MINERALS AND ROCKS IN MINERALS AND ROCKS IN THE EARTH’S CRUSTTHE EARTH’S CRUST

Igneous, Sedimentary, Metamorphic Igneous, Sedimentary, Metamorphic Rocks and EnvironmentsRocks and Environments

MINERALS AND ROCKS COME MINERALS AND ROCKS COME FROM ELEMENTSFROM ELEMENTS

• Chemical elements are the fundamental materials of which all matter is composed.– From the modern viewpoint:

• a substance that cannot be broken down or reduced further

MAKING MINERALS FROM MAKING MINERALS FROM ELEMENTSELEMENTS

• ALMOST ALL THE MINERALS FOUND IN THE EARTH ARE FORMED FROM THE BONDING OF EIGHT (8) ELEMENTS– OXYGEN (O)– SILICON (Si)– ALUMINIUM (Al)– IRON (Fe)– CALCIUM (Ca)– POTASSIUM (K)– SODIUM (Na)– MAGNESIUM (Mg)

MOST ABUNDANT

LEAST ABUNDANT

WHAT ARE MINERALS?WHAT ARE MINERALS?

• BUILDING BLOCKS FOR ROCKS• DEFINITION:

– NATURALLY OCCURRING, – INORGANIC SOLIDS, – CONSISTING OF SPECIFIC CHEMICAL

ELEMENTS, AND – A DEFINITE ATOMIC ARRAY

• CRYSTALLINE STRUCTURE – ‘CRYSTAL’• ‘CRYSTAL’ AND ‘MINERAL’

INTERCHANGEABLE TERMS

MINERALSMINERALSMinerals divided into two main groups

based on Silica contentSilica (SiO) compound of molecularly bonded silicon (Si) and oxygen (O) molecules (SiO, SiO2, SiO4, SiO6 etc.)

GROUP 1: SILICATES – CONTAIN SILICA

GROUP 2: NON-SILICATES (CONTAIN NO SILICA)

NON-SILICATE MINERALSNON-SILICATE MINERALS• Non-silicate minerals are very rare• Make up 5% of Earth’s continental crust

– Considered valuable commercially as building materials, gemstones, iron ores for steel, ceramics, and more.

• Native metals: gold, silver, copper, platinum• Native elements: diamonds, corundum: Ruby

(red) or Sapphire (blue)• Carbonates: calcite (used in cement)• Oxides: hematite (iron ores)• Sulfides: galena (lead ores) • Sulfates: gypsum (used in plaster, dry wall)• Halides: halite (table salt)

SILICATE MINERALSSILICATE MINERALS

• THE MOST ABUNDANT OF ALL MINERALS– MAKE UP APPROXIMATELY 95% OF WEIGHT OF

EARTH’S CRUST– CONTAIN VARYING AMOUNTS OF SILICA (SiO)

• DOMINANT COMPONENT OF MOST ROCKS: – IGNEOUS– SEDIMENTARY – METAMORPHIC

SILICATE MINERALS SILICATE MINERALS • LISTED BELOW IN DECREASING % OF SILICA ARE

MOST COMMON SILICATE MINERALS

– QUARTZ (SiO2) (“High” Silica content ~100%)

– FELDSPARS (PLAGIOCLASE -– MICAS (MUSCOVITE – BIOTITE )

– AMPHIBOLES (Hornblende)

– PYROXENES (Augite)

– OLIVINE (“Low” Silica content ~40%)

SILICATE MINERALSSILICATE MINERALS

• SILICATE MINERALS ARE BROKEN INTO THREE MAIN GROUPS ACCORDING TO % SILICA– FELSIC High percent

– MAFIC– ULTRAMAFIC Low percent

FELSIC SILICATE MINERALS FELSIC SILICATE MINERALS

• FELSIC SILICATE MINERALS HAVE A HIGH CONCENTRATION OF SILICON, OXYGEN, ALUMINIUM AND POTASSIUM

• FELSIC SILICATES – HIGH % SiO (75-100%)– QUARTZ (100% SiO2)– FELDSPARS (Plagioclase, Orthoclase)– MUSCOVITE MICA

