CH 4 - Intrusives

Are you ready for the test?

What is country rock?

• Existing rock already formed.

What are intrusives?

• Igneous rock formed underground between country rock.

What does concordant mean?

• Parallel to country rock

What does discordant mean?

• Perpendicular to country rock.

4 ways to classify intrusives

• Size

• Shape

• Depth

• Relation to country rock

Most abundant intrusive rock?

• Granite

Why is erosion important to studying intrusives?

• Expose intrusives.

Shallow vs deep intrusives make what type of rocks?

• Shallow – small grained crystals; aphanitic, like basalt

• Deep – large grained crystals; phaneritic, like granite

What are xenoliths?

• Alien rocks

Know real pictures of intrusives.

Name the intrusives:

Name the intrusives:

Know this picture

Use Bowen’s Reaction Series:Use Bowen’s Reaction Series:

• What minerals in what rocks?• What minerals form in what order?• What rocks & minerals come from what magma?• What rocks & minerals are most/least stable?• What minerals form at what temps?• Discontinuous vs continuous branches• Aphanitic vs Phranetic rocks

Rock Textures Physical Conditions

What rocks come from Mafic magma?

• Basalt, Gabbro

What rocks come from Felsic magma?

• Granite, Rhyolite

What rocks come from Intermediate magma?

• Andesite, diorite

What rocks are found at divergent boundaries?

• Mafic - Basalt, Gabbro

What rocks are found at convergent boundaries?

• Intermediate – andesite, diorite

• Felsic – granite, rhyolite

What three factors can lower minerals’ melting points?

• Pressure

• Mixing minerals

• Pressurized Water

What are 4 ways magma can change?

• Differentiation; crystal settling

• Magma mixing

• Assimilation

• Partial Melting

Be able to identify 9 igneous rocks.

Obsidian Andesite Fine-grained Basalt

Pumice Granite Vesicular basalt

Gabbro Rhyolite Porphorytic Basalt