An Experimental Study of Water in Nominally Anhydrous Minerals in the Upper Mantle near the Water-saturated Solidus

Kovàcs, István; Green, David H.; Rosenthal, Anja; Hermann, Jörg; O’Neill, Hugh St. C.; Hibberson, W.; Udvardi, Beatrix

doi:10.1093/petrology/egs044

Cited by 91 publications

(55 citation statements)

References 107 publications

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“…The main OH‐stretching bands for orthopyroxene are: two broadbands at ~3,070 and ~3,420 cm −1 , two narrower and partially overlapping peaks at 3,515 and 3,545 cm −1 , and another relatively narrow peak at ~3,600 cm −1 . These bands are similar to those described by Kovács et al () using natural orthopyroxene sensor material (despite the higher Al 2 O 3 content in their starting sensor orthopyroxene (2.83 and 6.30 wt %) compared to this study, <0.80 wt %) and those described by Férot and Bolfan‐Casanova () for the FMASH system below 5 GPa. Similar results were found by Demouchy et al (), during annealing at subsolidus conditions.…”

Section: Resultssupporting

confidence: 91%

“…At the supersolidus conditions observed in this work (1050°C) the water content associated to trivalent cations represent approximately 20% of the total integrated absorbance but are negligible (<3%) at subsolidus conditions (Tables and ). The occurrence of two peaks (3,354 and 3,329 cm −1 ) and a high proportion of trivalent defects were also reported by Kovács et al () at temperatures higher than 1000°C at 2.5 and 4.0 GPa. A minor contribution (<8% in total absorbance) of OH stretching associated to magnesium vacancies [Mg] =

{(2 H)}_{Mg}^{x}

(approximately 3,220 cm −1 ) was only observed at 950°C and 3.0 GPa when using olivine from Cerro del Almirez as sensor layer.…”

Section: Resultssupporting

confidence: 79%

“…We conducted a series of constant pressure experiments (from 750 to 1050°C with 50°C intervals at 3.0 GPa) and constant temperature experiments (from 0.5 to 6.0 GPa with 1.0 GPa intervals at 950°C, respectively) in addition to one experiment at 1.6 GPa and 710°C resulting in a total of 20 runs (Figure and Table ). We have modified the sensor layer technique of Kovács et al () by using a natural serpentinite as the water source layer in order to reproduce closely subduction zone processes. Mineral separates from two high‐pressure metaperidotites (i.e., dehydrated serpentinites) were used as sensor layers.…”

Section: Experimental Strategymentioning

confidence: 99%

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A Subsolidus Olivine Water Solubility Equation for the Earth's Upper Mantle

Padrón‐Navarta

Hermann

2017

JGR Solid Earth

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The pressure and temperature sensitivity of the two most important point hydrous defects in mantle olivine involving Si vacancies (associated to trace amounts of titanium [TiChu‐PD] or exclusively to Si vacancies [Si]) was investigated at subsolidus conditions in a fluid‐saturated natural peridotite from 0.5 to 6 GPa (approximately 20–200 km depth) at 750 to 1050°C. Water contents in olivine were monitored in sandwich experiments with a fertile serpentine layer in the middle and olivine and pyroxene sensor layers at the border. Textures and mineral compositions provide evidence that olivine completely recrystallized during the weeklong experiments, whereas pyroxenes displayed only partial equilibration. A site‐specific water solubility law for olivine has been formulated based on the experiments reconciling previous contradictory results from low‐ and high‐pressure experiments. The site‐specific solubility laws permit to constrain water incorporation into olivine in the subducting slab and the mantle wedge, as these are rare locations on Earth where fluid‐present conditions exist. Chlorite dehydration in the hydrated slab is roughly parallel to the isopleth of 50 ± 20 ppm wt H2O in olivine, a value which is independent of the pressure and temperature trajectory followed by the slab. Hydrous defects are dominated by [Si] under the relevant conditions for the mantle wedge affected by fluids coming from the slab dehydration (slab‐adjacent low viscosity/seismic low‐velocity channel, P > 3 GPa). In cold subduction zones at 5.5 km from the slab surface the storage capacity of the mantle wedge at depths of 100–250 km ranges from 400 to 2,000 ppm wt H2O.

