气候变化领域集成服务门户(CCPortal): Postcollisional transition from subduction- to intraplatetype magmatism in the eastern Sakarya zone, Turkey: Indicators of northern Neotethyan slab breakoff

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DOI	10.1130/B31993.1
	Postcollisional transition from subduction- to intraplatetype magmatism in the eastern Sakarya zone, Turkey: Indicators of northern Neotethyan slab breakoff
	Dokuz A.; Aydin F.; Karsli O.
发表日期	2019
ISSN	167606
起始页码	1623
结束页码	1642
卷号	131 期号:2021-09-10
英文摘要	Postcollisional magmatism in the eastern Sakarya zone was recorded by voluminous basic volcanism and repeated plutonism during the early Cenozoic. The temporal and geochemical evolution of these magmatic rocks is important for understanding the possible geodynamic history of the Sakarya zone. Here, we investigated three representative plutons lying between the towns of çamlihemşin (Rize) and Ispir (Erzurum), Turkey. These are largely composed of medium-K gabbroic diorites (Marselavat Pluton), shoshonitic monzonites (Güllübağ Pluton), and high-K granites (Ayder Pluton). We present whole-rock geochemistry, 40Ar/39Ar geochronology, and Sr, Nd, and Pb isotope analyses from the plutons to constrain the timing of variations in magmatism and source characteristics, and we provide a new approach to the proposed geodynamic models, which are still heavily debated. The 40Ar/39Ar geochronology reveals a cooling sequence from ca. 45 Ma for the Marselavat Pluton through ca. 41 Ma for the Güllübağ Pluton to ca. 40 Ma for the Ayder Pluton. Whole-rock geochemistry and Sr, Nd, Pb isotopes suggest that crustal contamination was not an important factor affecting magma compositions. Although there was no arc-related tectonic setting in the region during the middle Eocene, the Marselavat Pluton shows some subduction affinities, such as moderately negative Nb and Ta anomalies, and slightly positive Pb anomalies. These signatures were possibly inherited from a depleted mantle source that was modified by hydrous fluids released from the oceanic slab during Late Cretaceous subduction. Geochemical traces of the earlier subduction become uncertain in the Güllübağ samples. They display ocean-island basalt-like multi-element profiles and Nb/Ta, Ce/Pb, and La/Ba ratios. All these point to a mantle source in which earlier subduction signatures were hybridized by the addition of asthenospheric melts. Melting of calc-alkaline crustal material, probably emplaced during the first phase of middle Eocene magmatism (Marselavat), led to the formation of granitic plutonism (Ayder Pluton). Our data in conjunction with early Eocene adakite-like rocks show that melt generation, as in the given sequence, was most probably triggered by breakoff of the northern Neotethyan oceanic slab, ~13 m.y. after the early Maastrichtian collision between the Sakarya zone and Anatolide-Tauride block, and continued until the end of the middle Eocene. A shallow-marine transgression occurred contemporaneously with the middle Eocene magmatism throughout the Sakarya zone. An extension in this magnitude seems unlikely to be the result of orogenic collapse processes only. The main cause of this extension was most probably related to the northward subduction of the southern Neotethys Ocean beneath the Anatolide-Tauride block. The result is a volumetrically larger amount of middle Eocene magmatism than that expected in response to slab breakoff. © 2019 Geological Society of America.
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/184909
作者单位	Department of Geological Engineering, Gümüşhane University, Gümüşhane, TR-29000, Turkey; Department of Geological Engineering, Karadeniz Teknik University, Trabzon, TR-61080, Turkey; Department of Geological Engineering, Recep Tayyip Erdoğan University, Rize, TR-53100, Turkey
推荐引用方式 GB/T 7714	Dokuz A.,Aydin F.,Karsli O.. Postcollisional transition from subduction- to intraplatetype magmatism in the eastern Sakarya zone, Turkey: Indicators of northern Neotethyan slab breakoff[J],2019,131(2021-09-10).
APA	Dokuz A.,Aydin F.,&Karsli O..(2019).Postcollisional transition from subduction- to intraplatetype magmatism in the eastern Sakarya zone, Turkey: Indicators of northern Neotethyan slab breakoff.Bulletin of the Geological Society of America,131(2021-09-10).
MLA	Dokuz A.,et al."Postcollisional transition from subduction- to intraplatetype magmatism in the eastern Sakarya zone, Turkey: Indicators of northern Neotethyan slab breakoff".Bulletin of the Geological Society of America 131.2021-09-10(2019).