Enrichment of Ni-Zn-Cd-Mo-V in the Şırnak asphaltites, Türkiye: The effects of organic matter, sedimentary processes, and hydrothermal fluids on element concentrations and occurrences

Abstract

There are numerous asphaltite veins in southeastern Anatolia, Turkey. The Avgamasya, Anılmış, Harbul, Silip, and Üçkardeşler veins, which are the focus of this study, are enriched in elements such as As, Cd, Mo, Ni, Sb (except in Harbul), U, V, Zn, and Hg. Commonly detected minerals across all samples include dolomite, calcite, apatite, pyrite, sphalerite, alkali feldspar, quartz, illite, and iron oxides. Additionally, smectite, barite, celestine, ilmenite, galena, hematite, rutile, and strontianite were also observed. The mineral matter present can be both syngenetic and epigenetic. The microcrystalline minerals present within solid bitumen may have precipitated from supersaturated fluids during the maturation of hydrocarbons. In contrast, epigenetic minerals may have originated from hydrothermal fluids after the solid bitumen was formed or may have been incorporated from the surrounding host rocks during the hydrocarbon migration process. Organisms in the shelf environment likely played a crucial role in the enrichment of these elements. Sedimentary and diagenetic processes, sediment pore waters, and hydrothermal fluids may have significantly contributed to the formation of minerals that host these enriched elements. Solid bitumen, iron oxides, pyrite, and sphalerite can serve as major carriers of these enriched elements. Meanwhile, lithophile elements such as Sr, Ba, and Na are typically found in minerals like barite, strontianite, celestine, calcite, apatite, and fossil shells.