Details
| Original language | English |
|---|---|
| Pages (from-to) | 1-14 |
| Number of pages | 14 |
| Journal | Lithos |
| Volume | 56 |
| Issue number | 1 |
| Publication status | Published - 5 Feb 2001 |
Abstract
Recent results of studies aimed to determine the water solubilities and the liquidus temperatures in synthetic and natural granitic systems are used to constrain the minimum water contents of granitic melts generated in the crust as a function of pressure, temperature, melt composition, and water activity. It is concluded that melts generated in the crust at high temperature and low water activities (such as A-type granites) contain higher water contents than previously assumed (up to 20% at 800-900°C and 3-7 kbar). As a consequence, the melt fraction produced at a given amount of available water can be up to 20% lower. The minimum water content of melts generated by partial melting of crustal protoliths (especially quartzofeldspathic rocks) can be predicted adequately from the liquidus curves in granitic systems. This water content can be higher if the melt composition departs from a minimum or eutectic quartzofeldpathic composition. Melts generated from quartzofeldspathic rocks at low temperature (750°C and below) are necessarily water-rich (> 5 wt.% H2O) and have approximately the same viscosity or even slightly lower viscosities than melts generated at higher temperatures (viscosities in the range 104.3-105.4 Pa s). Recent experimental data also show that the value of the positive dP/dT slope of the liquidus curves for fixed water contents above 800°C is lower than predicted by previous models. Thus, adiabatic decompression produces a higher amount of melt than previously assumed (at high temperature, the formation of melt by adiabatic decompression can be up to 50% higher than assumed).
Keywords
- Granite, Liquidus, Rhyolite, Silicate melt, Viscosity, Water solubility
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geology
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: Lithos, Vol. 56, No. 1, 05.02.2001, p. 1-14.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Maximum and minimum water contents of granitic melts generated in the crust
T2 - A reevaluation and implications
AU - Holtz, Francois
AU - Johannes, Wilhelm
AU - Tamic, Nathalie
AU - Behrens, Harald
N1 - Funding Information: This paper results from a synthesis of results obtained in programs supported by the German Science Foundation (DFG) and the European Community. We are grateful to Marcus Freise for his technical assistance. Comments on the manuscript made by A. Castro, A. Patino Douce and L. Kriegsman were greatly appreciated. Copyright: Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2001/2/5
Y1 - 2001/2/5
N2 - Recent results of studies aimed to determine the water solubilities and the liquidus temperatures in synthetic and natural granitic systems are used to constrain the minimum water contents of granitic melts generated in the crust as a function of pressure, temperature, melt composition, and water activity. It is concluded that melts generated in the crust at high temperature and low water activities (such as A-type granites) contain higher water contents than previously assumed (up to 20% at 800-900°C and 3-7 kbar). As a consequence, the melt fraction produced at a given amount of available water can be up to 20% lower. The minimum water content of melts generated by partial melting of crustal protoliths (especially quartzofeldspathic rocks) can be predicted adequately from the liquidus curves in granitic systems. This water content can be higher if the melt composition departs from a minimum or eutectic quartzofeldpathic composition. Melts generated from quartzofeldspathic rocks at low temperature (750°C and below) are necessarily water-rich (> 5 wt.% H2O) and have approximately the same viscosity or even slightly lower viscosities than melts generated at higher temperatures (viscosities in the range 104.3-105.4 Pa s). Recent experimental data also show that the value of the positive dP/dT slope of the liquidus curves for fixed water contents above 800°C is lower than predicted by previous models. Thus, adiabatic decompression produces a higher amount of melt than previously assumed (at high temperature, the formation of melt by adiabatic decompression can be up to 50% higher than assumed).
AB - Recent results of studies aimed to determine the water solubilities and the liquidus temperatures in synthetic and natural granitic systems are used to constrain the minimum water contents of granitic melts generated in the crust as a function of pressure, temperature, melt composition, and water activity. It is concluded that melts generated in the crust at high temperature and low water activities (such as A-type granites) contain higher water contents than previously assumed (up to 20% at 800-900°C and 3-7 kbar). As a consequence, the melt fraction produced at a given amount of available water can be up to 20% lower. The minimum water content of melts generated by partial melting of crustal protoliths (especially quartzofeldspathic rocks) can be predicted adequately from the liquidus curves in granitic systems. This water content can be higher if the melt composition departs from a minimum or eutectic quartzofeldpathic composition. Melts generated from quartzofeldspathic rocks at low temperature (750°C and below) are necessarily water-rich (> 5 wt.% H2O) and have approximately the same viscosity or even slightly lower viscosities than melts generated at higher temperatures (viscosities in the range 104.3-105.4 Pa s). Recent experimental data also show that the value of the positive dP/dT slope of the liquidus curves for fixed water contents above 800°C is lower than predicted by previous models. Thus, adiabatic decompression produces a higher amount of melt than previously assumed (at high temperature, the formation of melt by adiabatic decompression can be up to 50% higher than assumed).
KW - Granite
KW - Liquidus
KW - Rhyolite
KW - Silicate melt
KW - Viscosity
KW - Water solubility
UR - http://www.scopus.com/inward/record.url?scp=0035069397&partnerID=8YFLogxK
U2 - 10.1016/S0024-4937(00)00056-6
DO - 10.1016/S0024-4937(00)00056-6
M3 - Article
AN - SCOPUS:0035069397
VL - 56
SP - 1
EP - 14
JO - Lithos
JF - Lithos
SN - 0024-4937
IS - 1
ER -