Zircon saturation re-revisited

Boehnke, P.; Watson, E. Bruce; Trail, Dustin; Harrison, T. Mark; Schmitt, Axel K.

doi:10.1016/j.chemgeo.2013.05.028

Cited by 900 publications

(468 citation statements)

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“…The large size of the crystals compared to the MI, and the low solubility of these minerals in granitic melts (e.g. Watson and Harrison 1983;Montel 1993;Acosta-Vigil et al 2003;Stepanov et al 2012;Boehnke et al 2013), indicates that they are solid inclusions (i.e. were already present during the entrapment of the MI) and hence are not expected to dissolve into the melt during the experiments (Table 1).…”

Section: Microstructures Of Remelted Nanogranitoidsmentioning

confidence: 99%

The composition of nanogranitoids in migmatites overlying the Ronda peridotites (Betic Cordillera, S Spain): the anatectic history of a polymetamorphic basement

Acosta-Vigil

Barich

Bartoli

et al. 2016

Contrib Mineral Petrol

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The study of the composition of primary melts during anatexis of high-pressure granulitic migmatites is relevant to understand the generation and differentiation of continental crust.Peritectic minerals in migmatites can trap dropless of melt that forms via incongruent melting reactions during crustal anatexis. These melt inclusions commonly crystallize and form nanogranitoids upon slow cooling of the anatectic terrane. To obtain the primary compositions of crustal melts recorded in these nanogranitoids, including volatile concentrations and information on fluid regimes, they must be remelted and rehomogenize before analysis. A new occurrence of nanogranitoids was recently reported in garnets of mylonitic metapelitic gneisses (former high pressure granulitic migmatites) at the bottom of the prograde metamorphic sequence of Jubrique, located on top of the Ronda peridotite slab (Betic Cordillera, S Spain). Nanogranitoids within separated chips of cores and rims of large garnets from these former migmatites were remelted at 15 kbar and 850, 825 or 800 ºC and dry (without added H 2 O), during 24 hours, using a piston cylinder apparatus. Although all experiments show glass (former melt) within melt inclusions, the extent of rehomogenization depends on the experimental temperature. Experiments at 850-825 ºC show abundant disequilibrium microstructures, whereas those at 800 ºC show a relatively high proportion of rehomogenized nanogranitoids, indicating that anatexis and entrapment of melt inclusions in these rocks was likely close to 800 ºC. Electron microprobe and NanoSIMS analyses show that experimental glasses are leucogranitoid and peraluminous, though define two distinct compositional groups. Type I corresponds to K-rich, Ca-and H 2 O-poor leucogranitic melts, whereas type II represents K-poor, Ca-and H 2 O-rich granodioritic to tonalitic melts. Type I and II melt inclusions are found in most cases at the cores and rims of large garnets, respectively. We tentatively suggest that these former migmatites underwent two melting events under contrasting fluid regimes, possibly during two different orogenic periods. This 3 study demonstrates the strong potential of melt inclusions studies in migmatites and granulites in order to unravel their anatectic history, particularly in strongly deformed rocks where most of the classical anatectic microstructures have been erased during deformation.

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Section: Microstructures Of Remelted Nanogranitoidsmentioning

confidence: 99%

The composition of nanogranitoids in migmatites overlying the Ronda peridotites (Betic Cordillera, S Spain): the anatectic history of a polymetamorphic basement

Acosta-Vigil

Barich

Bartoli

et al. 2016

Contrib Mineral Petrol

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“…We note that zircon crystals from some cogenetic enclaves display correlated spikes in Ti-in-zircon temperature and Eu/Eu* (e.g., Gran 1.1, 1.4c, or 1.4d), whereas others do not (e.g., SLJL52; Fig. 3A), likely because zircon stability is a function of zirconium abundance [Zr], melt chemistry, and temperature (27,28), and some cogenetic enclaves may not have saturated zircon at a sufficiently high temperature to record the spike. Indeed, we find a correlation between the magnitude of the temperature spike and the enclave [Zr] (Fig.…”

