stripes
Small cinder cones and lave flows make up the Tunkinskoe volcanic field. The lavas have vesicular and massive structures and in some places are covered by typical agglutinates. Analyses indicate that these rocks are alkali olivine basalts with normative nepheline up to 8% and are somewhat differentiated (Mg 54-58). The possibility of the presence of tholeiitic basalts in the Tunkinskoe field is at present a matter of debate. In Kononova et al. (1993) it is stressed that amongst the rocks studied so far tholeiites have not been recognised. The volcanic cones are not large: the height generally varies between 40 and 50 m, rarely reaching 125 m. Most of the cones are dome-shaped with flat or rounded summits. According to geophysical data the base of the basalt pile of the Tunkinskoe field is at 1,500-2,000 m below sea level. Assuming that the initial height of the Khamar-Daban ridge over the Tunkin Depression reached 500-700 m at the beginning of volcanic activity, the total amplitude of vertical movements due to deformation associated with the igneous activity attained 3,500 m.
BELOV, I.V. 1963. The trachybasalt formation of the Baikal region. USSR Academy of Sciences, Moscow. 371 pp.
KISELEV, A.I. 1981. Cainozoic volcanism of central and eastern Asia. In N.A. Logachev and S.I. Sherman (eds) Problems of fissure tectonics. 71-86. Nauka, Siberian Branch of the Academy of Sciences, Novosibirsk.
KONONOVA, V.A., KELLER, J. and PERVOV, V.A. 1993. Continental basaltic volcanism and the geodynamic evolution of the Baikal-Mongolian region. In. Magmatism of rifts and sedimentary belts. 234-64. Nauka, Moscow.