Melt evolution in subarc mantle: evidence from heating experiments on spinel-hosted melt inclusions in peridotite xenoliths from the andesitic Avacha volcano (Kamchatka, Russia)

Abstract Water influences geodynamic processes such as melting, deformation and rheology, yet its distribution in the oceanic upper mantle is primarily known indirectly from melt inclusions and glasses of erupted mantle melts (i.e. mid-ocean ridge and ocean island basalts). To better constrain the mechanisms influencing the distribution of H2O in the mantle, particularly regarding the role of metasomatism, we analyzed 15 peridotite xenoliths from Savai‘i and two dunite xenoliths from Ta‘ū (Samoa) for structural H2O (by polarized Fourier transform infrared spectroscopy), and major and trace element concentrations. Clinopyroxenes from the Ta‘ū dunites show trace element concentrations consistent with equilibration with their host lavas, but lower H2O contents than expected. Savai‘i peridotites are highly depleted harzburgites (melt depletion ≥17 %). They show strong evidence of transient metasomatism by both carbonatite and silicate melts, with highly variable Ti and Zr depletions and light rare earth element enrichments. However, despite metasomatism the H2O concentrations in olivines (0 − 4 ppm H2O) and orthopyroxenes (17 − 89 ppm H2O) are among the lowest reported in oceanic xenoliths, but higher than expected for the estimated degree of depletion. In general, H2O concentrations vary less than those of other incompatible trace elements in these samples. Transects across mineral grains show generally homogeneous distributions of H2O, indicating no significant H2O loss or gain during ascent. Raman spectroscopy on inclusions in minerals shows the presence of CO2 but an absence of molecular H2O. This agrees with the absence of H2O concentration variations between inclusion-rich and -poor domains in minerals. The above data can be explained by transient metasomatism along grain boundaries, now recorded as planes of inclusions within annealed grains. Fast diffusion of hydrogen (but not lithophile elements) from the inclusions into the host mineral phase will simultaneously enrich H2O contents across the grain and lower them in the inclusion-rich domains. The result is highly variable metasomatism recorded in lithophile elements, with smaller magnitude H2O variations that are decoupled from lithophile element metasomatism. Comparison with xenoliths from Hawai‘i shows that evidence for metasomatism from lithophile elements alone does not imply rehydration of the oceanic lithosphere. Instead, H2O concentrations depend on the overall amount of H2O added to the lithosphere through metasomatism, and the proximity of sampled material to areas of melt infiltration in the lithosphere.

Download Full-text

Coexisting silicate melt inclusions and H2O-bearing, CO2-rich fluid inclusions in mantle peridotite xenoliths from the Carpathian–Pannonian region (central Hungary)

Chemical Geology ◽

10.1016/j.chemgeo.2010.03.004 ◽

2010 ◽

Vol 274 (1-2) ◽

pp. 1-18 ◽

Cited By ~ 29

Author(s):

Károly Hidas ◽

Tibor Guzmics ◽

Csaba Szabó ◽

István Kovács ◽

Robert J. Bodnar ◽

...

Keyword(s):

Fluid Inclusions ◽

Melt Inclusions ◽

Mantle Peridotite ◽

Silicate Melt ◽

Peridotite Xenoliths

Download Full-text

Melt-wall rock interaction in the mantle shown by silicate melt inclusions in peridotite xenoliths from the central Pannonian Basin (western Hungary)

Island Arc ◽

10.1111/j.1440-1738.2009.00672.x ◽

2009 ◽

Vol 18 (2) ◽

pp. 375-400 ◽

Cited By ~ 11

Author(s):

Csaba Szabó ◽

Károly Hidas ◽

Enikő Bali ◽

Zoltán Zajacz ◽

István Kovács ◽

...

Keyword(s):

Melt Inclusions ◽

Pannonian Basin ◽

Wall Rock ◽

Silicate Melt ◽

Rock Interaction ◽

Peridotite Xenoliths

Download Full-text

Melt inclusions track melt evolution and degassing of Etnean magmas in the last 15 ka

Lithos ◽

10.1016/j.lithos.2018.11.023 ◽

2019 ◽

Vol 324-325 ◽

pp. 716-732 ◽

Cited By ~ 2

Author(s):

Emanuela Gennaro ◽

Giada Iacono-Marziano ◽

Antonio Paonita ◽

Silvio G. Rotolo ◽

Caroline Martel ◽

...