FELDSPARQUARTZ

MUSCOVITE MICA

MAFIC SILICATE MINERALSMAFIC SILICATE MINERALS

• MINERALS WITH HIGH CONCENTRATION OF MAGNESIUM AND IRON, PLUS CALCIUM AND SODIUM, AND LOWER AMOUNTS OF SILICON AND OXYGEN

• MAFIC SILICATES - LESS SiO (50-60%)– BIOTITE MICA– AMPHIBOLE (Hornblende)– PYROXENE (Augite)

BIOTITE MICA

AMPHIBOLE (HORNBLENDE)

PYROXENE (AUGITE)

ULTRAMAFIC SILICATESULTRAMAFIC SILICATES• MINERALS WITH GREATER

CONCENTRATION IN MAGNESIUM AND IRON. VERY RARE AT EARTH’S SURFACE

• ULTRA MAFIC SILICATES - VERY LOW % SiO (less than 50%)

• VERY RARE AT SURFACE– OLIVINE (FORSTERITE, FAYALITE)

WHAT ARE ROCKS?WHAT ARE ROCKS?

• AGGREGATIONS OF 2 OR MORE MINERALS– Same or different minerals combine

together

• THREE CATEGORIES– IGNEOUS– SEDIMENTARY– METAMORPHIC

IGNEOUS ROCKSIGNEOUS ROCKS• Ignis: Latin for “Fire”• FORMED FROM MOLTEN MATERIAL THAT

COOLED AND SOLIDIFIED AT, NEAR, OR DEEP BELOW, THE SURFACE

• TYPES:– PLUTONIC (INTRUSIVE) –IGNEOUS ROCKS

COOLED AND SOLIDIFIED BELOW SURFACE AT GREAT DEPTHS

– VOLCANIC (EXTRUSIVE) – IGNEOUS ROCKS COOLED AND SOLIDIFIED AT OR NEAR THE SURFACE THROUGH VOLCANIC ERUPTIONS

IDENTIFICATION OF IGNEOUS IDENTIFICATION OF IGNEOUS ROCKSROCKS

• TWO IDENTIFICATION PROCESSES FOR PLUTONIC OR VOLCANIC IGNEOUS ROCKS:– TEXTURE:

• Size, shape and manner of growth of individual crystals

– MINERAL COMPOSITION• Based on SiO content

– Felsic, Intermediate, Mafic– (high Silica low Silica)

TEXTURE IDENTIFICATIONTEXTURE IDENTIFICATION• SIZE, SHAPE OF CRYSTALS AND MANNER OF

GROWTH

• FINE GRAINED TEXTURE:– VERY TINY, MINERAL CRYSTALS VISIBLE ONLY

WITH MAGNIFICATION– INDICATES FAST COOLING AT SURFACE –

CRYSTALS SOLIDIFIED QUICKLY WITH NO TIME TO ‘GROW’

• COARSE-GRAINED TEXTURE: – LARGE, EASILY-VISIBLE MINERAL CRYSTALS– INDICATES SLOW COOLING AT DEPTH –

CRYSTALS SOLIDIFIED SLOWLY WITH LOTS OF TIME TO ‘GROW’

Fine-Grained Textures Coarse-Grained Textures

TEXTURE IDENTIFICATIONTEXTURE IDENTIFICATION

MINERAL COMPOSITIONMINERAL COMPOSITION

• CLASSIFIED BY SILICA (SiO) CONTENT

• FELSIC – MORE THAN 85% SILICA

• INTERMEDIATE – 60-85% SILICA

• MAFIC – LESS THAN 60% SILICA

COMMON IGNEOUS ROCKSCOMMON IGNEOUS ROCKS• FELSIC IGNEOUS ROCKS (>85% SiO)

– GRANITE: • PLUTONIC-INTRUSIVE; COARSE-GRAINED TEXTURE; FELSIC MINERAL

COMPOSITION– RHYOLITE:

• VOLCANIC-EXTRUSIVE; FINE-GRAINED TEXTURE; FELSIC MINERAL COMPOSITION

• INTERMEDIATE IGNEOUS ROCKS (60-85% SiO)– DIORITE:

• PLUTONIC-INTRUSIVE; COARSE-GRAINED TEXTURE; INTERMEDIATE MINERAL COMPOSITION

– ANDESITE: • VOLCANIC-EXTRUSIVE; FINE-GRAINED TEXTURE; INTERMEDIATE

MINERAL COMPOSITION

• MAFIC IGNEOUS ROCKS (<60% SiO)– GABBRO:

• PLUTONIC-INTRUSIVE;COARSE-GRAINED TEXTURE; MAFIC MINERAL COMPOSITION

– BASALT: • VOLCANIC-EXTRUSIVE; FINE-GRAINED TEXTURE; MAFIC MINERAL

COMPOSITION

IGNEOUS ROCK IDENTIFICATION CHART

Granitic Andesitic Basaltic

(Felsic) (Intermediate) (Mafic)

Coarse-Grained Granite Diorite Gabbro

Fine-Grained Rhyolite Andesite Basalt

Rock color Light-colored Medium-colored Dark grayblackbased on % <15% mafic 15-40% mafic >40% mafic mafic minerals minerals minerals minerals

Viscosity Highest Medium Low

Melting Temps 600-8000 C 800-11000 C 1 100-12000 C

FELSIC IGNEOUS ROCKSFELSIC IGNEOUS ROCKSRHYOLITE

GRANITE

VOLCANIC-EXTRUSIVE

PLUTONIC-INTRUSIVE

INTERMEDIATE IGNEOUS INTERMEDIATE IGNEOUS ROCKSROCKS

DIORITE

ANDESITE

PLUTONIC-INTRUSIVE

VOLCANIC-EXTRUSIVE

MAFIC IGNEOUS ROCKSMAFIC IGNEOUS ROCKS

BASALT

GABBRO

VOLCANIC-EXTRUSIVE

PLUTONIC-INTRUSIVE

OTHER IGNEOUS ROCKSOTHER IGNEOUS ROCKS• VOLCANIC GLASS:

– OBSIDIAN: VOLCANIC-EXTRUSIVE; NO CRYSTALS FORM; SILICA-RICH, COOLED INSTANEOUSLY

– PUMICE: VOLCANIC-EXTRUSIVE; NO CRYSTALS FORM; SILICA-RICH; SOLIDIFIED FROM ‘GASSY’ LAVA

• PYROCLASTIC ROCKS– TUFF: VOLCANIC-EXTRUSIVE;

SOLIDIFIED ‘WELDED’ ASH

VOLCANIC GLASSVOLCANIC GLASS

OBSIDIAN

PUMICE

PYROCLASTIC IGNEOUS ROCKSPYROCLASTIC IGNEOUS ROCKS

WELDED TUFF

SEDIMENTARY ROCKSSEDIMENTARY ROCKS

• WEATHERING PROCESSES BREAK ROCK INTO PIECES, SEDIMENT.

• HOW SEDIMENTATION HAPPENS :– TRANSPORTATION DEPOSITION

BURIAL AND LITHIFICATION INTO NEW ROCKS.

SEDIMENTARY PROCESSESSEDIMENTARY PROCESSES

• LITHIFICATION: • As sediment is buried several kilometers beneath the surface,

heated from below, pressure from overlying layers, heat, and chemically-active water converts the loose sediment into solid sedimentary rock

• Compaction - volume of a sediment is reduced by application of pressure

• Cementation - sediment grains are bound to each other by materials originally dissolved during chemical weathering of preexisting rocks – typical chemicals include silica and calcium carbonate.

CLASSIFYING SEDIMENTARY CLASSIFYING SEDIMENTARY ROCKSROCKS

• THREE SOURCES FOR SEDIMENTARY ROCKS

• (1) Detrital (or clastic) sediment is composed of transported solid fragments (or detritus) of pre-existing igneous, sedimentary or metamorphic rocks

• (2) Chemical sediment forms from previously dissolved minerals that either precipitated from solution in water, or were extracted from water by living organisms

