Details
| Originalsprache | Englisch |
|---|---|
| Seiten (von - bis) | 54-62 |
| Seitenumfang | 9 |
| Fachzeitschrift | Earth and Planetary Science Letters |
| Jahrgang | 433 |
| Frühes Online-Datum | 3 Nov. 2015 |
| Publikationsstatus | Veröffentlicht - 1 Jan. 2016 |
Abstract
Electrical conductivity of rhyolitic melts, combined with magnetotelluric data, can provide important constraints for the physicochemical conditions of active felsic magma reservoirs. Previous experimental investigations are limited to low H2O concentration (<3 wt% H2O) and low pressure (<0.2 GPa for hydrous melts). We here report new results from electrical conductivity measurements of peralkaline rhyolitic melts with 4.7 wt% Na2O and 0.1-7.9 wt% H2O at 868-1665 K and 0.5-1.0 GPa in piston cylinder apparatuses using sweeping-frequency impedance analyses. Logarithmic electrical conductivity (σ) is found to correlate linearly with H2O concentration and reciprocal temperature, and the influence of H2O has been considerably underestimated by previous work. The negative pressure effect on electrical conductivity appears to attenuate with increasing H2O concentration. Based on the new data, we develop the following electrical conductivity model for peralkaline rhyolitic melts under conditions up to 1665 K, 1.0 GPa, and 8 wt% H2O:logσ=2.983-0.0732w-3528-233.8w+(763-7.5w2)PT where σ is electrical conductivity in S/m, T is temperature in K, w is H2O concentration in wt%, and P is pressure in GPa. According to the Nernst-Einstein relation, this conductivity model can also be applied to metaluminous and peraluminous rhyolitic melts by scaling down according to the diffusivity and concentration of Na+ (the primary charge carrier). With the new model, we suggest that the highest electrical anomaly beneath the Tianchi volcano corresponds to a melt fraction of ~9% if the melt contains 5 wt% H2O, or to a melt fraction of ~32% for 2 wt% H2O. Similarly, the magma reservoir beneath the Taupo volcanic zone, New Zealand is inferred to contain a fully molten rhyolite with 7.5 wt% H2O or 36% water-saturated melt with 10 wt% H2O.
ASJC Scopus Sachgebiete
- Erdkunde und Planetologie (insg.)
- Geophysik
- Erdkunde und Planetologie (insg.)
- Geochemie und Petrologie
- Erdkunde und Planetologie (insg.)
- Astronomie und Planetologie
- Erdkunde und Planetologie (insg.)
- Erdkunde und Planetologie (sonstige)
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in: Earth and Planetary Science Letters, Jahrgang 433, 01.01.2016, S. 54-62.
Publikation: Beitrag in Fachzeitschrift › Artikel › Forschung › Peer-Review
}
TY - JOUR
T1 - Probing the status of felsic magma reservoirs
T2 - Constraints from the P-T-H2O dependences of electrical conductivity of rhyolitic melt
AU - Guo, Xuan
AU - Zhang, Li
AU - Behrens, Harald
AU - Ni, Huaiwei
N1 - Funding Information: We thank Andreas Audetat for providing the obsidian and carrying out the LA-ICP-MS analyses, Hans Keppler for providing access to experimental facilities at BGI, and Hubert Schulze, Sven Linhardt, Heinz Fischer and Haihao Guo for sample preparation and technical assistance. Discussion with Lingsen Zeng, Yongtai Yang, Peng Gao and Yi-Xiang Chen was beneficial. Insightful reviews from Fabrice Gaillard and an anonymous reviewer improved the manuscript. This study was supported by the National Natural Science Foundation of China ( 41322015 ), China Postdoctoral Science Foundation ( 2013M541833 ), the 111 Project of the Ministry of Education of China , the Fundamental Research Funds for the Central Universities of China , and the Recruitment Program of Global Experts (Thousand Talents) of China .
