GEOCHEMICAL APPLICATION IN UNRAVELING PALEOWEATHERING, PROVENANCE AND ENVIRONMENTAL SETTING OF THE SHALE FROM CHIA GARA FORMATION, KURDISTAN REGION, IRAQ
The geochemical characteristics of the shale of the Chia Gara Formation (Middle Tithonian-Berriasian) from the Imbricated Zone (Barsarin section) and High Folded Zone (Banik section) Kurdistan Region, Iraq, was carried out to constrain their paleoweathering, provenance, and depositional environment. There are no clear differences in the major and trace elements of the Chia Gara Formation between the two studied sections. The chemical index of alteration (CIA) is significantly higher in the Barsarin than the Banik shales, suggesting more intense weathering of the Barsarin than the Banik shales. The samples of the Banik and some of Barsarin are clustered near the A-K line in A-CN-K plot suggests intense chemical weathering (high CIA) without any clear-cut evidence of K-metasomatism. The other samples of Barsarin have a weathering trend parallel to the A-CN line, indicating relatively steady state weathering conditions. The geochemical parameters of the shale (Al2O3/TiO2, Th/Sc, La/Th, La/Sc, La/Co, Th/Co, Cr/Th, (La/Lu)cn and Eu/Eu*cn), and the diagrams (Th/Sc-Zr/Sc and La/Th-Hf) indicate that they were derived from felsic (from the Rutba Uplift and/or Mosul High) and intermediate (from volcanic material during the spreading of Southern Neo-Tethys Ocean) components. The chondrite-normalized REE patterns are similar to those of Post Archean Australian Shale (PAAS), with the light rare earth element (REE) enrichment, a negative Eu anomaly, and almost flat heavy REE pattern. The geochemical parameters such as authigenic uranium, U/Th, V/Cr, Ni/Co, and V/Sc ratios, and Al2O3-V and Al2O3-P2O5 diagrams indicate that these shales were deposited under deep marine suboxic to anoxic environment and shale of Banik section was deposited slightly under deeper environment than shale of Barsarin section.