Bigadiç (Balıkesir) Borat Havzası Ayana Sahasındaki Birimlerin Mineralojik ve Jeokimyasal İncelenmesi

Abstract

It is aimed to determine the mineralogical, petrographic and geochemical properties of the units in the Ayana Plain of the Bigadiç Borate Basin, to determine the lateral and vertical distribution of neoformation minerals (borate, clay, carbonate, zeolite and sulfate) and to interpret the paleogeographic development of the basin. A total of 363 core samples were taken from 4 different drillings (20BM - 613, 20BM - 619, 20BM - 632 and 20BM - 644) in Ayana Plain from Değirmenli Tuff Member, Uzun Tepe Member, Emirler Member and İskele Member of Bigadiç Formation. On these samples, mineralogical-petrographic examinations were conducted, including XRD (whole rock and clay fraction), optical microscopy, and SEM-EDS; geochemical analyses were performed, including major and trace element analyses as well as boron isotope analysis. XRD - whole rock analysis of all samples was performed and as a result, illite / mica, amphibole, clay, quartz, opal - CT, feldspar, calcite, dolomite, aragonite, analcime, clinoptilolite / heulandite, pyrite, gypsum and anhydrite minerals and borate minerals (colemanite, ulexite, probertite and howlite) were identified. XRD - clay fraction analysis was performed on 128 selected samples and the analysis revealed the presence of smectite, illite, kaolinite, chlorite and serpentine minerals. Within the scope of SEM - EDS analysis, apatite, chromite, zircon, allanite, galenite and torite minerals were determined in addition to the minerals determined from XRD - Whole rock analysis. 30 samples were analyzed for major and trace elements. According to the results of whole rock analyses, the highest Li values were found to be 60 ppm in Emirler Tuff Member, 90 ppm in Değirmenli Tuff Member, 1210 ppm in İskele Member and 1900 ppm in Uzun Tepe Member. It has been determined that the clay fraction samples containing only smectite are hectorite minerals according to the structural formulas calculated from the geochemical analysis results. It has been determined that samples with high smectite content also have high Li values. The highest value in terms of Li content was determined as 2720 ppm in the clay fraction containing only smectite in the sample taken from the borated zone of Uzun Tepe Member. According to these results, Li enrichment is associated with Mg-rich smectite minerals. Therefore, it was revealed that borate deposits are important in terms of lithium potential. Boron isotope analyses were performed on the minerals ulexite (δ¹¹B: - 4.3‰ and - 4.9‰), probertite (δ¹¹B: - 4.0‰), colemanite (δ¹¹B: - 9.1‰) and howlite (δ¹¹B: - 15.1‰ and δ¹¹B: - 14.7‰). According to boron isotope data, the origin of the borates was determined as non-marine evaporite. The observation of analcime mineral in the Uzun Tepe Member in drillings 20BM-619 and 20BM-644 indicates that salinity, alkalinity and pH were high during the deposition of the Uzun Tepe Member in this part of the Ayana Plain.