Occurrence and genesis of hectorite and mixed-layer-illite/hectorite in argillaceous sediments interlayered with Neogene borate deposits, Emet, Türkiye

KADİR S., ERKOYUN H., Külah T., Eren M., HELVACI C., DEMİRAL B.

Applied Clay Science, cilt.267, 2025 (SCI-Expanded) identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 267
  • Basım Tarihi: 2025
  • Doi Numarası: 10.1016/j.clay.2025.107737
  • Dergi Adı: Applied Clay Science
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, PASCAL, Aerospace Database, CAB Abstracts, Chemical Abstracts Core, Communication Abstracts, Compendex, Index Islamicus, INSPEC, Metadex, Pollution Abstracts, Veterinary Science Database, Civil Engineering Abstracts
  • Anahtar Kelimeler: Alteration, Clay minerals, Colemanite, Diagenesis, Pyroclastic rocks
  • Dokuz Eylül Üniversitesi Adresli: Evet

Özet

The Li-rich claystone was formed within the Miocene volcano-sedimentary units in Emet borate deposits, in western Anatolia. This research identified hectorite and mixed-layer-illite/hectorite-abundant claystone that have technological and economic potential and have not been studied to date. The claystone was formed through the diagenetic alteration of rhyolitic and zeolitic tuffaceous units in a shallow lacustrine playa lake environment under arid climatic conditions. The parent rocks comprise altered and sericitized plagioclase and sanidine, opacited and chloritized biotite/muscovite, zeolite, quartz, and rock fragments cemented by argillizied, sericitized, and carbonatized matrix. Abundant hectoritic smectite and mixed-layer-illite/hectorite accompanied by accessory feldspar, quartz, locally calcite/dolomite, gypsum, and orpiment/realgar. The Li concentration reaches a max of 2200 ppm in the hectorite-abundant claystone and 218 ppm in the tuffaceous units. Smectite flakes are associated with illite fiber, feldspar, and amphibole. The degradation of sanidine, plagioclase, biotite/muscovite, and hornblende contributed to the positive correlation of SiO2 vs. Al2O3, K2O, TiO2, and total rare-earth elements (ΣREE) vs. SiO2, Al2O3, and K2O; MgO vs. Li values, and enhancement of MgO + CaO, Li, Sr + Rb, and ΣREE values, and LREE/HREE ratio; negative Eu anomaly and high concentration of S and As. These physicochemical compositions favored the formation of hectorite and mixed-layer-illite/hectorite. The δD and δ18O values of hectorite and mixed-layer-illite/hectorite samples and the formation temperatures range from 98 to 119 °C reveal a burial diagenetic alteration process. The δ18O and δ13C values of the calcite samples suggest the mixing of thermal and fresh waters. The high 87Sr/86Sr ratios of calcite and gypsum reveal the consumption of Sr during the alteration processes. Additionally, the negative δ34S values of realgar and orpiment suggest formation under acidic-neutral conditions via sulfate reduction or microbial cycling.