TY - JOUR

T1 - Heat capacity and viscosity of basaltic melts with H2O ± F ± CO2

AU - Robert, Geneviève

AU - Knipping, Jaayke L.

AU - Scherbarth, Stefanie

AU - Robertson, Timothy E.

AU - Stechern, André

AU - Behrens, Harald

AU - Whittington, Alan G.

N1 - Funding Information: We thank A. Sehlke (MU) and S. Wilke at Leibniz Universität Hannover (LUH) for help with IR and Fe redox measurements, and O. Dietrich at LUH for impeccable sample preparation. This research is supported by the National Science Foundation through grant EAR-0748411 (AGW). Calorimetry facilities at MU are supported by the National Science Foundation through EAR-1220051 and by NASA through award PGG-NNX12A044G (AGW). Additional support by the German DFG grant BE 1720/24-1,2 (HB), a DAAD travel grant, and an NSERC PGS-D fellowship (GR) are acknowledged. Comments by three anonymous reviewers, the Special Volume guest editors and Klaus Mezger helped improve this paper.

PY - 2015/12/15

Y1 - 2015/12/15

N2 - We determined the viscosity and heat capacity of a series of two basaltic liquids containing H2O, F, H2O + CO2, H2O + F, and H2O + CO2 + F. One was a natural calc-alkaline basalt from Fuego volcano, Guatemala, and the other was an Fe-free synthetic analog. The viscosity measurements were performed in the low-temperature, high-viscosity range (~109-1012 Pa s) just above the glass transition, where the kinetics of volatile exsolution are slow. Differential scanning calorimetry measurements were performed at atmospheric pressure from room temperature up to ~100 K above the glass transition. The water contents ranged from nominally anhydrous to 3 wt.% H2O, with F contents up to 2 wt.%, and CO2 contents up to 0.2 wt.%. Volatiles do not noticeably affect the heat capacity of glasses. The glass transition temperatures obtained from calorimetry and viscometry are in good agreement. Water has a strong viscosity-reducing effect on basaltic melts. F has a measurable viscosity-reducing effect in basaltic melts, but it is significantly smaller than that of water. The combined effects of H2O and F on viscosity appear to be additive on a wt.% basis. Both the effects of H2O and F on basaltic melts are smaller than those for more polymerized melts. Small quantities of CO2 do not measurably affect basaltic melt viscosity, at least in the presence of >1 wt.% water. Future viscosity models incorporating fluorine need to account for the compositional dependence of its effects on dry and hydrous melts.

AB - We determined the viscosity and heat capacity of a series of two basaltic liquids containing H2O, F, H2O + CO2, H2O + F, and H2O + CO2 + F. One was a natural calc-alkaline basalt from Fuego volcano, Guatemala, and the other was an Fe-free synthetic analog. The viscosity measurements were performed in the low-temperature, high-viscosity range (~109-1012 Pa s) just above the glass transition, where the kinetics of volatile exsolution are slow. Differential scanning calorimetry measurements were performed at atmospheric pressure from room temperature up to ~100 K above the glass transition. The water contents ranged from nominally anhydrous to 3 wt.% H2O, with F contents up to 2 wt.%, and CO2 contents up to 0.2 wt.%. Volatiles do not noticeably affect the heat capacity of glasses. The glass transition temperatures obtained from calorimetry and viscometry are in good agreement. Water has a strong viscosity-reducing effect on basaltic melts. F has a measurable viscosity-reducing effect in basaltic melts, but it is significantly smaller than that of water. The combined effects of H2O and F on viscosity appear to be additive on a wt.% basis. Both the effects of H2O and F on basaltic melts are smaller than those for more polymerized melts. Small quantities of CO2 do not measurably affect basaltic melt viscosity, at least in the presence of >1 wt.% water. Future viscosity models incorporating fluorine need to account for the compositional dependence of its effects on dry and hydrous melts.

KW - Basalt

KW - Carbon dioxide

KW - Fluorine

KW - Heat capacity

KW - Viscosity

KW - Water

UR - http://www.scopus.com/inward/record.url?scp=84958621772&partnerID=8YFLogxK

U2 - 10.1016/j.chemgeo.2014.07.015

DO - 10.1016/j.chemgeo.2014.07.015

M3 - Article

AN - SCOPUS:84958621772

VL - 418

SP - 51

EP - 65

JO - Chemical geology

JF - Chemical geology

SN - 0009-2541

ER -