Abstract
The structure of silicate melts in the system Na2O·4SiO2 saturated with reduced C-O-H volatile components and of coexisting silicate-saturated C-O-H solutions has been determined in a hydrothermal diamond anvil cell (HDAC) by using confocal microRaman and FTIR spectroscopy as structural probes. The experiments were conducted in-situ with the melt and fluid at high temperature (up to 800°C) and pressure (up to 1435MPa). Redox conditions in the HDAC were controlled with the reaction, Mo+H2O=MoO2+H2, which is slightly more reducing than the Fe+H2O=FeO+H2 buffer at 800°C and less.The dominant species in the fluid are CH4+H2O together with minor amounts of molecular H2 and an undersaturated hydrocarbon species. In coexisting melt, CH3 - groups linked to the silicate melt structure via Si-O-CH3 bonding may dominate and possibly coexists with molecular CH4. The abundance ratio of CH3 - groups in melts relative to CH4 in fluids increases from 0.01 to 0.07 between 500 and 800°C. Carbon-bearing species in melts were not detected at temperatures and pressures below 400°C and 730MPa, respectively. A schematic solution mechanism is, Si-O-Si+CH4Si-O-CH3+H-O-Si. This mechanism causes depolymerization of silicate melts. Solution of reduced (C-O-H) components will, therefore, affect melt properties in a manner resembling dissolved H2O.
| Original language | English |
|---|---|
| Pages (from-to) | 4577-4588 |
| Number of pages | 12 |
| Journal | Geochimica et Cosmochimica Acta |
| Volume | 74 |
| Issue number | 15 |
| DOIs | |
| Publication status | Published - Aug 2010 |
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ASJC Scopus subject areas
- Geochemistry and Petrology
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Speciation of reduced C-O-H volatiles in coexisting fluids and silicate melts determined in-situ to ∼1.4GPa and 800°C. / Mysen, Bjorn O.; Yamashita, Shigeru.
In: Geochimica et Cosmochimica Acta, Vol. 74, No. 15, 08.2010, p. 4577-4588.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Speciation of reduced C-O-H volatiles in coexisting fluids and silicate melts determined in-situ to ∼1.4GPa and 800°C
AU - Mysen, Bjorn O.
AU - Yamashita, Shigeru
PY - 2010/8
Y1 - 2010/8
N2 - The structure of silicate melts in the system Na2O·4SiO2 saturated with reduced C-O-H volatile components and of coexisting silicate-saturated C-O-H solutions has been determined in a hydrothermal diamond anvil cell (HDAC) by using confocal microRaman and FTIR spectroscopy as structural probes. The experiments were conducted in-situ with the melt and fluid at high temperature (up to 800°C) and pressure (up to 1435MPa). Redox conditions in the HDAC were controlled with the reaction, Mo+H2O=MoO2+H2, which is slightly more reducing than the Fe+H2O=FeO+H2 buffer at 800°C and less.The dominant species in the fluid are CH4+H2O together with minor amounts of molecular H2 and an undersaturated hydrocarbon species. In coexisting melt, CH3 - groups linked to the silicate melt structure via Si-O-CH3 bonding may dominate and possibly coexists with molecular CH4. The abundance ratio of CH3 - groups in melts relative to CH4 in fluids increases from 0.01 to 0.07 between 500 and 800°C. Carbon-bearing species in melts were not detected at temperatures and pressures below 400°C and 730MPa, respectively. A schematic solution mechanism is, Si-O-Si+CH4Si-O-CH3+H-O-Si. This mechanism causes depolymerization of silicate melts. Solution of reduced (C-O-H) components will, therefore, affect melt properties in a manner resembling dissolved H2O.
AB - The structure of silicate melts in the system Na2O·4SiO2 saturated with reduced C-O-H volatile components and of coexisting silicate-saturated C-O-H solutions has been determined in a hydrothermal diamond anvil cell (HDAC) by using confocal microRaman and FTIR spectroscopy as structural probes. The experiments were conducted in-situ with the melt and fluid at high temperature (up to 800°C) and pressure (up to 1435MPa). Redox conditions in the HDAC were controlled with the reaction, Mo+H2O=MoO2+H2, which is slightly more reducing than the Fe+H2O=FeO+H2 buffer at 800°C and less.The dominant species in the fluid are CH4+H2O together with minor amounts of molecular H2 and an undersaturated hydrocarbon species. In coexisting melt, CH3 - groups linked to the silicate melt structure via Si-O-CH3 bonding may dominate and possibly coexists with molecular CH4. The abundance ratio of CH3 - groups in melts relative to CH4 in fluids increases from 0.01 to 0.07 between 500 and 800°C. Carbon-bearing species in melts were not detected at temperatures and pressures below 400°C and 730MPa, respectively. A schematic solution mechanism is, Si-O-Si+CH4Si-O-CH3+H-O-Si. This mechanism causes depolymerization of silicate melts. Solution of reduced (C-O-H) components will, therefore, affect melt properties in a manner resembling dissolved H2O.
UR - http://www.scopus.com/inward/record.url?scp=77954216080&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=77954216080&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2010.05.004
DO - 10.1016/j.gca.2010.05.004
M3 - Article
AN - SCOPUS:77954216080
VL - 74
SP - 4577
EP - 4588
JO - Geochmica et Cosmochimica Acta
JF - Geochmica et Cosmochimica Acta
SN - 0016-7037
IS - 15
ER -