The fate of subducted Upper Continental Crust: An experimental study

Wu, Yao; Fei, Yingwei; Zhang, Jin; Liu, Xiaoyang

doi:10.1016/j.epsl.2009.03.028

Cited by 89 publications

(68 citation statements)

References 62 publications

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“…CaTs component is always \3 mol% experiments at 13 GPa, which are confirmed by mass balance calculations, suggest that the presence of a small amount of fluid does not dissolve major fractions of the potassium-, sodium-or CO 2 -bearing phases. Furthermore, the presence and amount of fluid also depends on the H-solubility of other nominally anhydrous phases (Keppler and Smyth 2006) such as stishovite dissolving up to 3,000 ppm H 2 O (Litasov et al 2007) and clinopyroxene (1,200 ppm H 2 O in Di 60 Jd 40 , Wu et al 2009). The reported high solubility of H in stishovite and cpx suggest that the DG1 composition at 13 GPa could be fluid-absent.…”

Section: Melting Reactionsmentioning

confidence: 99%

“…Topaz-OH may be formed at the phengite to K-hollandite reaction at B1,000°C. At higher temperatures, a supercritical liquid results which is expected to mostly escape the system, leaving \0.1 wt% H 2 O that may be incorporated into nominally anhydrous minerals (Keppler and Smyth 2006;Litasov et al 2007;Wu et al 2009). …”

Section: Melting Systematics For Carbonated Lithologiesmentioning

confidence: 99%

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Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Grassi

Schmidt

2010

Contrib Mineral Petrol

104

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The melting behaviour of three carbonated pelites containing 0-1 wt% water was studied at 8 and 13 GPa, 900-1,850°C to define conditions of melting, melt compositions and melting reactions. At 8 GPa, the fluidabsent and dry carbonated pelite solidi locate at 950 and 1,075°C, respectively; [100°C lower than in carbonated basalts and 150-300°C lower than the mantle adiabat. From 8 to 13 GPa, the fluid-present and dry solidi temperatures then increase to 1,150 and 1,325°C for the 1.1 wt% H 2 O and the dry composition, respectively. The melting behaviour in the 1.1 wt% H 2 O composition changes from fluid-absent at 8 GPa to fluid-present at 13 GPa with the pressure breakdown of phengite and the absence of other hydrous minerals. Melting reactions are controlled by carbonates, and the potassium and hydrous phases present in the subsolidus. The first melts, which composition has been determined by reverse sandwich experiments, are potassium-rich Ca-FeMg-carbonatites, with extreme K 2 O/Na 2 O wt ratios of up to 42 at 8 GPa. Na is compatible in clinopyroxene with D cpx=carbonatite Na ¼ 10À18 at the solidus at 8 GPa. The melt K 2 O/Na 2 O slightly decreases with increasing temperature and degree of melting but strongly decreases from 8 to 13 GPa when K-hollandite extends its stability field to 200°C above the solidus. The compositional array of the sediment-derived carbonatites is congruent with alkali-and CO 2 -rich melt or fluid inclusions found in diamonds. The fluid-absent melting of carbonated pelites at 8 GPa contrasts that at B5 GPa where silicate melts form at lower temperatures than carbonatites. Comparison of our melting temperatures with typical subduction and mantle geotherms shows that melting of carbonated pelites to 400-km depth is only feasible for extremely hot subduction. Nevertheless, melting may occur when subduction slows down or stops and thermal relaxation sets in. Our experiments show that CO 2 -metasomatism originating from subducted crust is intimately linked with K-metasomatism at depth of [200 km. As long as the mantle remains adiabatic, lowviscosity carbonatites will rise into the mantle and percolate upwards. In cold subcontinental lithospheric mantle keels, the potassic Ca-Fe-Mg-carbonatites may freeze when reacting with the surrounding mantle leading to potassium-, carbonate/diamond-and incompatible element enriched metasomatized zones, which are most likely at the origin of ultrapotassic magmas such as group II kimberlites.

