Extremely low structural hydroxyl contents in upper mantle xenoliths from the Nógrád-Gömör Volcanic Field (northern Pannonian Basin): Geodynamic implications and the role of post-eruptive re-equilibration

Patkó, Levente; Liptai, Nóra; Kovàcs, István; Aradi, László Előd; Xia, Qunke; Ingrin, Jannick; Mihály, Judith; O’Reilly, Suzanne Y.; Griffin, William L.; Wesztergom, Viktor; Szabó, Csaba

doi:10.1016/j.chemgeo.2018.12.017

Cited by 26 publications

(16 citation statements)

References 109 publications

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“…The properties of OH defects have been theoretically investigated within the density functional theory (DFT) framework using the PWscf code of the Quantum ESPRESSO package (Giannozzi et al, 2009; http://www.quantum-espresso.org, last access: 1 October 2020). The modeling scheme used the generalized gradient approximation (GGA) to the exchangecorrelation functional as proposed by Perdew, Burke and Ernzerhof (PBE functional;Perdew et al, 1996), and periodic boundary conditions. The ionic cores were described using optimized norm-conserving Vanderbilt (ONCV) pseudopotentials (Hamann, 2013; Schlipf and Gygi, 2015) with a 80 Ry cutoff on the electronic wave functions, as in Balan et al (2019) and Jollands et al (2020).…”

Section: Theoretical Modeling Of Oh Defectsmentioning

confidence: 99%

Low-temperature infrared spectrum and atomic-scale structure of hydrous defects in diopside

et al. 2020

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Abstract. Hydrous defects in diopside (CaMgSi2O6) play an important role in the water budget of the Earth's mantle. Related OH-stretching modes lead to a variety of infrared absorption bands observed in natural or experimental samples. In the present study, we report new low-temperature infrared spectra of reference natural diopside samples in the OH-stretching range. In parallel, the structure and vibrational properties of a series of OH-bearing defects in diopside are theoretically determined at the density functional theory level. The infrared spectra make it possible to resolve additional bands in the region above 3600 cm−1 and reveal that their anharmonic behavior differs from that of the bands at lower frequency. A comparison of theoretical results with experimental data makes it possible to propose atomic-scale geometries corresponding to observed OH-stretching bands. It confirms that the bands observed at 3620–3651 cm−1 are related to M3+ ions substituted for Si in tetrahedral sites, while the 3420 cm−1 band is associated with the Na+ for Ca2+ substitution. In both cases, H+ incorporation compensates the charge deficit due to the heterovalent substitution. The other major mechanism of water incorporation in diopside relates to the charge compensation of cationic vacancies, among which Ca vacancies play a central role. The 3357 cm−1 band corresponds to doubly protonated Ca vacancies in pure diopside. In experimental diopside-bearing trivalent cations, the bands at 3432–3460 cm−1 correspond to singly protonated Ca vacancies with a nearby octahedral M3+ ion, while the 3310 cm−1 band likely involves a more remote charge compensation by M3+ ions. More complex defects associating Ca vacancies with tetrahedral M3+ and octahedral Ti4+ ions are proposed for the bands observed between 3500 and 3600 cm−1 in natural diopside. The Fe2+ for Mg2+ and Fe2+ for Ca2+ substitutions are also found to affect nearby OH-bearing defects, causing a shift and broadening of OH stretching bands in chemically more complex diopside samples.

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Section: Theoretical Modeling Of Oh Defectsmentioning

confidence: 99%

Low-temperature infrared spectrum and atomic-scale structure of hydrous defects in diopside

et al. 2020

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“…Clearly, small volumes of melt can easily be generated near the base of the lithosphere, which indeed is just where the REE inversion shows the melting columns are located. The presence of any water in the mantle—and it is likely that there is some beneath the Basin (e.g., Aradi et al., 2017; Falus et al., 2008; Kovács et al., 2020; Lange et al., 2019; Patkó et al., 2019)—would facilitate melting at the conditions of the dry solidus.…”

