Features of heat and mass transfer processes under the Avachinsky volcano (Kamchatka)
Authors: Kuznetsov Grigory , Sharapov Victor 
Published: March 2020

&lt;p&gt;We investigated the processes beneath the Avacha volcano using mantle peridotite xenoliths&amp;#160; the with the EPMA, electronic microscope and ICP methods and&amp;#160; numeric modeling of the mass transfer accounting the melt fluid reactions with peridotites&lt;/p&gt;&lt;p&gt;The decompression melting processes&amp;#160; in peridotites beneath Avachinsky volcano (Kamchatka) are associated with seismic events. After the reactions with the Si, Ca, Na, K&amp;#160; from partial&amp;#160; melts associated&amp;#160; with&amp;#160; the&amp;#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&amp;#160; the fluids appeared&amp;#160; due to retrograde boiling of the magma chamber beneath the volcano.&lt;/p&gt;&lt;p&gt;The processes of sublimation and recrystallization of&amp;#160; Avacha harzburgites was investigated at the facility in the Institute of&amp;#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&amp;#160; harzburgite.&lt;/p&gt;&lt;p&gt;Results of&amp;#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.&lt;/p&gt;&lt;p&gt;Mathematical model of convective heating and metasomatic reactions in harzburgites were modeled using the&amp;#160; Selector PC thermodynamic software. The obtained virtual dynamic patterns of metasomatic zoning across the mantle wedge show&amp;#160;&amp;#160; how&amp;#160;&amp;#160; composition&amp;#160;&amp;#160; variations&amp;#160;&amp;#160; of&amp;#160;&amp;#160; fluids&amp;#160;&amp;#160; and&amp;#160; PT&amp;#160; conditions&amp;#160;&amp;#160; at&amp;#160;&amp;#160; their&amp;#160;&amp;#160; sources&amp;#160;&amp;#160; influence&amp;#160;&amp;#160; the&amp;#160;&amp;#160; facies&amp;#160;&amp;#160; of&amp;#160;&amp;#160; metasomatized&amp;#160;&amp;#160; mantle&amp;#160;&amp;#160; wedge harzburgite.&amp;#160;&amp;#160; Such processes are apparently common to seismically&amp;#160; deformed&amp;#160;&amp;#160; permeable&amp;#160;&amp;#160; lithosphere&amp;#160;&amp;#160; above&amp;#160;&amp;#160; magma&amp;#160;&amp;#160; reservoirs.&amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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 &amp;#176; C &lt;T &lt;1200 &amp;#176; C.&lt;/p&gt;&lt;p&gt;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 &amp;#239;&amp;#172;&amp;#129;nancially supported by the Russian Foundation for Basic Research, Grants No. 16-29-15131, 16-01-00729.&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;Arai 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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;