RVCC GCH GEOL157 Introduction to Geology Laboratory Manual GCH GEOL157 Lab3.pdf · 2018-01-20 · RVCC GEOL 157 Introduction to Geology Lab Manual GCH 2018-01 • Igneous rock forms

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1) Igneous are derived from the hardening of

molten magma (intrusive or volcanic, with felsic,

intermediate, and mafic varieties)

2) Sedimentary are derived from detrital or

chemical sediment, the products of mechanical

and chemical weathering and chemical

precipitation.

3) Metamorphic are the result of burial,

increasing temperature and pressure, and fluid

transfer processes during recrystallization

(low, medium, and high grade)

RVCC GEOL 157 Introduction to Geology Lab Manual GCH 2018-01

• Igneous rock forms when hot magma cools and solidifies. Sedimentary rocks form when

sediment is compacted and cemented together (lithified), or when minerals precipitate from

solutions. Mechanical weathering and physical breakdown of a parent material (usually rock)

produces clastic or detrital sediment, whereas chemical sediment is accreted through

biological processes or precipitates directly from hydrothermal or briny waters. Metamorphic

rocks are compacted, heated, pressurized, and altered from burial, thermal contact, and fluid

transfer during recrystallization and alteration.

Laboratory 3. Igneous Rocks

• Rocks are identified by their colors, textures, and other physical properties like

hardness, weight (density or specific gravity), magnetism (magnetite), and

reactivity with acids (limestone and marble).

• The first exercise for this lab is to study and become familiar with 12 igneous rock

specimens included in a Ward’s scientific rock kit, differentiating between those

of plutonic (intrusive) and volcanic (extrusive) origin.

• A secondary exercise will be to examine the loose sample of igneous rocks held by

RVCC, discuss them among your peers and professor, and categorize them.

• A third exercise will be to complete a puzzle depicting an ordered sequence of

igneous rocks exposed in a mountainside using knowledge about the geological

progression of igneous intrusions.

• By the end of this lab you should have a working familiarity with the principal

types of igneous rocks, have identified the most common rock-forming minerals

in the specimens, and seen the textures commonly found in the mafic,

intermediate, and felsic rocks.32


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PLUTONIC

(intrusive varieties)Laboratory 3. Igneous Rocks

+1 os

+2 os

os – oxidation state

An element having a

+2 os (or charge) has

a higher electron

affinity because it has

twice the charge than

one with a +1 os.

• Calcium and magnesium (+2) are proportionately more abundant in mafic rocks

that crystallize form magma first with slow cooling and crystal growth.

•Parent magma composition largely determines the composition of igneous

rocks but a single magma can, however, yield different rock types.

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Texture in igneous rocks is related to cooling history; the slower the

magma cools, the more coarse-grained the rock becomes.

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•Typically, the coarsest-grained rocks formed in deep crustal chambers after rising out of the

mantle where it can accumulate and pond at the base of the crust or in the crust, or deep in

the roots of crustal mountain where rocks begin to melt from burial and heat. They become

exposed at the surface Eons after formation from crustal tectonics.

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Exercise 1.

An Igneous Rock

Collection by

Ward’s Scientific

Basalt

Diorite

Gabbro

Granite

Obsidian

Pegmatite

Peridotite

Pumice

Rhyolite (2)

Scoria

Syenite

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39


NOTES: NOTES:


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NOTES:


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Granite (Felsic)

Diorite (Intermediate)

Gabbro-Basic

RVCC loose

plutonic

material



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Rhyolite (Felsic)

Basalt-basic

Scoria

RVCC loose volcanic material

obsidian

Andesite (Intermediate)

Volcanic

bomb

Tuff



_____ SS - red sandstone _______ B - basalt dike leading to basalt flow ______ D - diorite stock and sills

______Gr – granite ________ Pg – pegmatite ______ Gb – Gabbro 43



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Exercise 1.

An Igneous Rock

Collection by

Ward’s Scientific

1.Obsidian

2. Pumice

3. Scoria

4.Basalt

5. Rhyolite

6. Rhyolite

7. Granite

8. pegmatite

9. Andesite

10. Diorite

11. Gabbro

12. Peridotite

Documents

RVCC GCH GEOL157 Introduction to Geology Laboratory Manual GCH GEOL157 Lab3.pdf · 2018-01-20 · RVCC GEOL 157 Introduction to Geology Lab Manual GCH 2018-01 • Igneous rock forms