Paleoproterozoic high-pressure metamorphic history of the Salma eclogite on the Kola Peninsula, Russia. / Imayama, Takeshi; Oh, Chang Whan; Baltybaev, Shauket K.; Park, Chan Soo; Yi, Keewook; Jung, Haemyeong.
In: Lithosphere, Vol. 9, No. 6, 2017, p. 855-873.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Paleoproterozoic high-pressure metamorphic history of the Salma eclogite on the Kola Peninsula, Russia
AU - Imayama, Takeshi
AU - Oh, Chang Whan
AU - Baltybaev, Shauket K.
AU - Park, Chan Soo
AU - Yi, Keewook
AU - Jung, Haemyeong
N1 - Publisher Copyright: © 2017 Geological Society of America. Copyright: Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2017
Y1 - 2017
N2 - The Precambrian Salma eclogites on the Kola Peninsula, Russia, represent some of the oldest eclogites in the world; however, there has been much debate regarding whether the timing of their eclogite facies metamorphism is Archean (2.72-2.70 Ga) or Paleoproterozoic (1.92-1.88 Ga). New microstructural observations, pressure-temperature (P-T ) analyses, zircon inclusion analyses, and U-Pb zircon dating performed in this study suggest that eclogite facies metamorphism occurred at ca. 1.87 Ga under P-T conditions of 16-18 kbar and 750-770 °C. Metamorphic zircons with the age of 1.87 Ga have inclusions of garnet (Grt) + omphacite (Omp) + Ca-clinopyoxene (Cpx) + amphibole (Amp) + quartz (Qz) + rutile (Rt) ± biotite (Bt), as well as flat heavy rare earth element (HREE) patterns due to the presence of abundant amounts of garnet during peak eclogite facies metamorphism. The Paleoproterozoic ages (1.92-1.88 Ga) presented in previous studies are reinterpreted to represent prograde ages, rather than peak ages, because these ages have been inferred from U-Pb dating in zoisite-bearing zircon and Sm-Nd and Lu-Hf geochronologic analyses of garnet showing growth zoning. In contrast, the 2.73-2.72 Ga unzoned zircons with dark cathodoluminescence contain inclusions of Grt + Amp + plagioclase (Pl) + Qz + rutile (Rt) ± Bt and are relatively enriched in HREEs, suggesting that an initial amphibolite facies metamorphic event occurred during the Archean. This study also proposes that the Salma eclogites underwent granulite facies retrograde metamorphism at 10-14 kbar and 770-820 °C, with rapid decompression occurring soon after peak metamorphism ca. 1.87 Ga. The final period of retrograde amphibolite facies metamorphism occurred at 8-10 kbar and 590-610 °C. Whole-rock chemical analyses indicate that the Salma eclogites were originally tholeiitic basalts formed at a mid-ocean ridge. The occurrence of eclogite facies metamorphism ca. 1.87 Ga suggests that the collision between the Kola and Karelian continents occurred during the Paleoproterozoic, rather than the Archean. These results, as well as those of previous studies, imply that the subduction required to form eclogites may have begun during or before the Paleoproterozoic.
AB - The Precambrian Salma eclogites on the Kola Peninsula, Russia, represent some of the oldest eclogites in the world; however, there has been much debate regarding whether the timing of their eclogite facies metamorphism is Archean (2.72-2.70 Ga) or Paleoproterozoic (1.92-1.88 Ga). New microstructural observations, pressure-temperature (P-T ) analyses, zircon inclusion analyses, and U-Pb zircon dating performed in this study suggest that eclogite facies metamorphism occurred at ca. 1.87 Ga under P-T conditions of 16-18 kbar and 750-770 °C. Metamorphic zircons with the age of 1.87 Ga have inclusions of garnet (Grt) + omphacite (Omp) + Ca-clinopyoxene (Cpx) + amphibole (Amp) + quartz (Qz) + rutile (Rt) ± biotite (Bt), as well as flat heavy rare earth element (HREE) patterns due to the presence of abundant amounts of garnet during peak eclogite facies metamorphism. The Paleoproterozoic ages (1.92-1.88 Ga) presented in previous studies are reinterpreted to represent prograde ages, rather than peak ages, because these ages have been inferred from U-Pb dating in zoisite-bearing zircon and Sm-Nd and Lu-Hf geochronologic analyses of garnet showing growth zoning. In contrast, the 2.73-2.72 Ga unzoned zircons with dark cathodoluminescence contain inclusions of Grt + Amp + plagioclase (Pl) + Qz + rutile (Rt) ± Bt and are relatively enriched in HREEs, suggesting that an initial amphibolite facies metamorphic event occurred during the Archean. This study also proposes that the Salma eclogites underwent granulite facies retrograde metamorphism at 10-14 kbar and 770-820 °C, with rapid decompression occurring soon after peak metamorphism ca. 1.87 Ga. The final period of retrograde amphibolite facies metamorphism occurred at 8-10 kbar and 590-610 °C. Whole-rock chemical analyses indicate that the Salma eclogites were originally tholeiitic basalts formed at a mid-ocean ridge. The occurrence of eclogite facies metamorphism ca. 1.87 Ga suggests that the collision between the Kola and Karelian continents occurred during the Paleoproterozoic, rather than the Archean. These results, as well as those of previous studies, imply that the subduction required to form eclogites may have begun during or before the Paleoproterozoic.
UR - http://www.scopus.com/inward/record.url?scp=85035102766&partnerID=8YFLogxK
U2 - 10.1130/L657.1
DO - 10.1130/L657.1
M3 - Article
AN - SCOPUS:85035102766
VL - 9
SP - 855
EP - 873
JO - Lithosphere
JF - Lithosphere
SN - 1941-8264
IS - 6
ER -
ID: 75534105