Akademik Veri Yönetim Sistemi
Carbonates and Evaporites, cilt.16, sa.1, ss.93-101, 2001 (SCI-Expanded, Scopus)
Celestite-bearing evaporite mineralization is common in the Tertiary evaporitic units of Ulas-Sivas basin, East-Central Turkey. The first occurrence of gypsum which is "laminated in character" (Balatino gypsum) took place in the shallow inner-lagoon or depressions during regression in the upper Eocene. Thick gypsum and overlying beds composed of the bedded, nodular gypsum and sandstone alternations were formed in a coastal sabkha and abandoned channels within the meandered rivers through the Oligocene time. The last occurrence of evaporitic units, represented by massive and bedded gypsum alternating with sandstones and fossiliferous limestones resulted from limited marine transgression in the early Miocene along the southern margin of the Sivas Tertiary basin. The celestite mineralization preferentially took place within the Miocene evaporites and subordinate amount in the shallow marine limestones and terrestrial siliciclastics ranging from late Eocene to Oligocene in age. Celestite shows different depositional characters such as stratabound, massive, fracture and cave filling. According to microscopic studies, three petrographic types have been determined in these different beds of celestite. They are prismatic and bar-like; sub-idiotopic and tabular; fibrous-radial. The source of the celestite in the Sivas Tertiary basin has been debated. There is little evidence for suggesting sedimentary-syngenetic origin. Many geologists believe that it formed during late diagenesis or epigenetic stages, but this interpretation reflects a lack of a comprehensive study and only depends on field observations. This paper includes both field and laboratory studies (light, ore and electron microscopes, microprobe, 87/86Sr isotopes) and obtained initial results which have inclined to the diagenetic-epigenetic origin.