U-Pb zircon geochronology of eclogites from the Scandian Orogen, Northern Western Gneiss Region, Norway

14-20 million years between eclogite crystallization and return to amphibolitefacies conditions

Thomas E. Krogh, Sandra L. Kamo, Peter Robinson, Michael P. Terry, Kim Kwok

Research output: Contribution to journalArticle

52 Citations (Scopus)

Abstract

Reconstructing tectonic histories involving continental collision, subduction, and exhumation at plate-tectonic rates of ~1 cm/year, requires precise U-Pb zircon geochronology. TheWestern Gneiss Region has exceptional exposures of high-pressure (HP) and ultra-high-pressure (UHP) rocks. The strategy adopted here involved sampling eclogite and associated late unstrained pegmatites to acquire the time of eclogite crystallization and subsequent exhumation, respectively. The oldest eclogite sampled is 415 ± 1 Ma from layered, probably UHP eclogite at Tevik, Averøya, also with a garnet-hornblende assemblage at 410 ± 1 Ma. The Flem Gabbro eclogite margin, with implied UHP conditions, is 410 ± 2 Ma. Hornblende eclogite at Seth, Lepsøya, never at UHP, is 412 ± 2 Ma. These compare to Devonian ages of 401 ± 1 Ma for overgrowths on Proterozoic baddeleyite in Selnes Gabbro, 402 ± 2 Ma for coesite eclogite at Hareidlandet, 405-400 Ma for coesite eclogite at Flatraket, and 405 ± 2 Ma for near-UHP eclogite at Hjelmelandsdalen. The 415 Ma eclogite at Tevik compares to granitic pegmatite in the same outcrop at 395.2 ± 1.3 Ma and to pegmatite in eclogite at Aspøya at 395.3 ± 2 Ma. The 410 Ma age at Flem compares to nearby pegmatite in eclogite at 396 ± 4 Ma. Collectively, these results imply 14-20 million years between deep eclogite crystallization at~130 km and return to amphibolite-facies conditions at ~30 km, with crystallization of locally derived granitoid melts. Nearby garnet-pyroxenite records older ages (~430) and greater depths (~200 km), but on similar exhumation paths at ~0.4-0.7 cm/year.

Original languageEnglish
Pages (from-to)441-472
Number of pages32
JournalCanadian journal of earth sciences
Volume48
Issue number2
DOIs
Publication statusPublished - Feb 2011
Externally publishedYes

Fingerprint Dive into the research topics of 'U-Pb zircon geochronology of eclogites from the Scandian Orogen, Northern Western Gneiss Region, Norway: 14-20 million years between eclogite crystallization and return to amphibolitefacies conditions'. Together they form a unique fingerprint.

  • Cite this