convergent plate boundaries

• Ocean ocean:

  Trapped water on the subducting plate the water turns to vapour and there is flux melting of the mantle wedge to make mafic magma. 
• Ocean convergent:

  Trapped water on the subducting plate turns into water vapour - flux melting of the mantle wedge. Rising of the mafic magma (stoping and assimilation) partially melts the silicic continental lithosphere - increasing the silica content of the magma. This is magma contamination. 

   
• Trap topography - when a mantle plume is underneath continental lithosphere. 
• Triple junctions - where there are three plates rifting. In the middle of the three plates is found a mantle plume. Can be unsuccessful. 
• Silicic magma:

  • Small blebs of magma are generated 
  • They are less dense and rise 
  • They meet other blebs and join together 
  • It makes a diapir 
• Diapir:

  • As it rises it forces the crustal rock apart 
  • Domes up overlying beds 
  • Drags bedding upwards
  • Upwards movement through stoping and assimilation 
  • Increasing silica content 
• Silicic gas content:

  • Increases viscosity with gas content 
  • Increased gas increases buoyancy 
  • More gas increases explosivity 
  • Decrease in density with gas content 
• Liquidus - the temperature above which a material is a liquid 
• Dry liquidus - dry rock without any water would be molten 
• Wet liquidus - wet rock with as much water as it can hold becomes molten