Metamorphic zones and physical conditions of metamorphism in Leros Island,Greece |
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| Authors: | Christos G Katagas |
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| Institution: | (1) Geological Laboratory, University of Patras, Patras, Greece |
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| Abstract: | On the basis of the systematic variation and the appearance and disappearance of some metamorphic minerals in metapelitic assemblages, the metamorphic terrain of Leros can be divided into chlorite, biotite, garnet and staurolite-kyanite zones of progressive regional metamorphism. The matapelites are interbedded with blueschists containing magnesioriebeckite in Fe3+-rich mafic assemblages in the chlorite zone and  more normal greenschist and amphibolite facies in higher grade zones. Combining the observed mineral assemblages in pelitic and mafic schists with the available experimental or calculated relevant phase equilibria, one can deduce temperature conditions of metamorphism ranging from about 350° C up to about 700° C and pressures ranging between a minimum value defined by the pressure of the triple point of the Al2SiO5 polymorphs and a possible minimum around 7 kb.The observed metamorphic sequence may be interpreted as the result of progressive transportation of the original sediments and the interbedded mafic rocks from a regime typified by low temperatures and relatively high pressures, to regimes characterized by higher temperature and medium pressures. |
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