Abstract
Zircon from the eclogite-like rocks of the Shirokaya and Uzkaya Salma area (Kola Peninsula) was studied using a complex of mineralogical and geochemical methods (CL, BSE, microprobe, and REE distribution). Different zones distinguished within zircon crystals were dated on a SHRIMP-II mass spectrometer. Mineral and chemical compositions of inclusions in the zircons were analyzed. Based on these studies, the following stages of the formation and transformation of the rocks were determined: (1) formation of basic protolith of the eclogite-like rocks of the Shirokaya and Uzkaya Salma area 2.94–2.93 Ga ago; (2) the granulite-facies metamorphism of the eclogite-like rocks of the Shirokaya Salma 2.72 Ga ago; (3) the onset of decompressional cooling with formation of Cpx-Pl symplectites at 2.70 Ga ago; and (4) final metamorphic reworking together with surrounding TTG under the amphibolite-facies conditions at 1.89 Ga ago. The studied rocks and minerals revealed no isotope-geochemical or geochronological signs of eclogite metamorphism. Geochemistry of the primary magmatic zircons showed that the protolith of eclogite-like rocks was gabbro rather than MOR basalts. The formation of garnet in the rocks of the Uzkaya and Shirokaya Salma area is dated at 2.70 and 1.89 Ga ago, which is consistent with petrological observations of later formation of garnet relative to omphacite. Obtained data led us to prefer a magmatogenic model, which suggests that omphacite in the rocks of the Shirokaya and Uzkaya Salma was presumably formed during crystallization from basic melt, rather than during eclogite-facies metamorphism.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call