FeTiMM – A new oxybarometer for mafic to felsic magmas

Robert, Aymeric; Audétat, Andreas

doi:10.7185/geochemlet.1740

Cited by 36 publications

(25 citation statements)

References 16 publications

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“…In addition to the Fe 3+ /ΣFe ratio, we applied other methods to estimate the redox conditions for the same group of samples. The oxybarometer method of Arató and Audétat (2017) estimations are close to those from previous studies (Fig. 9b), some of which applied to the products of the same eruptions (~NNO to NNO+2; e.g., Armienti et al, 1994;Kahl et al, 2011;Kamenetsky and Clocchiatti, 1996;Métrich and Clocchiatti, 1996;Métrich and Rutherford, 1998;Métrich et al, 2009;Morizet et al, 2017;Trigila et al, 1990).…”

Section: Redox Conditions Of Etnean Magmassupporting

confidence: 80%

“…Comparison of fO 2 estimates from XANES data to those from the oxybarometer methods oxybarometer methods of Ballhaus et al (1990Ballhaus et al ( , 1991 and Arató and Audétat (2017). oxybarometer methods of Arató and Audétat (2017) and Ballhaus et al (1990Ballhaus et al ( , 1991. Also…”

Section: Discussionmentioning

confidence: 99%

“…http://www.petrology.oupjournals.org/ (Métrich and Clocchiatti, 1996;Métrich et al, 2009;Morizet et al, 2017), experimental phase equilibria (Armienti et al, 1994;Métrich and Rutherford, 1998;Trigila et al, 1991), olivine-spinel equilibria (Kahl et al, 2011;Kamenetsky and Clocchiatti, 1996). c) Comparison of fO2 estimates from XANES data to those from the oxybarometer methods oxybarometer methods of Ballhaus et al (1990Ballhaus et al ( , 1991 and Arató and Audétat (2017).…”

Section: Discussionmentioning

confidence: 99%

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Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing

Gennaro

Paonita

Iacono-Marziano

et al. 2020

Journal of Petrology

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Sulphur behaviour and variations in redox conditions during magma differentiation and degassing in Mt. Etna (Italy) volcanic system have been explored by integrating the study of olivine-hosted melt inclusions (MIs) with an experimental survey of sulphur solubility in hydrous basaltic magmas. Sulphur solubility experiments were performed at conditions relevant to the Etnean plumbing system (1200 °C, 200 MPa and oxygen fugacity between NNO + 0.2 and NNO + 1.7, with NNO being the Nickel-Nickel Oxide buffer), and their results confirm the important control of oxygen fugacity (fO2) on S abundance in mafic magmas and on S partitioning between fluid and melt phases (DSfluid/melt). The observed DSfluid/melt value increases from 51 ± 4 to 146 ± 6 when fO2 decreases from NNO + 1.7 ± 0.5 to NNO + 0.3. Based on the calculated DSfluid/melt and a careful selection of previously published data, an empirical model is proposed for basaltic magmas in order to predict the variation of DSfluid/melt values upon variations in P (25–300 MPa), T (1030–1200 °C) and fO2 (between NNO-0.8 and NNO + 2.4). Olivine-hosted melt inclusions (Fo89-91) from tephra of the prehistoric (4 ka BP) sub-plinian picritic eruption, named FS (“Fall Stratified”), have been investigated for their major element compositions, volatile contents and iron speciation (expressed as Fe3+/ƩFe ratio). These primitive MIs present S content from 235 ± 77 to 3445 ± 168 ppm, while oxygen fugacity values, estimated from Fe3+/ƩFe ratios, range from NNO + 0.7 ± 0.2 to NNO + 1.6 ± 0.2. Iron speciation has also been investigated in more evolved and volatile-poorer Etnean MIs. The only primitive melt inclusion from Mt. Spagnolo eruption (4–15 ka BP) presents a S content of 1515 ± 49 ppm and an estimated fO2 of NNO + 1.4 ± 0.1. The more evolved MIs (from 2002/2003, 2006, 2008/2009 and 2013 eruptions) have S content lower than 500 ppm, and their Fe3+/ΣFe ratios result in fO2 between NNO-0.9 ± 0.1 and NNO + 0.4 ± 0.1. Redox conditions and S behaviour in Etnean magmas during degassing and fractional crystallization were modelled coupling MELTS code with our empirical DSfluid/melt model. Starting from a FS-type magma composition and upon decrease of T and P, fractional crystallization of olivine, clinopyroxene, spinel and plagioclase causes a significant fO2 decrease. The fO2 reduction, in turn, causes a decrease in sulphur solubility and an increase in DSfluid/melt, promoting S exsolution during magma ascent, which further enhances the reduction of fO2. For the evolved melt inclusions of 2002–2013 eruptions, magma differentiation may therefore have played a crucial role in decreasing redox conditions and favouring efficient S degassing. Differently, during the unusual FS eruption, only limited melt evolution is observed and S exsolution seems to have been triggered by a major pressure decrease accompanied by H2O and CO2 exsolution during fast magmatic ascent.

