1. Content 1.Geology of Isua (3.8Ga), Greenland, (1) presence of accretionary complex (horizontal stress field same as today), 2.(2) presence of water >1000m, and (3) AMORB is FeO-rich basalt, source T, 200K higher than today, and 2 wt% more FeO-rich than today. 2.Calculation of how rigid was the oceanic plate; thinner plate (40km vs 50km at 50Ma) with thicker crust (15-20km vs 6-7km) 3.Orogenic process at plate boundary, same as today (TTG formation & accretionary complex) 4.Dissimilarity, higher-T (200K higher, lower viscosity, double-layered mantle convection) 5.Orogenic belts over the world, i.e., island arcs, size of orogenic belt, collision- amalgamation to form continents Maruyama, S. (Tokyo Inst. Tech., Japan) When did plate tectonics start? Ans. Since 4.0 Ga When did plate tectonics start? Ans. Since 4.0 Ga

6. Dissimilarity Dissimilarity, higher-T (200K higher, lower viscosity, double-layered mantle convection) 5.Orogenic belts over the world, i.e., island arcs, size of orogenic belt, collision-amalgamation to form continents

10. Change of style of plate tectonics Archean style; young-hot buoyant subduction due to double-layered convection Mantle overturn (2.8-2.7Ga) Paleoproterozoic (2.3-0.7Ga); superplume, supercontinent-pPV cycle Phanerozoic (0.7Ga-present);Cold subduction zone

11. Orogenic belts of the world ■

14. Modern analog Western Pacific underlain by wet mantle with Archean viscosity Numbers of microplates (700km across, double-layered convection) Numbers of intra-oceanic arcs (70% of all arcs) Arc collisions to form a primitive continent

17. Orogenic belts of the world ■

29. Consuming plate boundary process (1)Pacific-type accretionary complex (2)Presence of ocean>1000m (pillowed basalt) (3)Followed by TTG plutonism (4)OPS tells origin of magma, MORB, OIB, or ARC, then source mantle T ＆ X