<Emphasis Type="Italic">P-T</Emphasis> conditions of the Jandagh metapelitic schists,Northeastern Isfahan Province,Iran |
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| Authors: | S M Tabatabaei Manesh M Sharifi A Romanko |
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| Institution: | 1.University of Isfahan,Isfahan,Iran;2.Geological Institute,Russian Academy of Sciences,Moscow,Russia |
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| Abstract: | The metapelitic schists of Jandagh or simply Jandagh metapelites can be divided into four groups based on mineral assemblages:
(1) quartz-muscovite schists, (2) quartz-muscovite-biotite schists, (3) garnet-muscovite-chlorite schists, and (4) garnet-muscovite-staurolite
schists. The Jandagh garnet-muscovite-chlorite schists show the first appearance of garnets. These garnets contain 58–76%
almandine, 1–18% spessartine, and 8–20% grossular. Microprobe analysing across the garnets demonstrates an increase in Mg#
from core to rim. This is a feature of the prograde metamorphism of metapelites. Well-preserved garnet growth zoning is a
sign that metapelites were rapidly cooled and later metamorphic phases had no effect here. The appearance of staurolite in
garnet-muscovite-chlorite schists signifies a beginning of the amphibolite facies. The absence of zoning in staurolite suggests
that its formation and growth during prograde metamorphism occurred at a widely spaced isograde. Thermobarometric investigations
show that the Jandagh metapelites were formed within a temperature range of 400–670°C and pressures of 2.0–6.5 kbar. These
results are in agreement with the mineral paragenetic evidence and show the development of greenschist and amphibolite facies
in the area studied. |
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