Diachronous Magmatic and Cu-Au-Mo Metallogenic Responses to Slab Roll-Back Initiation from Northwest Anatolia to the Balkans, Western Tethyan Eocene Magmatic Belt

Abstract

The Bursa mineral district in northwest Anatolia (Turkey) is an emerging prospective area for porphyry Cu-Mo (Au-Re) mineralization along the Western Tethyan Eocene magmatic belt that links the Balkan to Lesser Caucasus regions along the southern Black Sea coast. Field observations as well as time constraints on mineralized magmas of the Bursa district are limited. Additionally, the tectonic setting of Eocene magmatism in northwest Turkey is controversial and includes either Neotethyan slab roll-back or break-off scenario. We show that the Bursa mineral district consists of porphyry Cu-Mo, skarn Cu, and rare epithermal Au-Ag deposits, prospects, and occurrences on the footwall of the Eskişehir fault, south of the İzmir-Ankara-Erzincan suture zone. The porphyry prospects are hosted within porphyritic dioritic, granodioritic, and granitic rocks that were altered by potassic and phyllic assemblages and quartz-sulfide vein stockwork zones. Our new CA-TIMS and LA-ICP-MS U-Pb and 40Ar/39Ar ages indicate that porphyry mineralization of the Bursa district formed between 51 and 46 Ma and thus before the porphyry and epithermal Cu-Au mineralization of the Biga (~43–39 Ma) and Rhodope districts (~35–31 Ma) and the Serbo-Macedonian belt (~36–22 Ma). Therefore, we interpret that Eocene magmatism and associated Cu-Au-Mo mineralization migrated westward along the western part of the Western Tethyan Eocene magmatic belt. This migration, which is specific to the Eocene period, represents a second-order and diachronous response to the first-order southward magmatic front migration and roll-back initiation of the Hellenic slab beneath the Balkan-Aegean-western Anatolian region since the Late Cretaceous.

Late Paleocene – Middle Eocene magmatic flare-up in western Anatolia

“…9). The Sivrihisar Monzonite gave a zircon U-Pb age of 55.3 ± 0.2 Ma based on 57 zircon grains, which is compatible with its 55.2 ± 0.6 Ma zircon U-Pb age reported by Rabayrol et al (2021) but older than the 50.6 ± 0.3 Ma U-Pb zircon age reported by Özdamar et al (2018). The very scattered U-Pb zircon ages reported by Shin et al (2013) from the Sivrihisar Monzonite are most likely an artifact of the in situ dating in thin section, especially considering that all of the 109 concordant zircon ages from the Sivrihisar granite from our data, from Rabayrol et al (2021) and from Özdamar et al (2018) fall in the range of 49 Ma to 56 Ma.…”

“…The Kaymaz Granite is a small body intruding metamorphic rocks and serpentinite; gold and silver are mined in the silicified serpentinite at the contact with the granite (Rabayrol et al, 2021, Yavuz et al, 2022. The Kaymaz Granite has yielded an Early Eocene U-Pb zircon age of 55.3 ± 1.2 Ma (Fig.…”

“…1). The origin of the LP-ME magmatism is controversial and has been attributed to slab breakoff (Altunkaynak, 2007;Keskin et al, 2008;Karacık et al, 2008;Altunkaynak et al, 2012;Altunkaynak and Dilek, 2013;Ersoy and Palmer, 2013;Gülmez et al, 2013;Kasapoğlu et al, 2016;Ersoy et al, 2017a, b;Gürarslan and Altunkaynak, 2019), delamination of the lower part of the thickened lithosphere (Köprübaşı and Aldanmaz, 2004) and subduction (Okay and Satır, 2006;Ustaömer et al, 2009;Rabayrol et al, 2021). This paper deals with the LP-ME magmatic flare-up in northwestern Anatolia.…”