Thermal history and extensional exhumation of a high-temperature crystalline complex (Hirkadağ Massif, Central Anatolia)

Côme Lefebvre, M. Kalijn Peters, Philip C. Wehrens, Fraukje M. Brouwer, Herman L.M. van Roermund

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12 Scopus citations

Abstract

The Central Anatolian Crystalline Complex (CACC) is a large continental domain exposed in central Turkey that was affected by high temperature metamorphism during the Late Cretaceous. As a result of this event, Paleozoic sediments became metamorphosed, initially under Barrovian conditions, then overprinted locally by high temperature-low pressure metamorphism, and intruded by widespread batholiths. In this study we focus on the crystalline Hirkadağ Massif located in the central part of the CACC, where we applied an integrated approach involving metamorphic, structural and geochronological analysis in order to elucidate its tectonic history from burial to exhumation. Our metamorphic study reveals that conditions of metamorphism reached ~7-8kbar/700°C and were relatively homogeneous at the scale of the Hirkadağ Massif. Coeval with the regional metamorphism, the rocks were intensely deformed as reflected by isoclinal folding, the development of a pervasive foliation and top-to-the-SE shearing. This was followed by decompression to pressures of ~3-4kbar at 800°C, which may be linked to the emplacement of local granodioritic intrusions at ~77Ma. Subsequent cooling of the Hirkadağ high-grade metamorphic and intrusive rocks is indicated by 40Ar/39Ar cooling ages of 68.8±0.9Ma (biotite) and 67.0±1.2Ma (potassium feldspar). Evidence for tectonic exhumation has been identified within the marbles at the NE margin of the Hirkadağ Massif, in the form of discrete protomylonitic and mylonitic shear bands showing a consistent N40-60 top-to-NE sense of shear. Further east, the contact between brecciated mylonitic marbles and non-metamorphic conglomerates preserves the typical structural features of an upper-crustal detachment fault. Restoration of the Hirkadağ Massif and the CACC to their late Cretaceous configuration suggests that the LP-HT metamorphism, magmatism and extensional structures evolved as a result of the development and exhumation of a ~N-S trending magmatic arc experiencing regional E-W extension above an active subduction zone.

Original languageEnglish (US)
Pages (from-to)156-173
Number of pages18
JournalLITHOS
Volume238
DOIs
StatePublished - Dec 1 2015

Bibliographical note

Funding Information:
This research was financially supported by the Netherlands Research Center for Integrated Solid Earth Sciences , the Netherlands Organization for Scientific Research (NWO) and the DARIUS Programme . Kalijn M. Peters and Philip C. Wehrens acknowledge financial support from the Molengraaff Foundation . The final writing, revision and publication of this work were realizable thanks to the funding by the Continental Dynamics—Central Anatolian Tectonics project , NSF-EAR-1109762 . The 40 Ar/ 39 Ar and U/Pb age dating reported in Côme Lefebvre PhD thesis (mentioned here as Lefebvre (2011) ) has been processed by Bart W.H. Hendriks (Geological Survey of Norway, Trondheim) and Fernando Corfu (Department of Geosciences and CEED, University of Oslo) respectively. Tilly Bouten is thanked for her technical support with the microprobe analyses. Osman and Yasin (from Kirkit Pension in Avanos) are kindly thanked for their logistical support around the study area. The authors are grateful to the three anonymous reviewers who provided helpful comments that significantly improved the manuscript.

Publisher Copyright:
© 2015.

Keywords

  • Central Anatolia
  • Exhumation tectonics
  • High temperature metamorphism
  • P-T-t-d evolution

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