Comparison of Epithermal Kaolin Deposits From the Etili Area (canakkale, Turkey): Mineralogical, Geochemical, and Isotopic Characteristics [article]

Abstract

Hydrothermal solutions related to magmatic intrusions that occurred during the Oligo-Miocene resulted in advanced multi-stage alterations and, to varying degrees, kaolinization over a wide area of the Biga Peninsula. The most important formations in these kaolin deposits occurred along the NE-SW-trending can-Etili-Bayramic fault zone. The Bahadirli, Duman, and caltikara quarries are well preserved kaolin deposits throughout these fault zones located within the can Volcanics. Mineralogical, geochemical, and isotopic analyses were performed to identify the environments of formation of kaolins and the origin of the hydrothermal solution that led to the formation of these deposits. The mineralogical assemblages of each of the quarries differ from each other. The Bahadirli kaolin quarry comprises kaolinite + alunite & PLUSMN; quartz & PLUSMN; smectite & PLUSMN; plagioclase & PLUSMN; K-feldspar. The caltikara kaolin deposits consist of kaolinite + quartz + alunite & PLUSMN; iron-oxide and ore minerals. The Duman kaolin quarry was considered in two different slopes as a hanging wall block and a footwall block, and the blocks contain kaolinite + quartz + plagioclase & PLUSMN; smectite and kaolinite & PLUSMN; alunite & PLUSMN; smectite & PLUSMN; quartz & PLUSMN; plagioclase & PLUSMN; K-Feldspar & PLUSMN; gypsum, respectively. During petrographic investigations, it was observed that kaolinization occurred generally in K-feldspar and plagioclase phenocrysts and partially in the matrix. Mineralogical and micromorphological investigations revealed that the kaolin group includes the dioctahedral minerals kaolinite and halloysite. According to the trace element contents of the kaolinites, the caltikara and Bahadirli deposits had a hypogene origin, while the Duman deposit had a supergene origin. delta O-18 isotopic values of kaolinites ranged from +10.3 to +18.3 & PTSTHOUSND;. delta S-34 isotopic values ranged from -17.2 to +20.2 & PTSTHOUSND; of alunite, galena, and pyrite minerals, which indicate different formation environments for the kaolin quarries. Ar-40/Ar-39 dating of alunite revealed that the timing of acid-sulfate alteration was compatible with the magmatic intrusions. All these data revealed the mineralogical, chemical, and isotopic differences caused by the effect of different hydrothermal processes in three kaolin deposits located on the same fault zone, close to each other and similar in age.