Bibliographic Details
| Title: |
Geochemistry and geochronology of Middle Eocene subduction-related felsic volcanics in the Misis-Andirin Complex of the Southeast Anatolian Orogenic Belt. |
| Authors: |
Nurlu, Nusret, Akinci, Ahmet Can, Kohút, Milan |
| Source: |
Geosciences Journal; Dec2023, Vol. 27 Issue 6, p689-710, 22p |
| Subject Terms: |
VOLCANOLOGY, GEOCHEMISTRY, GEOLOGICAL time scales, FELSIC rocks, EOCENE Epoch, CESIUM isotopes, OROGENIC belts, GEODYNAMICS |
| Abstract: |
LA-ICP-MS zircon geochronology and geochemistry (whole-rock & mineral chemistry) from the Misis-Andirin Complex (MAC) volcanic rocks are reported. The MAC records magmatic, sedimentary, and tectonic processes operating at the northern active margin of the Neotethys (South Tethys) in the eastern Mediterranean district. The MAC represents an association of an originally active continental margin including the Engizek (in the NE), Andirin (central) and Misis (in the SW) segments. The felsic extrusives are depleted in HFSE (high-field-strength elements), enriched in LILE (large-ion lithophile elements) and have flat-type REE patterns; these trends and also biotite chemistry verify their supra-subduction zone tectonic environment. The studied volcanic unit consists of mainly rhyolite, dacite and rare andesite rocks, and is intercalated with Bulgurkaya Formation. These felsic extrusive rocks show relative depletions in Ti + Nb, and partial enrichment in Cs, Rb, Ba, and Th in the N-MORB (normal-mid ocean ridge basalt) normalized spider plot, suggesting their derivation from a supra-subduction geodynamic environment. The La/Nb (1.92–2.33) and Nb/Th (1.0–1.12) ratios of all the analysed extrusives from Andirin region present arc magmas or volcanic rocks affinity that could have been contributed by crustal source contents and also examined volcanics yield nearly flat Ba/La ratios with relatively increasing Th/Yb, suggesting the contribution of sediments or crustal contamination. The Al-in-hornblende thermobarometry (2.04 to 1.55 kbar) of Mg-Fe hornblende in the volcanics of the MAC represents their crystallization of amphibole in the moderate to shallow crustal level at a maximum 6.7 km to a minimum 5.1 km depth. The ilmenite-magnetite thermometer based on Fe-Ti oxide equilibria shows that the Andirin region felsic magmas were at 717 °C and at an fO2 of approximately 2.16 log units (+1.51 NNO). The MAC extrusive volcanic rocks were produced throughout the Eocene period, and our new U-Pb zircon dating (47.13 ± 0.5 Ma) confirmed mainly younger Lutetian age of the volcanic activity in the Andirin area. [ABSTRACT FROM AUTHOR] |
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