P-T evolution of metapelites from the Bajgan complex in the Makran accretionary prism,south eastern Iran |
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| Institution: | 1. Centre of Excellence in Mineralogy, University of Balochistan, Quetta, Pakistan;2. School of Earth and Ocean Sciences, Cardiff University, Main Building, Park Place, Cardiff, Wales CF10 3AT, UK;3. Department of Earth Sciences, University of Sargodha, Sargodha, Pakistan;4. Tectonics, Resources and Exploration (TRaX), School of Earth and Environmental Sciences, University of Adelaide, SA 5005, Australia;5. Department of Geology, University of Balochistan, Quetta, Pakistan;1. Observatoire des Sciences de l''Univers de Rennes, Géosciences Rennes - UMR 6118, 263 Avenue du General Leclerc CS 74205, 35042 Rennes Cedex, France;2. Institut de Minéralogie, de Physique des Matériaux, et de Cosmochimie (IMPMC), Sorbonne Universités - UPMC Univ Paris 06, UMR CNRS 7590, 4 Place Jussieu, F-75005 Paris, France;3. Géosciences Montpellier, Université Montpellier 2, CNRS UMR 5243, CC60, 34095 Montpellier Cedex 05, France |
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| Abstract: | The Bajgan Complex, one of the basement constituents of the arc massif in Iranian Makran forms a rugged, deeply incised terrain. The complex consists of pelitic schists with minor psammitic and basic schists, calc silicate rocks, amphibolites, marbles, metavolcanosediments, mafic and felsic intrusives as well as ultramafic rocks. Metapelitic rocks show an amphibolite facies regional metamorphism and contain garnet, biotite, white mica, quartz, albite ± rutile ± apatite. Thermobarometry of garnet schist yields pressure of more than 9 kbar and temperatures between 560 and 675 °C. The geothermal gradient obtained for the peak of regional metamorphism is 19 °C/km, corresponding to a depth of ca. 31 km. Replacement of garnet by chlorite and epidote suggest greenschist facies metamorphism due to a decrease in temperature and pressure through exhumation and retrograde metamorphism (370–450 °C and 3–6 kbar). The metapelitic rocks followed a ‘clockwise’ P–T path during metamorphism, consistent with thermal decline following tectonic thickening. The formation of medium-pressure metamorphic rocks is related to presence of active subduction of the Neotethys Oceanic lithosphere beneath Eurasia in the Makran. |
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| Keywords: | Bajgan Complex Makran Metapelitic rock Garnet schist Thermobarometry Clockwise P–T path |
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