Section: Significancementioning

confidence: 99%

Warm storage for arc magmas

Barboni

Boehnke

Schmitt

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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100

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Felsic magmatic systems represent the vast majority of volcanic activity that poses a threat to human life. The tempo and magnitude of these eruptions depends on the physical conditions under which magmas are retained within the crust. Recently the case has been made that volcanic reservoirs are rarely molten and only capable of eruption for durations as brief as 1,000 years following magma recharge. If the "cold storage" model is generally applicable, then geophysical detection of melt beneath volcanoes is likely a sign of imminent eruption. However, some arc volcanic centers have been active for tens of thousands of years and show evidence for the continual presence of melt. To address this seeming paradox, zircon geochronology and geochemistry from both the frozen lava and the cogenetic enclaves they host from the Soufrière Volcanic Center (SVC), a long-lived volcanic complex in the Lesser Antilles arc, were integrated to track the preeruptive thermal and chemical history of the magma reservoir. Our results show that the SVC reservoir was likely eruptible for periods of several tens of thousands of years or more with punctuated eruptions during these periods. These conclusions are consistent with results from other arc volcanic reservoirs and suggest that arc magmas are generally stored warm. Thus, the presence of intracrustal melt alone is insufficient as an indicator of imminent eruption, but instead represents the normal state of magma storage underneath dormant volcanoes.volcano | eruption | arc magma | zircon D etermining the timescale of magma storage and remobilization in the upper crust is key to understanding the tempo and magnitude of volcanic eruptions (1-13). Whether a volcano can erupt is controlled by the recharge rate to the magma reservoir (13) (reservoir in this context refers to the portion of the igneous complex that is potentially eruptible), which in turn determines the duration of the "eruption window" [generally defined as the rheological state during which the subvolcanic reservoir is below ∼60% crystals and hence capable of eruption (4)]. However, estimates for how long this eruption window remains open vary over four orders of magnitude; this suggests either profound problems in assumptions underlying one or more of these estimates or a continuum of physical mechanisms that resist formulation of a unified model for the state of magma reservoirs before eruption (1-13). The preservation of sharp compositional gradients in plagioclase phenocrysts, assumed to have crystallized >10 ka before eruption, has recently been interpreted to indicate that arc volcanic reservoirs characteristically remain in "cold storage" at temperatures below the eruption window, possibly below the solidus, and thus only capable of erupting during brief recharge events (<10 ka) (1). In contrast, zircon dating and heat budget considerations are difficult to reconcile with this scenario; instead, they are consistent with continuously partially molten reservoirs capable of erupting (i.e., with melt portion ≥40%) ov...

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“…Se ha tomado para D Zr la relación propuesta más reciente [125]: Si se considera que la energía superficial sólido-líquido, γ SL , disminuye con la temperatura al igual que el contenido en sólidos, lo que dificulta el crecimiento cristalino, y que, por contra, D S y S aumentan con la temperatura, el valor de la energía aparente de activación obtenida por el crecimiento cristalino es consistente con los escasos resultados que figuran en la bibliografía.…”

Section: Figura 556 Variación εAbierta/εtotal Con El Grado De Avancunclassified

Sinterización de compactos de vidrio y de composites vidrio-circón. Mecanismo y cinética del proceso

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Zircon saturation re-revisited

Cited by 900 publications

References 44 publications

The composition of nanogranitoids in migmatites overlying the Ronda peridotites (Betic Cordillera, S Spain): the anatectic history of a polymetamorphic basement

The composition of nanogranitoids in migmatites overlying the Ronda peridotites (Betic Cordillera, S Spain): the anatectic history of a polymetamorphic basement

Warm storage for arc magmas

Sinterización de compactos de vidrio y de composites vidrio-circón. Mecanismo y cinética del proceso

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