TY - JOUR

T1 - Viscosity of flux-rich pegmatitic melts

AU - Bartels, Alexander

AU - Vetere, Francesco

AU - Holtz, Francois

AU - Behrens, Harald

AU - Linnen, Robert L.

N1 - Funding Information: Acknowledgments This research has been supported by the German Science Foundation (DFG project Be 1720/24). We would like to thank O. Diedrich for preparing the samples and thin sections, Ullrich Kroll, Markus Köhler and Fabian Christ for the technical support as well as Dr. Lothar Borchers from the Hannover Medical School for the help in recording the X-ray images. Copyright: Copyright 2011 Elsevier B.V., All rights reserved.

PY - 2010/10/27

Y1 - 2010/10/27

N2 - Viscosity experiments were conducted with two flux-rich pegmatitic melts PEG0 and PEG2. The Li2O, F, B2O3 and P2O5 contents of these melts were 1.04, 4.06, 2.30 and 1.68 and 1.68, 5.46, 2.75 and 2.46 wt%, respectively. The water contents varied from dry to 9. 04 wt% H2O. The viscosity was determined in internally heated gas pressure vessels using the falling sphere method in the temperature range 873-1,373 K at 200 and 320 MPa pressure. At 1,073 K, the viscosity of water-rich (~9 wt% H2O) melts is in the range of 3-60 Pa s, depending on the melt composition. Extrapolations to lower temperature assuming an Arrhenian behavior indicate that highly fluxed pegmatite melts may reach viscosities of ~30 Pa s at 773 K. However, this value is a minimum estimation considering the strongly non-Arrhenian behavior of hydrous silicate melts. The experimentally determined melt viscosities are lower than the prediction of current models taking compositional parameters into account. Thus, these models need to be improved to predict accurately the viscosity of flux-rich water bearing melts. The data also indicate that Li influences significantly the melt viscosity. Decreasing the molar Al/(Na + K + Li) ratio results in a strong viscosity decrease, and highly fluxed melts with low Al/(Na + K + Li) ratios (~0. 8) have a rheological behavior which is very close to that of supercritical fluids.

AB - Viscosity experiments were conducted with two flux-rich pegmatitic melts PEG0 and PEG2. The Li2O, F, B2O3 and P2O5 contents of these melts were 1.04, 4.06, 2.30 and 1.68 and 1.68, 5.46, 2.75 and 2.46 wt%, respectively. The water contents varied from dry to 9. 04 wt% H2O. The viscosity was determined in internally heated gas pressure vessels using the falling sphere method in the temperature range 873-1,373 K at 200 and 320 MPa pressure. At 1,073 K, the viscosity of water-rich (~9 wt% H2O) melts is in the range of 3-60 Pa s, depending on the melt composition. Extrapolations to lower temperature assuming an Arrhenian behavior indicate that highly fluxed pegmatite melts may reach viscosities of ~30 Pa s at 773 K. However, this value is a minimum estimation considering the strongly non-Arrhenian behavior of hydrous silicate melts. The experimentally determined melt viscosities are lower than the prediction of current models taking compositional parameters into account. Thus, these models need to be improved to predict accurately the viscosity of flux-rich water bearing melts. The data also indicate that Li influences significantly the melt viscosity. Decreasing the molar Al/(Na + K + Li) ratio results in a strong viscosity decrease, and highly fluxed melts with low Al/(Na + K + Li) ratios (~0. 8) have a rheological behavior which is very close to that of supercritical fluids.

KW - Falling sphere

KW - Pegmatite

KW - Viscosity

KW - Water

UR - http://www.scopus.com/inward/record.url?scp=79958082199&partnerID=8YFLogxK

U2 - 10.1007/s00410-010-0582-3

DO - 10.1007/s00410-010-0582-3

M3 - Article

AN - SCOPUS:79958082199

VL - 162

SP - 51

EP - 60

JO - Contributions to Mineralogy and Petrology

JF - Contributions to Mineralogy and Petrology

SN - 0010-7999

IS - 1

ER -