Geology, Geochemistry, Stable Isotope, and Fluid Inclusion Investigation of the Iron Oxide-Gold Mineralization in Bakir Tepe, Kangal-Sivas, East-Central Turkey

Abstract

The Bakir Tepe area is characterized by four different lithologic units of Devonian-Carboniferous age. These units, from bottom to top, are metasiltstone, metacarbonate, metasandstone, and metaquartz sandstone. Metamorphic rocks in the study area are tectonically overlain by the recrystallized Mesozoic Munzur limestone.

Iron oxide-gold mineralization in the Bakir Tepe area occurs in two different localities. The first is an alteration zone, which was formed at the thrust contact of metasiltstone with metacarbonate and metasandstone; the second locality is in metaquartz sandstone. The dominant minerals are quartz + hematite/magnetite ± pyrite ± gold in veins of various lengths and widths. Magnetite occurred after hematite, along fractures in hematite.

Oxygen isotope data (δ¹⁸O = 6.2-13.3‰) from fluids in equilibrium with quartz, and hydrogen isotope data (δD = -55 to -75‰) from fluid inclusions trapped in quartz, indicate that the hydrothermal fluids responsible for formation of the gold mineralization were dominated by metamorphicderived waters.

Hydrothermal solutions were of the NaCl-CO₂-H₂O type. Salinity values as NaCl equivalent wt% range between 34 and 39. Total homogenization temperatures range between 132 and 382°C in secondary L+V inclusions, and 237 to 324°C in primary L+V+H inclusions. Calculated temperatures of vein formation using oxygen isotopes in quartz-hematite mineral pairs yields formation temperatures between 200 and 330°C, consistent with the fluid inclusion measurements.