Section: Resultsmentioning

confidence: 99%

Estimates of the Temperature and Melting Conditions of the Carpathian‐Pannonian Upper Mantle From Volcanism and Seismology

Gartner

McKenzie

2020

Geochem Geophys Geosyst

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What drives the formation of basaltic melts beneath intraplate volcanoes not associated with extensive thermal anomalies or lithospheric extension? Detailed constraints on the melting conditions and source region are imperative to resolve this question. Here we model the geochemistry of alkali basalts and mantle nodules brought up by young (12-0.1 Ma) intraplate volcanoes distributed across the Carpathian-Pannonian region and combine the results with geophysical observations. Rare earth element inversion and forward calculation of elemental concentrations show that the basalts require the mantle to have undergone less than 1% melting in the garnet-spinel transition zone, at depths of about 63-72 km. The calculated melt distributions correspond to a mantle potential temperature of ∼1257°C, equivalent to a real temperature of 1290°C at 65 km beneath the Pannonian Basin. The composition, modal mineralogy, and clinopyroxene geochemistry of some of the entrained mantle nodules closely resemble the basalt source, though the latter equilibrated at greater depths. The gravity anomalies and topography of the Basin reveal no large-scale features that can account for the post-extensional volcanism. Instead, the lithospheric thickness and geotherm show that melting occurs because the base of the lithosphere, at ∼50-km depth, is close to or at the solidus temperature over a large part of the Basin. Hence, only a small amount of upwelling is required to produce minor volumes (up to a few cubic kilometers) of melt. We conclude that the Pannonian volcanism originates from upwelling in the asthenosphere just below thinned lithosphere, which is likely to be driven by thermal buoyancy. Plain Language Summary On Earth's continents, there are surprising instances of basaltic volcanism that are not related to plate stretching or hotspots. To understand just such activity in the Carpathian-Pannonian region, in eastern central Europe, during the last 12 million years, we studied the chemical composition of the erupted lavas. Using a computer code that takes as input the concentrations of elements in basaltic rocks, we calculated the fraction of melt and the depth at which it formed within Earth's mantle. We find that the mantle has undergone less than 1% melting in the garnet-spinel transition zone-a region at about 63-to 72-km depth where these minerals both occur. Using a model of mantle melting, we find that the temperature of the mantle at 65 km below the Pannonian Basin is about 1290°C. The plate's thickness and the temperature variations with depth tell us that the magma source region is at a temperature close to that at which melting begins (the solidus). This means that if mantle material is moved upwards just slightly, it will produce small volumes of melt that can rise to the surface. The most likely cause of such upward movement is convection in the mantle below the rigid plate.

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“…2a), whereas olivine-rich areas show the characteristic texture of the wehrlite suite (Patkó et al 2020). The sample bears microstructural evidence of deformation and subsequent annealing, interpreted to be the result of metasomatizing melts percolating through the sample prior to ascent to the surface (Liptai et al 2019).…”

Section: Sample Petrography and Mineral Chemistrymentioning

confidence: 97%

Characterization of the metasomatizing agent in the upper mantle beneath the northern Pannonian Basin based on Raman imaging, FIB-SEM, and LA-ICP-MS analyses of silicate melt inclusions in spinel peridotite

Liptai

Berkesi

Patkó

et al. 2021

American Mineralogist

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Extremely low structural hydroxyl contents in upper mantle xenoliths from the Nógrád-Gömör Volcanic Field (northern Pannonian Basin): Geodynamic implications and the role of post-eruptive re-equilibration

Cited by 26 publications

References 109 publications

Low-temperature infrared spectrum and atomic-scale structure of hydrous defects in diopside

Low-temperature infrared spectrum and atomic-scale structure of hydrous defects in diopside

Estimates of the Temperature and Melting Conditions of the Carpathian‐Pannonian Upper Mantle From Volcanism and Seismology

Characterization of the metasomatizing agent in the upper mantle beneath the northern Pannonian Basin based on Raman imaging, FIB-SEM, and LA-ICP-MS analyses of silicate melt inclusions in spinel peridotite

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