Evidence of Magma Mixing and Hybrid Source on Calc-Alkaline Sarihan (Bayburt) Granitoid, NE Turkey

Abstract

The study area is in the South Zone of Eastern Pontides (NE Turkey). The basement is Pre-PermoCarboniferous aged Pulur Massif which contains greenschist, micaschist, para-amphibole schist, ortoamphibolite, gneiss, marble, quarzite and intruding Middle-Carboniferous aged Saraycik Granodiyorite. Liassic aged Hamurkesen Formation overlying unconformably the massif begins with Dikmetas Conglomerate and continues with volcano-sedimentary rocks containing tuff, sandstone and andesite, all of which are cut by diabase dykes. Maim-Lower Cretaceous aged Hozbirikyayla Formation overlies conformably Hamurkesen Formation and contains limestone and sandy limestones. Hozbirikyayla Formation is overlied by conformably Otlukbeli Melange containing red-limestone, pyroclastics, serpentinite, radiolarite, limestone olistoliths and breciated basalt. Campanien aged Sarihan Granitoid cuts all these lithologies. Sarihan Granitoid covering an area of km 2 contains quartz-monzodiorite (60%), granodiorite (35%) and quartz-diorite (5%), and is cut by 5 to 10 cm width aplite dykes. These rocks show similar petrographical features. In the center of intrusion, 0.5-1 cm width cracks were filled by black tourmaline. The rocks of the intrusion shows medium-grained, poikilitic, anti-rapakivi and sometimes myrmekitic textures, and contains 43-64% plagioclase, 7-15% orthoclase, 10-29% quartz, 5-20% hornblende, 1-8% biotite and 1-6% opaque oxides. Plagioclase is subhedral, mainly oligoclase and rare andesite in composition (Anls-37 Ab55-79 Or22_9). Large crystals show generally oscillatory zoning and albite twinning. Crystals with oscillatory zoning range in composition from An33 in the core to Anls in the rim. Mirmekitic textm'es developed at the contact of orthoclase. Large plagioclase may contain plagioclase, apatite, magnetite and rare hornblende inclusions.