and Iran,respectively. Both regional geological and geochemical evidencepropose that Late Devonian magmatism in the Anatolide-Tauride Block occurredin a within-plate tectonic setting. This magmatic activity might have beentriggered by the northward subduction of the Paleotethys beneath the Pontidesduring the Devonian, a process that would produce a slab-pull force, creatingan extensional tectonic regime along the northern margin of Gondwana.</p

Timing of granulite facies metamorphism in the Pan African basement of the Menderes Massif western Anatolia Turkey Evidence from SHRIMP and LA ICP MS U Pb zircon geochronology

The Pan-African basementof the Menderes Massif consists of partially migmatized metasediments, i.e.paragneisses and metapelites, which were intruded by numerous poly-metamorphicPrecambrian gabbros and syn-to post-metamorphic Pan-African metagranites /orthogneisses. The relict phases and assemblages attributed to the Pan-Africanmetamorphic evolution at granulite- and eclogite-facies conditions have beenrecognized in the basement. The relicts of granulite facies metamorphism arerepresented by orthopyroxene bearing-orthogneisses and paragneisses, peliticgranulites and metatonalites. In addition to granulite facies metamorphism,widespread migmatization and anatectic granite generation occur in the basement.In this study, SHRIMP and LA-ICP-MS were applied to provide timingconstraints on the granulite facies metamorphism and overprinting migmatization,which affected the Pan-African basement of the Menderes Massif. Cathodoluminescence imaging of zircons separated from pelitic granulites occurring inthe southern part of middle submassif (SE of Tire) reveals that many of the grains contain unzonedand/or planar zoned overgrowth textures on inherited cores. Textural relationshipsclearly reveal that unzoned zircon overgrowths indicate granulite facies metamorphismand must have occurred prior to planar zoned overgrowth reflectingcrystallization from anatectic melts. SHRIMP analyses yield concordia ages of 582.0 ± 5.3 Maand 565.0 ± 5.4 Ma from unzoned and planar zoned zirconovergrowths, respectively. Additionally, LA-ICP-MS analyses of unzonedovergrowths give similar concordia age of 586.0 ± 15.0 Ma. Furthermore,unzoned zircon overgrowths from ortopyroxene bearing orthogneiss yield concordia age of 578.7 ± 8.1 Ma. The zircons from metatonalite of middle submassif(northeast of Birgi area) showthat many of the grains contain magmatic crystallization texture and unzoned overgrowths representing the high temperature metamorphism. Magmaticcores showing oscillatory zoning and unzoned overgrowths yieldconcordia ages of 591.0 ± 6.9 Ma and 578.4 ± 8.2 Maby LA-ICP-MS U-Pb analyses, respectively. Thus, ca. 590 Ma is interpreted thecrystallization age of the protolith of metatonalite. An age of 580-585 Ma isinterpreted the age of granulite facies metamorphism and 565 Ma can be acceptedas the age of migmatization affected the basement series. All ages coincidewith assembly processes resulting in the formation of the Gondwana supercontinent as a consequence of the closure of the Mozambique Ocean during LateNeoproterozoic.</p

Petrography, geochemistry, and provenance of Jurassic sandstones from the Sakarya Zone, NW Turkey

The Jurassic sandstones exposed in the western part of the Sakarya Zone are yellowish to brown, moderate to well sorted, medium to coarse-grained, grain-supported, and cemented by calcareous and minor silica. Sandstones are mainly classified as litharenite, subarkose, and arkose according to the relative proportions of quartz, feldspar and rock fragments, and major element ratios. On the SiO2 variation diagram, Na2O and K2O show slight positive correlations, which could reflect abundance of sodic plagioclase and K-feldspar with quartz within high Si-content sandstones. Sandstones generally exhibit slight LREE enrichment with respect to HREEs. The REE plots are characteristic for sedimentary rocks derived from the upper continental crust. Combining the results of several provenance discrimination diagrams, elemental ratios (Th/Sc, Zr/Sc, La/Th), and REE contents in sandstones, they reveal that the sandstones originated from intermediate to felsic source rocks. Accordingly, the probable source of the Jurassic sandstones is the crystalline basement of the Sakarya Zone consisting of Devonian, Carboniferous, and Permian granitoids, and high-grade metamorphic basement rocks. The Jurassic sandstones mostly have characteristic features of passive continental margin basins. It can be noted that the sandstones may have been deposited in a marginal basin that began to open in Early Jurassic time. CIA and CIW values for the Jurassic sandstones suggest that the source area was subject to low to moderate chemical weathering under semihumid to semiarid climatic conditions