• (3) Organic sedimentary rock consisting mainly of plant remains

CLASTIC/DETRITAL CLASTIC/DETRITAL SEDIMENTARY ROCKSSEDIMENTARY ROCKS

• CLASSIFIED ON GRAIN OR PARTICLE SIZE

• Shales: finest-grained• Sandstones: medium-grained• Conglomerates – Breccias: coarse-

grained

SHALES : CLASTIC SHALES : CLASTIC SEDIMENTARYSEDIMENTARY

• SHALES: finest-grained clastic sedimentary rocks – composed of very small particles– 50% of all sedimentary rocks are Shales– Consist largely of Clay minerals (weathered

granite in many cases)– Subcategories: Claystones – Siltstones -

Mudstones– Economic value: building material; china and

ceramics; spark plug housings

SHALESSHALES

Limestone on black shale

Burgess Shale in Canada

MUDSTONES, SILTSTONESMUDSTONES, SILTSTONESIdentified by decreasing amounts of sand and increasing amounts of clay

SANDSTONESSANDSTONES• SANDSTONES: medium-grained

clastic sedimentary rocks• 25% of all sedimentary rocks fall into

this category • Economic value: glass; natural

reservoirs for oil, gas, and groundwater

SANDSTONESSANDSTONES

CONGLOMERATES - BRECCIASCONGLOMERATES - BRECCIAS

• CONGLOMERATES AND BRECCIAS:

• The coarsest of all the clastic sedimentary rocks

• Composed of particles >2 mm in diameter – Conglomerate - the particles are

rounded – Breccia - the particles are angular

CONGLOMERATESCONGLOMERATES

BRECCIASBRECCIAS

CHEMICAL SEDIMENTARY CHEMICAL SEDIMENTARY ROCKSROCKS

• TWO CATEGORIES:

– INORGANIC CHEMICAL SEDIMENTARY

– ORGANIC CHEMICAL SEDIMENTARY

INORGANIC CHEMICAL INORGANIC CHEMICAL SEDIMENTARY ROCKSSEDIMENTARY ROCKS

• Formed when dissolved products of chemical weathering precipitate (‘form out of’) from solution

• Most common types:– Inorganic limestones and cherts: precipitates

directly from seawater and fresh water– Evaporites: precipitates when ion-rich water

evaporates

INORGANIC - LIMESTONESINORGANIC - LIMESTONES

• Limestones - account for 10% - 15% of all sedimentary rocks formed from Calcite or Calcium Carbonate (CaCO3).

• Formed as pure carbonate muds accumulate on the sea floor

• Also formed on land: – Tufa - a soft spongy inorganic limestone that forms where

underground water surfaces – Travertine - forms in caves when droplets of carbonate-rich

water on the ceiling, walls and floors precipitate a carbonate rock: stalactites and stalagmites

LIMESTONESLIMESTONESTRAVERTINE

Tufa Towers, Mono LakeTufa Towers, Mono Lake

ORGANIC LIMESTONESORGANIC LIMESTONES• Formed with calcite from marine environment: CaCO3 shells

and internal/external skeletons of marine animals

• Coquina - “crushed” shell fragments cemented with CaCO3 • Chalk - made from billions of microscopic carbonate-

secreting organisms • Coral Reefs - Formed from the skeletons of millions of tiny

invertebrate animals who secrete a calcite-rich material. Live “condo” style while algae acts as the cement to create the large structures called “reefs”.

• Organic Chert - formed when silica-secreting microscopic marine organisms die (radiolaria {single-celled

animals} and diatoms {skeletons of singled-celled plants})

• Flint - an example of an Inorganic Chert

COQUINA, CHALK AND COQUINA, CHALK AND FOSSILIFEROUS LIMESTONESFOSSILIFEROUS LIMESTONES

COQUINA

CHALK

FOSSILIFEROUS LIMESTONE

ORGANIC SEDIMENTARY ORGANIC SEDIMENTARY ROCKSROCKS

• Coal - Organic sedimentary rock consisting mainly of plant remains

• Formation: – Burial of decaying vegetation;– Increasing pressure from the overlying layers expels

water, CO2 and other gases;– Carbon accumulates.

• STAGES:• Peat - formed early in the process, when the original plant

structure can still be distinguished. • Lignite - a more hardened form of Peat• Bituminous - more pressure and more heat produce this

moderately hard coal. • Anthracite - the hardest coal - formed from metamorphic

processes under extreme heat and pressure - Hard - Shiny - the most desired as an energy resource.

