VOLCANIC COMPLEXES AND TECTON-MAGMATIC STAGES OF THE EVOLUTION OF THE MAGELLAN SEAMOUNTS (PACIFIC OCEAN). MESSAGE 1: VOLCANIC COMPLEXES

The paper presents original and published data of radioisotope dating of volcanic rocks of the Magellan Seamounts. These data and available geological materials allow us to distinguish five major volcanic complexes of different ages in the guyots of the Magellan Seamounts: 1 — Late Jurassic-Early Cretaceous (earliest Cretaceous); 2 — Early Cretaceous (Apt-Albian); 3 — Late Cretaceous (Late Cenomanian-Turonian- Early Campanian); 4 — Late Cretaceous (Late Campanian-Maastrichian); 5 — Cenozoic. Each of these age complexes corresponds to a specific tectonic-magmatic stage of the evolution of the Magellan Seamounts and characterizes a specific geomorphological space (pedestal, main body, small complicating superimposed structures of the second order). This division is based on numerous isotopic age determinations for 11 guyots obtained by K-Ar and Ar-Ar methods. The tectonic-magmatic evolutionary stages of the Magellan Seamounts correspond, in general, to the periods of tectonic activation for other structures of the Pacific Ocean bed.