Chapter 7 -- Metamorphism Flashcards
Which agent of metamorphism is provided by intrusive magmas or deep burial? Increases the rate of chemical reactions that produce minerals…Causes minerals in sedimentary rocks to re crystallize or form new minerals…Temperature increases with depth. The geothermal gradient averages about 25 degrees C.
Heat
The process that changes either the mineralogy, texture, or both of a pre existing rock due to heat and or pressure and or fluids
Metamorphism
What agent of metamorphism is produced by overlying rocks or is differential pressure produced by various stresses?
Pressure
What agent of metamorphism increases the rate of metamorphism?
Fluid Activity
Type of pressure…
Applied equally in all directions
Mineral grains get packed closer together.
Re-Crystallization produce smaller and more dense minerals
Lithostatic Pressure
Type of pressure…
Pressure applied on opposite sides
Mineral grains are more closely packed.
Re-Crystallization may occur, producing elongated and denser minerals.
Differential Pressure
What types of fluids are associated with fluid activity?
Water trapped in the pore space of sedimentary rocks.
Fluids in magma
Water bearing minerals in the rock
Type of Metamorphism
Magma alters the surrounding country rock.
High temp and low pressure.
This depends on: The initial temperature and size of intrusion.
Contact Metamorphism
Type of Metamorphism
Found in regions with numerous faults
Rocks are forced to slip past other rocks in the opposite directions
High Pressure/Low Temp
Mylonites form by Re-Crystallization of the rock due to shear stress and deformation.
Dynamic Metamorphism
Type of Metamorphism
Produces the most metamorphic rocks and make up a large part of all continents.
High Temp and High Pressure
Covers large areas and shows a progression of deformation relating to areas of the most intense heat and pressure.
Regional Metamorphism
Differential pressure causes minerals to arrange themselves in a parallel fashion called….
Slate…Phyllite…Schist…Gneiss
Size and shape of crystals determines texture; fine to coarse
Foliated Metamorphic Rocks
Minerals do not show a preferred orientation…Commonly composed of one mineral or very fine grained textures…Pore space is completely gone and is a result of equal pressure on all sides.
Marble…Quartzite
Non Foliated
Groups of rocks characterized by similar mineral assemblages formed under the same temperature or pressure conditions.
Metamorphic Facies
Metamorphism in Relation to Plate Techtonics.
Temperature and pressure increase in collisions…Several facies are recognized in this model, defined by temp/pressure conditions.
Convergent Boundaries