COALCOALPEAT LIGNITE

BITUMINOUSANTHRACITE

SEDIMENTARY ENVIRONMENTSSEDIMENTARY ENVIRONMENTS

• Lakes• Lagoons• Rivers• Ocean bottoms

• Estuaries• Salt Flats• Playas• Glacial environments

METAMORPHIC ROCKSMETAMORPHIC ROCKS

• METAMORPHISM : process by which conditions within the Earth alter the mineral content and structure of any rock - igneous, sedimentary or metamorphic - without melting it.

• Metamorphism occurs when heat and pressure exceed certain levels, destabilizing the minerals in rocks...but not enough to cause melting

• Ion-rich fluids circulating in and around rocks also influences metamorphism

METAMORPHIC PROCESSESMETAMORPHIC PROCESSES• HEAT:

– (2000 C or 4000 F) reached near 10 km (6 miles) beneath the surface.

• PRESSURE: – > 2 bar or 2000 mb, which

is generally found ~ 6 km (4 miles) beneath the Earth’s surface

• FLUIDS: Chemically-active water is the usual fluid and comes from various sources

TEMPERATURE/PRESSURE For every 3 kilometers depth in the Earth, pressure increases by about 1 kb. Average temperature gradient in the Earth increases 30° C per km

CHANGES IN METAMORPHIC CHANGES IN METAMORPHIC ROCKSROCKS

• Metamorphic processes cause many changes in rocks – Increased density– Growth of larger crystals– FOLIATION : reorientation of the mineral

grains into layers or banded texture – Transformation of low-temperature

minerals into high-temperature minerals

CLASSIFYING METAMORPHIC CLASSIFYING METAMORPHIC ROCKSROCKS

• TEXTURE: the size, shape and distribution of particles in a rock – texture is determined by grade of

metamorphism • Low grade: (less than 6000C and lower than 4

kilobars pressure)

• Intermediate grade: occurs at a variety of temperatures and pressures.

• High grade: (greater than 6000C and more than 4 kilobars pressure)

FOLIATED TEXTURESFOLIATED TEXTURES

• Foliated texture: more pressure and mineral grains realign themselves and grow into larger crystals

• Three types of foliated texture: – Slaty Texture (Low grade metamorphism)

– Schistosity (Medium grade metamorphism) – Gneissic Texture (High grade metamorphism)

ROCK – SLATY TEXTURE - ROCK – SLATY TEXTURE - SLATESLATE

• Shale metamorphosed to Slate: – clay minerals become unstable and

recrystallize into mica crystals – Slate is formed under Low-Grade

Metamorphism

SLATESLATE

SCHISTOCITY - SCHISTSCHISTOCITY - SCHIST• More extreme pressures and temperatures: mica

crystals grow even larger - ~ 1 cm in diameter. – rock has “scaly” appearance - schistosity, – referred to as a Schist.

• Schists formed under Intermediate-Grade Metamorphism

• Schists named for the mineral constituents in the parent rock: – mica schist– talc schist– garnet schist

SCHISTSCHIST

Ruby schist

Mica schist

GNEISSIC TEXTURE - GNEISSIC TEXTURE - GNEISSGNEISS

• Light and dark silicate minerals separate and re-align themselves into bands

• Rocks with this texture are called Gneiss • Gneiss forms from High Grade

Metamorphism• Typical ‘parent’ rocks for Gneiss

– granite – diorite– gabbro – shale

GNEISSGNEISS

NON-FOLIATED TEXTURESNON-FOLIATED TEXTURES

• Rocks with only one mineral metamorphose without a visibly foliated texture

• Limestone metamorphoses into Marble as the interlocking calcite crystals grow larger

• Quartz Sandstone metamorphoses into Quartzite

MARBLE AND QUARTZITEMARBLE AND QUARTZITE

MARBLE

QUARTZITE

METAMORPHIC ENVIRONMENTSMETAMORPHIC ENVIRONMENTS

• CONTACT METAMORPHISM – Metamorphism of a rock touched by the

intense heat of migrating magma.

• REGIONAL METAMORPHISM – Burial metamorphism - occurs when rocks

are overlain by more than 6 miles of rock or sediment

– Dynamothermal metamorphism - occurs when rocks are caught between two convergent plates during mountain building

Contact and Regional Contact and Regional MetamorphismMetamorphism

Contact Metamorphism

Regional Metamorphism

ROCK FORMING ROCK FORMING PROCESSESPROCESSES

THE ROCK CYCLE