Late Cretaceous Orbicular Gabbro Cropping Out West Of Elazig (Turkey): Mineralogy, Petrography And Magma Mixing Processes

Abstract

The lithological units outcropping in the study area, located in the Southeast Anatolian Orogenic Belt, one of the most important parts of the Alpine-Himalayan Orogenic Belt. The study area crops out in a local area within the Hısırık creek in the north of Sarıgül village of Baskil county, which is located in the west of Elazig province in Southeast Turkey. Elazig Magmatics contains plutonic and sub-volcanic rocks, mainly felsic and mafic compositions. Plutonic rocks with felsic composition include granite, granodiorite, tonalite and quartz monzonites, while sub-volcanic rocks include aplite. Plutonic rocks with mafic composition are represented by diorite, quartz diorite, gabbro and orbicular gabbro, and sub-volcanic rocks are represented by diabase and diorite porphyries. The orbicular gabbros, which are the subject of the study, macroscopically contain orbicles ranging in size from 1 cm to 15 cm, formed by repetitive concentric circles of fine and coarse grains. All these orbicles consist of concentric circles that show magmatic textures both in macro specimens and under the microscope. The orbicles contain olivine, pyroxene amphibole and plagioclase minerals. Olivines are characteristic of their yellow, orange and bluish interference colours and abundant cracked structures. Pyroxenes show one or two planes of cleavage and have high interference colours. Plagioclase inclusions point to magma mixing from the sub-ophitic and ophitic textures. Orbicular circles were formed by the crystallization of basic magma in the form of a circular texture by conventional repetition as a result of adding a basic new magma that was later included in the magma chamber during the crystallization of basic magma. Mineralogical and petrographic features suggest that the orbicular gabbro is part of mafic igneous enclaves within intrusive mafic rocks.