Details
| Original language | English |
|---|---|
| Pages (from-to) | 225-231 |
| Number of pages | 7 |
| Journal | Geologische Rundschau |
| Volume | 80 |
| Issue number | 2 |
| Publication status | Published - Jun 1991 |
Abstract
New results obtained by the investigation of liquidus and solidus phase relationships in the haplogranite system Qz-Ab-Or are used to discuss the evolution of magmas during their ascent in the crust. It is assumed that the magmas are formed at 720°C, 820°C, 920°C and at a depth corresponding to a pressure of 8 kbar. The starting composition of the magma is taken as 50% melt plus 50% quartz and feldspars. In case of a closed system (no heat exchange and no transfer of elements) the melt fraction of magmas, the water activity and the viscosity increase with decreasing pressure. The temperature slightly decreases. At 700°C the viscosity is approximatively 2 orders of magnitude lower than at 900°C. This is related to the higher amount of water in the (H2O-undersaturated) melt at low T. It is also shown that dehydration melting is only realistic at high T (900°C). At lower temperatures water has to be added from outside to obtain an intrusive magma with approximatively 50% melt.
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In: Geologische Rundschau, Vol. 80, No. 2, 06.1991, p. 225-231.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Formation and ascent of granitic magmas
AU - Johannes, Wilhelm
AU - Holtz, François
N1 - Copyright: Copyright 2007 Elsevier B.V., All rights reserved.
PY - 1991/6
Y1 - 1991/6
N2 - New results obtained by the investigation of liquidus and solidus phase relationships in the haplogranite system Qz-Ab-Or are used to discuss the evolution of magmas during their ascent in the crust. It is assumed that the magmas are formed at 720°C, 820°C, 920°C and at a depth corresponding to a pressure of 8 kbar. The starting composition of the magma is taken as 50% melt plus 50% quartz and feldspars. In case of a closed system (no heat exchange and no transfer of elements) the melt fraction of magmas, the water activity and the viscosity increase with decreasing pressure. The temperature slightly decreases. At 700°C the viscosity is approximatively 2 orders of magnitude lower than at 900°C. This is related to the higher amount of water in the (H2O-undersaturated) melt at low T. It is also shown that dehydration melting is only realistic at high T (900°C). At lower temperatures water has to be added from outside to obtain an intrusive magma with approximatively 50% melt.
AB - New results obtained by the investigation of liquidus and solidus phase relationships in the haplogranite system Qz-Ab-Or are used to discuss the evolution of magmas during their ascent in the crust. It is assumed that the magmas are formed at 720°C, 820°C, 920°C and at a depth corresponding to a pressure of 8 kbar. The starting composition of the magma is taken as 50% melt plus 50% quartz and feldspars. In case of a closed system (no heat exchange and no transfer of elements) the melt fraction of magmas, the water activity and the viscosity increase with decreasing pressure. The temperature slightly decreases. At 700°C the viscosity is approximatively 2 orders of magnitude lower than at 900°C. This is related to the higher amount of water in the (H2O-undersaturated) melt at low T. It is also shown that dehydration melting is only realistic at high T (900°C). At lower temperatures water has to be added from outside to obtain an intrusive magma with approximatively 50% melt.
UR - http://www.scopus.com/inward/record.url?scp=0026281852&partnerID=8YFLogxK
U2 - 10.1007/BF01829362
DO - 10.1007/BF01829362
M3 - Article
AN - SCOPUS:0026281852
VL - 80
SP - 225
EP - 231
JO - Geologische Rundschau
JF - Geologische Rundschau
SN - 0016-7835
IS - 2
ER -