Very-low-temperature record of the subduction process: A review of worldwide lawsonite eclogites

Tatsuki Tsujimori, Virginia B. Sisson, Juhn G. Liou, George E. Harlow, Sorena S. Sorensen

Research output: Contribution to journalArticlepeer-review

194 Citations (Scopus)

Abstract

Lawsonite eclogites preserve a record of very-low-temperature conditions in subduction zones. All occur at active margin settings, typically characterized by accretionary complexes lithologies and as tectonic blocks within serpentinite-matrix mélange. Peak lawsonite-eclogite facies mineral assemblages (garnet + omphacite + lawsonite + rutile) typically occur in prograde-zoned garnet porphyroblasts. Their matrix is commonly overprinted by higher-temperature epidote-bearing assemblages; greenschist- or amphibolite-facies conditions erase former lawsonite-eclogite relics. Various pseudomorphs after lawsonite occur, particularly in some blueschist/eclogite transitional facies rocks. Coesite-bearing lawsonite-eclogite xenoliths in kimberlitic pipes and lawsonite pseudomorphs in some relatively low-temperature ultrahigh-pressure eclogites are known. Using inclusion assemblages in garnet, lawsonite eclogites can be classified into two types: L-type, such as those from Guatemala and British Columbia, contain garnet porphyroblasts that grew only within the lawsonite stability field and E-type, such as from the Dominican Republic, record maximum temperature in the epidote-stability field. Formation and preservation of lawsonite eclogites requires cold subduction to mantle depths and rapid exhumation. The earliest occurrences of lawsonite-eclogite facies mineral assemblages are Early Paleozoic in Spitsbergen and the New England fold belt of Australia; this suggests that since the Phanerozoic, secular cooling of Earth and subduction-zone thermal structures evolved the necessary high pressure/temperature conditions. Buoyancy of serpentinite and oblique convergence with a major strike-slip component may facilitate the exhumation of lawsonite eclogites from mantle depths.

Original languageEnglish
Pages (from-to)609-624
Number of pages16
JournalLithos
Volume92
Issue number3-4
DOIs
Publication statusPublished - 2006 Dec 1
Externally publishedYes

Keywords

  • Cold subduction
  • Eclogite
  • HP-UHP metamorphism
  • Lawsonite
  • P-T trajectory

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

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