Details
| Original language | English |
|---|---|
| Pages (from-to) | 213-224 |
| Number of pages | 12 |
| Journal | Contributions to Mineralogy and Petrology |
| Volume | 130 |
| Issue number | 3-4 |
| Publication status | Published - Feb 1998 |
Abstract
Liquidus phase relations have been experimentally determined in the systems Qz-Ab-Or-(H2O), Qz-Ab-(H2O) and Qz-Or-(H2O) at H2O-undersaturated conditions (a(H2O) = 0.07) and P = 5 kbar. Starting materials were homogeneous synthetic glasses containing 1 wt% H2O. The liquidus temperatures were bracketed by crystallization and dissolution experiments. The results of kinetic studies showed that crushed glasses are the best starting materials to overcome undercooling and to minimize the temperature difference between the lowest temperature of complete dissolution (melting) and the highest temperature at which crystallization can be observed. At P = 5 kbar and a(H2O) = 0.07, the Qz-Ab eutectic composition is Qz32Ab68 at 1095 °C (± 10 °C) and the Oz-Or eutectic is Qz38Or62 at 1030 °C (± 10 °C). The minimum temperature of the ternary system Qz-Ab-Or is 990 °C (± 10 °C) and the minimum composition is Qz32Ab35-Or33. The Qz content of the minimum composition in the system Qz-Ab-Or-H2O remains constant with changing a(H2O). The normative Or content, however, increases by approximately 10 wt% with decreasing a(H2O) from 1 to 0.07. Such an increase has already been observed in the system Qz-Ab-Or-H2O-CO2 at high a(H2O) and it is concluded that the use of CO2 to reduce water activities does not influence the composition of the minima in quartz-feldspar systems. The determined liquidus temperature in melts with 1 wt% H2O is very to that obtained in previous nominally 'dry' experiments. This discrepancy is interpreted to be due to problems in obtaining absolutely dry conditions. Thus, the hitherto published solidus and liquidus temperatures for 'dry' conditions are probably underestimated.
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geophysics
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Contributions to Mineralogy and Petrology, Vol. 130, No. 3-4, 02.1998, p. 213-224.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Liquidus temperatures and phase compositions in the system Qz-Ab-Or at 5 kbar and very low water activities
AU - Becker, Andreas
AU - Holtz, Francois
AU - Johannes, Wilhelm
N1 - Funding Information: Acknowledgments This work was supported by the German Science Foundation (DFG Az. Jo28). We are thankful for critical comments of H. Yoder, W. Schreyer, and H. Keppler. We are also grateful to H. Behrens, O. Diedrich and W. Hurkuck for analytical and technical assistance. Copyright: Copyright 2005 Elsevier B.V., All rights reserved.
PY - 1998/2
Y1 - 1998/2
N2 - Liquidus phase relations have been experimentally determined in the systems Qz-Ab-Or-(H2O), Qz-Ab-(H2O) and Qz-Or-(H2O) at H2O-undersaturated conditions (a(H2O) = 0.07) and P = 5 kbar. Starting materials were homogeneous synthetic glasses containing 1 wt% H2O. The liquidus temperatures were bracketed by crystallization and dissolution experiments. The results of kinetic studies showed that crushed glasses are the best starting materials to overcome undercooling and to minimize the temperature difference between the lowest temperature of complete dissolution (melting) and the highest temperature at which crystallization can be observed. At P = 5 kbar and a(H2O) = 0.07, the Qz-Ab eutectic composition is Qz32Ab68 at 1095 °C (± 10 °C) and the Oz-Or eutectic is Qz38Or62 at 1030 °C (± 10 °C). The minimum temperature of the ternary system Qz-Ab-Or is 990 °C (± 10 °C) and the minimum composition is Qz32Ab35-Or33. The Qz content of the minimum composition in the system Qz-Ab-Or-H2O remains constant with changing a(H2O). The normative Or content, however, increases by approximately 10 wt% with decreasing a(H2O) from 1 to 0.07. Such an increase has already been observed in the system Qz-Ab-Or-H2O-CO2 at high a(H2O) and it is concluded that the use of CO2 to reduce water activities does not influence the composition of the minima in quartz-feldspar systems. The determined liquidus temperature in melts with 1 wt% H2O is very to that obtained in previous nominally 'dry' experiments. This discrepancy is interpreted to be due to problems in obtaining absolutely dry conditions. Thus, the hitherto published solidus and liquidus temperatures for 'dry' conditions are probably underestimated.
AB - Liquidus phase relations have been experimentally determined in the systems Qz-Ab-Or-(H2O), Qz-Ab-(H2O) and Qz-Or-(H2O) at H2O-undersaturated conditions (a(H2O) = 0.07) and P = 5 kbar. Starting materials were homogeneous synthetic glasses containing 1 wt% H2O. The liquidus temperatures were bracketed by crystallization and dissolution experiments. The results of kinetic studies showed that crushed glasses are the best starting materials to overcome undercooling and to minimize the temperature difference between the lowest temperature of complete dissolution (melting) and the highest temperature at which crystallization can be observed. At P = 5 kbar and a(H2O) = 0.07, the Qz-Ab eutectic composition is Qz32Ab68 at 1095 °C (± 10 °C) and the Oz-Or eutectic is Qz38Or62 at 1030 °C (± 10 °C). The minimum temperature of the ternary system Qz-Ab-Or is 990 °C (± 10 °C) and the minimum composition is Qz32Ab35-Or33. The Qz content of the minimum composition in the system Qz-Ab-Or-H2O remains constant with changing a(H2O). The normative Or content, however, increases by approximately 10 wt% with decreasing a(H2O) from 1 to 0.07. Such an increase has already been observed in the system Qz-Ab-Or-H2O-CO2 at high a(H2O) and it is concluded that the use of CO2 to reduce water activities does not influence the composition of the minima in quartz-feldspar systems. The determined liquidus temperature in melts with 1 wt% H2O is very to that obtained in previous nominally 'dry' experiments. This discrepancy is interpreted to be due to problems in obtaining absolutely dry conditions. Thus, the hitherto published solidus and liquidus temperatures for 'dry' conditions are probably underestimated.
UR - http://www.scopus.com/inward/record.url?scp=0032449931&partnerID=8YFLogxK
U2 - 10.1007/s004100050361
DO - 10.1007/s004100050361
M3 - Article
AN - SCOPUS:0032449931
VL - 130
SP - 213
EP - 224
JO - Contributions to Mineralogy and Petrology
JF - Contributions to Mineralogy and Petrology
SN - 0010-7999
IS - 3-4
ER -