They show high-K calc-alkaline affinity. On primitive-normalized spider diagrams, negative anomalies of Ba, Nb, Sr, P, and Ti and positive anomalies of Pb are noteworthy. Their chondrite-normalized REE patterns are characterized by strongly fractionated patterns with demonstrative negative Eu anomaly, whereby middle REE are not fractionated relative to the heavy REE. These geochemical features suggest a fractionating mineral assemblage of feldspar, apatite, and biotite without significant involvement of garnet. The Lutetian rhyolites of the Princes’ Islands are a part of the Middle Eocene magmatic associations of the West Pontides, related to collision of the Menderes-Taurus block with the Pontides. | Turkish Journal of Earth Sciences Turkish J Earth Sci 2020 29 208-219 http earth TÜBİTAK Research Article doi yer-1905-19 Middle Eocene high-K acidic volcanism in the Princes Islands İstanbul and its geodynamic implications Fatih ŞEN Institute of Graduate Studies in Sciences İstanbul University Vezneciler İstanbul Turkey Received Accepted Published Online Final Version Abstract The rock assemblages of the Princes Islands which are located to the south of mainland İstanbul are regarded as parts of the Lower Paleozoic quartz sandstones although they were initially considered as volcanic rocks by Swan in 1868. They differ from quartz sandstones by their vesicular texture and are devoid of any stratigraphic layering. Their mineral constituents are plagioclase 30 35 feldspar 35 40 and quartz 20 25 corresponding to rhyolite. The crystallization age of the rhyolites is Ma on the basis of the U-Pb zircon data. They show high-K calc-alkaline affinity. On primitive-normalized spider diagrams negative anomalies of Ba Nb Sr P and Ti and positive anomalies of Pb are noteworthy. Their chondrite-normalized REE patterns are characterized by strongly fractionated patterns with demonstrative negative Eu anomaly whereby middle REE are not fractionated relative to the heavy REE. These geochemical features suggest a fractionating mineral assemblage of feldspar apatite and biotite without significant involvement of garnet. The Lutetian rhyolites of the Princes Islands are a part of the Middle Eocene magmatic associations of the West Pontides related to collision of the Menderes-Taurus block with the Pontides. Key words İstanbul quartz sandstone rhyolite Middle Eocene West Pontides 1. Introduction 2004 Karslı et al. 2010 Kaygusuz et al. 2011 Arslan et The Tethys Ocean which began to subduct under al. 2013 . Laurasia during the late Paleozoic-early Mesozoic Topuz It is stated that Eocene magmatism is not present
