Metamorphism and diachronous cooling in a contractional orogen: the Strandja Massif, NW Turkey


GEOLOGICAL MAGAZINE, vol.148, no.4, pp.580-596, 2011 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 148 Issue: 4
  • Publication Date: 2011
  • Doi Number: 10.1017/s0016756810001020
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.580-596
  • Keywords: P-T estimates, Rb-Sr dating, metamorphism and diachronous cooling, compressional exhumation, Strandja Massif, Turkey, RB-SR, HIGH-PRESSURE, FACIES METAMORPHISM, EXHUMATION, COMPLEX, RHODOPE, EVOLUTION, VARISCAN, ROCKS, GEOCHRONOLOGY
  • Istanbul Technical University Affiliated: Yes


The southern part of the Strandja Massif, northern Thrace, Turkey, comprises a basement of various gneisses, micaschists and rare amphibolite, and a cover of metaconglomerate and metasand-stone, separated from each other by a pre-metamorphic unconformity. Metamorphic grade decreases from the epidote-amphibolite facies in the south to the albite-epidote-amphibolite/greenschist-facies transition in the north. Estimated P-T conditions are 485-530 degrees C and 0.60-0.80 GPa in the epidote-amphibolite facies domain, and decrease towards the transitional domain between greenschist- and epidote-amphibolite facies. Rb-Sr muscovite ages range from 162.9 +/- 1.6 Ma to 149.1 +/- 2.1 Ma, and are significantly older (279-296 Ma) in the northernmost part of the study area. The Rb-Sr biotite ages decrease from 153.9 +/- 1.5 Ma in the south to 134.4 +/- 1.3 Ma in the north. These age values in conjunction with the attained temperatures suggest that the peak metamorphism occurred at around 160 Ma and cooling happened diachronously, and Rb-Sr muscovite ages were not reset during the metamorphism in the northernmost part. Structural features such as (i) consistent S-dipping foliation and SW to SE-plunging stretching lineation, (ii) top-to-the-N shear sense, and (iii) N-vergent ductile shear zones and brittle thrusts suggest a N-vergent compressional deformation coupled with exhumation. We tentatively ascribe this metamorphism and subsequent diachronous cooling to the northward propagation of a thrust slice. The compressional events in the Strandja Massif were most probably related to the coeval N-vergent subduction/collision system in the southerly lying Rhodope Massif.