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Petrotectonics of lawsonite eclogite exhumation: Insights from the Sivrihisar massif, Turkey
Author(s) -
Davis Peter B.
Publication year - 2011
Publication title -
tectonics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.465
H-Index - 134
eISSN - 1944-9194
pISSN - 0278-7407
DOI - 10.1029/2010tc002713
Subject(s) - geology , lawsonite , eclogite , massif , blueschist , omphacite , lineation , phengite , geochemistry , amphibole , mylonite , shear zone , petrology , subduction , seismology , quartz , paleontology , tectonics
The Sivrihisar massif of the Tavşanlı Zone of Turkey is 1 of less than 10 known lawsonite eclogite localities worldwide. Rocks of the Sivrihisar massif consist of eclogite and blueschist in contact with metasedimentary host rocks and record decreasing maximum pressure conditions across three WNW‐ESE striking belts from 16–24 kbar in the northern Halilbağı belt to 14–16 kbar in the Karacaören belt and 8–10 kbar in the Kertek belt. Where present, sodic‐amphibole, phengite, chlorite, and quartz define a pervasive S 0 /S 1 foliation; garnet, omphacite, and lawsonite define stretching lineations and kinematic indicators. D 1 and D 2 structures are similar in the Halilbağı and Karacaören belts but differ to those in the Kertek belt. D 3 structures are uniform across the massif including fibrous calcite that occurs parallel to F 3 fold axes. Shear sense indicators from field observations and asymmetric type‐I cross girdle of quartz c axes obtained from electron backscatter diffraction (EBSD) show top to the south thrusting throughout much of the massif. D 1 and D 2 structures are interpreted to have formed during exhumation by extrusion along a ∼5°C/km gradient. The Halilbağı and Karacaören belts were juxtaposed possibly as deep as 45 km within the subduction channel and exhumed by the arrival of the Anatolide microcontinent at approximately 70 Ma. Homogeneity of F 3 axes and calcite fibers across the massif suggests that assembly occurred at blueschist conditions before exhumation through the aragonite‐calcite transition (∼350°C) above 8 kbar.