Date: ______________________

Sedimentary and Metamorphic RockChapter 6.2: Types of Sedimentary Rocks

Clastic

• Formed by the abundant deposits of loose sediments that accumulate• Course-grained rocks:

• Gravel-sized grains and miner fragments• Conglomerates – are gravel-sized with rounded edges; are transported by

fast-moving water• Breccia – angular, gravel-sized particles

• Fine-grained rocks:• Silt- and clay-sized particles found in places like swamps, ponds, and deep

ocean basins• Deposited by slow-moving water without strong currents or wave action

Chemical• Are known as evaporates• Dissolved minerals in a body of water becomes saturated and crystal precipitate out of

the solution and settle to the bottom• Mainly form in arid regions, drainage basis on continents with lower water flow, and in

coastal settings• Have a minimal input of freshwater and high rates of evaporation which maintains a

high concentration of dissolved minerals• Over time the minerals accumulate on the bottom of the basin

Biochemical• Formed from the remains of once-living organisms

• Limestone is the most abundant type and composed mainly of calcite (CaCO3); common in shallow water environments

• Coal: the fossilized remains of plant material

• Fossiliferous: limestone that contains an abundance of fossils or fossil traces

Chapter 6.3: Metamorphic Rock

Recognizing Metamorphic Rock• These are rocks that have been

further exposed to increases in temperature, pressure, and hydrothermal solutions to create entirely new types of rock

• The texture, mineral composition, or chemical composition of the rock changes without becoming completely molten

• High temperature occurs when rock is buried deeply or through nearby igneous intrusion

• High pressure occurs when the rock is buried deeply or during mountain building

Metamorphic minerals• According to Bowen’s reaction

series all minerals are stable at certain temperatures

• These ranges of stability also apply to mineral in solid rock

• During metamorphism, the minerals change into new minerals that are stable under the new temperature and pressure conditions

• As the metamorphic grade increases, the more the new rock is changed from its original composition

Metamorphic texturesFoliated

• Characterized by layers and bands of minerals• High pressure cause the minerals to form flat or needle-like crystals• The long axes are perpendicular to the pressure• Eg. Shale, phyllite, schist, gneiss

Non-foliated

• Mainly composed of minerals that form blocky crystal shapes• Marble and quartzite are the most common• Porphyroblasts – under certain conditions, some minerals form large crystals while

the surrounding crystals remain small• Eg garnet

Types of metamorphism

1. Regional metamorphism• Large areas of the Earth’s crust are affected• Causes an increase in temperature and pressure• Results in:

Changes in mineral and rock types Foliation Folding and deforming the rock layers

2. Contact metamorphism• Affects a relatively small area of the Earth’s crust• Occurs when magma comes into contact with solid rock• Characterized by high temperatures and low-to-moderate pressures• The heat from the intrusion does not reach far into the surrounding rock layers so

the metamorphic effects are limited to thin zones

3. Hydrothermal metamorphism• Very hot water can migrate into and out of rock during metamorphism• Chemical changes are common during contact metamorphism near igneous

intrusion and active volcanoes• Valuable ore deposits of gold (Au), copper (Cu), zinc (Zn), tungsten (W), and lead (Pb)

form in this manner

The Rock Cycle