PLUTONIC INCLUSIONS IN LAVAS OF THE PORPHYRITE SERIES OF SOVIET GEORGIA (FIRST FINDS)

Abstract

The 'porphyrite series' of Georgia consists of basalt, andesite-basalt and andesite lava flows and sheets, pyroclastic units, and comagmatic hypabyssal intrusive bodies, chiefly of the gabbro-dolerite composition. This thick volcano-sedimentary sequence, Aalenian to Bajocian in age, extends in an almost continuous band parallel to the Main Caucasus Range from Abhazia to Trans-Alazani Kakhetia and Azerbaydzhan. Three main types of inclusions are known: 1) xenoliths of the host rocks, 2) cumulates of phenocrysts, and 3) fragments of the rocks that constituted the magma source. During field work in 1987 on the south flank of the Greater Caucasus, in the basin of the Kodori River (near the mouth of the Zima), the authors found ultramaficmafic inclusions in spilitized basalt and picrite of the 'porphyrite series'. In this region these rocks form lava flows and sheets 20 to 30 m thick, often of pillow structure. The space between pillows is filled with epidote-zoisite and carbonate material. The paper discusses these finds.