In this section critical rock types of the Selçuk, Ampelos and Agios Nikolaos nappes will be described followed by estimates of P-T conditions of metamorphic events. Details of the metamorphic history are given in Will et al. (1998) and Ring et al. (2007).
The Selçuk nappe metagabbros are usually massive, sodic amphibole-bearing rocks; omphacitic pyroxene may be present. Strongly mylonitized metagabbros from the Selçuk normal shear zone contain sodic amphibole and diopsidic pyroxene, but lack omphacite. Garnet-bearing amphibolites of the Selçuk nappe occur in adjacent western Turkey (Ring et al. 2007).
The massive glaucophane-bearing metagabbros without omphacite are predominantely made up of sodic and calcic amphiboles, epidote, albite and chlorite. In addition, various amounts of biotite, titanite, magnetite, ilmenite and traces of white mica occur. The rocks have a coarse-grained, relic magmatic texture, which was modified during metamorphism. The metamorphic mineral assemblage sodic amphibole-epidote-white mica is ascribed to blueschist-facies metamorphic conditions, and the assemblage calcic to barroisitic amphibole-epidote-chlorite-albite to a subsequent decompression stage.
The massive omphacite-bearing metagabbros also preserve high pressure assemblages. The rocks contain green and colourless hornblende, diopsidic and omphacitic pyroxene (31-52 mole% jadeite), epidote, chlorite, albite, quartz, and accessory titanite. Generally, these rocks preserve a relic magmatic texture: large, anhedral magmatic green hornblende is rimmed by pale green to colourless actinolite and actinolite-chlorite±titanite intergrowths. Magmatic clinopyroxene is rimmed by green hornblende and, in places, replaced by colourless chlorite. Plagioclase occurs as (i) large poikiloblasts containing fine-grained actinolite, chlorite and epidote and, (ii) as fine-grained recrystallized matrix minerals. Pseudomorphs of paragonite, zoisite and quartz after lawsonite are preserved in some rocks.
The strongly mylonitized metagabbros contains relicts of magmatic diopsidic pyroxene and brown, Ti-bearing amphibole. Furthermore green-blue and colourless amphibole, chlorite, albite, epidote and quartz are present. Accessory titanite, biotite and opaque phases, which are generally transformed to leucoxene, occur.
The metapelitic rocks from the Ampelos nappe are strongly foliated, fine-grained rocks. Kyanite and chloritoid are sometimes abundant in metapelitic rocks (Fig. 6). Up to 0.6 mm large (in diameter) twinned chloritoid poikiloblasts occur in a fine-grained matrix of quartz, phengitic muscovite (3.06 to 3.13 Si per formula unit for 11 oxygens), paragonite and minor chlorite. Zoisite is present in some samples, and Mg-carpholite was found in one sample from Samos by Okrusch (1981). The foliation is defined by white mica and a shape preferred orientation of quartz and wraps around chloritoid. Inclusions in chloritoid are plagioclase, quartz, opaque phases and white mica. Locally, kyanite crystals exhibit undulose extinction, commonly they are surrounded by quartz-filled pressure shadows and contain plagioclase and quartz inclusions.
Figure 6. Metamorphic assemblages
Assemblage chloritoid (blue in different shades) + ankerite + phengite in silicate-ankerite marble, sample Sa91-5, Psili Amos Bay, Eastern Samos (crossed-polarized light, photo width 1.9 mm). (b) Assemblage chloritoid (predominant, light olive green or blue) + chlorite (subordinate, light green) + phengite + quartz in metapelitic schist, sample Sa80-165, Moni Megali Panagias, central Samos (plane-polarized light, photo width 1.25 mm).
The garnet-bearing glaucophanites of the Agios Nikolaos nappe (field trip stop #1.6) contain varying proportions of sodic and calcic amphiboles, garnet, paragonite, muscovite, zoisite, chlorite, albite, titanite and quartz (Fig. 7). Pseudomorphs of zoisite, quartz and little paragonite after lawsonite are preserved as inclusions in garnet testifying the prograde stability of lawsonite (Will et al. 1998). Calcic amphibole together with, or without, chlorite surrounds sodic amphibole in some cases. Coexisting garnet and sodic amphibole are restricted to the Agios Nikolaos nappe glaucophanites.
Figure 7. Metamorphic assemblage
Assemblage garnet + glaucophane + epidote + chlorite + phengite + quartz in blueschist; garnet is rotated. Sample Sa80-154, road near Ampelos, central Samos (plane-polarized light, width of photo 3 mm).