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Section: Redox Conditions Of Etnean Magmassupporting

confidence: 80%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing

Gennaro

Paonita

Iacono-Marziano

et al. 2020

Journal of Petrology

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“…The oxidation state of magmas was constrained by the FeTiMM magnetite-liquid oxybarometer (Arató and Audétat 2017). The magnetite composition was obtained from LA-ICP-MS analyses of entire, unexposed magnetite inclusions to circumvent re-equilibration and exsolution effects during cooling (Table S6), and the composition of the liquid was constrained from melt inclusion and wholerock data.…”

Section: Thermobarometrymentioning

confidence: 99%

Tectono-magmatic controls on decratonic gold deposits

Chang

Audétat

2021

Contrib Mineral Petrol

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Magmatic-hydrothermal gold–copper deposits in post-subduction settings represent essential targets for mineral exploration, but controls on their formation remain controversial. The early Cretaceous lode Au districts that formed during lithosphere destruction of the North China Craton provide an ideal opportunity to better understand the key tectono-magmatic factors responsible for the genesis of Au-rich deposits in post-subduction settings. Here, we present a LA-ICP-MS study of silicate melt inclusions and sulfide inclusions from ore-related mafic to intermediate rocks in the central Taihangshan Au district in the interior of the North China Craton to constrain the content and evolution of magmatic ore metals ± volatiles. The results, combined with numerical modeling, suggest that the ore-related magmas contained only a few ng/g Au, which is similar to the Au content of non-mineralization-related mafic to intermediate magmas worldwide. The low Au content of the lode Au-related magmas suggest that large volumes of magmas had to accumulate in the middle to lower crust through trans-lithospheric fault systems to produce the lode Au deposits. It is further suggested that the lode Au-related magmas were alkali-rich, hydrous, oxidized and relatively rich in sulfur and chlorine (mafic melt inclusions contain 0.14‒0.24 wt% S and 0.1‒0.2 wt% Cl). These properties are considered critical for the generation of auriferous ore fluids. By comparing the tectono-magmatic setting of the giant Jiaodong Au province (~ 4000 t Au) with the central Taihangshan district (~ 150 t Au), we propose that the much larger total Au tonnage of the Jiaodong district results from the accumulation of a much larger volume of ore-forming magmas at deep crustal levels, induced by a stronger degree of lithosphere modification. In addition, given that the composition of lode Au-related magmas is similar to that of porphyry Cu–Au-related magmas, the lack of giant, early Cretaceous porphyry Cu–Au deposits in the North China Craton suggests that strong extensional settings favor the formation of lode Au deposits instead of porphyry Cu–Au deposits. The present study, therefore, has general implications for the genesis of Au-rich deposits in strongly extensional settings.

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“…Because of the different coordination numbers of Ti in Fe-Ti oxides (sixfold) and silicate melts (four-, five-, and sixfold depending on the melt composition) (12), Fe-Ti oxides preferentially incorporate light Ti isotopes such that fractional crystallization of Fe-Ti oxides produces isotopically heavy residual melts (10,11,(13)(14)(15). At Fe-Ti oxide saturation, Fe-Ti oxide crystallization is promoted by the decreasing solubility of total FeO (FeOtot) due to a change in either melt composition or oxygen fugacity (16)(17)(18). In terms of melt composition, cooling leads to crystallization of olivine or pyroxene, thereby lowering the Mg# and the FeOtot contents at Fe-Ti oxide saturation in silicate melts.…”

Section: Introductionmentioning

confidence: 99%

Early oxidation of the martian crust triggered by impacts

et al. 2020

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Despite the abundant geomorphological evidence for surface liquid water on Mars during the Noachian epoch (>3.7 billion years ago), attaining a warm climate to sustain liquid water on Mars at the period of the faint young Sun is a long-standing question. Here, we show that melts of ancient mafic clasts from a martian regolith meteorite, NWA 7533, experienced substantial Fe-Ti oxide fractionation. This implies early, impact-induced, oxidation events that increased by five to six orders of magnitude the oxygen fugacity of impact melts from remelting of the crust. Oxygen isotopic compositions of sequentially crystallized phases from the clasts show that progressive oxidation was due to interaction with an 17O-rich water reservoir. Such an early oxidation of the crust by impacts in the presence of water may have supplied greenhouse gas H2 that caused an increase in surface temperature in a CO2-thick atmosphere.

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FeTiMM – A new oxybarometer for mafic to felsic magmas

Cited by 36 publications

References 16 publications

Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing

Sulphur behaviour and redox conditions in etnean magmas during magma differentiation and degassing

Tectono-magmatic controls on decratonic gold deposits

Early oxidation of the martian crust triggered by impacts

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