Origin of Miocene halite from Tuz Golu basin in Central Anatolia, Turkey: Evidences from the pure halite and fluid inclusion geochemistry

Abstract

The study area is located in the south of Konya Closed Basin which is the largest Miocene inner basin in Central Anatolia. The aim of this study is to determine the chemical composition of the Miocene halite deposits and depositional environments of Tuz Golu lacustrine basin. For this scope, fluid inclusion analyses (K+, Mg2+, SO42-) of nine pure halites were performed and twenty six pure halite samples have been examined. Additionally, K+, Mg2+, SO42- ion concentrations of the fluid inclusions and pure halite samples were compared to Gulf of Suez (GS), Red Sea (RS) and other Cenozoic seawaters (CS). Results from analyses show that K+ content of the fluid inclusions of the halites in the Tuz Golu basin, which are considerably higher than the K+ contents both of the pure halites and the GS and RS and CS, result from dissolution of the primary K+-salts. The Br-content of the pure halite samples is ranging from 5 to 637 ppm. The high Br-(> 40 ppm) content indicates the marine origin while the low Br-content is related to dissolution and recycled of the previously deposited marine halites. Mg2+ and SO42- contents of the Tuz Golu basin samples are higher than those of the GS and RS and CS except for TG4 samples. The high Mg2+ and SO42- contents were resulted from the dissolution of previously deposited gypsum and de-dolomitization process. delta S-34 isotope (18.80 to 21.00 parts per thousand) and low delta O-18 (8.10 to 9.50 parts per thousand) values of the Tuz Golu basin samples, which are compatible with isotope values of the CS, indicate marine origin. In addition, the high delta O-18 values (16.20 to 20.50 parts per thousand) and the delta S-34 content can be explained by recycling of marine sulphate as well as dissolution and re-crystalization of previously deposited sulphates. The possible effective mechanisms causing chemical differences in the Tuz Golu basin, which is a sedimentary basin formed under highly complex different physico-chemical mechanisms, have been detected as (1) the changes in chemistry of halites due to dissolution and re-crystallization processes of previously deposited halites and evaporites, (2) de-dolomitization processes and (3) seawater input.