Early Variscan magmatism along the southern margin of Laurasia: geochemical and geochronological evidence from the Biga Peninsula, NW Turkey

Massive, fine-grained metavolcanic rocks of the CamlA +/- ca metamorphic unit exposed in the Biga Peninsula, northwestern Anatolia, have provided new Carboniferous ages and arc-related calc-alkaline petrogenesis constraints, suggesting that the Biga Peninsula was possibly involved in the Variscan orogeny. The metavolcanic rocks are mainly composed of metalava and metatuff and have the composition of andesite. Chondrite-normalized REE patterns from these rocks are fractionated (La-N/Yb-N 2.2 to 8.9). Europium anomalies are slightly variable (Eu/Eu* = 0.6 to 0.7) and generally negative (average Eu/Eu* = 0.68). The metavolcanic rocks have a distinct negative Nb anomaly and negative Sr, Hf, Ba, and Zr anomalies. These large negative anomalies indicate crustal involvement in their derivation. Tectonic discrimination diagrams show that all metavolcanic rocks formed within a volcanic arc setting. Zircon ages (LA-ICP-MS) of two samples yield 333.5 +/- 2.7 and 334.0 +/- 4.8 Ma. These ages are interpreted to be the time of protolith crystallization. This volcanic episode in the Biga Peninsula correlates with other Variscan age and style of magmatism and, by association with a collisional event leading to the amalgamation of tectonic units during the Variscan contractional orogenic event. Carboniferous calc-alkaline magmatism in the Sakarya Zone is ascribed to arc-magmatism as a result of northward subduction of Paleo-Tethys under the Laurasian margin. Geochemical and U-Pb zircon data indicate that the Sakarya Zone is strikingly similar to that of the Armorican terranes in central Europe. The Biga Peninsula shows a connection between the Sakarya Zone and the Armorican terranes

Early Variscan arc magmatism in NW Turkey Evidence of geochemistryand U Pb zircon ages

Massive, fine-grained metavolcanic rocks of the Çamlıca metamorphic unit exposed in the Biga Peninsula, northwest Turkey, have provided new Carboniferous ages and arc-related calc-alkaline volcanics indicating that theBiga Peninsula was possibly involved in the Variscan orogeny. The metavolcanic rocks are mainly composed ofmetalava- metatuff intercalation and have an andesitic composition. Chondrite-normalized REE patterns withinthese rocks are fractionated (LaN/YbN ∼ 2.2 to 8.9), Europium anomalies are slightly variable (Eu/Eu* 0.6 to0.7) and generally negative (average Eu/Eu* 0.68). The metavolcanic rocks have a distinct negative Nb anomalyand negative Sr, Hf, Ba and Zr anomalies. These large negative anomalies indicate crustal involvement in theirderivation. The crustal influence may be related to either partial melting at the base of continental crust or contamination of mafic magma with crustal material. Tectonic discrimination diagrams show that all metavolcanic rockswere formed within a volcanic arc setting. Zircon ages (LA-ICPMS) of two samples yield 333.5±2.7 Ma and334.0±4.8 Ma. These ages are interpreted to be the time of protolith crystallization. This volcanic episode in theBiga Peninsula can be correlated with the Central Europian Variscides. Carboniferous calc-alkaline magmatism inthe Sakarya Zone can be ascribed to arc-magmatism as a result of northward subduction of the Palaeo-Tethys underthe southern margin of Laurasia. Geochemical and U-Pb zircon data indicate that the Sakarya Zone is strikinglysimilar to that of the Armorican terranes in central Europe. The Biga Peninsula can provide a link between theSakarya Zone and the Armorican terranes.</p