Geochemistry of Granitization and Magmatic Replacement
of Basic Volcanic Rocks in the Contact Aureole
of the Yurchik Gabbronorite Intrusion, Ganal Range,
Kamchatka

I. A. Tararin^a, Z. G. Badredinov^a, S. I. Dril’^b, N. S. Gerasimov^b,
G. P. Sandimirova^b, and T. A. Vladimirova^b

^aFar East Geological Institute, Far East Branch, Russian Academy of Sciences,
pr. Stoletiya Vladivostoka 159, Vladivostok, 690022 Russia

e-mail: itararin@mail.ru

^bVinogradov Institute of Geochemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1a, Irkutsk, 664033 Russia

e-mail: sdril@igc.irk.ru

Received July 7, 2011, in final form, February 16, 2013

Abstract—Geological and geochemical data indicate that the formation of the granulite-like rocks in the con-
tact aureole of the Yurchik gabbronorite intrusion of the Ganal Range, Kamchatka, was caused by the contact
metamorphism, metasomatism, and local melting of the initial volcanosedimentary rocks of the Vakhtalka
Sequence of the Ganal Group. The temperature in the inner part of the aureole reached 700–800C and caused
the transformation of the basic volcanic rocks of the sequence into two pyroxene–plagioclase, clinopyroxene–
amphibole–plagioclase, and amphibole–plagioclase hornfelses, while sedimentary rocks were converted into
garnet–biotite ± cordierite hornfelses. The hornfelsed basic volcanic rocks were locally subjected to metaso-
matic alteration and magmatic replacement with formation of biotite–orthopyroxene–plagioclase metasomatic
bodies containing biotite–orthopyroxene–plagioclase ± garnet veinlets and aggregates. During these processes,
sedimentary interlayers were converted into garnet enderbites at 700–800C and 3.2–4.8 kbar. The comparison
of the chemical composition of basic volcanic rocks of the Vakhtalka Sequence and their transformation prod-
ucts indicates that the metasomatic alteration and magmatic replacement correspond to siliceous–alkaline meta-
somatism (granitization) and cause subsequent and uneven influx of SiO₂, Al₂O₃, Na₂O, K₂O, Rb, Ba, Zr, Nb,
and Cl and removal of Fe, Mg, Mn, Ca, Cr, Co, Ti, Y, and S. REE data on basic metavolcanic rocks, hornfelses,
and metasomatites suggest that the processes of hornfelsation, metasomatism, and magmatic replacement of
the initial volcanic rocks were accompanied by significant increase in LREE and slight decrease in HREE. The
Sr and Nd isotope study of the rocks in the aureole showed that the initial basic volcanic rocks of the Vakhtalka
Sequence are isotopically close to both mature island arc tholeiites and mid-ocean ridge basalts. The metaso-
matic alteration and magmatic replacement of volcanic rocks in the aureole lead to the decrease of ¹⁴³Nd/¹⁴⁴Nd
and increase of ⁸⁷Sr/⁸⁶Sr approximately parallel to mantle array. Pb isotopic ratios in the studied rocks become
more radiogenic from initial metavolcanic rocks to metasomatites.
It is suggested that the processes of metamorphism, metasomatism, and magmatic replacement were caused by
highly mineralized mantle fluids, which percolated along magmatic channels serving as pathways for gabbroid
magma.

Keywords: basic volcanics, hornfelses, gabbronorites, metasomatites, granitizaition, magmatic replacement,
Ganal Range, Kamchatka

DOI: 10.1134/S0016702913080065

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