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K–Ar dating of mineral separates extracted from various granitoid rock units of the eastern Pontides and central Anatolia,
Turkey, has provided some new insights unravelling various stages of the Neo-Tethyan convergence system, which evolved with
northward subduction between the Eurasian plate (EP) to the north and the Tauride-Anatolide platform (TAP) to the south along
the İzmir-Ankara-Erzincan suture (IAES) zone. Arc-related granitoid rocks are only encountered in the eastern Pontides and
yield K–Ar cooling ages of both Early Cretaceous (138.5 ± 2.2 Ma) (early arc), and Late Cretaceous, ranging from 75.7 ± 0.0
to 66.5 ± 1.5 Ma (mature arc), respectively. The multi-sourced granitoids of the eastern Pontides, with a predominant mantle
component and K–Ar ages between 40 and 50 Ma, are considered to be a part of post-collisional slab break-off magmatism accompanied
by tectonic denudation of pre-Late Cretaceous granitoid rocks following juxtaposition of the EP and the TAP around 55–50 Ma
in the eastern Pontides. The K–Ar cooling ages of collision-related S-, I- and A-type granitoids in central Anatolia reflect
good synchronism between 80 and 65 Ma, suggesting a coeval genesis in a unique geodynamic setting but with derivation from
various sources—namely, purely crustal, purely mantle and/or of mixed origin. This sort of simultaneous generation model for
these S-I-A-type intrusives seems to be consistent with a post-collisional lithospheric detachment related geodynamic setting.
I-type granodioritic to tonalitic intrusives with K–Ar cooling ages ranging from 40 to 48 Ma in east-central Anatolia are
interpreted to have been derived from a post-collisional, within-plate, extension-related geodynamic setting following the
amalgamation of the EP and the TAP in east-central Anatolia. 相似文献
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In order to estimate the distribution, as well as the magnitude, of dynamic material pressures on ground-supported silos a simplified seismic analysis procedure was utilized. The seismic analysis of silos can be complex, as the evaluation of several parameters must be taken into consideration, including the properties of bulk materials used and how the bulk materials and silo wall are joined together. It is therefore useful to develop an analytical approximation in order to better assess results. In addition to a simplified model for the seismic analysis of a silo–bulk material system being utilized, a three-dimensional finite element model was also incorporated. Using the finite element method, a more realistic representation of the structure is possible. Moreover, the finite element method also takes into consideration contact problems between the bulk material and the silo wall, which results in easier analyses. Both a squat and a slender silo were selected for this study. The results obtained in the study of selected examples were compared with those findings obtained via EN1998-4. Modified Veletsos and Younan approximations, which are commonly used for the analysis of grain silos, were also used. Results and analysis concluded that the proposed analytical model provided, overall, a good outcome, especially in regards to the analysis of dynamic material pressure. It should be noted that using the analytical method as proposed in Eurocode, the dynamic material pressure for squat silos can be underestimated, but the results for slender silos are stronger. 相似文献
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Utkucu Murat Durmuş Hatice Nalbant Süleyman 《International Journal of Earth Sciences》2017,106(6):1841-1861
International Journal of Earth Sciences - Earthquake ruptures perturb stress within the surrounding crustal volume and as it is widely accepted now these stress perturbations strongly correlates... 相似文献
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Mehmet Arslan İrfan Temizel Emel Abdioğlu Hasan Kolaylı Cem Yücel Durmuş Boztuğ Cüneyt Şen 《Contributions to Mineralogy and Petrology》2013,166(1):113-142
The Eocene volcano-sedimentary units in the southern part of the Eastern Pontides (NE Turkey) are confined within a narrow zone of east–west trending, semi-isolated basins in Bayburt, Gümü?hane, ?iran and Alucra areas. The volcanic rocks in these areas are mainly basalt and andesite through dacite, with a dominant calc-alkaline to rare tholeiitic tendency. 40Ar–39Ar dating of these volcanic rocks places them between 37.7 ± 0.2 and 44.5 ± 0.2 Ma (Middle Eocene). Differences in the major and trace element variations can be explained by the fractionation of clinopyroxene ± magnetite in basaltic rocks and that of hornblende + plagioclase ± magnetite ± apatite in andesitic rocks. Primitive mantle-normalized multi-element variations exhibit enrichment of large-ion lithophile elements and to a lesser extent, of light rare earth elements, as well as depletion of high field strength elements, thus revealing that volcanic rocks evolved from a parental magma derived from an enriched mantle source. Chondrite-normalized rare earth element patterns of the aforementioned volcanic rocks resemble each other and are spoon-shaped with low-to-medium enrichment (LaN/LuN = 2–14), indicating similar spinel lherzolitic mantle source(s). Sr, Nd and Pb isotopic systematics imply that the volcanic rocks are derived from a subduction-modified subcontinental lithospheric mantle. Furthermore, post-collisional thickened continental crust, lithospheric delamination and a subduction-imposed thermal structure are very important in generating Tertiary magma(s). The predominantly calc-alkaline nature of Eocene volcanic rocks is associated with increasing geodynamic regime-extension, whereas tholeiitic volcanism results from local variations in the stress regime of the ongoing extension and the thermal structure, as well as the thickness of the crust and the mantle-crust source regions. Based on volcanic variety and distribution, as well as on petrological data, Tertiary magmatic activity in Eastern Pontides is closely related to post-collisional thinning of the young lithosphere, which, in turn, is caused by extension and lithospheric delamination after collisional events between the Tauride–Anatolide Platform and the Eurasian Plate. 相似文献
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