TY - JOUR

T1 - METAMORPHIC MINERAL REACTIONS AND MINERAL ASSEMBLAGES IN ROCKS OF THE MEYERI TECTONIC ZONE, SOUTHEASTERN FENNOSCANDIAN SHIELD, RUSSIA

AU - Вивдич, Эмилия Сергеевна

AU - Балтыбаев, Шаукет Каимович

AU - Galankina, O. L.

PY - 2024/10/26

Y1 - 2024/10/26

N2 - Mineral reactions were studied in metamorphic rocks from the Meyeri tectonic zone, and the P–T path of the development of this structure was calculated. According to the P–T path, the Proterozoic granulite complex of the Svecofennian Belt was thrust onto low-temperature rocks of the Archean Karelian Craton. Relict staurolite and other minerals preserved as inclusions in the garnet porphyroblasts made it possible to identify the pre-peak stage of metamorphism with P–T parameters no higher than the low-temperature amphibolite facies of moderate and low pressure. The peak metamorphic conditions of the tectonic zone are estimated at T > 700°C and P ~ 7 kbar using the composition of relict minerals, while the temperature on the prograde trend of metamorphism was 500–600°C at a pressure of about 5 kbar. The post-peak stage began with a distinct decompressional P–T path at the aforementioned high temperatures, with a change from granulite hypersthene-containing assemblages to lower-temperature hydrous ones. The subsequent metamorphic retrogression was characterized by the development of numerous hydrous minerals as a result of the activation of fluids in the shear zone. The P–T path of the tectonic zone is clockwise and reflects the exhumation of the Svecofennian granulite complex during the orogenic events.

AB - Mineral reactions were studied in metamorphic rocks from the Meyeri tectonic zone, and the P–T path of the development of this structure was calculated. According to the P–T path, the Proterozoic granulite complex of the Svecofennian Belt was thrust onto low-temperature rocks of the Archean Karelian Craton. Relict staurolite and other minerals preserved as inclusions in the garnet porphyroblasts made it possible to identify the pre-peak stage of metamorphism with P–T parameters no higher than the low-temperature amphibolite facies of moderate and low pressure. The peak metamorphic conditions of the tectonic zone are estimated at T > 700°C and P ~ 7 kbar using the composition of relict minerals, while the temperature on the prograde trend of metamorphism was 500–600°C at a pressure of about 5 kbar. The post-peak stage began with a distinct decompressional P–T path at the aforementioned high temperatures, with a change from granulite hypersthene-containing assemblages to lower-temperature hydrous ones. The subsequent metamorphic retrogression was characterized by the development of numerous hydrous minerals as a result of the activation of fluids in the shear zone. The P–T path of the tectonic zone is clockwise and reflects the exhumation of the Svecofennian granulite complex during the orogenic events.

U2 - 10.1134/S0869591124020097

DO - 10.1134/S0869591124020097

M3 - Article

VL - 32

SP - 215

EP - 235

JO - Petrology

JF - Petrology

SN - 0869-5911

IS - 2

ER -