Slab break-off-related magnesian andesites and dacites with adakitic affinity from the early Quaternary Keciboyduran stratovolcano, Cappadocia province, central Turkey: evidence for slab/sediment melt-mantle interaction and magma mixing

AYDİN F., Sonmez M., Siebel W., KARSLI O., Lermi A.

CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, cilt.177, sa.7, 2022 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 177 Sayı: 7
  • Basım Tarihi: 2022
  • Doi Numarası: 10.1007/s00410-022-01931-8
  • Dergi Adı: CONTRIBUTIONS TO MINERALOGY AND PETROLOGY
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aquatic Science & Fisheries Abstracts (ASFA), Artic & Antarctic Regions, Chemical Abstracts Core, Environment Index, Geobase
  • Anahtar Kelimeler: Slab break-off, Magnesian andesite, Adakite, Magma mixing, Cappadocia, Turkey, CENTRAL ANATOLIAN PLATEAU, HIGH-MG ANDESITES, TRACE-ELEMENT SIGNATURE, SETOUCHI VOLCANIC BELT, CONTINENTAL-CRUST, CALC-ALKALINE, EASTERN ANATOLIA, S-TYPE, AR-40/AR-39 GEOCHRONOLOGY, SUBDUCTION TERMINATION
  • Karadeniz Teknik Üniversitesi Adresli: Evet

Özet

Voluminous moderate- to high-magnesian [Mg# = molar Mg/(Mg- + Fe2+) = 44-64] andesitic and dacitic rocks with high silica (mostly 61-66 wt%) adakitic affinity (Y = 13-22, Yb = 1.3-2.1, Sr/Y = 18-44, La/Yb = 10-25) and common mafic magmatic enclaves (MMEs) are first reported in the Keciboyduran stratovolcano (KSV) from the Cappadocia volcanic province (CVP), Central Anatolia, Turkey. We present comprehensive whole-rock geochemistry and Sr-Nd-Pb isotope data, mineral chemical compositions and Ar-40-Ar-39 ages for KSV samples. Based on the volcanostratigraphy and Ar-40-Ar-39 dating results, two successive eruption ages of 2.2-1.6 Ma (stage I: amphibole-rich) and 1.6-1.2 Ma (stage II: pyroxene-rich) were established for the KSV, corresponding to the Gelasian and Calabrian stages of Early Pleistocene, respectively. Textural and geochemical evidence indicates that the KSV magnesian andesites-dacites are products of a hybrid magma formed by mixing between mantle-derived mafic and crust-derived felsic magmas with further fractionation and minor contamination during magma storage and ascent. Our new data, combined with previous geological and geophysical results suggest that parental magnesian mafic melts of the KSV rocks originated from a heterogenous mantle source generated through the metasomatism of mantle wedge material by subducted sediment-derived melts, and then partially melted through asthenospheric upwelling in response to slab break-off. The mafic magma underplated the overlying lower crust, resulting in its partial melting to generate crustal felsic magma. Both magmas mixed at lower crustal levels creating MME-rich hybrid magmas. Subsequently, the hybrid magmas were emplaced at different depths of the crust (c. 4-11 and 11-15 km for the stage I and II, respectively), where they crystallized at moderate temperatures (c. 1180-840 degrees C) and under relatively high oxygen fugacity (LogfO(2) = - 11.4 to - 9.2), water-rich (H2Omelt = 5.6-3.6 wt%) and polybaric (similar to 1.2 to 5.1 kbars) conditions, and underwent fractionation of primarily amphibole +/- pyroxene causing adakitic affinity. We propose a new petrogenetic model for the early Quaternary magnesian/adakitic andesites/dacites of the CVP in a post-subduction tectonic setting. Our results provide robust evidence for slab break-off of the eastern Cyprus oceanic lithosphere and put further constraints on the tectonic evolution of the eastern Mediterranean collision zone during the Early Quaternary.