G.P. Avdeiko1, D.P. Saveliev2,
S.V. Popruzhenko2, A.A. Palueva1
1Institute
of Volcanic Geology and Geochemistry FED RAS, Petropavlovsk-Kamchatsky,
683006
2Natural Resources Department of the
Kamchatka region and Koryak autonomous district,
Ministry of Natural Resources of Russia, Petropavlovsk-Kamchatsky,
683006
Analysis
of the tectonic structure and volcanism of the present-day subduction
zones and comparison of these results with similar characteristics
and stages of tectonic history and volcanic activity of the Kurile-Kamchatka
region has been made. It is shown that the present-day structure
of the Kurile-Kamchatka region is determined by the three different-age
volcanic belts, which are volcanic arcs, located above the subduction
zones. These subduction zones and arcs discretely rejuvenate and
shift towards the Pacific Ocean. These data provide a basis for
clarifying the criteria for paleotectonic reconstructions. The most
reliable criteria for the subduction stage of development are volcanogenic
formations of island-arc (subductional) geochemical type. In certain
tectonic conditions occurence of rocks of the “intraplate” geochemical
type is possible alongside with predominant island-arc type rocks.
The other petrological, geochemical or formational criteria may
only play a subsidiary role for more precise definition of relative
spatial location of the frontal (tectonic) arc, deep-sea trench,
pre-arc and back-arc basins of sedimentation. The revealed geodynamic
parameters allow us to determine direction of the subduction and
to evaluate qualitatively the angle of subduction by the width of
the volcanic arc. When reconstructing the tectonic history it should
be taken into account that each subduction zone has its own basement,
different from the one of the neighbouring older and younger arcs.
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