Distribution pattern of heavy minerals assemblages in recent sediments of Lesser Zab River Basin (LZRB), NE Iraq

摘要

The Lesser Zab River (LZR), the largest tributary in Iraq, with a catchment area of about 20,000 km(2), and majority of its basin lying in Iraq, drains into the Tigris River. It runs through highly folded and faulted igneous and metamorphic zone in the northeastern part of Iraq. We studied the heavy minerals in recent sediments of the Lesser Zab River Basin (LZRB) to determine their mineralogies, assemblages pattern, distribution manner, spatial variability, microtexture, provenance, and tectonic setting. We analyzed 24 sediment samples for heavy mineral assemblage determination, using the standard petrographic method. Scanning Electron Microscopy was used to determine the morphology of the grains of selected heavy minerals. Heavy minerals identified in the studied sediments include: dark color such as magnetite, ilmenite, hematite, and goethite; and transparent minerals represented by hornblende, tremolite-actinolite; pyroxenes, epidotes, zircon, tourmaline, rutile, garnet, staurolite, kyanite, and layered minerals assemblage such as muscovite, chlorite, biotite, and phlogopite. The studied sediments are considered immature, because they have the lowest concentration of ultrastable minerals compared to unstable heavy minerals, which confirms that the surface sediments of LZR and its sub-basin tributaries were deposited in an active continental-margin tectonic setting.