Petrography and Mineralogy of Amphibolite Rocks in Penjween Complex, Northeastern Iraq

Penjween igneous complex is situated in the northeastern part of the Iraqi Zagros Thrust Zone (IZTZ) which is considered as integral part of the Alpine-Himalayan Orogenic Belt of Cretaceous age. The amphibolite rocks exist in Penjween as pods of lensoid-shape of variable sizes (2-3m). These amphibolite pods are surrounded by sheared tectonized serpentinite and peridotite and one is in contact with amphibole-bearing gabbro dike. In addition, there is an albitite dyke in contact with the amphibolite. These amphibolites exhibit deformation and alteration which is evident by the existence of chlorite veins cutting through or as patches within these rocks. Petrographic observations reveal that the main mineral constituents are amphibole; both primary and secondary, plagioclase with accessory clinopyroxene, quartz, titanite, apatite, zircon and iron oxides. Secondary minerals include chlorite, epidote, secondary amphibole and iron oxides as a consequence of alteration. Dominated textures are porphyroblastic, poikiloblastic, nematoblastic , blasto-ophitic and blasto-subophitic which are inherited from the original rocks. Accordingly, two mineral assemblages are identified: 1- Hb. + plag. + cpx.± qtz. ± titanite ± zircon ± apatite ± iron oxides, 2- Hb. + plag. ± qtz. ± titanite ± apatite ± zircon ± iron oxides ± chl. ± sericite ± ep. The secondary assemblage is more altered. On the basis of Mg/(Mg+Fe)-Si per formula of the analyzed amphibole, two types of amphibole are observed; Mg-hornblende and tschermakite. Chemical analyses of the plagioclase grains give two types; oligoclase (An23.9 Ab75.9 ) and albite (An1.7 Ab97.9).