John Grotzinger Thomas H Jordan Frank Press Raymond

Concepts you will need to know for the exams CHAPTER 6 • • •

Factors that control the type and degree Metamorphism • Heat • Pressure • Fluids

Temperature increases with depth A typical continental geothermal gradient is 30 degrees C per

Confining Pressure Confining pressure is the same in all directions (incl. 3 rd dimension)

Directed Pressure When one pressure is greater than the other three (incl. 3 rd

Fluids • Accelerate chemical reactions • Dissolve ions and move them from one mineral

TYPES OF METAMORPHISM Pressure (Impacts) Subduction Zones e Regional Metamorphism d ra Burial e

Types of metamorphism shock, contact, regional, and burial

Shock metamorphism Depth, km 0 Con tine 35 nta l cr Con ust tine

Regional metamorphism Shock metamorphism Depth, km 0 Con tine 35 nta l cr Con

Textures to distinguish metamorphic rocks

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Concepts you will need to know for the exams CHAPTER 6 • • • • METAMORPHIC ROCKS Controls on metamorphism by: P, T, fluids Isotherm Geothermal gradient Confining pressure Directed pressure Regional metamorphism Contact metamorphism High-P metamorphism Burial or low-grade metamorphism Foliated texture Crystal Growth Pressure-Temperature Paths (pro-grade and retrograde metamorphism)

Factors that control the type and degree Metamorphism • Heat • Pressure • Fluids

Temperature increases with depth A typical continental geothermal gradient is 30 degrees C per kilometer Where is the 1300 degree isotherm? Old lithosphere - 150 km New lithosphere (Divergent) - 30 km Volcanic regions (Convergent)- 50 km

Confining Pressure Confining pressure is the same in all directions (incl. 3 rd dimension) In water, that is one ton per m 2 each meter of depth 10 m ~ 1 atm or 10 tons of pressure

Directed Pressure When one pressure is greater than the other three (incl. 3 rd dimension) If directed pressure is great enough rocks can break and/or fold

Fluids • Accelerate chemical reactions • Dissolve ions and move them from one mineral to another • (A change in rock composition by fluid transport is metasomatism) metasomatism

TYPES OF METAMORPHISM Pressure (Impacts) Subduction Zones e Regional Metamorphism d ra Burial e r c g g in s a In Mountain belts (low-P, low-T), low-grade Fluids metasomatism) Contact Temperature

Types of metamorphism shock, contact, regional, and burial

Shock metamorphism Depth, km 0 Con tine 35 nta l cr Con ust tine nta lm 75 ant le As th en osp he re Regional metamorphism lith osp Oceanic crust Oceanic lithosphere her e

Regional metamorphism Shock metamorphism Depth, km 0 Con tine 35 nta l cr Con ust tine nta lm 75 ant le As th en osp he re Regional metamorphism lith osp Oceanic crust Oceanic lithosphere her e

Regional metamorphism Shock metamorphism Depth, km 0 Con tine 35 nta l cr Con ust tine nta lm 75 ant le As th en osp he re Regional high-pressure metamorphism Regional metamorphism lith osp Oceanic crust Oceanic lithosphere her e

Regional metamorphism Shock metamorphism Depth, km 0 Con tine 35 nta l cr Con ust tine nta lm 75 ant le As th en osp he re Regional high-pressure metamorphism Contact metamorphism Regional metamorphism lith osp Oceanic crust Oceanic lithosphere her e

Regional metamorphism Shock metamorphism Depth, km 0 Con tine 35 nta l cr Con ust tine nta lm 75 ant le As th en osp Regional high-pressure metamorphism Contact metamorphism Regional metamorphism lith osp Oceanic crust Oceanic lithosphere her e he re Water Seafloor metamorphism

Textures to distinguish metamorphic rocks