Petrology
Maryam Dorani; Mohsen Arvin; Roland Oberhänsli; Hadi Omrani; Sara Dargahi
Abstract
Bajgan Complex is a part of Iranian Makran including many kinds of metapelites, metabasites, calcsilicates, amphibolites, marbles, meta volcanosediments, felsic, mafic and ultramafic intrusives. The calcsilicates are divided into amphibole bearing epidote schist, epidote - amphibole schist, epidote – ...
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Bajgan Complex is a part of Iranian Makran including many kinds of metapelites, metabasites, calcsilicates, amphibolites, marbles, meta volcanosediments, felsic, mafic and ultramafic intrusives. The calcsilicates are divided into amphibole bearing epidote schist, epidote - amphibole schist, epidote – amphibole - garnet schist and carbonate bearing mica schist. Among of all calc silicates the epidote – amphibole - garnet schist shows the highest metamorphic condition and consists of garnet, amphibole, epidote, calcite, quartz, secondary chlorite and minor amount of titanite, apatite, white mica and magnetite. In this study the mineral chemical compositions, temprature, pressure and fluid activity in different metamorphic stages of epidote – amphibole - garnet schist were detected. In according to chemical data, garnet has almandine, grossular, spessartine and pyrope solid solution (Alm 35-50, Grs 23-31, Sps 14.6-36, Prp < sub> 2.6-9.8 ; mol%) and shows chemical zoning as almandine and spessartine have an increasing and decreasing trend, respectively, from core to rim. Amphiboles are classified in sodic- calcic group and are Barroisite. Chlorites are kown as Ripidolite and epidotes are classified in Clinozoisite subgroup. Peak metamorphic condition of epidote – amphibole - garnet schist has been estimated about 610° C and 8 kbar and molar fraction of Co2 and H2O have been calculated about 0.32 and 0.68, respectively. The retrograde metamorphic condition are about 525° C, 4.5 kbar and molar fraction of Co2 and H2O have been calculated about 0.31 and 0.69, respectively. The epidote – amphibole - garnet schist followed a ‘clockwise’ P–T path during prograde and retrograde metamorphism.
