Ig Met Final Review Notes

Metamorphic Samples

• Minerals in Metamorphic Rocks:

  • It is essential to understand which minerals are present based on the bulk composition of the rock.

Igneous Samples

• Normalization of Mineral Composition:

  • Understanding how to normalize mineral composition to essential minerals.

  • Ability to plot these on a ternary diagram.

• Igneous Textures and Rock Names:

  • Critical to differentiate between igneous and metamorphic rock names and textures.

  • Porphyroblasts vs. Phenocrysts:

  • Porphyroblasts: Large crystals typically formed in metamorphic rocks.

  • Phenocrysts: Crystals that form in igneous rocks during the cooling of magma.

• Texture Formation:

  • Describe the processes that lead to specific textures in igneous rocks.

  • Intrusive vs. Extrusive Textures:

  • Textures that indicate whether a rock is formed intrusively (within the Earth) or extrusively (on the surface).

Metamorphic Facies

• Protolith of Metamorphic Facies:

  • Understanding what rock types (protoliths) are associated with specific metamorphic facies.

  • Mineral Assemblage of Facies:

  • Examples include the mineral assemblage of greenschist facies or amphibolite facies.

Tectonic Settings for Igneous Rocks

• Tectonic Settings:

  • Granite: Not found at mid-ocean ridges.

  • Basalt Locations: Exploration of where basalt can be found and variations such as MORB (Mid-Ocean Ridge Basalt), OIB (Ocean Island Basalt), and continental rift basalt.

Compatible vs. Incompatible Elements

• Definitions:

  • Compatible Elements: Prefer to stay in the melt during crystallization (e.g., Mg, Fe).

  • Incompatible Elements: Prefer to crystallize out of the melt (e.g., LILE - Large Ion Lithophile Elements, such as K, Ba; HFSE - High Field Strength Elements, such as Nb, Zr).

Magma Generation

• Ways to Form Magma:

  • Adding volatiles to source rock.

  • Decreasing pressure (e.g., mantle processes).

  • Settings that Produce Melts: Subduction zones, hotspots, spreading centers.

• Types of Magma:

  • Alkaline vs. Tholeiitic: Description of where each type is typically found.

Lava Textures

• Types of Lava Textures:

  • A.A. (A'a): Rough, jagged surfaces.

  • Pahoehoe: Smooth, ropy surface.

Igneous Structures

• Sizes and Formation:

  • Stock: Smaller, less extensive magma body.

  • Pluton: A larger igneous body.

  • Intrusion: Any body of magma in another rock.

  • Batholith: The largest type of igneous body.

Types of Granites

• Granite Types:

  • S-type: Derived from sedimentary rocks.

  • I-type: Derived from igneous sources.

  • A-type: Alkaline, typically found in rift settings.

  • M-type: Mantle-derived.

Igneous Textures

• Grain Size:

  • Aphanitic: Fine-grained texture.

  • Phaneritic: Coarse-grained texture.

  • Pegmatitic: Very coarse-grained texture, often with large crystals.

  • Porphyritic: Contains larger crystals in a fine-grained matrix (not to be confused with porphyroblastic).

• Crystallinity:

  • Holohyaline: Entirely glassy.

  • Hypohyaline: Partially crystallized.

  • Holocrystalline: Entirely crystalline.

• Grain Shape:

  • Euhedral: Well-formed crystals.

  • Subhedral: Partially formed crystals.

  • Anhedral: Poorly formed crystals.

Vesicular Textures

• Types of Vesicular Textures:

  • Vesicular: Containing gas bubbles.

  • Amygdaloidal: Vesicular texture filled with secondary minerals.

Other Important Textures

• Various notable textures that characterize igneous rocks:

  • Trachytic: Aligned feldspar laths.

  • Corona/Reaction Rim: Indicates mineral reaction zones.

  • Zoning: Compositionally varied across a crystal.

  • Graphic: Intergrowth of quartz and feldspar.

  • Poikilitic: A texture where large crystals enclose smaller crystals.

  • Ophitic: A texture characterized by plagioclase laths enclosing augite.

  • Perthite: A mixture of alkali feldspar with sodium-rich plagioclase.

  • Antiperthite: Opposite of perthite; plagioclase with alkali feldspar.