Thermobarometry Gone Astray

Essene, Eric J.

doi:10.1007/978-1-4419-0346-4_6

Cited by 8 publications

(4 citation statements)

References 195 publications

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“…Titania activity in metamorphic systems is primarily buffered by the oxide mineral assemblage (Ashley & Law, 2015) but is also influenced by the silicate mineral assemblage, pressure, and temperature (Essene, 2009;Ghent & Stout, 1984). Titania activity as a function of temperature and oxidation state for sample M48 is shown in Figure 14a.…”

Section: Ti-in-zircon Thermometrymentioning

confidence: 99%

Petrochronology of oxidized granulites from southern Peru

Yakymchuk

Rehm

Liao

et al. 2019

Journal Metamorphic Geology

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Sapphirine–quartz granulites from the Cocachacra region of the Arequipa Massif in southern Peru record early Neoproterozoic ultrahigh‐temperature metamorphism. Phase equilibrium modelling and zircon petrochronology are used to quantify timing and pressure–temperature (P–T) conditions of metamorphism. Modelling of three magnetite‐bearing sapphirine–quartz samples indicates peak temperatures of >950°C at ~0.7 GPa and a clockwise P–T evolution. Elevated concentrations of Al in orthopyroxene are also consistent with ultrahigh‐temperature conditions. Neoblastic zircon records ages of c. 1.0–0.9 Ga that are interpreted to record protracted ultrahigh‐temperature metamorphism. Th/U ratios of zircon of up to 100 reflect U‐depleted whole‐rock compositions. Concentrations of heavy rare earth elements in zircon do not show systematic trends with U–Pb age but do correlate with variable whole‐rock compositions. Very large positive Ce anomalies in zircon from two samples probably relate to strongly oxidizing conditions during neoblastic zircon crystallization. Low concentrations of Ti‐in‐zircon (<10 ppm) are interpreted to result from reduced titania activities due to the strongly oxidized nature of the granulites and the sequestration of titanium‐rich minerals away from the reaction volume. Whole‐rock compositions and oxidation state have a strong influence on the trace element composition of metamorphic zircon, which has implications for interpreting the geological significance of ages retrieved from zircon in oxidized metamorphic rocks.

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Section: Ti-in-zircon Thermometrymentioning

confidence: 99%

Petrochronology of oxidized granulites from southern Peru

Yakymchuk

Rehm

Liao

et al. 2019

Journal Metamorphic Geology

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“…Detailed comparison of the three types of thermometers has been presented in previous reviews (e.g. De Caritat et al, 1993;Essene, 2009;Inoue et al, 2009Inoue et al, , 2010Bourdelle & Cathelineau, 2015;Vidal et al, 2016) and will not be repeated here. Nevertheless, there are some points to be considered.…”

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confidence: 99%

Application of chlorite thermometry to estimation of formation temperature and redox conditions

Inoue

Inoué

Utada³

2018

Clay miner.

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Diverse applications of chlorite thermometry have been considered for better understanding the formation process in nature. Here, an approach which combined a semi-empirical thermometer (Inoue et al., 2009) with the method of Walshe (1986) was tested to estimate the redox conditions (log fO2) and the formation temperature, using the literature data from Niger, Rouez and St Martin and new data for chlorite which coexists with pink-coloured epidote in the Noboribetsu geothermal field. The log fO2 predicted for the former data sets were compatible with those estimated by Vidal et al. (2016), suggesting that the present approach is valid for quantifying the variations in log fO2. The Noboribetsu chlorites have lower Fe/(Fe + Mn + Mg) and greater Fe3+/ΣFe ratios than those observed in adjacent propylite rocks. The peculiar mineral assemblage and chemical composition are attributed to the formation under higher fO2 conditions and possibly low Fe concentration in the alteration fluids.

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“…Although these approaches are still used widely for low-grade rocks, the lack of theoretical backgrounds and the reliability of the temperatures estimated have been criticized (e.g. de Caritat et al, 1993;Essene & Peacor, 1995;Essene, 2009;Bourdelle et al, 2013a), and their application to metamorphic rocks remains questionable (Vidal et al, 2006). The thermodynamic models of chlorite proposed by several authors (e.g.…”

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Deciphering temperature, pressure and oxygen-activity conditions of chlorite formation

et al. 2016

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A B S T R AC T :The advantages and limits of empirical, semi-empirical and thermodynamic methods devoted to the estimation of chlorite-formation temperature are discussed briefly. The results of semiempirical and thermodynamic approaches with different assumptions regarding the redox state of iron in chlorite are compared for a large set of natural data covering a range of pressure conditions from a few hundred bars to 18 kbar and temperature from 100 to 500°C. The T-XFe 3+ evolution estimated using the thermodynamic approach of Vidal et al. (2005) shows a systematic increase in XFe 3+ with decreasing temperature, which is compatible with the decrease in aO 2 buffered by magnetite-or hematite-chlorite equilibrium. This trend as well as the observed increase in vacancies in chlorite with decreasing temperature is interpreted as the incorporation of Fe 3+ -sudoite. The standard-state properties of this endmember have been derived to reproduce the observed T-aO 2 -XFe 3+ evolutions. It can be used to estimate T-aO 2 -XFe 3 values with a Chl-Qtz-H 2 O multi-equilibrium approach. When combining our results with those of other studies published recently, it appears that thermodynamic approaches and mapping techniques developed for metamorphic rocks can be used to discuss the conditions of formation of very low-grade rocks where kinetics is much more sluggish than in metamorphic rocks. This requires use of appropriate analytical tools and techniques with a spatial resolution of a few hundred nanometres.KEYWORDS: chlorite, oxidation state, thermodynamics.In the 1980s and 1990s, several empirical calibrations were proposed to link the tetrahedral Al or vacancy content of chlorite with temperature (Cathelineau & Nieva, 1985;Kranidiotis & MacLean, 1987;Cathelineau, 1988;Hillier & Velde, 1991;Jowett, 1991;Zang & Fyfe, 1995). Although these approaches are still used widely for low-grade rocks, the lack of theoretical backgrounds and the reliability of the temperatures estimated have been criticized (e.g. de Caritat et al., 1993;Essene & Peacor, 1995;Essene, 2009;Bourdelle et al., 2013a), and their application to metamorphic rocks remains questionable . The thermodynamic models of chlorite proposed by several authors (e.g. Vidal et al., 2001Vidal et al., , 2005Vidal et al., , 2006Walshe, 1986;Lanari et al., 2014) offer an alternative to empirical approaches. Vidal et al. (2006) and Lanari et al. (2014) proposed thermodynamic models constrained from high-temperature experiments and natural data from low-to medium-grade metamorphic rocks. They showed that these models could be used to constrain the temperature of chlorite formation in quartz-bearing rocks over a large range of temperature conditions. Vidal et al. (2006) claimed that the proportion of Fe 3+ in chlorite could be estimated from a criterion based on the convergence of two Chl-Qtz-H 2 O equilibria that are compositionally dependant but assumed to be thermodynamically independent. The same authors and also de Andrade et al. (2011), Ganne et al. (2012, Lanari et al. (...

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Thermobarometry Gone Astray

Cited by 8 publications

References 195 publications

Petrochronology of oxidized granulites from southern Peru

Petrochronology of oxidized granulites from southern Peru

Application of chlorite thermometry to estimation of formation temperature and redox conditions

Deciphering temperature, pressure and oxygen-activity conditions of chlorite formation

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