Petrography and Geochemistry of Kolosh Clastic Unit in Selected Location North and North-East Iraq

Kolosh Formation (Paleocene Lower Eocene) is located in the Unstable Shelf within the High Folded Zone of Zagros belt northeastern Iraq. The sandstones of two sections from Kolosh Formation, one in Dyana area northeastern and one in Koisinjac southeastern Erbil Governorate, (the latter represents the type section), were studied covering mineralogy and geochemistry. These sandstones are classified as litharenite dominated by lithic fragments which are mainly carbonate followed by metamorphic, igneous, (both plutonic and volcanic), and chert. Next to the lithic fragments, quartz appeared of both monocrystalline and polycrystalline. Feldspar is found in minor amount dominated by K-feldspar and rarely plagioclase. Pyroxenes both ortho- and clinopyroxene are in high amount. The accessory minerals are iron oxides, chromite, micas, clay, and spinel. These sandstones are texturally immature. The cementing materials are mainly carbonate with rare iron oxide cement. The Qt-F-L provenance plot of these sandstones suggests arc-derived sediments. Major elements geochemical data show that the sandstones of the type section have lower SiO2, Al2O3, Fe2O3, MgO, TiO2 and higher CaO, MnO contents than those of Dyana section. The sandstones of the type section are highly depleted in SiO2, Al2O3, Fe2O3, and TiO2 relative to UCC than the sandstones of Dyana section. Positive and negative correlations between these oxides reveal the mineral phases present. The trace element data normalized to UCC show depletions in LILE and HFSE and enrichment in transitional elements. With high concentration of Cr and Ni compared to UCC. The chondrite-normalized REE patterns is homogeneous with LREE enrichment relative to HREE, (La/Yb) N = 4.43 and 1.11 and have negative slopes, (La/Sm) N = 3.35 and 1.5 in the type section and Dyana section respectively. Both sections also show negative Eu anomalies especially the type section which reflects Eu fractionation with the major element Ca. These sandstoes are classified geochemically as wacke.