Ion microprobe survey of the grain-scale oxygen isotope geochemistry of minerals in metamorphic rocks

Ferry, John M.; Kitajima, Kouki; Strickland, Ariel; Valley, John W.

doi:10.1016/j.gca.2014.08.021

Cited by 23 publications

(14 citation statements)

References 72 publications

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“…Crystal-scale oxygen isotope analysis is now routinely carried out using the SIMS technique2345. For example, the oxygen isotopic composition of zircon is a robust source of information on the crystallisation environment346 and, as zircon also lends itself to U-Pb dating, it can help to identify and place constraints on the timing of geological events (e.g., refs 6 and 7).…”

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confidence: 99%

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

Budd

Troll

Deegan

et al. 2017

Sci Rep

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Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ18O values. Overall, Toba quartz crystals exhibit comparatively high δ18O values, up to 10.2‰, due to magma residence within, and assimilation of, local granite basement. However, some 40% of the analysed quartz crystals display a decrease in δ18O values in outermost growth zones compared to their cores, with values as low as 6.7‰ (maximum ∆core−rim = 1.8‰). These lower values are consistent with the limited zircon record available for Toba, and the crystallisation history of Toba quartz traces an influx of a low-δ18O component into the magma reservoir just prior to eruption. Here we argue that this late-stage low-δ18O component is derived from hydrothermally-altered roof material. Our study demonstrates that quartz isotope stratigraphy can resolve magmatic events that may remain undetected by whole-rock or zircon isotope studies, and that assimilation of altered roof material may represent a viable eruption trigger in large Toba-style magmatic systems.

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confidence: 99%

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

Budd

Troll

Deegan

et al. 2017

Sci Rep

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“…56 Unexpectedly, the presence of barium presented a significant role in the K-feldspar model. The high capacity of barium to interact with oxygen would support the hypothesis that small percentages of barium (0-2%) could have a perceptible effect on IMF.…”

Section: Compositional Variablesmentioning

confidence: 95%

Predicting instrumental mass fractionation (IMF) of stable isotope SIMS analyses by response surface methodology (RSM) [Dataset]

Duocastella¹,

Rossell²,

Alsina³

et al. 2017

UPCommons. Portal Del Coneixement Obert De La UPC

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Instrumental mass fractionation (IMF) of isotopic SIMS analyses (Cameca 1280HR, CRPG Nancy) was predicted by response surface methodology (RSM) for 18 O/ 16O determinations of plagioclase, K-feldspar, and quartz. The three predictive response surface models combined instrumental and compositional inputs. The instrumental parameters were: (i) X and Y stage position, (ii) the values of LT1DefX and LT1DefY electrostatic deflectors, (iii) chamber pressure and, (iv) primary-ion beam intensity. The compositional inputs included: (i) anorthite content (An%) for the plagioclase model and, (ii) orthoclase (Or%) and barium (BaO%) contents for the K-feldspar model. The three models reached high predictive powers.

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“…2) over a pressure range of 1.3-2.6 GPa, corresponding to a depth of ∼ 45 to ∼ 85 km to encompass the conditions of interest for the investigated processes. The modelled temperatures range from a minimum of 350 • C to a maximum of 700 • C. The lower limit was chosen to take into account the large uncertainties in the thermodynamic databases for many common low-T metamorphic minerals that lead to unsatisfactory models for phase equilibria and mineral parageneses for low-grade rocks (Frey et al, 1991;Vidal et al, 2016). The upper limit is fixed by the wet solidus of metasediments -the present model strictly applies to subsolidus conditions.…”

Section: Model Geometrymentioning

confidence: 99%

Tracing fluid transfers in subduction zones: an integrated thermodynamic and <i>δ</i><sup>18</sup>O fractionation modelling approach

et al. 2020

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Abstract. Oxygen isotope geochemistry is a powerful tool for investigating rocks that interacted with fluids, to assess fluid sources and quantify the conditions of fluid–rock interaction. We present an integrated modelling approach and the computer program PTLoop that combine thermodynamic and oxygen isotope fractionation modelling for multi-rock open systems. The strategy involves a robust petrological model performing on-the-fly Gibbs energy minimizations coupled to an oxygen fractionation model for a given chemical and isotopic bulk rock composition; both models are based on internally consistent databases. This approach is applied to subduction zone metamorphism to predict the possible range of δ18O values for stable phases and aqueous fluids at various pressure (P) and temperature (T) conditions in the subducting slab. The modelled system is composed of a mafic oceanic crust with a sedimentary cover of known initial chemical composition and bulk δ18O. The evolution of mineral assemblages and δ18O values of each phase is calculated along a defined P–T path for two typical compositions of basalts and sediments. In a closed system, the dehydration reactions, fluid loss and mineral fractionation produce minor to negligible variations (i.e. within 1 ‰) in the bulk δ18O values of the rocks, which are likely to remain representative of the protolith composition. In an open system, fluid–rock interaction may occur (1) in the metasediment, as a consequence of infiltration of the fluid liberated by dehydration reactions occurring in the metamorphosed mafic oceanic crust, and (2) in the metabasalt, as a consequence of infiltration of an external fluid originated by dehydration of underlying serpentinites. In each rock type, the interaction with external fluids may lead to shifts in δ18O up to 1 order of magnitude larger than those calculated for closed systems. Such variations can be detected by analysing in situ oxygen isotopes in key metamorphic minerals such as garnet, white mica and quartz. The simulations show that when the water released by the slab infiltrates the forearc mantle wedge, it can cause extensive serpentinization within fractions of 1 Myr and significant oxygen isotope variation at the interface. The approach presented here opens new perspectives for tracking fluid pathways in subduction zones, to distinguish porous from channelled fluid flows, and to determine the P–T conditions and the extent of fluid–rock interaction.

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Ion microprobe survey of the grain-scale oxygen isotope geochemistry of minerals in metamorphic rocks

Cited by 23 publications

References 72 publications

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

Predicting instrumental mass fractionation (IMF) of stable isotope SIMS analyses by response surface methodology (RSM) [Dataset]

Tracing fluid transfers in subduction zones: an integrated thermodynamic and <i>δ</i><sup>18</sup>O fractionation modelling approach

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Ion microprobe survey of the grain-scale oxygen isotope geochemistry of minerals in metamorphic rocks

Cited by 23 publications

References 72 publications

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz

Predicting instrumental mass fractionation (IMF) of stable isotope SIMS analyses by response surface methodology (RSM) [Dataset]

Tracing fluid transfers in subduction zones: an integrated thermodynamic and &lt;i&gt;δ&lt;/i&gt;&lt;sup&gt;18&lt;/sup&gt;O fractionation modelling approach

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Tracing fluid transfers in subduction zones: an integrated thermodynamic and <i>δ</i><sup>18</sup>O fractionation modelling approach