Upstairs-downstairs: supercontinents and large igneous provinces, are they related?

摘要

There is a correlation of global large igneous province (LIP) events with zircon age peaks at 2700, 2500, 2100, 1900, 1750, 1100, and 600 and also probably at 3450, 3000, 2000, and 300Ma. Power spectral analyses of LIP event distributions suggest important periodicities at 250, 150, 100, 50, and 25million years with weaker periodicities at 70-80, 45, and 18-20Ma. The 25million year periodicity is important only in the last 300million years. Some LIP events are associated with granite-forming (zircon-producing) events and others are not, and LIP events at 1900 and 600Ma correlate with peaks in craton collision frequency. LIP age peaks are associated with supercontinent rifting or breakup, but not dispersal, at 2450-2400, 2200, 1380, 1280, 800-750, and <= 200Ma, and with supercontinent assembly at 1750 and 600Ma. LIP peaks at 2700 and 2500Ma and the valley between these peaks span the time of Neoarchaean supercraton assemblies. These observations are consistent with plume generation in the deep mantle operating independently of the supercontinent cycle and being controlled by lower-mantle and core-mantle boundary thermochemical dynamics. Two processes whereby plumes can impact continental assembly and breakup are (1) plumes may rise beneath supercontinents and initiate supercontinent breakup, and (2) plume ascent may increase the frequency of craton collisions and the rate of crustal growth by accelerating subduction.