Biomarker geochemsistry, major-trace elements characteristcs and organic facies variation of Yaylakoy, Kalemkoy and Eynez (Soma) neogene coals

Organic geochemical features of Yaylakoy-Kalemkoy-Eynez coals located in the south of the Soma Neogen basin were investigated within this study. Furthermore, inorganic geochemical and petrographic features of coals were investigated to determine origin relations, mode of occurrence and enrichments of major-trace elements. Within this scope, lower coal seam (KM2) was evaluated using well samples of the study area which were chosen to represent the basin. High TOC amount (average 56.62%), type III kerogen and immature level (Tmax; average 420 0C) were determined according to the organic geochemical features of KM2 lignite-subbituminous coal and immature level was also supported by Ro and SCI values. Although coals represented potential source rock characteristics, they were immature for gas/oil production. Facies C-CD was determined according to the organic facies evaluation. Coalification and paleoenvironmental characteristics of investigated units were evaluated using biomarker geochemistry data. n-alkane and isoprenoid values, sterane and terpane data indicated that terrestrial higher plants and algal/bacterial source organisms were deposited and peatified in paleoswamp and presented suboxic-oxic conditions. Coals generally showed immature-early mature characteristics. UCM observed in gas chromatograms indicated immature organic matter and biodegradation. Moreover, coals in the study area were immature according to the Tmax, CPI and OEP indexes and Ro values. Clay minerals, calcite, dolomite, aragonite, feldspar minerals, quarts, cristobalite, ankerite, pyrite, mica minerals, siderite and amorphous were found in evaluated samples, respectively to their semiquantitative abundance. Clay minerals identified in the basin were illite, halloysite, kaolinite, smectite and palygorskite mixed layer clays. Mg, Ca and P elements were enriched according to the major-trace element evaluations. These enrichments were supported by XRD data. V, Ni, Cu, As, Sr, Y, Nb, Mo, Cs, Ba, ΣREE, Ta, Au, Hg, Th and U elements were enriched according to the trace element enrichment in coal/coal units. Especially, As (78.06 ppm), Hg (10.73 ppm) and U (33.61 ppm) showed higher enrichments. It was determined that originally enrichment in the basin mostly was derived from volcanic and volcanic/sedimentary rock community while organic based enrichment was determined to be less.