Genetic investigation of magnesite occurrences in Yakacık region (NW-Ankara)

In Turkey, magnesite occurrences are formed in the form of veins and stockworks in fractured of ultramafic rocks and sedimentary rocks. In this thesis, mineralogy and petrography, XRD characteristics, geochemical investigations, C-O isotope systematics of the ophiolitic units and magnesite formations outcropping around Yakacık (Ankara). Magnesite mineralization is in the form of stockworks and veins within the serpentinites of the Kapaklı member, which consists of olistostromal layers containing serpentinite, gabbro, diabase, basalt, radiolarite, and limestones around Yakacık. Vein-type and stockworks magnesites show cryptocrystalline and microcrystalline structures and are accompanied by quartz, chlorite, dolomite, olivine residues, serpentine minerals. In order to determine the mineralogical compositions of the magnesite, serpentinite, limestone, whole-rock and clay fraction analyzes were carried out within the scope of the XRD extraction method. Geochemical analyses were performed on magnesite and ultramafic rocks and major oxide, trace elements and REE were investigated. In order to determine the origin of magnesites, δ13C(VPDB) and δ18O(VSMOW) stable isotope studies were carried out on magnesite and limestone. δ13C and δ18O values are -3.07 to 9.67‰ and 23.05 to 27.49‰ for magnesite minerals and are 0.20‰ to 3.74 and 27.05 to 28.96‰ for limestones, respectively. It has been determined that marine limestones and metamorphic CO2 have contributed to the formation of magnesite deposits. Foremost rocks that can be the main source for C and O of magnesite formations are Jurassic limestones. Most of the samples follow the decabonation line indicates that CO2 was released during the decarbonation of the limestones in the region.