MANTLE PLUMES AND THEIR ROLE IN THE FORMATION OF ANOROGENIC GRANITOIDS

Abstract

The periodicity of plume magmatism has been reviewed in this paper, which also demonstrates a correlation between trap magmatism and Permo-Triassic granitoids as well as general regularities of collision and postcollision granitoid magmatism and the role of plumes in their manifestation. It has been established that the Permo-Triassic superplume is expressed over vast spaces of Asia in two forms: (1) at places with cold lithosphere, in the form of Siberian and Emeishan traps: (2) at places with thickened lithosphere and crust, as a result of preceding collision events, in the form of syenites and A-granites. Effusions of the Siberian traps and intrusion of associating granitoids are largest-scale events in the Earth's history. At their peaks, the effusions of both Siberian and Ontong Java plumes were about 8-10·106 km3 for 1 myr. With gaps between effusions taking 90 % of the time, the effusions could reach 100 km3 a year or, with intrusions taken into account, twice as much. The superplumes are good labels for event synchronization on a global scale, with superplumes appearing at time of 120, 250, and, possibly, about 360 and 485 myr. An interval of 120 myr can also be supposed for the Late Precambrian superplumes: at about 610, 730, and 850-860 Ma. Smaller local plumes are expressed between superplumes, with a periodieity of about 30 myr.