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 language | English |
|---|---|
| Pages (from-to) | 52-69 |
| Number of pages | 18 |
| Journal | Island Arc |
| Volume | 7 |
| Issue number | 1-2 |
| Publication status | Published - Mar 1998 |
| Externally published | Yes |
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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 journal › Article
}
TY - JOUR
T1 - Multi-anvil re-equilibration experiments of a Dabie Shan ultrahigh-pressure eclogite within the diamond-stability fields
AU - Okamoto, K.
AU - Maruyama, S.
PY - 1998/3
Y1 - 1998/3
N2 - 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.
AB - 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.
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UR - http://www.scopus.com/inward/citedby.url?scp=0031710268&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0031710268
VL - 7
SP - 52
EP - 69
JO - Island Arc
JF - Island Arc
SN - 1038-4871
IS - 1-2
ER -