Serpentinisation of Guleman Ophiolite in the Southeast Anatolian Orogenic Belt (Türkiye)

The Guleman ophiolite is a part of the Southeast Anatolian Orogenic Belt (SAOB) ophiolites. The Guleman ophiolite, which is located to the northeast of Maden and covers an area of 200 square km east of the Hazar Lake, is situated 50 km southeast of Elazığ, and it is one of the important ophiolitic massifs in the SAOB. The Guleman ophiolite formed in the southern branch of the Neo-Tethys ocean and was emplaced beneath the Anatolide-Tauride platform. It is usually in tectonic contact with the other units, and some of it has been intruded by Late Cretaceous granitic rocks and is covered by younger sediments. The Guleman Ophiolite is composed of serpentinised mantle tectonites, ultramafic-mafic cumulates, isolated gabbro and sheeted (diabasic) dykes. The mantle section of Guleman ophiolite mainly consists of serpentinised harzburgites and dunites with significant, economically level podiform chromitites. The serpentinised mantle peridotites consist of relicts of olivine and orthopyroxene, serpentine minerals and Cr-spinel ± carbonate minerals. Petrographic study of serpentinised peridotites shows that the rocks consist predominantly of lizardite and portlandite serpentines and olivine and have the opaque mineral assemblage of magnesioferrite+spinel developed during serpentinisation of the rock. Carbonate-bearing veins were observed in the serpentinite. The typical pseudomorphic textures consist of meshes and bastites. There are two types of alteration mineralogy and textural relationships. Firstly, lizardite mesh-textured vein networks with relict olivine cores, and secondly, bastite texture with serpentinisation of orthopyroxene. Mesh-textured serpentine veins with fresh olivine cores occur in all samples, while bastite texture occurs in harzburgite samples. The XRD pattern shows that the main constituents of the sample were the lizardite (Mg₃(Si₂O₅)(OH)₄) and portlandite (the calcium analogue of brucite) Ca(OH)₂ minerals, which have various microstructure features. This study was supported by the TUBITAK project numbered 124Y011.

Key Words: Guleman Ophiolite, Serpantinisation, Petrography, XRD, Türkiye