TY  - JOUR
A1  - Saki, A.
A1  - Moazzen, Mohssen
A1  - Oberhänsli, Roland
T1  - P-T evolution of the precambrian metamorphic complex, NW Iran a study of metapelitic rocks
JF  - Geological journal
N2  - The Mahneshan Metamorphic Complex (MMC) is one of the Precambrian terrains exposed in the northwest of Iran. The MMC underwent two main phases of deformation (D-1 and D-2) and at least two metamorphic events (M-1 and M-2). Critical metamorphic mineral assemblages in the metapelitic rocks testify to regional metamorphism under amphibolite-facies conditions. The dominant metamorphic mineral assemblage in metapelitic rocks (M-1) is muscovite, biotite I, Garnet I, staurolite, Andalusite I and sillimanite. Peak metamorphism took place at 600-620 degrees C and similar to 7 kbar, corresponding to a depth of ca. 24 km. This was followed by decompression during exhumation of the crustal rocks up to the surface. The decrease of temperature and pressure during exhumation produced retrograde metamorphic assemblages (M-2). Secondary phases such as garnet II biotite It. Andalusite II constrain the temperature and pressure of M, retrograde metamorphism to 520-560 degrees C and 2.5-3.5 kbar, respectively. The geothermal gradient obtained for the peak of metamorphism is 33 degrees C km(-1), which indicates that peak metamorphism was of Barrovian type and occurred under medium-pressure conditions. The MMC followed a 'clockwise' P T path during metamorphism, consistent with thermal relaxation following tectonic thickening. The bulk chemistry of the MMC metapelites shows that their protoliths were deposited at an active continental margin. Together with the presence of palaeo-suture zones and ophiolitic rocks around the high-grade metamorphic rocks of the MMC, these features suggest that the Iranian Precambrian basement formed by an island-arc type cratonization.
KW  - Mahneshan Metamorphic Complex
KW  - Iran
KW  - metapelitic rock
KW  - bulk chemistry
KW  - Barrovian-type metamorphism
KW  - clockwise P-T path
Y1  - 2011
U6  - https://doi.org/10.1002/gj.1236
SN  - 0072-1050
VL  - 46
IS  - 1
SP  - 10
EP  - 25
PB  - Wiley-Blackwell
CY  - Malden
ER  -