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:

Know this picture

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 AndesiteFine-grained Basalt Pumice GraniteVesicular basalt Gabbro Rhyolite Porphorytic Basalt