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Magmatic signature of the closure of the northern branch of Neo-Tethys : Upper Paleocene-Middle Eocene magmatism at the boundary of Tavşanlı-Sakarya Zone (Turkey)

Güllü Bahattin, Kadiıoğlu Yusuf Kağan

Geological Quarterly

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2022

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Vol. 66, No. 2

art. no. 13

EN

Numerous plutons composed of granite, granodiorite, diorite-porphyry, monzonite, granodiorite-porphyry and diorite/microdiorite-porphyry occur at the boundary of the TavêanlÏ-Sakarya Zone, in the eastern part of the northwestern Anatolian magmatic belt, Turkey. These rocks belong to two different types: a medium-K calc-alkaline granodiorite series (with associated dykes and sub-volcanic rocks) and a shoshonitic series of granites. The rocks of the shoshonitic series have SiO₂from 67.5 to 75.6 wt.% with Mg# from 35.1 to 59.5, whereas the medium-K calc-alkaline series rocks have SiO₂ between 54.6 and 67.7 wt.% with Mg# from 43.5 to 60.8. There is a clear enrichment of LILE with respect to the HFSE in all magmatic units of the region. These magmatic rocks reflect properties of collision-related arc magmatism in the various geochemical discrimination diagrams. The initial Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd istopic ratios of the magmatic units range from 0.705506 to 0.710902 and 0.512178 to 0.512594, respectively. Collision-related granitoids yielded a ⁴⁰Ar/³⁹Ar cooling age age of 59.13 ±1.87 Ma, and arc-related granitoids and associated sub-volcanic units 44.3 ±0.47 and 44.11 ±0.89 Ma. The data obtained revealed that continent-continent collision in the Paleocene together with the initiation of the closure of the Neo-Tethys took place between the Anatolide-Tauride Platform and Sakarya Plate from the end of the Cretaceous. The shoshonotic granite may cooled in the Middle Paleocene, as regards the subduction-accretion zone in which subduction impacts have been observed. The medium-K calc-alkaline magmatic products in the region were formed by partial melting of the continental lithospheric mantle caused by the upwelling of asthenospheric mantle after the subducted slab was delaminated.

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Magma mingling textures in granitic rocks of the eastern part of the Strzegom-Sobótka Massif (Polish Sudetes)

Domańska-Siuda Justyna, Bagiński Bogusław

Acta Geologica Polonica

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2019

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Vol. 69, no. 1

143--160

EN

Many granitic intrusions display evidence of magma mixing processes. The interaction of melts of contrasting composition may play a significant role during their generation and evolution. The Strzegom-Sobótka massif (SSM), located in the Sudetes (SW Poland) in the north-eastern part of the Bohemian Massif of the Central European Variscides, exhibits significant evidence of magma mingling on the macro- and micro-scales. The massif is a composite intrusion, with four main varieties: hornblende-biotite granite (with negligible amount of hornblende) and biotite granite in the western part, and two-mica granite and biotite granodiorite in the eastern part. Field evidence for magma mingling is easily found in the biotite granodiorite, where dark enclaves with tonalitic composition occur. Enclaves range from a few centimeters to half a meter in size, and from ellipsoidal to rounded in shape. They occur individually and in homogeneous swarms. The mixing textures in the enclaves include fine-grained texture, acicular apatite, rounded plagioclase xenocrysts, ocellar quartz and blade-shaped biotite. The most interesting feature of the enclaves is the presence of numerous monazite-(Ce) crystals, including unusually large crystals (up to 500 μm) which have grown close to the boundaries between granodiorite and enclaves. The crystallization of numerous monazite grains may therefore be another, previously undescribed, form of textural evidence for interaction between two contrasting magmas. The textures and microtextures may indicate that the enclaves represent globules of hybrid magma formed by mingling with a more felsic host melt. Chemical dating of the monazite yielded an age of 297±11 Ma.

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Przestrzeń publiczna w miecie - schody

Haupt P.

Czasopismo Techniczne. Architektura

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2004

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R. 101, z. 2-A

35--39

EN

Public spaces are substantial to urban landscape. Usually when specifying their types squares and streets are mentioned. But when the lines and figures become present in the third dimension they often represent terraces and stairways. The purpose they serve in urban design may differ from the stairway communicating city districts through terracing square concentrating urban tissue to a composition accenting the void substituting buildings. Whether the shape was inspired by natural topography or purely abstract concept since the antiquity steps were used as an element in urban planning. Nowadays the meaning of stairs has not diminished; it is constantly changing following the evolution of contemporary city.