Keyword(s):

Melt Inclusions ◽

Melt Evolution

Download Full-text

Features of heat and mass transfer processes under the Avachinsky volcano (Kamchatka)

10.5194/egusphere-egu2020-362 ◽

2020 ◽

Author(s):

Grigory Kuznetsov ◽

Victor Sharapov

Keyword(s):

Mass Transfer ◽

Mantle Wedge ◽

Melt Inclusions ◽

Publishing House ◽

Mantle Xenoliths ◽

Convective Heating ◽

Fluid Filtration ◽

Crust And Upper Mantle ◽

Peridotite Xenoliths ◽

Melt And Fluid Inclusions

We investigated the processes beneath the Avacha volcano using mantle peridotite xenoliths&#160; the with the EPMA, electronic microscope and ICP methods and&#160; numeric modeling of the mass transfer accounting the melt fluid reactions with peridotitesThe decompression melting processes&#160; in peridotites beneath Avachinsky volcano (Kamchatka) are associated with seismic events. After the reactions with the Si, Ca, Na, K&#160; from partial&#160; melts associated&#160; with&#160; the&#160; subduction related fluids the spinel and orthopyroxene were melted and essentially clinopyroxene veins were formed. Secondary crystals growth in the mantle xenoliths (with melt and fluid inclusions) are associated possibly with&#160; the fluids appeared&#160; due to retrograde boiling of the magma chamber beneath the volcano.The processes of sublimation and recrystallization of&#160; Avacha harzburgites was investigated at the facility in the Institute of&#160; Nuclear Physics (Novosibirsk, Russia), which generates high-density electron beams and makes it possible to obtain boiling ultrabasic and basic liquids and condensates of magmatic gas on the surface of&#160; harzburgite.Results of&#160; experiments provides a satisfactory explanation for the observed local heterophase alterations within ultramafic rocks that have experienced multistage deformation beneath volcanoes of the Kamchatka volcanic front.Mathematical model of convective heating and metasomatic reactions in harzburgites were modeled using the&#160; Selector PC thermodynamic software. The obtained virtual dynamic patterns of metasomatic zoning across the mantle wedge show&#160;&#160; how&#160;&#160; composition&#160;&#160; variations&#160;&#160; of&#160;&#160; fluids&#160;&#160; and&#160; PT&#160; conditions&#160;&#160; at&#160;&#160; their&#160;&#160; sources&#160;&#160; influence&#160;&#160; the&#160;&#160; facies&#160;&#160; of&#160;&#160; metasomatized&#160;&#160; mantle&#160;&#160; wedge harzburgite.&#160;&#160; Such processes are apparently common to seismically&#160; deformed&#160;&#160; permeable&#160;&#160; lithosphere&#160;&#160; above&#160;&#160; magma&#160;&#160; reservoirs.&#160;&#160;There are two regions fluid filtration conditions under the Avachinsky volcano which are regulated by the tectonic conditions. The lower field where compression conditions prevail. And the upper field, where the prevailing tensile conditions and intense seismic destruction of the rocks of the crust and upper mantle. The heat flux distribution shows the manifestation of the convective heating mechanism in the earth's crust over the most permeable fault zones.The study of the composition of the gas phases and melt inclusions suggests that the partial melting of metasomatized ultrabasites occurs in the range of 1150 &#176; C <T <1200 &#176; C.In accord with the composition of the glassy phase in the melt inclusions of spinel crystals, the harzburgite metasomatism in the local melting sites is associated with brine melts that bringing Ca, K, Na, Si. C. The work was &#239;&#172;&#129;nancially supported by the Russian Foundation for Basic Research, Grants No. 16-29-15131, 16-01-00729.ReferencesArai S., Ishimaru S. Insights into Petrologycal Characteristics of the Lithosphere Mantle Wedge beneath Arcs through Peridotite Xenoliths: a Review.// J. Petrol., 2008. V.49(4), 359-395.Tomilenko A.A., Kovyazin S.V., Sharapov V.N., Timina T.Yu., Kuzmin D.V. Metasomatic recrystallization and melting of ultrabasic rocks of mantle wedge beneath Avacha Volcano, Kamchatka // ACROFI III and TBG XIV Abstracts Volume / SB RAS IGM, Novosibirsk: Publishing House of SB RAS, 2010, p. 248-249.

Download Full-text