Petrography, Mineral Chemistry and Crystallization Conditions of Tertiary Plutonic Rocks Located to the North of Bayburt (Eastern Pontides, Turkey)

Abstract

The Eastern Pontides comprise many intrusive bodies varying in composition, size and age from Palaeozoic to Cenozoic. Especially Cenozoic aged bodies are commonly observed in the southern part, while they are rarely exposed in the northern part of the Eastern Pontides. In this study, the petrography and mineral chemistry of the Cenozoic aged Çiçekli, Somarova, Sorkunlu, Şaşurluk, Aydıntepe, Kemerlikdağı and Pelitli plutons located to the north of Bayburt are determined, and the crystallisation conditions of the studied bodies were estimated by means of thermobarometer calculations. The studied plutons extend mostly in NE-SW directions and are approximately ellipsoid in shape. The contacts between the plutons and surrounding rocks are sharp, and plutons commonly contain mafi c microgranular enclaves (MMEs) of different sizes. Petrographic and mineral chemistry studies reveal some disequilibrium textures refl ecting the magma mixing process. Based on modal mineralogy, the plutonic rocks are gabbroic diorite, diorite, tonalite, granodiorite and monzogranite in composition. The rocks have fi ne to medium granular, porphyric, monzonitic, poikilitic, occasionally myrmekitic and micrographic textures. The main minerals are labradorite and albite (An 68-02 ), magnesiohornblende and actinolite (Mg# = 0.6-0.9), diopside and augite (Wo 44-46 ), clinoenstatite (En 53-57 ) and Fe-Ti oxide minerals. Crystallization temperatures calculated from amphibole, biotite, clinopyroxene, magnetite and ilmenite minerals are 405°C to 1161°C, pressure values are 0.1 to 2.7 kbar, and oxygen fugacity (log10 ƒO 2 ) is -20 to -12. Estimation of water content calculated by using amphiboles is between 2.9 and 6.8%. Based on obtained data, it is suggested that the studied plutons were emplaced at shallow depths (~ 1-8 km).

Settlement conditions of magma (s) forming Jurassic plutonic rocks in the Gümüşhane (Eastern Pontides, Turkey)

“…The hornblendes in the studied plutons are calcic hornblendes with Al (t) values lower than 2.0. This value (Al (t) <2.00) generally indicates shallow depth intrusion (Hammarstrom and Zen, 1986;Kaygusuz et al, 2018). Additionally, the textural properties like porphyritic and regrowth supporting the shallow intrusion of the plutons are noteworthy in the studied plutons ( Figure 5).…”

“…The Eastern Pontide Orogenic Belt (NE Turkey), where the study area is located, comprises volcanic and plutonic rock assemblages (Karslı et al, 2007(Karslı et al, , 2012; Kaygusuz et al, 2008Kaygusuz et al, , 2018Dokuz, 2011;Temizel et al, 2012Temizel et al, , 2018Temizel et al, , 2019aTemizel et al, , 2019bAydınçakır and Şen, 2013;Arslan et al, 2013;Aydın, 2014;Yücel et al, 2017). The region dominantly hosts plutonic and volcanic rocks formed over long periods of time from the Permo-Carboniferous to the end of the Eocene (Figure 1).…”

“…Cretaceous-aged plutonic rocks known to be subduction related (Şahin et al, 2004;Aydınçakır, 2009, 2011;Karslı et al, 2010;Kaygusuz et al, 2013;Sipahi et al, 2017;Eyüboğlu et al, 2019;Temizel and Kurt, 2019;Temizel et al, 2019a) have contact relations with volcanic and/or volcanoclastic rocks. Eocene-aged plutons (Yılmaz and Boztuğ, 1996;Arslan and Aslan, 2006;Karslı et al, 2007Karslı et al, , 2011Kaygusuz and Öztürk, 2015;Eyüboğlu et al, 2017;Kaygusuz et al, 2018;Temizel et al, 2018Temizel et al, , 2019b were emplaced by cutting the whole series.…”

40Ar–39 Ar dating, whole-rock and Sr-Nd isotope geochemistry of the Middle Eocene calc-alkaline volcanic rocks in the Bayburt area, Eastern Pontides (NE Turkey): Implications for magma evolution in an extension-related setting

“…All these rocks are conformably overlain by Late Cretaceous volcanic rocks (Özdamar, 2016;Eyuboğlu, 2010;Aydın, 2014), and crosscut by plutonic rocks of late Cretaceous age (Şipahi et al, 2018;Karslı et al, 2010;Temizel et al, 2019;Kaygusuz et al, 2021). The Cenozoic rocks are represented by the first cycle adakitic rocks (Karslı et al, 2011;Topuz et al, 2005;Dokuz et al, 2013), the second cycle volcanic-subvolcanic (Aslan et al, 2014;Eyuboğlu et al, 2013b;Arslan et al, 2013;Aydınçakır, 2014;Yücel et al, 2017;Kaygusuz et al, 2011Kaygusuz et al, , 2019Aydınçakır et al, 2022) and plutonic rocks (Karslı et al, 2007;Boztuğ et al, 2004;Özdamar et al, 2017;Eyuboğlu et al, 2017;Kaygusuz and Öztürk, 2015;Kaygusuz et al, 2018Kaygusuz et al, , 2020Kaygusuz et al, , 2021Temizel et al, 2018Temizel et al, , 2020Vural and Kaygusuz, 2021), the third cycle volcanic rocks (Aydın et al, 2008;Arslan et al, 2013;Karslı et al, 2020) and the fourth cycle volcanic-subvolcanic and adakitic rocks (Temizel et al, 2012;Aydın et al, 2008;Dokuz et al, 2013;Yücel et al, 2017).…”

The Sr, Nd, Pb and Hf isotopes and crystallization conditions of the middle Eocene Dağdibi Pluton in the eastern Sakarya Zone, Turkey

“…The Dağdibi Pluton is located in the eastern part of the Sakarya Zone, Turkey, a crustal segment lying in the middle parts of the Alpine-Himalayan Orogenic Belt. Although the igneous rocks with ages varying from Carboniferous to Miocene are found in the eastern Sakarya Zone, those formed in the time interval from the Late Cretaceous to the end of Eocene are very common (Sipahi, 2005, 2017, 2019; Arslan & Aslan, 2006; Boztuğ et al 2007; Kaygusuz et al 2012, 2018, 2020; Temizel et al 2012; Aydınçakır, 2014; Sipahi & Sadıklar, 2014; Gücer et al 2017; Dokuz et al 2019; Sipahi et al 2020a, 2020b, 2022; Gücer, 2021). Particularly the eastern part of the Sakarya Zone is therefore regarded as a paleo-magmatic arc and a natural laboratory to study the tectonic and petrogenetic processes that occurred through the time interval from the final stages of subduction to post-collision.…”