Chapter 8 Test Flashcards
What is metamorphism?
It means to “change form”. Metamorphism is a process that leads to changes in the mineralogy, texture, and sometimes the chemical composition of rocks.
What is Parent rock?
The rock from which it formed. Parent rocks can be igneous, sedimentary, or other metamorphic rock.
What rocks show low-medium-and high?
Slate, Phyllite, Schite, and Gneiss
What does Slate look like?
Slate is very fine-grained has excellent rock cleavage
What does Phyllite look like?
Phyllite has a glossy sheen and wavy surfaces and exhibits rock cleavage
What does Schist look like?
Schist is medium to coarse-grained and has platy minerals ( mainly micas ) predominate and it can also contain porphyroblasts.
What does Gneiss look like?
Gneiss is composed of light-colored, feldspar-rich layers with bands of dark ferromagnesian minerals
What is Recrystallization?
The process of forming new, stable minerals larger than the original
How is metamorphic rock related to parent rock?
Metamorphic rocks have the same overall chemical composition as the original parent rock
What is foliation?
Foliation describes any planar arrangement of mineral grains or structural features within a rock
What forces create foliation?
The forces are rotation of platy minerals, recrystallization that produces new minerals perpendicular to the direction of maximum stress, and flattening spherically shaped grains.
What is Porphyroblastic texture?
Unusually large grains, called porphyroblasts, are surrounded by a fine-grained matrix of other minerals.
What are the environments of metamorphism and how they form?
Contact or Thermal Metamorphism, Hydrothermal Metamorphism, Burial Metamorphism, Subduction Zone Metamorphism, Regional Metamorphism, Metamorphism along Fault Zones, Impact Metamorphism
Contact or Thermal Metamorphism
results from a rise in temperature when magma invades a host rock and it occurs in the upper crust ( low pressure, high temperature ). Aureole forms in the rock surrounding the magma
Hydrothermal Metamorphism
is chemical alteration caused by hot, ion-rich fluids circulating through pore spaces and rock fractures. It typically occurs along the axes of mid-ocean ridges. Ex: Black smokers
Burial Metamorphism
associated with very thick sedimentary strata in a subsiding basin. Ex: Gulf of Mexico
Subduction Zone Metamorphism
is sediments and oceanic crust are subducted fast enough that pressure increases before temperature
Regional Metamorphism
produces the greatest quantity of metamorphic rock and is associated with mountain building and the collision of continental clocks
Metamorphism along Fault Zones
occurs at depth and high temperatures and pre-existing minerals deform by ductile flow. Mylonites form in these regions
Impact Metamorphism
occurs when meteorites strike Earth’s surface. The product of these impacts are fused fragmented rock plus glass-rich ejecta that resemble volcanic bombs called impactiles.
What are Index minerals?
Index minerals are good indicators of metamorphic environments
What are agents of metamorphism?
Heat, pressure ( stress ), and chemically active fluids
What is the Value of Geothermal Gradient?
25 degrees Celsius per kilometer.
What are 2 types of metamorphic texture?
Foliation and Non Foliated