PY - 2016/1/1
Y1 - 2016/1/1
N2 - Electrical conductivity of rhyolitic melts, combined with magnetotelluric data, can provide important constraints for the physicochemical conditions of active felsic magma reservoirs. Previous experimental investigations are limited to low H2O concentration (<3 wt% H2O) and low pressure (<0.2 GPa for hydrous melts). We here report new results from electrical conductivity measurements of peralkaline rhyolitic melts with 4.7 wt% Na2O and 0.1-7.9 wt% H2O at 868-1665 K and 0.5-1.0 GPa in piston cylinder apparatuses using sweeping-frequency impedance analyses. Logarithmic electrical conductivity (σ) is found to correlate linearly with H2O concentration and reciprocal temperature, and the influence of H2O has been considerably underestimated by previous work. The negative pressure effect on electrical conductivity appears to attenuate with increasing H2O concentration. Based on the new data, we develop the following electrical conductivity model for peralkaline rhyolitic melts under conditions up to 1665 K, 1.0 GPa, and 8 wt% H2O:logσ=2.983-0.0732w-3528-233.8w+(763-7.5w2)PT where σ is electrical conductivity in S/m, T is temperature in K, w is H2O concentration in wt%, and P is pressure in GPa. According to the Nernst-Einstein relation, this conductivity model can also be applied to metaluminous and peraluminous rhyolitic melts by scaling down according to the diffusivity and concentration of Na+ (the primary charge carrier). With the new model, we suggest that the highest electrical anomaly beneath the Tianchi volcano corresponds to a melt fraction of ~9% if the melt contains 5 wt% H2O, or to a melt fraction of ~32% for 2 wt% H2O. Similarly, the magma reservoir beneath the Taupo volcanic zone, New Zealand is inferred to contain a fully molten rhyolite with 7.5 wt% H2O or 36% water-saturated melt with 10 wt% H2O.
AB - Electrical conductivity of rhyolitic melts, combined with magnetotelluric data, can provide important constraints for the physicochemical conditions of active felsic magma reservoirs. Previous experimental investigations are limited to low H2O concentration (<3 wt% H2O) and low pressure (<0.2 GPa for hydrous melts). We here report new results from electrical conductivity measurements of peralkaline rhyolitic melts with 4.7 wt% Na2O and 0.1-7.9 wt% H2O at 868-1665 K and 0.5-1.0 GPa in piston cylinder apparatuses using sweeping-frequency impedance analyses. Logarithmic electrical conductivity (σ) is found to correlate linearly with H2O concentration and reciprocal temperature, and the influence of H2O has been considerably underestimated by previous work. The negative pressure effect on electrical conductivity appears to attenuate with increasing H2O concentration. Based on the new data, we develop the following electrical conductivity model for peralkaline rhyolitic melts under conditions up to 1665 K, 1.0 GPa, and 8 wt% H2O:logσ=2.983-0.0732w-3528-233.8w+(763-7.5w2)PT where σ is electrical conductivity in S/m, T is temperature in K, w is H2O concentration in wt%, and P is pressure in GPa. According to the Nernst-Einstein relation, this conductivity model can also be applied to metaluminous and peraluminous rhyolitic melts by scaling down according to the diffusivity and concentration of Na+ (the primary charge carrier). With the new model, we suggest that the highest electrical anomaly beneath the Tianchi volcano corresponds to a melt fraction of ~9% if the melt contains 5 wt% H2O, or to a melt fraction of ~32% for 2 wt% H2O. Similarly, the magma reservoir beneath the Taupo volcanic zone, New Zealand is inferred to contain a fully molten rhyolite with 7.5 wt% H2O or 36% water-saturated melt with 10 wt% H2O.
KW - Electrical conductivity
KW - HO concentration
KW - Magma reservoirs
KW - Melt fraction
KW - Rhyolitic melt
UR - http://www.scopus.com/inward/record.url?scp=84948649161&partnerID=8YFLogxK
U2 - 10.1016/j.epsl.2015.10.036
DO - 10.1016/j.epsl.2015.10.036
M3 - Article
AN - SCOPUS:84948649161
VL - 433
SP - 54
EP - 62
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
SN - 0012-821X
ER -