Transcript Igneous_rocks

How do mantle rocks melt ?
1. Adding water to the system: flux melting
2. Decompress the rocks- decompression melting
3. Heating
Path 2
Path 1
Magmatic activity and plate tectonic setting
Liquid line of descent
How do igneous rocks evolve?
Fractional crystallization
How do igneous rocks evolve?
Fractional crystallization
How do igneous rocks evolve?
Fractional crystallization
Igneous Textures
Phaneritic
Aphanitic
Porhpyritic
Glassy
Vesicular
Pyroclastic
Phaneritic
Phaneritic – individual grains in an igneous rock are large
enough to be identified without the aid of a microscope
Aphanitic
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Porhpyritic
Porphyritic-igneous texture referring to relatively large isolated crystals
in a mass of fine texture (aphanitic) groundmass
Glassy
Glassy textured igneous rocks are non-crystalline.
Generally indicate very rapid cooling.
Vesicular
Vesicular –Texture characterized by
Vesicles (holes, pores, or cavities) within
the igneous rock. Vesicles are
the result of gas expansion
(bubbles). Bubbles can by filled by
secondary minerals due to fluid infiltration
(Amygdule).
Pyroclastic
Pyroclastic – composed chiefly of (variable) rock fragments.
Gabbro
Granite
Andesite
Classifying igneous rocks
Streckeisen diagram (1974)
How to classify a igneous rock
Estimate plutonic or volcanic based on texture
modal abundance of mafic vs felsic minerals (dark vs light colored)
If M (%mafic minerals) is <90% use Streckeisen diagram
Determine modal abundances K-feldspar, Plagioclase , Quartz,
renormalize to 100%, plot in QAPF diagram.