Abstract: The study area included low-grade metamorphic units representing the Karakaya Complex (LowerKarakaya-LKC) outcropping in the Armutlu-Ovacık zone in the Armutlu Peninsula. In this study, samples werecollected during field work in the Iznik and Yenişehir (Bursa) regions, and petrographic (optical microscope,SEM) and mineralogical (XRD) examinations were performed. Among the LKC units, the Iznik Metamorphics arerepresented by greenstone facies rocks (metasandstone, slate, schist, quartzite, metagabbro, metavolcanic, dolomiticmarble). Quartz, phyllosilicate (illite, chlorite, C-V, kaolinite, I-V, smectite, stilpnomelane, paragonite, antigorite),feldspar, calcite, pyroxene (augite), dolomite, amphibole (hornblende, tremolite/actinolite, anthophyllite) andopaque minerals (hematite and goethite) were identified in descending order of abundance among the LKC unit.The trioctahedral chlorites with chamosite composition had the IIb polytype, whereas the illites had 2M1 and2M+1M polytypes. The Kübler Index (KI; Δο2θ) values were in the range of 0.19-0.41 Δο2θ (mean: 0.25 Δο2θ), which indicates epi-metamorphic and very low metamorphic grade. The AI (Δο2θ) values were in the range of 0.26-0.32 Δο2θ (mean: 0.29 Δο2θ), which is compatible with the Kübler Index data from illites. Dioctahedral illites withphengite compositions had b0 values (Å) in the range of 8.952-9.030 Å (mean: 8.995 Å), and they were in the low- tomoderate-pressure facies sequence. Comparing the lithological, mineralogical and crystal chemistry parameterdata (crystallinity, polytype and b0) of the Iznik metamorphics representing LKC to those of equivalent units found incentral-northeastern Anatolia (Nilüfer Unit and Turhal Metamorphics), the unit showed diagenesis-metamorphismconditions with greenstone facies corresponding to the upper part of the Lower Karakaya (LKC-UP). Petrographicand mineralogical data (paragenesis, KI, AI, b0, index mineral associations) revealed that the Iznik Metamorphicswere affected by lower greenschist (high anchizone-epizone) metamorphism during the Permian-Early Cretaceousperiod.