Classification of Igneous, Sedimentary and Metamorphic Rocks

ROCK CYCLE Equilibrium Interrelationships between igneous rocks sediment sedimentary rocks metamorphic rocks weathering and erosion

EXTRUSIVE Volcanic- Fine-grained INTRUSIVE Plutonic- Coarse-grained IGNEOUS ROCKS EXTRUSIVE Volcanic- Fine-grained INTRUSIVE Plutonic- Coarse-grained

MAGMA Molten Rock Generated at depth Usually with dissolved gasses Generated at depth Eruptions if magma (lava) reaches surface If doesn’t reach surface, Solidifies underground Intrudes country or host rock Intrusive contact Xenolith- ‘foreign body’ 2

Igneous Rocks Names based on mineral composition reflects chemical composition of the magma and... Grain size Very coarse-grained Pegmatitic Coarse-grained: Phaneritic > 1 mm. Fine-grained: Aphanitic < 1 mm. Porphyritic- 2 crystal sizes 3

Igneous Rocks- Classification Coarse-grained- Plutonic (Intrusive) Granite (Sialic) (SIlica and ALuminum rich) Diorite Gabbro (Mafic) (MAgnesium and iron (FE) rich) Dunite & Peridotite (Ultramafic) Fine-Grained Volcanic (Extrusive) Rhyolite (Sialic) Andesite Basalt (Mafic) 4

Igneous Rock Identification Granite (& Rhyolite) High in Si + O Low in Fe + Mg Mostly feldspar & quartz Light-colored Basalt (& Gabbro) “Low” in Si + O High in Fe + Mg no quartz, abundant ferromagnesian minerals Dark colored Andesite (& Diorite- intermediate) 5

WEATHERING, EROSION, TRANSPORTATION Weathering- Physical disintegration and chemical decomposition of rocks Erosion- Physical removal Transportation- Movement of eroded particles Chemical vs. Physical Weathering Effects of weathering Surface alteration of outcrops Spheroidal weathering Differential weathering

Physical Weathering

Differential Weathering

Frost Action

Exfoliation

Organic Action

ROCK CYCLE

Relative Percentages of Sedimentary Rocks

SEDIMENT Particle size Pebbles, cobbles, boulders Gravel- > 2mm Sand- 2mm - 0.063mm Silt - 0.063mm - 0.004mm Clay- < 0.004 Deposition Clay-sized particle vs. clay mineral

TYPES OF SEDIMENTARY ROCKS Clastic or Detrital Chemical- inorganic precipitation or evaporation Biochemical- Organic remains shells, charcoal, plant fragments

CLASTIC (Detrital) ROCKS Breccia and Conglomerate (> 2mm) Sedimentary Breccia- angular fragments Conglomerate- rounded fragments Sandstone (2mm - 0.063mm) Quartz sandstone Arkose (feldspar) Graywacke (appreciable amounts of silt/clay) Fine-grained Matrix Usually from turbidity currents

Quartz Sandstone

CHEMICAL SEDIMENTARY ROCKS Carbonate Rocks Limestone- made of calcite Inorganic varieties micrite, oolites, travertine Dolomite Recrystallization Chert- silica Evaporites Rock gypsum Rock salt

BIOCHEMICAL SEDIMENTARY ROCKS Coal Develops from peat plant fragments Lignite Bituminous Coal Carbonate Rocks Limestone- made of calcite organic varieties Coquina Fossiliferous Limestone Chalk

SEDIMENTARY STRUCTURES Cross-bedding Graded bed Mud cracks Ripple marks Fossils

Mudcracks

Sedimentary Rocks as Resources Non-Metallic Sand and gravel Limestone Clay Gypsum Energy Resources Oil and Gas Coal

Formation of Oil and Gas

U.S. Coal Production

Metamorphic Rocks Metamorphism Metamorphic rock Increase in Pressure; increase in Temperature Burial Contact Regional Metamorphic rock Pre-existing rock Parent rock

Foliation

Classification A- Slate C- Phyllite D- Schist E- Gneiss F- Migmatite

Classification