TURKIYE JEOLOJI BULTENI-GEOLOGICAL BULLETIN OF TURKEY, vol.60, no.2, pp.189-208, 2017 (ESCI)
The Miocene-Pliocene lacustrine units comprises bituminous shale, coal seam, conglomerate, siltstone, sandstone and claystone were deposited in a graben developed along the Eskisehir Fault Zone at the east of Eskisehir. The geological, mineralogical and geochemical analyses were performed on samples obtained from ES4 and ES7 core drilling holes at the Alpu coal basin. Abundant smectite associated with kaolinite, illite, quartz, feldspar, dolomite, siderite, accessory amphibole, gypsum, alunite and pyrite. the muscovite, chlorite, feldspar, serpantine crystals and their groundmass are partly to completely argillized in host rocks. Micromorphologically, development of smectite flakes and platy illite crystals on relicts of feldspar suggest dissolution and a precipitation mechanism under alkaline micro-environmental conditions during diagenesis. Enrichment of light rare-earth elements relative to middle rare-earth elements and heavy rare-earth elements and positive Eu anomalies reflect alteration of feldspar. Alteration of feldspar, biotite and serpentine resulted in the concentration of Al, F and Mg in a stagnant envrionment and precipitation smectite and in an alkaline environment. The low to moderate Ni/Co and high V/(V+Ni) ratios are indicative of oxic to dysoxic and anoxic to dysoxic conditions, respectively. TiO/Ni and SiO2 versus (Al2O3+K2O+Na2O) discrimination diagram show that weathered samples is indicative of formation from the locally basic igneous rocks and alteration formed predominantly via sedimentation process under arid and semiarid conditions and formation of clay minerals.