Mineralogical and Geochemical Characteristics and Genesis of the Gülzelyurt Alunite-Bearing Kaolinite Deposit Within the Late Miocene Gödeles Ignimbrite, Central Anatolia, Turkey

Abstract

The Güzelyurt kaolinite deposit is an important source of raw material for the ceramics industry in Turkey. No detailed mineralogical or geochemical characterizations of this deposit have been undertaken previously and these were the goals of the present study. The Güzelyurt alunite-bearing kaolinite occurs along a fault zone in the Late Miocene Gödeles ignimbrite, which consists of dacitic and andesitic tuffs. Horizontal and vertical mineralogical zonations with gradual transitions were observed within the alteration zone. The inner kaolinite, alunite, and 7 Å halloysite zones progress horizontally outward to a smectite zone; and native sulfur- and cinnabar-bearing alunite with 7 Å halloysite and porous silica zones increase as one progresses up through the profile. Fe-(oxyhydr)oxide phases associated with native sulfur and cinnabar demonstrate that multiple hydrothermal-alteration processes resulted in kaolinization and alunitization of the deposit. The kaolinization of feldspar, Fe-(oxyhydr)oxidation of hornblende and mica, the presence of kaolinite as stacked and, locally, book-like forms, and of 7 Å halloysite tubes, and smectite flakes as a blanket on altered volcanic relicts indicate an authigenic origin for this deposit. The leaching of Si + Mg + K and Ba + Rb, the retention of Sr, the enrichment of light rare earth elements relative to the heavy rare earth elements, and the negative Eu anomalies suggest that fractionation of plagioclase and hornblende occurred within the volcanics. The oxygen- and hydrogen-isotopic values of the kaolinite, 7 Å halloysite, smectite, and smectite + kaolinite fractions reflect a steam-heated environment at temperatures in excess of 100°C. An increase in the δD and δ18O values of 7 Å halloysite relative to kaolinite suggests its formation under steam-heated magmatic water, the mixing of steam and meteoric water near the surface, and evaporation. The oxygen- and sulfur-isotopic compositions of alunite suggest the direct influence of steam-derived sulfur. The Güzelyurt alunite-bearing kaolinite deposit is inferred to have formed after an increase in the (Al±Fe)/Si ratio and the leaching of alkali elements, which are driven by the sulfur-bearing low-temperature hydrothermal alteration of feldspar, hornblende, and volcanic glass under acidic conditions within the Neogene dacitic and andesitic tuffs.

Optimum Calcination Condition of Waste Stabilized Adobe for Alkali Activated High Volume Adobe-Slag Binder Cured at Room Temperature

“…To get the greatest amorphous phase [14], the temperature selected for calcination must be lower than the temperature of formation of the crystalline phase, and higher than the temperature corresponding to the end of the last endothermic peak. The selected calcined temperature in this study was comparable to the suggestion of [34], which suggests a temperature range of 650°C-800°C for a calcination process. The DTA curves for the waste-stabilized Adobe calcined at 750°C for different durations 1, 3, 5, and 7 h are presented in Figs.…”

Preparation and structure’s analyses of lanthanide (Ln) -exchanged bentonites

“…A source of lanthanide cations is the relatively abundant lanthanide ores in a concentration between about 150 to 220 ppm [10] in the Earth's crust [11,12,13,14,15].…”

Genesis of smectite in siliciclastics and pyroclastics of the Eocene İslambeyli Formation in the Lalapaşa region, NW Thrace, Turkey

“…5d-f ). This smectite is considered to have developed via a dissolution-precipitation mechanism (Chamley, 1989;Vitali et al, 1999;Kadir et al, 2014). Smectite also developed as a blanket on relicts of glass shards that rarely exhibit cast morphology in tuff and tuffaceous samples with dimensions of 3-10 µm (Fig.…”