M. Yu. Khotina and M. N. Shapirob
aGeological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia
e-mail: av10553@comtv.ru
bInstitute of Physics of the Earth, Russian Academy of Sciences, Bol’shaya Gruzinskaya ul. 10, Moscow, 123995 Russia
Received May 16, 2005
Abstract—Ophiolites of the Afrika Mys Block of the Kamchatsky Mys Peninsula, eastern Kamchatka, are a
fragment of an accretionary prism that formed in the Late Cretaceous–Eocene on the southern side of the Kro-
notsky island arc as a result of its collision with the Smagino volcanic uplift that arose at the post-Neocomian
time on the subducting plate. On the basis of the geologic, geochemical, and paleomagnetic data available to
date, it is established that ophiolites are heterogeneous in their origin and were formed in different geodynamic
settings that changed progressively with time. The heterogeneous structure of ophiolites displays the evolution
of a fragment of the oceanic lithosphere, which was not submerged into subduction zone, from its origination
in the spreading center via transformation under conditions of the plume-related volcanic uplift to the involve-
ment in the structure of the Kronotsky island arc, which is currently a constituent of the accretionary system of
Kamchatka. The reconstruction of ophiolites tectonically fragmented in the accretionary prism allows recogni-
tion of (1) derivatives of an ocean ridge (ultramafic–gabbro–basaltic complex of the Mount Olen’ya Massif)
conjugated with a transform fault and volcanosedimentary rocks of the Smagino volcanic uplift (cover of the
oceanic crust) and (2) a fragment of the lithospheric mantle (ultramafic rocks of the Lake Stolbovoe Massif)
exhumed in the process of collision and genetically related to the evolution of the volcanic uplift. In the course
of evolution of the Kronotsky island arc, all these elements were overlapped by tephrogenic turbidites (Pikezh
Formation) and quartz–feldspar graywackes (Pikezh Sandstone) that were involved in the accretionary prism
as well. The paleotectonic reconstructions broadly support the petrologic conclusions about the complementary
nature of different igneous complexes and ascertain the temporal sequence of events.
DOI: 10.1134/S0016852106040042
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