Flashcards in Earth Materials Deck (39)
What igneous rock forms ar MOR
What is the mantle made of?
What is peridotie?
A coarse grained ultramafic rock
How does basaltic magma form from an ultramafic mantle?
heating and decompression melting
What is fertile mantle, and what is it called?
the mantle before melting occurs- Lherzolite
What does lherzorite contain
Ortho + clioropyroxene
What does hazburgite contain?
Olivene and chlinopyroxene
What is oceanic crust made of?
Bassalt, dolerite, gabbro
Where do island arcs occur? give an example
Oceanic crust beneath oveanic crust
Monseerat- Atlantic ocean crust under carrebbian plate
Where do continental arcs occur?
Oceanc under continental
Mt St helens, one of chain of volcanoes- carrebien under atlantic
How are granitoids produced?
1) melting of continental crusts
2) fractionisation of basaltic crust
What compesition is andersite?
-Plagioclase, pyroxene, amphibole (water bearing)
What is an amphibole?
Mafic water bearing minerals
Describe an amphibole under the microscope
ppl-colourless, green-brown, prismatic, moderate relief
What kind of volcanoes does continental subduction create?
Give examples of continental subduction volcanoes
-Andes (south america)
-costa rica centeral america
What kind of mineralisetion does continental subdicion give rise to?
Porphyry copper- from hydrothermal fluids
What is a stratvolcano?
Pyroclastic fragmeented rocks produced by violent erruption
Describe a subduction volcano?
Errution of ANDERSITIC lavas and PYROCLASTIC deposits
STEEP SIDED COMPERSITE STRATAVOLCANOES
What chain ov volcanoes does mt st helens belong too?
What is diorite?
-coarse grained intermediate
-biotite pyroxene and plagioclaise
What does a pyroclastic flow consist of?
-Fragments of lava
-Ignimbrite flows cool and form ash flow tuffs
What kind of magmasdo arc volcanoes commonly errrupt?
-More silica rich
-DACITES AND RHYOLITES
-cold and freexe quickly- obsidian
What is pummice?
Pummive forms when extreemly viscous magmas become frothy due to gas exolving out
When pressure drops it solididies to form PUMMICE
What are the most common inerals in RHYOLITE and DACITE
alkali felspas and quartz
-some micas and hornblende in dacite
What minerals are common in granite?
alkali fspa, qts, mica and hornblende
What dominares felsic rocks
QTZ and FSPA
What plates produce the Italian volcanoes
African under european
-Feeder dykes STRATAVOLCANO
-Strombolian cones found at lower levels
- volcanic gasses from creaters