Coral reef area in northwest of the Arabian Gulf was investigated for mineralogy and geochemistry to throw lights on such unique Iraqi Marine Environment; six specimens of two main species of coral reefs, Platygyra pini Chevalier, 1975 and Octocoral Menella were collected at two sites. While eight samples of the surrounding sediments are chosen from other two sites. The mineralogy is determined by XRD, and reveals that calcite, low magnesium-calcite, and aragonite are the main minerals that comprise the Octocoral Menella in site 1, whilst aragonite and calcite are dominate in the P. pini coral reef at site 4.
The non–carbonate fractions indicate that these coral reefs contain quartz, anorthite feldspare , halite, and gypsum; the highest content of aragonite was observed in the P. pini compared to calcite. The abundance of carbonate minerals (92.1%) in the P. pini is in contrast to (73.1%) in the Menella. The main minerals in the sediments of site 2 are represented by chlorite and talc, whereas quartz and phengite are the most prominent minerals that diagnose in sediments of site 3; phengite mineral is a first discovery in the sediments of Arabian Gulf, whilst talc is a first detection in Iraqi marine sediments.
The concentration of CaO is the most abundant oxide in all the analyzed specimens of the coral reef followed by SiO2. There are high proportions of calcium oxide in P. pini Chevalier coral (56.65 %) than the Menella (48.81%). There are some special pattern of distribution for major and trace elements in coral reef area based on calcium content. Most of the silica came from quartz, phengite and clay minerals; the highest concentrations of Al2O3, Fe2O3, K2O, Na2O, MgO, SiO2, TiO2, V2O5, Cr, Ni, Cu, Rb and Zr are found in the sediments of site 2 as opposed to the other sites. These results could affect the association of these elements with clay minerals through adsorption or absorption, the highest content of P2O5, Ga, W and As in the sediments of site 3 may reflect the adsorption of these elements on surface of the quartz and phengite; from the other hand, the highest concentrations of Sr, Zn, Br, Sn, Ta, and Pb in the P. pini may indicate the relative effects of the environmental variation within the studied area.
