EAS 220 Lab 4: Igneous Rocks

Overview

Today's lab focuses on the study of igneous rocks, covering their formation, textures, and classification based on Bowen’s Reaction Series.

Lab Components

• Introduction
• Formation of Igneous Rocks
• Textures of Igneous Rocks
• Bowen’s Reaction Series
• Igneous Rock Identification
• Use of Petrographic Microscopes

Formation of Igneous Rocks

• Igneous rocks are formed through the cooling and solidification of magma or lava.

Textures of Igneous Rocks

• Aphanitic: Fine-grained texture where mineral crystals are not visible to the naked eye.
• Phaneritic: Coarse-grained texture with visible mineral crystals.
• Porphyritic: Texture featuring large crystals embedded in a finer-grained matrix.
• Vesicular: Characterized by small cavities known as vesicles.
• Glassy: Smooth, glass-like texture due to rapid cooling.

Bowen’s Reaction Series

• A classification scheme that describes the sequence of mineral crystallization from cooling magma.

Classification Scheme

• Differentiates between intrusive rocks (formed below the Earth’s surface) and their extrusive equivalents (formed at or above the surface).

Petrographic Microscopes

• Utilized to observe minerals in thin sections.

Minerals

• Quartz
• Feldspars
• Micas
• Pyroxene
• Olivine
• Hornblende
• Biotite
• Muscovite