The chemical and thermal evolution of rifts

摘要: Abstract Any concept of the development continental rifts requires integration observations on lithosphere structure, movements, and magmatic geology, with more customary geologic geophysical evidence. Timing is crucial, only magmatism can chronicle chemical thermal changes in underlying mantle. Control activity by older structures clear from repetition alkaline magmatism, which marks release gas-charged magmas deep sources repeatedly tapped reopening lesions plate. Frequently this found ancient cratons where it perforates deeply eroded sections granulites, themselves highly depleted volatiles presumably indicating a similar condition This pattern, abundance incompatible elements, capricious volcanic distributions, are explicable if acts as template through channelled Earth's interior. A large mantle reservoir would then be drained narrow rift zone, causing metasomatism, expansion melting. The will express interplay previous composition structure volatile activity. spectrum may delineated isolated kimberlite pipes craton nucleii to multifarious affecting recently deformed belts. igneous (chemistry, distribution, timing, volumes) inexplicable source upwelling below lithosphere. contrasting activities oceanic compatible they result different stages splitting. Fissuring plate releases volatiles, any melt generation takes place itself. When separation occurs, sub-lithosphere must rise into opening, providing voluminous tholeiitic decompression