ABSTRACT
The sediments adjacent to the collisional mountain belts provide important information about the tectonics and basin evolutions. The Red Bed Series (RBS) exists in a narrow intermontane basin, deposited along the present-day northwestern Arabia-Eurasia suture zone in the Kurdistan region of Iraq. The non-marine clastic Suwais Group, the marine carbonate Govanda Formation, and the non-marine Merga Group make up the RBS. The allochthonous rock units of the Walash-Naopurdan and ophiolitic terranes thrusted over the RBS units. The Govanda Formation deposited in a shallow marine backreef-fore reef marine environments and it was influenced by the sediment supply from nearby paleo highs. The lower contact of the Govanda Formation is unconformable with the underlying Suwais Group and the upper contact is gradational and conformable, that gradually transitioning into the red shales and sandstones of the overlying Merga Group.
This research investigated the geochemistry and petrography of three sections of carbonate (limestone) rocks overlain by siliciclastic rocks (mudstones and sandstones) cropped out in the Mergasur and Soran districts. The carbonate unit’s thickness decreased from NW to SE along the Arabia-Eurasia suture zone in the NW Zagros fault-thrust belt. Five main classified microfacies were recognized in the carbonate rocks of the Govanda Formation, which referred to the diverse depositional settings, ranging from low-energy, restricted areas to high-energy, shallow environments representative of the narrow intermontane basin during the early-middle Miocene.
Depending on the contents of Al2O3% and SiO2% and the purity of limestones, the carbonate samples were subdivided into massive limestone (MSL) and marly limestone (ML), composed predominantly of calcite (CaCO3) mineral. The limestone beds have a consistent seawater-like REE pattern, slightly negative Ce anomalies (Ce/Ce* = 0.83), relatively positive Eu anomalies (Eu/Eu* = 1.17), and moderately high Y/Ho ratios (37.70 n = 29). The REE + Y pattern of samples mainly retains its original characters influenced by detrital material inputs. Authigenic U, negative Ce anomalies, and trace element ratio indices such as V/Cr, U/Th, Ni/Co, and V/(V + Ni) indicate oxic–suboxic deposition conditions.
The geochemical parameters (CIA, CIW, and PIA) and A-CN-K diagram reveal the compositionally immature nature of the Merga Group sandstones and claystones, indicating that they have undergone weak to moderate weathering processes. Petrographically, the Qm-Ft-L+Qp and Qt-F-L triplots reveal the dissected arc source for the studied Merga Group sandstones, suggesting a derivation from nearby uplifted and eroded volcanic arcs. Oxidizing conditions of the depositional environment are recognized by the total average of U/Th (0.31), V/Cr (0.84) ratios, and the authigenic U (-0.21) values for the siliciclastic rocks of the Merga Group, which were deposited in the intermontane basin in the non-marine alluvial environments.
After assessing the mentioned rock succession for industrial uses, especially at the Sherwan Mazin section, producing cement with good quality is more possible. On the other hand, after using the raw material mixture with LSF 90.9 with little iron as additive material, as well as at LSF 94, the cement quality enhances the stable clinker properties with a low cost.