Metamorphic evolution of Late Precambrian eclogites and associated metabasites, Gorny Altai, southern Russia

Tsutomu Ota, Mikhail M. Buslov, Teruo Watanabe

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

In the Vendian-Cambrian orogenic belt of the Chagan-Uzun and Kurai areas, Corny Altai. high-pressure, low-temperature (HP/LT) metabasites and associated schists comprise a metamorphic complex less than 2 km thick. The Chagan-Uzun metabasites occur as lenticular interealations in a recrystallized serpentinite. They include eclogite. garnet-amphibolite, amphibolite, and lower-grade schist; the first two contain glaucophane in the strict sense. The Kurai metabasites occur as a coherent body with interealations of calcareous and siliceaus schists. They are divided into four mineral zones: actinolite, hornblende, garnet-barroisite, and garnet-hornblende, based on mineral assemblages. Their metamorphic grade corresponds to greenschist to epidote-amphibolite facies, and decreases from tbe garnet-hornblende zone in the central part of the body to the actinolite zone in the western and eastern margins through the garnet-barroisite and hornblende zones. Estimated peak P-T conditions of the Altai metabasites from the Chagan-Uzun and Kurai areas range from 300°C at 0.4 GPa to 660°C at 2.0 GPa with successive P-T increases. On a P-T diagram, the Altai metamorphic facies series define a single curve convex toward the T axis. The Chagan-Uzun eclogites record prograde and retrograde histories, tracing a hairpin-like P-T path, which is characteristic of Mesozoic HP/LT metamorphic rocks in Pacific-type orogens. Such a P-T evolution suggests that the Altai HP/LT metamorphism occuried in conditions in which hot lithosphere subducted beneath a cool mantle wedge, or subducted lithospbere changed from hot to cold. Hot lithosphere would have been common in the Precambrian Earth with at younger average age of the subducting plate and a thicker oceanic crust, reflecting mantle activities at that time. However, the P-T evolution of the Altai metabasites indicates that the Late Precambrian Altai subduction-zone geotherm was low enough to form HP/LT rocks similar to Mesozoic analogues.

Original languageEnglish
Pages (from-to)837-858
Number of pages22
JournalInternational Geology Review
Volume44
Issue number9
Publication statusPublished - Sep 2002
Externally publishedYes

Fingerprint

metabasite
Precambrian
garnet
hornblende
schist
amphibolite
lithosphere
mantle
metamorphic facies
glaucophane
Vendian
greenschist
serpentinite
P-T conditions
mineral
epidote
eclogite
orogenic belt
amphibolite facies
oceanic crust

ASJC Scopus subject areas

  • Geology

Cite this

Metamorphic evolution of Late Precambrian eclogites and associated metabasites, Gorny Altai, southern Russia. / Ota, Tsutomu; Buslov, Mikhail M.; Watanabe, Teruo.

In: International Geology Review, Vol. 44, No. 9, 09.2002, p. 837-858.

Research output: Contribution to journalArticle

Ota, Tsutomu ; Buslov, Mikhail M. ; Watanabe, Teruo. / Metamorphic evolution of Late Precambrian eclogites and associated metabasites, Gorny Altai, southern Russia. In: International Geology Review. 2002 ; Vol. 44, No. 9. pp. 837-858.
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