V. V. Matveenkov and O. G. Sorokhtin
Shirshov Institute of Oceanology, Russian Academy of Sciences, Nakhimovskii pr. 36, Moscow, 117218 Russia
Received March 3, 1997
Abstract—Research of the ocean floor using Mir submersibles carried out south of the Hawaii Archipelago
allowed us to recover the flows of recent picrite–basalts. Lava vents are confined to the field of development of
open fractures of the gjar type. Basalts represent the initial lava flows in the structure of the Hawaiian volcanic
archipelago. Considering their contents of alkali and rare-earth elements, the picrite–basalts of the bottom could
be assigned to a series of island tholeiites. They are the products of high level melting of asthenospheric matter
at a depth of about 75–80 km as a result of decompression near a deep fracture that occurred in the lithosphere
and asthenosphere. Similar picrite–basalts were found in the base of the youngest volcano of the Hawaiian
chain—the Loihi Volcano. With respect to the alkali contents, these rocks are assigned to the subalkaline series
of rocks formed during melting of garnet lherzolites. This could probably be explained by a supply of melts
from deeper levels of the asthenosphere after partial packing of the initial magma effluent fracture.
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