In situ Rb-Sr dating of K-bearing minerals from the orogenic Akçaabat gold deposit in the Menderes Massif, Western Anatolia, Turkey

Fırat Şengün, Viktor Bertrandsson Erlandsson, Johan Hogmalm, Thomas Zack

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The Akçaabat gold deposit is mainly composed of massive arsenopyrite veins in strongly foliated augen gneisses of the Çine Sub-massif in western Turkey. K-bearing minerals from orogenic gold veins were dated by the in situ Rb-Sr method in order to determine the formation age of the Akçaabat gold deposit. Textural relationships between the vein minerals suggest that arsenopyrite, K-feldspar, quartz, and muscovite formed in one paragenetic stage. Native gold, native bismuth, scorodite, and galena were introduced in a later paragenetic stage. The isochron derived from K-feldspar and muscovite occurring in the veins yielded 31.3 ± 4.7 Ma. In situ Rb-Sr dating of the same assemblage (K-feldspar and muscovite) in the host rock gave an isochron age of 40.8 ± 3.8 Ma, 10 Ma older than the vein ages, and corresponding to peak metamorphism of the regional main Menderes metamorphism during the Alpine-Himalayan orogenic event. Biotite from the host rock gave an isochron age of 28.1 ± 2.2 Ma and probably reflects the cooling age. Homogenization temperatures from fluid inclusions in quartz show that quartz formed at 280 – 390 ℃ but has a dominant mode in the 350 – 360 ℃ temperature interval. The age of vein formation was successfully distinguished from the age of the Alpine-Himalayan orogenic event associated with main Menderes metamorphism. This study demonstrates that in situ Rb-Sr isotopic study can be applied to resolve absolute dating of orogenic deposits in metamorphic complexes.
Original languageEnglish
Article number104048
JournalJournal of Asian earth sciences
Issue numberNovember
Publication statusPublished - 28 Sept 2019

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