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The study of hidden and appear zoning in existed garnets in metamorphic rocks of Hamadan region

Research Paper | January 1, 2015

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Zahra Hossein mirzaee, Nafiseh Salehi Siavashani

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J. Bio. Env. Sci.6( 1), 737-742, January 2015


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Understudied region is located in south and south east of Hamadan and is part of the metamorphic belt named Sanandaj-Sirjan zone. Metamorphic rocks of the region include slate, phyllite, schist, migmatites and hornfels. Garnet is one of the main minerals in schist, migmatits and hornfels and sometimes it is found in some of the granites and aplitic-pegmatite. Zoning is common in most of the gernets existing in region’s metamorphic rocs. In some of the region’s garnets zoning phenomenon is observable, and this is divided in to three groups of appear, hidden (inverted and normal) and mixed groups. Appear zoning is detectable under the microscope and mostly comes along with discontinuities in crystals’ growth and in amphibole garnet; regions schist of this type of zoning are observable. Hidden zoning (chemical) are not observable by polarizing microscope, but it can be distinguished by quantitative analysis pictures. This type of zoning mostly is along with continuity in crystals’ growth, and there are chemical compounds’ changes in the environment during their growth. Hidden zoning (chemical) can be classified in to two groups of normal and inverted classes. In mixed zoning, part of the zoning relating to changes in elements’ amount is observable under the microscope, and the other part only appears in quantitative analysis pictures. This type of zoning can be the indicator of change in dominant conditions in crystals growth during multi-changing events in the understudied region. Therefore garnets zoning of understudied region has lots of varieties that can be related to multi-changing event in understudied region.


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The study of hidden and appear zoning in existed garnets in metamorphic rocks of Hamadan region

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