VOLCANOGENIC AND VOLCANICLASTIC RESERVOIR ROCKS IN MESOZOIC-CENOZOIC ISLAND ARCS - EXAMPLES FROM THE CAUCASUS AND THE NW PACIFIC

Subduction of the Tethys oceanic plate beneath the Lesser Caucasus isl and are in the Late Cretaceous - Eocene produced conditions favourable for the generation and accumulation of hydrocarbons. Subduction of cr ust in the Transcaucasus Massif led to the formation of various types of trap. Also, geothermal gradients here were high, resulting in the g eneration of hydrocarbons in shallow-water sediments on the margins of the Massif and their accumulation in both sedimentary and volcaniclas tic reservoirs (e.g. in the Samgori-Patardzeuli and Muradkhanly fields ). The geodynamic setting of the NW margins of the Pacific Ocean was s imilar in the Neogene to that of the Transcaucasus Massif. Oceanic cru st was subducted during the Oligo-Miocene, and a series of inter-arc r ifts were formed The principal oilfields of Japan, where accumulations are reservoired in volcaniclastic strata (Neogene-Pleistocene) are lo cated here. A possible analogue is the rift located in the southern Ea st Kuril Basin, where the occurrence of petroleum has been inferred. L ithological studies of the Komandorsky Islands, eastern Kamchatka, the Kuril Islands and western Sakhalin indicate that the distribution of the reservoirs depends on the stage of evolution of the rifts and adja cent island arcs.