KLent Presentation: Changes in Rock Minerals

THE CHANGES OF MINERAL COMPONENTS OF ROCKS DUE TO CHANGES IN PRESSURE AND TEMPERATURE LEARNING OBJECTIVES At the end of the lesson, you should be able to: 1. define metamorphism. 2. describe the physical and chemical changes in rocks due to changes in pressure and temper...

THE CHANGES OF MINERAL COMPONENTS OF ROCKS DUE TO CHANGES IN PRESSURE AND TEMPERATURE LEARNING OBJECTIVES At the end of the lesson, you should be able to: 1. define metamorphism. 2. describe the physical and chemical changes in rocks due to changes in pressure and temperature (metamorphism). THE CHANGES OF MINERAL COMPONENTS OF ROCKS DUE TO CHANGES IN PRESSURE AND TEMPERATURE Inside the earth new types of rocks is being Have you ever wondered how rocks were formed or formed from other type change from one type to of rocks in the process another? called metamorphism. METAMORPHISM comes from ancient Greek words (meta) for “change’’ and (morp) for “form’’. Metamorphism means the after form. In geology this refers to the changes in mineral assemblage and texture that result from subjecting a rock to pressures and temperatures different from those under which the rock originally formed THE CHANGES OF MINERAL COMPONENTS OF ROCKS DUE TO CHANGES IN PRESSURE AND TEMPERATURE METAMORPHISM -the original Rock is transformed. And this process Called Metamorphism -The original rock can either be igneous rock or Sedimentary rock -The original rock charges in its mineral composition and texture - often forming larger crystals THE CHANGES OF MINERAL COMPONENTS OF ROCKS DUE TO CHANGES IN PRESSURE AND TEMPERATURE This Photo by Unknown Author is licensed under CC BY-SA-NC  THE CHANGES OF MINERAL COMPONENTS OF ROCKS DUE TO CHANGES IN PRESSURE AND TEMPERATURE the isochemical process by which METAMORPHIS rocks are changed by heat and M pressure or some chemically active fluids. Main Factors -Pressure -Heat and Reactive Fluids PRESSURE: Measure of the stress of physical force applied to the surface of a mineral The higher the pressure, the greater the degree of metamorphism This usually happen in subduction zone  When rocks undergo folding or faulting due to very high pressures exerted over relatively short periods of time This type of pressure: Is called Tectonic pressure  TEMPERATURE IS ALSO A FACTOR OF METAMORPHISM As temperature increases, the rate of metamorphic reactions also increases If rocks are buried within the Earth, the deeper the rock gets, INCREASING the higher the TEMPERATUR temperature it E experiences. Temperature also increases with depth, due to the geothermal gradient.  chemically active fluid that is mostly water FLUID PHASE with dissolved ions. The fluid phase is essential because chemical reactions that involve altering a solid mineral into a new solid mineral can be greatly speeded up by having dissolved ions transported by the fluid.  The Two Primary Types of Metamorphism 1) CONTACT METAMORPHISM - HEAT When intruding molten rock moves up through the crust. The molten Rock 'Cooks' the country rock when the magma comes in contact with it. -The country rock will change in minerology and texture when it is cooked by the hot molten rock -Only occurs in small Contained regions  2)REGIONAL METAMORPHISM = HEAT + PRESSURE Commonly occurs in regions of mountain building - Where there two converging continental plates -Subduction zones were oceanic plates is moving below a continental plate Extreme compressional forces on the crust along with heat causes changes in the rock minerals and texture It occurs across large regions associated with folding of Rock The rock will fold because of the compressional force act open it  THE DIFFERENCE BETWEEN THE TWO Contact metamorphism involves small-scale rock alterations due to contact with magma, while regional metamorphism relates to large-scale rock deformation due to tectonic forces.  a general term for describing the relative METAMORPHIC GRADEtemperature and pressure conditions under which metamorphic rocks form. "As the temperature and pressure increases on a body of rock then grade of metamorphism increases." LOW-GRADE METAMORPHISM Takes place at temperatures between 200 to 320°C, and relatively low pressure. Hydrous Minerals (minerals that contain water in their crystal structure). MEDIUM-GRADE METAMORPHISM ✓ Takes place at approximately at 320 - 450 °C and at moderate pressures HIGH-GRADE METAMORPHISM ✓ Takes place at temperatures above 450 °C.