TECTONICS OF VENUS - A REVIEW

The article presents a new tectonic scheme of Venus and gives the following interpretation of the planet's main structural units: (1) plains - areas of flood volcanism over stretched crust; (2) dome-like uplifts - areas of uplifting and volcanic activity above the mantle hot-spots; (3) coronae - former dome-like uplifts, partially subsided and diffused by gravity; (4) ridge belts - fold zones; (5) tesserae - fragments of ductile compression and shortening of crust; (6) supercoronae - coronae formed in the course of further evolution and relaxation of Beta-type uplifts. Ishtar Terra is considered to be a fragment of an ancient tessera paleocontinent, on the edge of which the Lakshmi supercorona is superimposed. Aphrodite Terra is considered as a belt of mantle hot-spot structures (dome-like uplifts, coronae, supercoronae, volcanoes, rifts). Three types of planetary belts have been distinguished on Venus: uplifted 'weakened' belts with an abundance of mantle hot-spot structures; a northern fan of ridge belts; and belts of low basalt plains. The center of the planetary system of uplifted weakened belts is situated in Atla Regio. The present tectonic structure of Venus is inferred to have formed during two stages of evolution characterized by different tectonic regimes. Stage I is a regime of soft ductile plates (formation of tessera uplifts and volcanic plains). Stage II is a formation of 'weakened' uplifted planetary belts, various tectonic regimes of mantle hot-spots, and plains-forming volcanism.