Details
| Originalsprache | Englisch |
|---|---|
| Seiten (von - bis) | 417-422 |
| Seitenumfang | 6 |
| Fachzeitschrift | Transactions of the Royal Society of Edinburgh: Earth Sciences |
| Jahrgang | 83 |
| Ausgabenummer | 1-2 |
| Publikationsstatus | Veröffentlicht - 1992 |
Abstract
Melting experiments with plagioclases were performed in the systems Ab-An, Ab-An-H2O, Qz-Ab-An-H2O, and Qz-Or-Ab-An-H2O-CO2. The experimental products were analysed by electron microprobe, and the kinetics of the reactions were studied qualitatively.Melting of the plagioclase in the system Ab-An (P = 1 atm, T = 1420°C) is very fast in the first minutes but becomes slower with increasing run duration and is incomplete even after 1000 hours. The Ab/An fractionation between melt and residual plagioclase is similar to that described by Bowen (1913).Melting kinetics of plagioclase in the system Ab-An-H2O (PH2O = 5 kbar, T = 1000°C) is controlled by the diffusion of water into the plagioclase structure. Melting is especially fast parallel to the a-axis. The experimental products show separation of melts and crystals.In the tonalite system Qz-Ab-An-H2O, equilibrium melting could be observed down to 830°C (PH2O = 2 kbar) but not a lower temperatures. The kinetics of the reaction is enhanced by deficiency or excess of alumina in the aluminosilicate melt surrounding the plagioclase crystals. The fractionation of Ab and An between melt and plagioclase crystals is more pronounced in the presence of quartz than in the Ab-An-H2O system. The ratio An/An + Ab is approximately 0·35 in the melt and 0·85 in the coexisting plagioclase T = 880°C).In the haplogranodiorite system Qz-Or-Ab-An-H2O–CO2, melting reactions were performed at P = 0·5 kbar, T = 880°C, and αH2O of approximately 0·5. It is assumed that near equilibrium compositions of melt and coexisting residual plagioclase could be obtained in long duration runs (run time = 60 days). The distribution of Ab and An between melt and minerals is similar to that observed in the tonalite system. The partial melt coexisting with an An-rich plagioclase and Or-rich K-feldspar is relatively poor in An.
ASJC Scopus Sachgebiete
- Erdkunde und Planetologie (insg.)
- Erdkunde und Planetologie (sonstige)
- Erdkunde und Planetologie (insg.)
- Paläontologie
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in: Transactions of the Royal Society of Edinburgh: Earth Sciences, Jahrgang 83, Nr. 1-2, 1992, S. 417-422.
Publikation: Beitrag in Fachzeitschrift › Artikel › Forschung › Peer-Review
}
TY - JOUR
T1 - Melting of plagioclase in granite and related systems
T2 - Composition of coexisting phases and kinetic observations
AU - Johannes, Wilhelm
AU - Holtz, François
N1 - Copyright: Copyright 2016 Elsevier B.V., All rights reserved.
PY - 1992
Y1 - 1992
N2 - Melting experiments with plagioclases were performed in the systems Ab-An, Ab-An-H2O, Qz-Ab-An-H2O, and Qz-Or-Ab-An-H2O-CO2. The experimental products were analysed by electron microprobe, and the kinetics of the reactions were studied qualitatively.Melting of the plagioclase in the system Ab-An (P = 1 atm, T = 1420°C) is very fast in the first minutes but becomes slower with increasing run duration and is incomplete even after 1000 hours. The Ab/An fractionation between melt and residual plagioclase is similar to that described by Bowen (1913).Melting kinetics of plagioclase in the system Ab-An-H2O (PH2O = 5 kbar, T = 1000°C) is controlled by the diffusion of water into the plagioclase structure. Melting is especially fast parallel to the a-axis. The experimental products show separation of melts and crystals.In the tonalite system Qz-Ab-An-H2O, equilibrium melting could be observed down to 830°C (PH2O = 2 kbar) but not a lower temperatures. The kinetics of the reaction is enhanced by deficiency or excess of alumina in the aluminosilicate melt surrounding the plagioclase crystals. The fractionation of Ab and An between melt and plagioclase crystals is more pronounced in the presence of quartz than in the Ab-An-H2O system. The ratio An/An + Ab is approximately 0·35 in the melt and 0·85 in the coexisting plagioclase T = 880°C).In the haplogranodiorite system Qz-Or-Ab-An-H2O–CO2, melting reactions were performed at P = 0·5 kbar, T = 880°C, and αH2O of approximately 0·5. It is assumed that near equilibrium compositions of melt and coexisting residual plagioclase could be obtained in long duration runs (run time = 60 days). The distribution of Ab and An between melt and minerals is similar to that observed in the tonalite system. The partial melt coexisting with an An-rich plagioclase and Or-rich K-feldspar is relatively poor in An.
AB - Melting experiments with plagioclases were performed in the systems Ab-An, Ab-An-H2O, Qz-Ab-An-H2O, and Qz-Or-Ab-An-H2O-CO2. The experimental products were analysed by electron microprobe, and the kinetics of the reactions were studied qualitatively.Melting of the plagioclase in the system Ab-An (P = 1 atm, T = 1420°C) is very fast in the first minutes but becomes slower with increasing run duration and is incomplete even after 1000 hours. The Ab/An fractionation between melt and residual plagioclase is similar to that described by Bowen (1913).Melting kinetics of plagioclase in the system Ab-An-H2O (PH2O = 5 kbar, T = 1000°C) is controlled by the diffusion of water into the plagioclase structure. Melting is especially fast parallel to the a-axis. The experimental products show separation of melts and crystals.In the tonalite system Qz-Ab-An-H2O, equilibrium melting could be observed down to 830°C (PH2O = 2 kbar) but not a lower temperatures. The kinetics of the reaction is enhanced by deficiency or excess of alumina in the aluminosilicate melt surrounding the plagioclase crystals. The fractionation of Ab and An between melt and plagioclase crystals is more pronounced in the presence of quartz than in the Ab-An-H2O system. The ratio An/An + Ab is approximately 0·35 in the melt and 0·85 in the coexisting plagioclase T = 880°C).In the haplogranodiorite system Qz-Or-Ab-An-H2O–CO2, melting reactions were performed at P = 0·5 kbar, T = 880°C, and αH2O of approximately 0·5. It is assumed that near equilibrium compositions of melt and coexisting residual plagioclase could be obtained in long duration runs (run time = 60 days). The distribution of Ab and An between melt and minerals is similar to that observed in the tonalite system. The partial melt coexisting with an An-rich plagioclase and Or-rich K-feldspar is relatively poor in An.
KW - granite
KW - melting
KW - plagioclase
KW - reaction kinetics
KW - tonalite
UR - http://www.scopus.com/inward/record.url?scp=0027075414&partnerID=8YFLogxK
U2 - 10.1017/S0263593300008087
DO - 10.1017/S0263593300008087
M3 - Article
AN - SCOPUS:0027075414
VL - 83
SP - 417
EP - 422
JO - Transactions of the Royal Society of Edinburgh: Earth Sciences
JF - Transactions of the Royal Society of Edinburgh: Earth Sciences
SN - 0263-5933
IS - 1-2
ER -