Abstract: Alteration minerals determined in the ultramafic rocks of Güneş Ophiolite were divided in  three maingroups as pre-, syn- and post-serpentinization. Of these, phlogopite from pre-serpentinization mineralsis one of the main components of mica-peridotites and is contemporaneous with the formation of theophiolitic sequence. Listwaenitization and pyrometasomatism from later alterations caused an increase ingrain size and accumulation of phlogopites in certain zones and also mixed-layer phlogopite-vermiculite(P-V) and vermiculite transformations in local. Syn-serpentinization alterations cover the conversionsfrom felsic and mafic minerals to various clay and/or phyllosilicates. Post-serpentinization alterationcovers the occurrences of ophicarbonate (commonly calcite and dolomite, rarely siderite and hydrotalcite),ophioxide-hydroxide (hematite, goethite, pyrite, marcasite and brucite) and locally ophisilicate (quartz) thatrefers to listwaenitization. Phlogopite, actinolite, epidote, johannsenite, scapolite, schorl and Fe-minerals(magnetite, hematite, pyrite, marcasite) form of the products of metasomatism in the pyrometasomaticrocks, and pyroxene and feldspar are residual primary magmatic phases. Divriği phlogopites differ partlyin respect to end-member of theoretical oxide compositions of phlogopite-biotite series. Biotite componentof phlogopites is low (8-14 %) and they are called as Fe-Al phlogopite according to their average unit-cellcomposition. The main cation of P-V in the ultramafic-hosted rocks is Mg and this mineral is partiallyrich in Fe and poor in Al. Serpentines have tetrahedral and octahedral Fe substitutions which indicateFe-lizardite. The concentrations of total trace element in the phyllosilicate minerals decrease fromserpentine–phlogopite to P-V, whereas their rare earth element contents increase in the same directionin the Divriği area. δ18O and δD values (SMOW) are determined as ‰ +10.6-11.8 and ‰ −64 - −102 forphlogopites, ‰ +14.2 and ‰ −121 for P-V, and ‰ +14.4 and ‰ −129 for serpentine. Phlogopites areplot hypogene and supergene fields, but P-V and serpentine are found under kaolinite weathering line onthe basis of δ18O and δD values. Formation temperatures as ~ 130-150 °C for phlogopite and ~ 100 °Cfor P-V are obtained on the comparison of minimum isotopic value of granitic water. Additionally, stableisotopic values showed that serpentinization, phlogopitization and vermiculitization formed with differentsubsequent processes.