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- MakaleAçık Erişim2019Scopus SJRQ1Petrology and 40Ar-39Ar dating of paragneisses from the Devrekani Massif (Central Pontides, Northern Turkey): Implications for the Jurassic high-T metamorphism in an extensional tectonic environment
Gücer, Mehmet Ali; Arslan, Mehmet; Çimen, Okay; Sherlock, Sarah C.
The Devrekani Massif in the northern part of the Central Pontides (Northern Turkey) provides important clues to the regional tectonics and geodynamic processes associated with Jurassic high grade metamorphic conditions. This study reports new paragenetic assemblages, mineral compositions, whole-rock geochemistry and 40Ar-39Ar geochronological data from the paragneisses in the massif, and, discusses the P–T conditions and geodynamic implications of the Jurassic metamorphism during continental extension in the Central Pontides. Upper amphibolite to lower granulite facies paragneisses form one of the main lithological units in the massif. Within these, there are five different mineral parageneses with diagnostic mineral assemblages of: quartz, K-feldspar (An0-1Ab4-26Or73-96), plagioclase (An18-35), biotite [XPhl: 0.28–0.57; Mg/(Mg + Fe2+): 0.33–0.61], sillimanite, cordierite [Mg/(Mg + Fe2+): 0.48–0.71] and garnet (Alm43-80Grs0-18Prp5-23And0-4Sps10-33) with minor hercynite. Based on Na-in-Crd thermometry and GASP barometry results, the peak metamorphic conditions are 775 ± 25 °C and 6 ± 1 kbar in the massif. The field relations, petrography and bulk chemical data suggest that the paragneisses, derived from shale-wackestone and pelitic sedimentary protoliths, are typical rock lithologies of an active continental margin. They display enrichments in LILE over HFSE, coupled with negative Nb and Ti anomalies, which are geochemical signatures of subduction-related sources. It is likely that the peak metamorphism took place during the Middle–Upper Jurassic period (ca. 174–156 Ma), suggesting that the metamorphic rocks cooled to 300–350 °C at ca. 156 Ma. The mineral assemblages reveal that the prograde history passed from sillimanite zone conditions up to the cordierite-garnet-K-feldspar zone. The petrological and geochronological data indicate that the protoliths are related to multiple sources such as volcano-sedimentary successions. We conclude that the Devrekani Massif represents the products of pre-Jurassic sedimentation, and Permo-Carboniferous continental arc magmatism, overprinted by Jurassic metamorphism.
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İncele - MakaleYalnız künye2012Scopus SJRQ1Two-Dimensional Geothermal Modelling Along the Central Pontides Magmatic Arc: Implications for the Geodynamic Evolution of Northern Turkey
Maden, Nafiz
The Pontides, which can be divided tectonically into three main segments as Eastern, Central, and Western Pontides, is one of the most complex geodynamic settings within the Alpine belt. The Central Pontides, where the Eastern and Western Pontides met and formed a tectonic knot, represent an amalgamated tectonic mosaic consisting of remnants of oceanic, continental, and island arc segments. Subduction polarity, which is responsible for the formation of the Pontides, is still under debate because of limited geological, geophysical, and geochemical data. Two-dimensional (2-D) thermal modelling studies along the Central Pontides magmatic arc (Northern Turkey), Sakarya and Ki{dotless}rşehir continents are investigated in order to delineate the crustal thermal structure and subduction polarity. The obtained numerical results indicate that arc and back-arc regions are hot because of the cooling effects of a subducting plate. Moho temperatures in the investigated region are found between 992°C in the south (back-arc) and 415°C in the north (arc). Moreover, mantle heat flow values vary from 57.2 mWm -2 in the south (back-arc) to 34.7 mWm -2 in the north (arc). It is shown from this study that the Eurasia plate had moved from north to south under the Anatolia plate along the south Black Sea coast.
AtıfScopus10WoS13OpenAlex12İncele - MakaleAçık Erişim2009Scopus SJRQ1Crustal thermal properties of the central Pontides (Northern Turkey) deduced from spectral analysis of magnetic data; [Orta pontidlerin (Kuzey Türkiye) kabuksal isıl özelliklerinin manyetik verilerin spektral analizi ile belirlenmesi]
Maden, Nafiz
The Pontides can be divided tectonically into three main sectors: Eastern, Central, and Western Pontides. Each of these represents an amalgamated tectonic mosaic consisting of remnants of oceanic, continental, and island arc segments. The Eastern and the Western Pontides meet in the Central Pontides, where they are structurally mixed and form a tectonic knot. The Central Pontides of northern Turkey is one of the best exposed segments of the southern margin of Eurasia adjacent to the Tethys Ocean. The study area also extends to parts of the Sakarya and Ki{dotless}rşehir continents. Magnetic spectral analysis, which has been used to estimate the Curie point depths and heat flow values, is employed to identify the thermal regime of the Central Pontides. The magnetic data of the region are separated into five subregions and the power spectra of each region is achieved by using 2D Fourier transform method to attain the average curie depth. The curie depth values changes across the studied region from 14.8 km in the south to 21.8 km in the north. The obtained results imply a high thermal gradient (39.2 °Ckm-1) and corresponding heat flow values (94.1 mWm-2) in the south of the research area. The northern part of the study area displays a low thermal gradient (26.6 °Ckm-1) and low heat flow value (63.9 mWm-2), corresponding to the Central Pontides consisting of accreted oceanic crustal material. The determined values show the heat flow decrease within the accretionary prism toward the island arc-like Pontides.
AtıfScopus20WoS15OpenAlex28İncele