THE HEAT EFFECT OF TRAP INJECTION ON THE SIBERIAN PLATFORM IN THE CONTEXT OF THE PLUME CONCEPT Available to Purchase

Problems of the relationship between mantle plumes and production of trap melts beneath continental platforms (cratons) at high temperatures and pressures are discussed. Generation of magnesian melts from ultrabasic mantle material yields, after their segregation in intermediate chambers followed by fractionation, a residual liquid fraction of tholeiitic basalts. Effusion of this fraction leads to vast lava fields, nappes, and abundant extended subvolcanic interbed intrusions. The heat effect of the Permo-Triassic trap magmatism on the Siberian Platform is estimated on the assumption that the trap melt is somewhat overheated by the primary melt of ultrabasic composition supplied by the head part of the plume. The maximum and minimum heat effects are used in the calculated diagram, which permits one to evaluate possible overheating (in calories) of traps at any temperature in the range mentioned. Frequent occurrence of holocrystalline and aphyric textures in effusive traps and great extension of thin subvolcanic sills as well as high-temperature exocontact effects indicate that trap-basaltic melts are actually overheated. The trap-melt overheating and the mantle plume concept are in agreement.