ORE PETROLOGY &DISTRIBUTION OF MINERALIZATION AREAS, IN PENJWEEN OPHILITE COMPLEX, KURDISTAN PROVINCE NE-IRAQ

Abstract

The northeastern corner of Iraq has an ophiolitic belt, the Zagros thrust zone, and many mineralization zones have been traced at Penjween Ophiolite Complex. The main type of these zones is chromium mineralization. There are also slightly iron, copper and nickel mineralization observed associated with ultramafic rocks of penjween ophiolite complex. These mineralizations were found mainly around Kanimangah, Kirikapla and Boban villages. Although these mineralization are typically enveloped by dunite, but the chromitite bodies are also hosted in harzburgite. These bodies are mainly lensoidal but some occur as veins, stringers and linear or planer segregation. Ore microscopy, Backscattered images supported by Energy Disperse Spectroscopy showed that chromian spinel forms euhedral – subhedral grains, and commonly inhomogeneous, displaying a zoning pattern of Cr-rich core to Cr-poor rim; as well as is nearly opaque to dark reddish brown in thin sections. The petrographical observations also suggest that the chromite grains contain solid inclusions of silicate minerals. In the project area, the chromite crystals often associate with thin rims of magnetite. This rim is probably developed during multiple episodes of metamorphism and serpeninization. Three types of chrmoitite have been observed from penjween ophiolite which is: massive chromite ore where chromite content is more than 80 modal %, schlieren type chromite (18 modal % chromite content) and accessory chromites (approximate 2 modal % in harzburgite and dunite). The massive type consists of mineral assemblage chromian spinel + olivine + amphibole + serpentine + chlorite. The olivine is of Mg-rich type (Fo95-97). The dominated amphibole is anthopyllite. Spinel is of Cr-spinel type. The discrimination diagrams of Mg vs. Cr, TiO2-Cr and TiO2vs. Al2O3 indicate that these rocks are of alpine type formed in of supra-subduction zone tectonic settings