Mineralogical and geochemical comparison between the shales of Beduh and Baluti formations in the northern thrust zone, Kurdistan region, Iraq : implication for provenance and tectonic setting

Abstract EN

The mineralogical and geochemical data are employed to determine the provenance, paleoweathering, and depositional setting of the shales from the Beduh (L.

Triassic) and Baluti (U.

Triassic) formations at Sararu area N of Iraq.

The mineralogical data (e.g., high illite content and moderate illite crystallinity index in Beduh shale and kaolinite in Baluti shale) and geochemical parameters of the shales (major, trace, and REE-based discrimination diagrams, Al2O3/TiO2, and LREE/HREE ratios) indicate that both shales were evolved from acidic source rocks.

This is reclined by the enrichment of LREEs, depletion of HREEs, and negative Eu anomaly.

The paleoweathering parameters (chemical index of alteration and chemical index of weathering), in addition to the A-CN-K (Al2O3-CaO + Na2O-K2O) diagram of the Beduh shale induce that the source terrain was moderately to intensively and for Baluti shale was intensively chemically weathered.

The Beduh shale was plot perpendicular to the A-K line indicates the K-metasomatism, and for Baluti shale was fall parallel to the A-K line suggesting intense weathering with no evidence for K-metasomatism.

The discriminant diagrams based on major elements in addition to critical trace and REE parameters suggest that the origin of the sediments was probably from passive (Arabian Shield and the Rutba Uplift) tectonic environments for both with the effect of the active (volcanic activity) tectonism on the Beduh shale.

The geochemical parameters such as U / Th, V / Cr, and Ni / Co ratios and negative Eu anomalies indicate the study shales were deposited in an oxic environment.