The Upper And lower Limits of Metamorphism At the lower end, metamorphism occurs in sedimentary and igneous rocks that are subjected to temperatures greater than about 100C, usually under pressures of hundreds of atmospheres, caused by the weight of a few thousand meters of overlying rock. At the upper end, metamorphism ceases to occur at temperatures that melt rock
The Upper And Lower Limits Of Metamorphism ◼ At the lower end, metamorphism occurs in sedimentary and igneous rocks that are subjected to temperatures greater than about 100oC, usually under pressures of hundreds of atmospheres, caused by the weight of a few thousand meters of overlying rock. ◼ At the upper end, metamorphism ceases to occur at temperatures that melt rock
Role of water in Determining the Limits of Metamorphism The water present controls the temperature at which wet partial melting commences and the amount of magma that can form from a metamorphic rock When a tiny amount of water is present only a small amount of melting occurs. ■ Migmatites混合岩 are composite rocks that contain an igneous component formed by a small amount of melting plus a metamorphic portion
Role of Water in Determining the Limits of Metamorphism ◼ The water present controls the temperature at which wet partial melting commences and the amount of magma that can form from a metamorphic rock. ◼ When a tiny amount of water is present, only a small amount of melting occurs. ◼ Migmatites 混合岩 are composite rocks that contain an igneous component formed by a small amount of melting plus a metamorphic portion