Multi-anvil re-equilibration experiments of a Dabie Shan ultrahigh-pressure eclogite within the diamond-stability fields

K. Okamoto, S. Maruyama

Research output: Contribution to journalArticle

46 Citations (Scopus)

Abstract

An eclogite (UHP303) formed at ~700°C and P >4 GPa from the Dabie Shan ultrahigh-pressure (UHP) terrane and the same sample +1.1 wt% K2O (UHK303) were used for re-equilibrium experimental studies at P = 2.6-3.2 GPa and T = 900-1000°C, employing a piston cylinder apparatus, and at P = 3-7 GPa and T = 900-1200°C, employing a 1000 ton uniaxial multi-anvil apparatus (SPI-1000). Run products of UHP303 are composed of garnet, sodic augite, with or without a SiO2 phase and phengite. Textural evidence indicates that the solidus lies between 900 and 1000°C at 5 GPa, and above 1000°C at 3 and 7 GPa for UHP303. The solidus temperature decreases to 1000°C at 3-5 GPa and below 900°C at 5 GPa in UHK303. Composition of rock-forming minerals of all run products were determined and compared with those of starting materials. Garnets of all run products have a relatively higher almandine + spessartine component (alm + sps 24-30 mol%) and lower grossular component (12-16) with constant pyrope component (58-61), compared to the starting garent (grs 16-26, alm 21-26, pyp 42-61). The stable Ca-Na pyroxenes are sodic augite rather than omphacite at T higher than 900°C in the P = 3-7 GPa pressure range, and the Cpx compositional gap is completely closed. The K2O content of Ca-Na pyroxenes is a function of P and T, and serves as a potential barometer in the diamont-stability field. Sodium content in garnet is negligible. Using the proposed K2O content in Ca-Na pyroxene as a function of pressure, the maximum Kokchetav UHP condition is suggested to have been 7 GPa at T = 900°C.

Original languageEnglish
Pages (from-to)52-69
Number of pages18
JournalIsland Arc
Volume7
Issue number1-2
Publication statusPublished - Mar 1998
Externally publishedYes

Fingerprint

eclogite
diamond
garnet
augite
experiment
spessartine
grossular
almandine
pyrope
omphacite
phengite
pyroxene
terrane
experimental study
sodium
mineral
rock
product
temperature

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Multi-anvil re-equilibration experiments of a Dabie Shan ultrahigh-pressure eclogite within the diamond-stability fields. / Okamoto, K.; Maruyama, S.

In: Island Arc, Vol. 7, No. 1-2, 03.1998, p. 52-69.

Research output: Contribution to journalArticle

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