The Salma eclogites of the Belomorian Province, Russia. HP/UHP metamorphism through the subduction of Mesoarchean oceanic crust

Alexander N. Konilov*, Andrey A. Shchipansky, Michael V. Mints, Ksenia A. Dokukina, Tatiana V. Kaulina, Tamara B. Bayanova, Lev M. Natapov, Elena A. Belousova, William L. Griffin, Suzanne Y. O'Reilly

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapter

25 Citations (Scopus)

Abstract

Eclogite-facies mafic rocks occur within gray gneisses of TTG affinity in the northeastern part of the Belomorian Province, Kola Peninsula. These are characterized by widespread omphacite-breakdown textures and locally preserved relics of omphacite. Thermobarometry indicates a clockwise PT path. Garnet inclusions suggest a prograde path passing from surface-weathering conditions through the low-grade green schist facies (pumpellyiteactinolite facies) before reaching the eclogite facies. Peak metamorphic conditions are estimated to be about 700-750°C and > 14-15 kbar. Needle-shaped inclusions (rods) of quartz in omphacite suggest that the peak P-T conditions of studied eclogites could reach significantly higher pressure than estimated in the present study. The retrograde path passed through granulite facies to upper amphibolite facies by near-isothermal decompression. The results of UPb dating and Hf-isotope analysis of zircons from the eclogites and cross-cutting felsic vein can be used to infer an approximate 2.89 Ga age for the oceanic crust, which was subducted and underwent eclogite-facies metamorphism between 2.87 and 2.82 Ga. The granulite-facies overprint is likely to have occurred at 2.72 Ga. Thermal overprinting and growth of new zircon also occurred during the Svecofennian (1.9-1.8 Ga) orogeny. These new data imply that plate tectonic processes ("hot subduction") operated at least locally in the late Mesoarchean. The petrology and geochemistry of the Salma eclogites and related TTG rocks can be best explained by subduction of Archean oceanic crust. The adakitic nature of the felsic vein inside the Salma eclogites suggests that partial melting of hydrated eclogites could produce Archean TTG-type magmas.

Original languageEnglish
Title of host publicationUltrahigh-Pressure Metamorphism
Subtitle of host publication25 years after the discovery of coesite and diamond
EditorsLarissa Dobrzhinetskaya, Shah Wali Faryad, Simon Wallis, Simon Cuthbert
Place of PublicationAmsterdam; Boston
PublisherElsevier
Pages623-670
Number of pages48
Edition1st
ISBN (Print)9780123851444, 0123851440
DOIs
Publication statusPublished - 2011

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