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Section: Resultssupporting

confidence: 91%

{(2 H)}_{Mg}^{x}

(approximately 3,220 cm −1 ) was only observed at 950°C and 3.0 GPa when using olivine from Cerro del Almirez as sensor layer.…”

Section: Resultssupporting

confidence: 79%

Section: Experimental Strategymentioning

confidence: 99%

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A Subsolidus Olivine Water Solubility Equation for the Earth's Upper Mantle

Padrón‐Navarta

Hermann

2017

JGR Solid Earth

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“…Assuming that the pyroxenes would retain their water, the average H 2 O content of the sub‐arc xenoliths in the absence of amphibole is approximately 121 ppm. This is very close to the 190 ppm storage capacity estimated for an upper mantle composition close to the vapour‐saturated solidus (Kovacs et al, ). This range of calculated amounts of H 2 O in the sub‐arc peridotites is also similar to the 50–200 ppm range inferred for the depleted mantle (e.g.…”

Section: Discussionsupporting

confidence: 86%

Water contents of clinopyroxenes from sub‐arc mantle peridotites

Turner

Blatter

et al. 2017

Island Arc

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One poorly constrained reservoir of the Earth's water budget is that of clinopyroxene in metasomatised, mantle peridotites. This study presents reconnaissance Sensitive High‐Resolution, Ion Microprobe–Stable Isotope (SHRIMP–SI) determinations of the H2O contents of (dominantly) clinopyroxenes in rare mantle xenoliths from four different subduction zones, i.e. Mexico, Kamchatka, Philippines, and New Britain (Tabar‐Feni island chain) as well as one intra‐plate setting (western Victoria). All of the sub‐arc xenoliths have been metasomatised and carry strong arc trace element signatures. Average measured H2O contents of the pyroxenes range from 70 ppm to 510 ppm whereas calculated bulk H2O contents range from 88 ppm to 3 737 ppm if the variable presence of amphibole is taken into account. In contrast, the intra‐plate, continental mantle xenolith from western Victoria has higher water contents (3 447 ppm) but was metasomatised by alkali and/or carbonatitic melts and does not carry a subduction‐related signature. Material similar to the sub‐arc peridotites can either be accreted to the base of the lithosphere or potentially be transported by convection deeper into the mantle where it will lose water due to amphibole breakdown.

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“…Bár a köpenyben nominálisan vízmentes ásványok (olivin, piroxének, gránát) uralkodnak, óriási jelentősége van annak, hogy az 1980-as évek végétől egyre több kutató ismerte fel azt, hogy a köpenyásványok rácshibáiba hidrogénionok épülhetnek be (lásd HIRSCHMANN & KOHLSTEDT 2012, KOVÁCS et al 2012, DEMOUCHY & BOLFAN-CASANOVA 2016. A hidrogén szerkezetileg hidroxil (OH) formájában kötött és bár a mennyisége korlátozott, de miután a köpeny messze a legnagyobb része Földünknek, így becslések szerint 1-2 óceáni tömegnek megfelelő víz lehet benne (1 óceáni tömeg = 1,4×10 21 kg).…”

Section: A Köpeny Víztartalmaunclassified

Köpenyeredetű kőzetek felismerésének története és szerepe a geológiai gondolkodás fejlődésében

Embey-Isztin

2017

Földt. Közl.

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Since the beginning of the 1960 th two new events have revolutionized the evolution of geological thought. One of them, the plate tectonics, which is well known to the public, the other one is the recognition of mantle-derived rocks and the new results related to the investigation of the latter samples. Even if these results have also revolutionized the earth sciences, the real significance of this issue is known to a narrower group of specialists only. The present paper discusses the history of recognition of mantle samples and tries to demonstrate the immense progress of our knowledge due to the detailed investigations of these rock samples. Keywords: history of science, mantle, peridotite ÖsszefoglalásAz 1960-as évek elejétől két új momentum forradalmasította a geológiai gondolkodás fejlődését. Az egyik, a lemeztektonika, mely széles körben vált ismerté, a másik a köpenyszármazású kőzetek azonosítása és az ebből fakadó új eredmények. Bár ez utóbbi is gyökerestül változtatta meg a geológia tudományát, ennek igazi jelentőségét inkább csak a szakemberek ismerik. Ez a dolgozat a köpenykőzetek felismerésének történetét követi nyomon, valamint néhány kira gadott példán keresztül igyekszik bemutatni azt az óriási fejlődést, melyet e kőzetek részletes vizsgálatainak köszön hetünk.

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An Experimental Study of Water in Nominally Anhydrous Minerals in the Upper Mantle near the Water-saturated Solidus

Cited by 91 publications

References 107 publications

A Subsolidus Olivine Water Solubility Equation for the Earth's Upper Mantle

A Subsolidus Olivine Water Solubility Equation for the Earth's Upper Mantle

Water contents of clinopyroxenes from sub‐arc mantle peridotites

Köpenyeredetű kőzetek felismerésének története és szerepe a geológiai gondolkodás fejlődésében

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