Epidote - lawsonite coexistence in blueschist-facies block from the Tavsanli Zone - Turkey: petrological implications

Metamorphic evolution of an epidote-lawsonite blueschist sample characterized by the coexistence of lawsonite and epidote from Sivrihisar area (Taysanli Zone) was studied herein in terms of petrology and mineral equilibria. Based on the textural evidence and phase composition, 2 prograde stages, defined by assemblage-I and -II and 1 retrograde stage were recognized. Assemblage-I indicates epidote-blueschist facies conditions (12 +/- 1 kbar / 485 +/- 10 degrees C). Assemblage-II is characterized by the coexistence of epidote and lawsonite (17 +/- 1 kbar / 515 +/- 10 degrees C) corresponding to the interface of lawsonite blueschist and epidote blueschist facies. Phase diagram calculations and mineral compositions revealed that along this interface, an equilibrium field with lawsonite and epidote is stable. This closed-equilibrium field is controlled by high aH(2)O and an elevated Fe3+/Al ratio of minerals. Pressure-temperature (P-T) estimates and textural observations indicated a counter-clockwise path during the subduction and exhumation history. The preservation of lawsonite and epidote during the retrograde stage pointed to the fact that the path followed the stability field of lawsonite and epidote during exhumation

Multi-Stage P-T-t Evolution of Precambrian Aged Rocks in Anamur (Alanya Massif, Mersin) Region

The Anamur region in the eastern part of the Alanya Massif is defined by high temperature metamorphism. Metamorphic rocks (Sariagac unit), under the conditions of the upper amphibolite facies which are interrupted by basic and acidic meta-magmatics in the region, constitute the para-autochtonous basis. Kapidag nappe, has undergone metamorphism the Barrow-type medium-pressure metamorphism in the greenschist facies is overlain by the tectonic contact of the Sariagac unit with the ductile conditions. The Kapidag nappe, which forms a regular and thick sequence, begins with a probable infra-cambrian aged assemblage in the base consisting of dolomite, marble, muscovite-quartz schist and chlorite schist alternation. This assemblage is overlain by low-grade metamorphics of Tauride units consist of quartzite, meta-carbonate and schists derived from Hudai, Caltepe and Seydisehir formations in Cambro-Ordovician aged. All these metamorphic units are unconformably overlain by conglomerates belonging to Late Eocene-Oligocene Anamur Formation and then Hadim nappe thrusted over to all units

First occurrence of Fe-Mg-carpholite documenting a high-pressure metamorphism in metasediments of the Lycian Nappes, SW Turkey

In the basal thrust sheets of the Lycian nappes fresh Fe-Mg-carpholite documents low-grade. high-pressure (HP) metamorphism. Here we describe the first occurrences of this HP indicator mineral in Turkey, its regional distribution and geodynamic consequences. Carpholite and its breakdown products, such as chloritiod and pyrophyllite, occur in the Lycian nappes s.s. Relics of Fe-Mg-carpholite were also found in klippen of Lycian nappe material located on top of the Menderes crystalline massif. The distribution of the Fe-Mg-carpholite and its relies traces an extensive area of HP metamorphism in the sediments of a passive continental margin

Pressure-temperature evolution of lawsonite eclogite in Sivriihisar; Tavsanli Zone-Turkey

The Cretaceous blueschist belt, Tavsanli Zone, representing the subducted and exhumed northern continental margin of the Anatolide-Tauride platform is exposed in Western Anatolia. The Sivihisar area east of Tavsanli is made Lip of tectonic units consisting of i) metaclastics and conformably overlying massive marbles (coherent blueschist unit), ii) blueschist-eclogite unit, iii) marble-calcschist intercalation and iv) metaperidotite slab. The metaclastics are composed of jadeite-lawsonite-glaucophane and jadeite-glaucophane-chloritoid schists, phengite phyllitei, and calcschists with glaucophane-lawsonite metabasite layers. The blueschist-eclogite unit representing strongly sheared, deeply buried and imbricated tectonic slices of accreted uppermost levels of the oceanic crust with minor metamorphosed serpentinite bodies consists of lawsonite-bearing eclogitic metabasites (approximately 90% of the field), lawsonite eclogites, metagabbros, serpentinites., pelagic marbles, omphacite-glaucophane-lawsonite metapelites and metacherts. The mineral assemblage of the lawsonite eclogite (garnet+omphacite >70%) is omphacite, garnet, lawsonite, glaucophane, phengite and rutile. Lawsonite eclogite lenses are enclosed by garnet-lawsonite blueschist envelopes. Textural evidence from lawsonite eclogites and country rocks reveals that they did not leave the stability field of lawsonite during subduction and exhumation. The widespread preservation of lawsonite in eclogitic metabasites and eclogites can be attributed to rapid subduction and subsequent exhumation in a low geothermal gradient of the oceanic crust material without experiencing a thermal relaxation. Peak P-Tconditions of lawsonite eclogites are estimated at 24 +/- 1 kbar and 460 +/- 25 degrees C. These P-T conditions indicate a remarkably low geotherm of 6.2 degrees C/km corresponding to a burial depth of 74 km. (C) 2007 Elsevier B.V. All rights reserved