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Section: Melting Reactionsmentioning

confidence: 99%

Section: Melting Systematics For Carbonated Lithologiesmentioning

confidence: 99%

Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Grassi

Schmidt

2010

Contrib Mineral Petrol

104

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“…3.16. Secondly, our database predicts high pressure garnets (P > 10 GPa) with relatively low contents in Na and high in Fe with respect to experiments on continental crust compositions (Irifune et al 1994;Wu et al 2009). Clinopyroxene, on the other hand, tend to be deficient in Fe and Mg.…”

Section: A6 Thermodynamic Databases and Free Energy Minimization Strmentioning

confidence: 99%

“…are calculated a priori for different compositions, water contents, and P-T range of interest, and saved in "look-up" tables that are read by the thermomechanical solver during execution. One of the main differences with previous models is that while they make use of thermodynamic databases strictly suitable at pressures ≲ 3 Gpa, we use an augmented-modified version of the Holland andPowell (1998) database (revised in 2002) valid up to~25 GPa that includes all major phases obtained in UHP experiments on compositions relevant to the continental crust (e.g., Irifune et al 1994;Wu et al 2009;Ono 1998;Zhai and Ito 2008;Rapp et al 2008). Since it has been suggested that some dense silicates such as K-hollandite (KAlSi 3 O 8 ) and CAS (CaAl 4 Si 2 O 11 ) could be responsible for the recycling of continental material and important trace elements into the transition zone or lower mantle (Zhai and Ito 2008;Rapp et al 2008;Wu et al 2009), using a database that correctly predicts phase relations at such conditions is of particular relevance.…”

Section: Bulk Properties Of Rocksmentioning

confidence: 99%

“…Another set of evidence for deep subduction is provided by experimental data at extremely high pressures (e.g., Irifune et al 1994;Dobrzhinetskaya and Green 2007;Rapp et al 2008;Zhai and Ito 2008;Wu et al 2009). These studies indicate that a "depth of no return" for continental derived materials may exist at around 8.5 9 GPa, where dense silicates start to form (e.g., Irifune et al 1994;Dobrzhinetskaya and Green 2007;Rapp et al 2008;Zhai and Ito 2008).…”

Section: Introductionmentioning

confidence: 99%

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The Subductability of Continental Lithosphere: The Before and After Story

Afonso

Zlotnik

2011

Frontiers in Earth Sciences

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First‐principles prediction of fast migration channels of potassium ions in KAlSi₃O₈ hollandite: Implications for high conductivity anomalies in subduction zones

Sun

et al. 2016

Geophysical Research Letters

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Materials sharing the hollandite structure were widely reported as fast ionic conductors. However, the ionic conductivity of KAlSi3O8 hollandite (K‐hollandite), which can be formed during the subduction process, has not been investigated so far. Here first‐principles calculations are used to investigate the potassium ion (K+) transport properties in K‐hollandite. The calculated K+ migration barrier energy is 0.44 eV at a pressure of 10 GPa, an energy quite small to block the K+ migration in K‐hollandite channels. The calculated ionic conductivity of K‐hollandite is highly anisotropic and depends on its concentration of K+ vacancies. About 6% K+ vacancies in K‐hollandite can lead to a higher conductivity compared to the conductivity of hydrated wadsleyite and ringwoodite in the mantle. K+ vacancies being commonly found in many K‐hollandite samples with maximum vacancies over 30%, the formation of K‐hollandite during subduction of continental or alkali‐rich oceanic crust can contribute to the high conductivity anomalies observed in subduction zones.

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The fate of subducted Upper Continental Crust: An experimental study

Cited by 89 publications

References 62 publications

Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

The Subductability of Continental Lithosphere: The Before and After Story

First‐principles prediction of fast migration channels of potassium ions in KAlSi₃O₈ hollandite: Implications for high conductivity anomalies in subduction zones

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The fate of subducted Upper Continental Crust: An experimental study

Cited by 89 publications

References 62 publications

Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

Melting of carbonated pelites at 8–13 GPa: generating K-rich carbonatites for mantle metasomatism

The Subductability of Continental Lithosphere: The Before and After Story

First‐principles prediction of fast migration channels of potassium ions in KAlSi3O8 hollandite: Implications for high conductivity anomalies in subduction zones

Contact Info

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First‐principles prediction of fast migration channels of potassium ions in KAlSi₃O₈ hollandite: Implications for high conductivity anomalies in subduction zones