Mineralogy and petrology of the gabbroic pegmatites from Karaurgan Sarıkamış-Kars)

Gabbro pegmatites located in Karaurgan (Sarıkamış/Kars) region are igneous rocks with a crystal grain size of 5-30 cm and crop out in dunitic serpentinite along the banded gabbro borders. Pegmatites outcrop in the form of small stockpiles of 1-3 to 5-10 m. Mineralogically, they differ from the banded gabbros outcropping in the environment, but they offer similar features to isotropic gabbros. However, unlike isotropic gabbro, they occasionally contain natrolite intensely. The gabbroic pegmatites, which were petrochemically compared with two other gabbroic rocks in the field, have low SiO2 and high MgO values (high Mg#). Their low Co contents indicate that they are mantle derived. All geochemical features indicate that these rocks are tholeiitic and are derived from a potassium-poor depleted mantle source. All chemical data indicate that these gabbro pegmatites can be formed again by partial melting from a depleted mantle source. These rocks often show high Nb/La (>1.5) values and are more compatible with OIB-like asthenospheric mantle melts rather than lithospheric mantle-derived melts. Eu/Eu* values range from 1.66 to 2.58, indicating that fractional crystallization was not effectively work on those pegmatites. Relatively high Sr and low Heavy Rare Earth Element (ANTE) contents indicate that resemble rocks that are derived in a typical island arc environment. The light rare earth element (LREE) contents of the rocks were partially enriched compared to heavy rare earth (HREE) and were consumed by high field strength siderophile elements (HFSE, i.e., Nb). All these geochemical features and tectonic discrimination diagrams support this finding. Keywords: Gabbro Pegmatite, REE, LA, tholeiitic, depleted mantle source, SSZ