Sakhalin-Primorye volcanic belt 

(late Tertiary and Quaternary) 

(Sea of Japan and adjacent continental areas, unit QTvm)

Consists chiefly of late Cenozoic basalt that occurs in relatively small eruptive fields that are closely 
associated with grabens and bounding faults. Basalts range in composition from quartz tholeiite to olivine 
nephelenite and basanite. The basanite locally contain xenoliths of spinel and garnet peridotite, pyroxenite, 
and harzburgite. The proportion of alkalic and tholeiitic lava and geochemical characteristics differ with 
location. Alkali basalt is predominant in the continental area of eastern China, whereas tholeiite, with an 
unusually low K2O content (less than 0.25%), are present in the East Sikhote-Alin region adjacent to the 
riftogenic basin of the Sea of Japan. Basalt in the East Sikhote-Alin region and Hokkaido is more enriched 
in the mobile incompatible elements, such as Rb, Ba, Sr, and is depleted in Nb and Ta relative to Chinese 
and Korean basalt and most basalts plot within a mantle array, with initial Sr ratios ranging from 0.7037 to 
0.7057. Geochemical and isotopic data indicate at least two-component magma mixing between magmas 
resulting from depleted and enriched mantle sources. The latter is proposed to be metasomatized 
subcontinental lithosphere mantle.

On Sakhalin Island, the volcanic belt consists of three complexes: (1) Miocene subalkalic andesite-basalt, 
basalt, rarely rhyolite, and subvolcanic intrusions of diorite; and rare rhyolite, (2) Late Miocene to early 
Pliocene trachybasalt, trachydiabase, subvolcanic intrusions of monzonite, essexite, and other alkalic rocks; 
and (3) Pliocene olivine basalt and diabase, and rare andesite and dacite. Local subvolcanic intrusions of 
gabbro. Both marine and nonmarine eruptive settings. Numerous macrofossils and flora fossils.

The western part of the Sakhalin-Primorye belt in the western Russian Southeast is interpreted as forming 
during asymmetric extension; the eastern part of belt is interpreted as forming during rifting of the Sea of 
Japan that may be related to the Late Cenozoic Kuril and East Japan igneous arcs. REFERENCES: 
Geology of the U.S.S.R., Sakhalin Island, 1970, Semenov, 1975; Martynov, 1994; Martynov and 
Levashov, 1988; Nakamura and others, 1990; Martynov and Okamura, 1993.