EVALUATION OF GEOCHEMICAL PROPERTIES OF AGATES IN ALMUS (TOKAT) REGION

Abstract

The Upper Cretaceous Artova ophiolite complex, represented by metabasic and ultrabasic rocks, overlies the Paleozoic aged Tokat metamorphites, which form the basis of the study area, by the tectonic boundary. Haydaroğlu formation, which includes Middle Eocene aged volcanogenic units, cuts and covers the older units. Agates (agates) in the Almus region are found in the form of nodules in the volcanogenic sandstones of the Haydaroğlu formation along an approximately E-W trending fault. The Lower Miocene aged Almus formation, which consists of sedimentary rocks such as sandstone, conglomerate and marine limestone, also unconformably overlies all units. Almus region agates contain on average 93.4% SiO2, 3.59% Fe2O3, 0.03% MgO, 0.72% CaO, 793 ppm Cr2O3, 12 ppm Ni, 13.4 ppm Cu, 4.7 ppm Pb, 35.4 ppm Zn. The high Cr and Ni in agates are associated with the Artova ophiolite complex in the region. Cu, Pb and Zn are associated with the early stages of volcanism. The high Fe2O3 content in agates is associated with hematite and goethite, and they were transported into agates before SiO2 emplacement. The CaO in the agate is the product of the last phase of the solution forming the agate, and MgO is associated with the presence of dolomite. Evaluation of the results of geochemical analysis shows that SiO2, which is the main component due to the hydrothermal activities that occurred after the rock formation of the Haydaroğlu formation, unlike the volcanic bedrocks of the agates according to the main oxides, trace and rare earth elements, was emplaced epigenetically as a result of the circulations in the volcanogenic sandstones.