Metamorphic history of glaucophane‐paragonite‐zoisite eclogites from the Shanderman area,northern Iran |
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| Authors: | H Omrani M Moazzen R Oberhänsli T Tsujimori R Bousquet M Moayyed |
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| Institution: | 1. Department of Geology, University of Golestan, , Gorgan, 49138 Iran;2. Department of Geology, University of Tabriz, , Tabriz, 51664 Iran;3. Institute of Earth and Environmental Sciences, Potsdam University, , Potsdam, D–14476 Germany;4. Institute for Study of the Earth's Interior, Okayama University, , Tottori, 682‐0193 Misasa, Japan;5. Institute of Geosciences, Christian‐Albrechts University of Kiel, , Kiel, D‐24118 Germany |
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| Abstract: | The Shanderman eclogites and related metamorphosed oceanic rocks mark the site of closure of the Palaeotethys ocean in northern Iran. The protolith of the eclogites was an oceanic tholeiitic basalt with MORB composition. Eclogite occurs within a serpentinite matrix, accompanied by mafic rocks resembling a dismembered ophiolite. The eclogitic mafic rocks record different stages of metamorphism during subduction and exhumation. Minerals formed during the prograde stages are preserved as inclusions in peak metamorphic garnet and omphacite. The rocks experienced blueschist facies metamorphism on their prograde path and were metamorphosed in eclogite facies at the peak of metamorphism. The peak metamorphic mineral paragenesis of the rocks is omphacite, garnet (pyrope‐rich), glaucophane, paragonite, zoisite and rutile. Based on textural relations, post‐peak stages can be divided into amphibolite and greenschist facies. Pressure and temperature estimates for eclogite facies minerals (peak of metamorphism) indicate 15–20 kbar at ~600 °C. The pre‐peak blueschist facies assemblage yields <11 kbar and 400–460 °C. The average pressure and temperature of the post‐peak amphibolite stage was 5–6 kbar, ~470 °C. The Shanderman eclogites were formed by subduction of Palaeotethys oceanic crust to a depth of no more than 75 km. Subduction was followed by collision between the Central Iran and Turan blocks, and then exhumation of the high pressure rocks in northern Iran. |
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| Keywords: | eclogite late Palaeozoic North Iran Palaeotethys P– T path Shanderman |
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