Details
| Original language | English |
|---|---|
| Pages (from-to) | 347-357 |
| Number of pages | 11 |
| Journal | Contributions to Mineralogy and Petrology |
| Volume | 141 |
| Issue number | 3 |
| Publication status | Published - Jun 2001 |
Abstract
Liquidus phase relations hve been determined in the system Qz-Ab-Or-H2O at H2O-undersaturated conditions (melt water content of 1 wt% H2O) in the pressure range 200-800 MPa. Starting materials were homogeneous synthetic glasses containing 1 wt% H2O. The minimum liquids temperatures of the ternary system Qz-Ab-Or are 925 ± 15 °C at 200 MPa, 990 ± 10 °C at 500 MPa, and 1,050 ± 10 °C at 800 MPa. The normative Qz content of the minimum is 34 ± 2% at 200 MPa (the exact Ab/Or ratio could not be determined). The composition of the minimum is Qz32Ab35Or33 at 500 MPa, and Qz29Ab37Or34 at 800 MPa (Qz/Ab/Or expressed as normative proportions). At a given pressure, the Qz content of the minimum composition in the system Qz-Ab-Or-H2O remains constant with changing aH2O. The Qz content of the minimum composition increases with decreasing pressure and the normative Ab/Or ratio remains approximately constant (for a water content of the melt of 1 wt%). The determined liquidus temperatures in eutectic or minimum melts with 1 wt% H2O, and the effect of pressure on the liquidus temperature are higher than estimated previously (ca. ±0.2 °C/MPa between 200 and 800 MPa instead of less than ±0.1 °C/MPa in previous estimations). Thus, at a given pressure, temperature and water content, the melt productivity in quartzofeldspathic rocks (such as metagreywackes) is lower than predicted from previous models. The experimental results show (1) that adiabatic decompression in the quartz-alkali feldspar system containing 0-3 wt% H2O produces more melt than expected, which is of importance for the evolution of ascending dacitic and rhyolitic magmas, and (2) that previously published dry liquidus temperatures are strongly underestimated at high pressure (approximately 75 °C at 500 MPa).
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. 141, No. 3, 06.2001, p. 347-357.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - The water-undersaturated and dry Qz-Ab-Or system revisited. Experimental results at very low water activities and geological implications
AU - Holtz, Francois
AU - Becker, Andreas
AU - Freise, Marcus
AU - Johannes, Wilhelm
N1 - Funding Information: Acknowledgements This work was supported by the German Science Foundation (DFG Az. Jo 63/64). We are grateful to O. Diedrich and W. Hurkuck for their technical assistance. The paper benefited from the comments of A. Patino Douce and an anonymous reviewer. Copyright: Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2001/6
Y1 - 2001/6
N2 - Liquidus phase relations hve been determined in the system Qz-Ab-Or-H2O at H2O-undersaturated conditions (melt water content of 1 wt% H2O) in the pressure range 200-800 MPa. Starting materials were homogeneous synthetic glasses containing 1 wt% H2O. The minimum liquids temperatures of the ternary system Qz-Ab-Or are 925 ± 15 °C at 200 MPa, 990 ± 10 °C at 500 MPa, and 1,050 ± 10 °C at 800 MPa. The normative Qz content of the minimum is 34 ± 2% at 200 MPa (the exact Ab/Or ratio could not be determined). The composition of the minimum is Qz32Ab35Or33 at 500 MPa, and Qz29Ab37Or34 at 800 MPa (Qz/Ab/Or expressed as normative proportions). At a given pressure, the Qz content of the minimum composition in the system Qz-Ab-Or-H2O remains constant with changing aH2O. The Qz content of the minimum composition increases with decreasing pressure and the normative Ab/Or ratio remains approximately constant (for a water content of the melt of 1 wt%). The determined liquidus temperatures in eutectic or minimum melts with 1 wt% H2O, and the effect of pressure on the liquidus temperature are higher than estimated previously (ca. ±0.2 °C/MPa between 200 and 800 MPa instead of less than ±0.1 °C/MPa in previous estimations). Thus, at a given pressure, temperature and water content, the melt productivity in quartzofeldspathic rocks (such as metagreywackes) is lower than predicted from previous models. The experimental results show (1) that adiabatic decompression in the quartz-alkali feldspar system containing 0-3 wt% H2O produces more melt than expected, which is of importance for the evolution of ascending dacitic and rhyolitic magmas, and (2) that previously published dry liquidus temperatures are strongly underestimated at high pressure (approximately 75 °C at 500 MPa).
AB - Liquidus phase relations hve been determined in the system Qz-Ab-Or-H2O at H2O-undersaturated conditions (melt water content of 1 wt% H2O) in the pressure range 200-800 MPa. Starting materials were homogeneous synthetic glasses containing 1 wt% H2O. The minimum liquids temperatures of the ternary system Qz-Ab-Or are 925 ± 15 °C at 200 MPa, 990 ± 10 °C at 500 MPa, and 1,050 ± 10 °C at 800 MPa. The normative Qz content of the minimum is 34 ± 2% at 200 MPa (the exact Ab/Or ratio could not be determined). The composition of the minimum is Qz32Ab35Or33 at 500 MPa, and Qz29Ab37Or34 at 800 MPa (Qz/Ab/Or expressed as normative proportions). At a given pressure, the Qz content of the minimum composition in the system Qz-Ab-Or-H2O remains constant with changing aH2O. The Qz content of the minimum composition increases with decreasing pressure and the normative Ab/Or ratio remains approximately constant (for a water content of the melt of 1 wt%). The determined liquidus temperatures in eutectic or minimum melts with 1 wt% H2O, and the effect of pressure on the liquidus temperature are higher than estimated previously (ca. ±0.2 °C/MPa between 200 and 800 MPa instead of less than ±0.1 °C/MPa in previous estimations). Thus, at a given pressure, temperature and water content, the melt productivity in quartzofeldspathic rocks (such as metagreywackes) is lower than predicted from previous models. The experimental results show (1) that adiabatic decompression in the quartz-alkali feldspar system containing 0-3 wt% H2O produces more melt than expected, which is of importance for the evolution of ascending dacitic and rhyolitic magmas, and (2) that previously published dry liquidus temperatures are strongly underestimated at high pressure (approximately 75 °C at 500 MPa).
UR - http://www.scopus.com/inward/record.url?scp=0034963525&partnerID=8YFLogxK
U2 - 10.1007/s004100100245
DO - 10.1007/s004100100245
M3 - Article
AN - SCOPUS:0034963525
VL - 141
SP - 347
EP - 357
JO - Contributions to Mineralogy and Petrology
JF - Contributions to Mineralogy and Petrology
SN - 0010-7999
IS - 3
ER -