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Neues Jahrbuch fur Mineralogie, Abhandlungen, vol.198, no.3, pp.235-256, 2023 (SCI-Expanded)
A complete section of the Bitlis Massif crops out in the Avnik and Ünaldı regions (E Türkiye). It comprises a core of Precambrian-Early Cambrian gneisses, mafic metavolcanic rocks with Kiruna-type magnetite-apatite ores and metagranite bodies. Unconformably overlying this core is a cover succession made up of Silurian to late Cretaceous micaschists and marbles. The Kiruna-type ore beds, focused on this paper, range from centimetres up to 20 m in thickness and are concordantly interbedded with mafic metalavas, detrital magnetite-rich metavolcanoclastic rocks, and metachert beds. Geological characteristics of the metamorphosed ore-bearing volcanic and volcanosedimentary succession indicate that the magnetite-apatite ores were formed in a shallow marine environment by volcanic exhalative and sedimentary processes. U-Pb zircon ages obtained from the interlayered basaltic flows are 578 – 542 Ma, marking the maximum age of ore formation. Geological and petrological characteristics of the basaltic association in the Precambrian units indicate that their formation took place in a forearc environment along the northern margin of Gondwana. This active magmatic margin was formed above the south dipping Prototethys oceanic crust, which was carrying a small oceanic or continental fragment. When this microcontinent collided with Gondwana, south-verging compressional deformation, high-grade regional metamorphism, and syntectonic intrusion of the Avnik and Yayla metagranites occurred. U-Pb zircon ages of 521– 506 and 521– 503 Ma for the Avnik and Yayla metagranites, respectively, date this collision, and thus the termination of ore deposition in the Bitlis Massif.