Geochemistry of Kestelek Colemanite Deposit, Bursa, Turkey

The Kestelek borate deposit has been the subject of geological and mineralogical research over the last decades, but major and trace element geochemistry of this deposit was first investigated in the present study. A total of 22 samples collected from surface exposures and different depths of deposit in boreholes (e.g., lower, middle and upper) comprise the material of this study. Major, trace and REE element analyses of samples were conducted with ICP-MS and ICP-ES methods. The Kestelek borate deposit of Miocene age was formed in playa lakes in an intermountain closed basin which was developed in volcanically and seismically active areas associated with growth faults and grabens affected the whole Anatolia at the beginning of Paleogene. Only colemanite was found as the borate mineral accompanied in lesser amount by calcite, aragonite, smectite, illite, chlorite, corrensite, heulandite and quartz. In colemanite samples, all major elements, except for Ca, show depletion trends with respect to average of earth crust and andesite. For the trace elements, Li, Cs, Sb, As, Sr and Se are characterized by significantly high concentrations. Evaluation of element concentrations and geochemical characteristics reveal that As, Cs, Sb and Li are of detrital origin, Se together with B and Ca are of non-detrital and Sr is indicative of both detrital and non-detrital origin. REE distributions indicate that at least two different depositional regimes prevail in the environment. Corrensite, a clay mineral forming in lake waters, is derived from volcanism. Negative Ce and positive Eu anomalies are indicative of contribution from hydrothermal solutions and fluids.