Formation and genesis of Paleozoic sediment-hosted barite deposits in Turkey

Abstract

Most barite deposits in Turkey are sediment-hosted deposits which are located in different lithologies within passive margin sediments from the Paleozoic. The Şarkikaraağaç, Hüyük and Tordere deposits occur in the western part of the Tauride-Anatolide tectonic unit, whereas the Şekeroba and Önsen region deposits located in the eastern part of Turkey occur on both Arabian and Tauride-Anatolide microplates. While the former deposits occur as both concordant and discordant bodies within Early Paleozoic carbonates, the latter deposits are found as discordant, fracture filling and replacement-type ore bodies.O, D, S, Sr and Pb isotope studies were used to determine and correlate the formation conditions of these deposits. δ18OSMOW mean values of the Tordere barite deposit are slightly higher (mean 16.2‰) than the mean values for the Şekeroba (10.8‰) and Önsen (11.3‰) deposits. The δ18OSMOW (mean 15.83‰) and δDSMOW (mean −67‰) values obtained from fluid inclusions in quartz veins in the Şekeroba barite deposit correspond to metamorphic or deep circulation hydrothermal waters. Mean δ34 SCDT values from Şekeroba, Tordere and Önsen deposits are 31.7, 33.8 and 20.6‰, respectively, which are compatible with the early Paleozoic seawater, except for the Önsen deposit.87Sr/86Sr mean values for the barite deposits of Turkey are defined as follows (‰); Şekeroba: 0.713, Önsen: 0.711, and Tordere: 0.711, which are higher 87Sr/86Sr isotope ratios than Paleozoic seawater. The Pb isotope values in Şekeroba and Tordere deposits are similar and mean is 206Pb/204Pb = 18.28, 207Pb/204Pb = 15.67 and 208Pb/204Pb = 38.50. High radiogenic Sr and Pb isotope data from the deposits indicate that Ba was generated from thick Paleozoic clastics or the older crust beneath them.Sr, S, and O isotopes and the positive Gd anomaly in the barites are very similar to those of Paleozoic stratiform cold-seep barites. The primary stratiform-stratabound barite deposits, like Şarkikaraağaç-Hüyük deposit, could have formed either by cold seep or diagenetic processes at the sediment–seawater interface or within the sediment related to sulfate-methane boundary. Although there are similar Sr and Pb isotopic signatures between the western and eastern region deposits, the eastern region Şekeroba, Önsen and Tordere barite deposits show discordant ore geometry and highly radiogenic isotope values indicating that primary stratabound-stratiform barite was dissolved and remobilized along deep-seated fault zones during the Hercynian orogenesis and deposited in different Paleozoic lithologies related to cooling and/or increase in Eh.