Volume 8, Issue 1 (صفحات انگلیسی از 1 تا 6(چکیده) 2009)                   2009, 8(1): 57-74 | Back to browse issues page

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Characteristics and condition of andalusite formation in Dehsalm Metamorphic Complex, East of Iran. Journal title 2009; 8 (1) :57-74
URL: http://jsci.khu.ac.ir/article-1-1224-en.html
Abstract:   (5666 Views)
Dehsalm metamorphic complex (DMC), located in the east of Lut microcontinent margin, east Iran. It is mainly consist of pelitic schists, marble, amphibole schist, intruded by granitic intrusions and pegmatite veins. Andalusite occurred in both metamorphic and igneous rocks at DMC, with distinctive textural and geochemical features, and crystallographic habits. Andalusite is one of the Al2SiO5 polymorphs, usually formed in high temperature and low pressure metamorphism. New experimental study showed that andalusite may form in magmatic and metasomatic condition. EPMA point analyses shows that Fe, K, and REE signatures are different in DMC andalusites. Iron and potassium concentration in andalusite formed in magmatic rocks is 0.97-0.12 and 0.79 respectively while in metamorphic andalusite is 0.16-0.11, with negligible amount of K (less than 0.02%). The concentration of other major elements in the both andalusite are comparable. Recent investigations show that andalusite may form in magmatic rocks. Metamorphic andalusite in DMC, andalusite schists, formed as chiastolite with distinctive orientation along schistosity as a result of progressive metamorphism of a pelitic sequence. The metamorphic paragenetic sequence indicates that it may form at 380-450 C and 2-3 Kb pressure. Andalusite in magmatic rocks occurred in rim of granitic and pegmatite bodies as pink crystals without any carbon inclusion and no preferred orientation. It is possibly derived from Meta aluminous and alkali magma which has been in ionic exchange with surrounding metamorphic rocks in DMC. The K/Na ratios trends from schists in metamorphic halos toward granitic bodies confirm the occurrence of ion exchange and metasomatic reactions between magmas and its surrounding rocks

Published: 2009/12/15

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