Mineralogy, geochemistry, and the origin of lower clastic unit in Hussainiyat formation (early Jurassic)‎ western desert of Iraq

Abstract EN

A mineralogical and geochemical study has been done on (20) Hussainiyat Formation (Early Jurassic) samples in western Iraq.

Mineralogical analysis of clays by X-ray diffraction (XRD) shows that the predominant clay mineral is kaolinite and traces of montmorillonite-illite mixed layer with palygorskite.

The non-clay minerals are mostly quartz, goethite, hematite, and anatase.

Heavy minerals were separated from (sandstone) clastic samples and studied by both polarized and reflected microscopes.

These heavy minerals are detected in fewer than 1% quantities and consist of silicates and oxides.

The most common of these mineral grains are stable heavy minerals ZTR (zircon, tourmaline, rutile) and apatite, staurolite, and garnet, which indicate that the acidic granite rocks with almost metamorphic rocks were a source of kaolinite.

In a geochemical study by XRF, claystone samples were analyzed for SiO2, Al2O3, TiO2, Fe2O3, MgO, CaO, Na2O, K2O, MnO, P2O5, and L.

O.

I.

kaolinite (claystone) of the Hussainiyat Formation contains a high concentration of iron, which is interbedded with kaolinite as hematite, goethite, and limonite.

Kaolinite occurs as kaolinitic pellets and as nuclei of the majority of ironstone ooids and pisoids, together with the alternating concentric laminae of their cortices.

Manganese is associated with the kaolinite of the Hussainiyat due to its high iron content.

The present study showed that the kaolinite deposits within the Hussainiyat Formation are less mature than other clays (montmorillonite-illite mixed layer and palygorskite), because the Hussainiyat Formation suffered from less intense chemical weathering, leading to the dissolution of only alkalis and earth alkali metals but not iron.

However, the alumina is still stable with li, due to their high resistance, the alumina is still stable with little silica to form kaoliniteintensive chemical weathering, and kaolinite builds by Si and Al.

This is because these two oxides are, typically, stable within different physical and chemical weathering.

After kaolinite, the rest only gibbsite and boehmite bauxite mineral at the end of the intensive chemical weathering.