Oxygen isotope thermometry, speedometry, and hygrometry: Apparent equilibrium temperature versus closure temperature

Huaiwei Ni

doi:10.1002/2014gc005574

The relationship between apparent equilibrium temperature and closure temperature with application to oxygen isotope geospeedometry

Chinese Journal of Geochemistry ◽

10.1007/s11631-014-0667-1 ◽

2014 ◽

Vol 33 (2) ◽

pp. 125-130 ◽

Cited By ~ 2

Author(s):

Huaiwei Ni

Keyword(s):

Oxygen Isotope ◽

Equilibrium Temperature ◽

Closure Temperature ◽

The Relationship ◽

Apparent Equilibrium

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Ore Genesis of the Takatori Tungsten–Quartz Vein Deposit, Japan: Chemical and Isotopic Evidence

Minerals ◽

10.3390/min11070765 ◽

2021 ◽

Vol 11 (7) ◽

pp. 765

Author(s):

Yuichi Morishita ◽

Yoshiro Nishio

Keyword(s):

Oxygen Isotope ◽

Early Stage ◽

Isotope Ratios ◽

Equilibrium Temperature ◽

Granitic Rocks ◽

Granitic Magma ◽

Lithium Isotope ◽

Vein Deposit ◽

Pressure Independent ◽

Isotope Equilibrium

The Takatori hypothermal tin–tungsten vein deposit is composed of wolframite-bearing quartz veins with minor cassiterite, chalcopyrite, pyrite, and lithium-bearing muscovite and sericite. Several wolframite rims show replacement textures, which are assumed to form by iron replacement with manganese postdating the wolframite precipitation. Lithium isotope ratios (δ7Li) of Li-bearing muscovite from the Takatori veins range from −3.1‰ to −2.1‰, and such Li-bearing muscovites are proven to occur at the early stage of mineralization. Fine-grained sericite with lower Li content shows relatively higher δ7Li values, and might have precipitated after the main ore forming event. The maximum oxygen isotope equilibrium temperature of quartz–muscovite pairs is 460 °C, and it is inferred that the fluids might be in equilibrium with ilmenite series granitic rocks. Oxygen isotope ratios (δ18O) of the Takatori ore-forming fluid range from +10‰ to +8‰. The δ18O values of the fluid decreased with decreasing temperature probably because the fluid was mixed with surrounding pore water and meteoric water. The formation pressure for the Takatori deposit is calculated to be 160 MPa on the basis of the difference between the pressure-independent oxygen isotope equilibrium temperature and pressure-dependent homogenization fluid inclusions temperature. The ore-formation depth is calculated to be around 6 km. These lines of evidence suggest that a granitic magma beneath the deposit played a crucial role in the Takatori deposit formation.

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Behavior of magmatic components in fumarolic gases related to the 2018 phreatic eruption at Ebinokogen Ioyama volcano, Kirishima Volcanic Group, Kyushu, Japan

Earth Planets and Space ◽

10.1186/s40623-021-01405-4 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Takeshi Ohba ◽

Muga Yaguchi ◽

Urumu Tsunogai ◽

Masanori Ito ◽

Ryo Shingubara

Keyword(s):

Hot Spring ◽

Equilibrium Temperature ◽

Phreatic Eruption ◽

Vapor Flux ◽

High Enthalpy ◽

Liquid Phases ◽

Direct Sampling ◽

Fumarolic Gases ◽

Apparent Equilibrium ◽

Fumarolic Gas

AbstractDirect sampling and analysis of fumarolic gas was conducted at Ebinokogen Ioyama volcano, Japan, between December 2015 and July 2020. Notable changes in the chemical composition of gases related to volcanic activity included a sharp increase in SO2 and H2 concentrations in May 2017 and March 2018. The analyses in March 2018 immediately preceded the April 2018 eruption at Ioyama volcano. The isotopic ratios of H2O in fumarolic gas revealed the process of formation. Up to 49% high-enthalpy magmatic vapor mixed with 51% of cold local meteoric water to generate coexisting vapor and liquid phases at 100–160 °C. Portions of the vapor and liquid phases were discharged as fumarolic gases and hot spring water, respectively. The CO2/SO2 ratio of the fumarolic gas was higher than that estimated for magmatic vapor due to SO2 hydrolysis during the formation of the vapor phase. When the flux of the magmatic vapor was high, effects of hydrolysis were small resulting in low CO2/SO2 ratios in fumarolic gases. The high apparent equilibrium temperature defined for reactions involving SO2, H2S, H2 and H2O, together with low CO2/SO2 and H2S /SO2 ratios were regarded to be precursor signals to the phreatic eruption at Ioyama volcano. The apparent equilibrium temperature increased rapidly in May 2017 and March 2018 suggesting an increased flux of magmatic vapor. Between September 2017 and January 2018, the apparent equilibrium temperature was low suggesting the suppression of magmatic vapor flux. During this period, magmatic eruptions took place at Shinmoedake volcano 5 km away from Ioyama volcano. We conclude that magma sealing and transport to Shinmoedake volcano occurred simultaneously in the magma chamber beneath Ioyama volcano.

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