Present Lect1

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A NATURALLY OCCURRING,INORGANIC, SOLID, WITH DEFINITE

CHEMICAL STRUCTURE & CRYSTALSTRUCTURE

A Naturally Occurring Solid Made of

One or More Minerals or Other Solid Substances

MINERALCOMPOSITION

TEXTURES

IGNEOUSMelting Of Rocksin Hot Deep

Crust & Upper

Mantle

(LIQUID & GASES)

SEDIMENTARYWeathering &

erosion of rocksexposed atsurface

METAMORPHICRocks Under HighTemperatures &

Pressures in

Deep Crust &Upper Mantle

SOLID STAGE

IGNEOUSCrystallization

(Differentiation &Solidification ofMagma)

Deposition, burial& lihtification

SEDIMENTARY

Recrystallization insolid state ofnew minerals

METAMORPHIC

Igneous (ig nee us) isthe term applied to the

rocks that form by thecrystallization of theirconstituent mineralsout of magma (molten

materials below thesurface) or from lava on the earth's surface

BATHOLITH

PYROCLASTIC ASH

AT LEAST PARTLY SMALL CRYSTALS AND/OR GLASS

- produced by relatively fast cooling, usually at or near the

earth’s surface

- typical of extrusive (volcanic) rocks

- sometimes in intrusive rocks (small, shallow intrusions)

glassy texture - no crystals

APHANITIC TEXTURE - very small crystalsPORPHYRITIC TEXTURE - mixed sizes

OTHER TEXTURESBUBBLES: vesicular texture

Gas bubbles trapped in an igneous rock are called vesicles.

Examples: vesicular basalt and pumice

BROKEN FRAGMENTS: pyroclastic texture

If there is enough gas, expanding bubbles may cause lava

to explosively break into fragments.Examples: volcanic ash and pumice

AQP CLASSIFICATION (Feldspathic Rocks)

QAP CLASSIFICATION (Volcanic Rocks)

AQP CLASSIFICATION (Plutonic Rocks)

BASALTIC CLASSIFICATION

CLASSIFICATION PYROCLASTIC ROCKS

Sedimentary rocks arerocks that are formed

from unconsolidatedcollections of rocks,mineral grains and

organic materials that

have been moved anddeposited by the actionof water, wind, or ice.

rock fragments collect

consolidated

coherent sediment mass

become lithified (convertedinto a truly cohesive solid)

LITHIFICATION PROCESS (LOW T)

As sedimentary rock show

signs of change

to be undergoing

DIAGENESIS

LITHIFICATION PROCESS (LOW T)

COMPACTION AND RECRYSTALLIZATION - As sediments pile up, the ones on the

bottom are placed under pressure. The result of this pressure is a compaction of the

sediment; it is squeezed together causing a reduction in pore space and a sticking together

of the grains. Under pressure, some chemical sediments, like halite, may recrystallize into a

solid state.

CEMENTATION- Most sediments are deposited in water. This water, containing dissolved

minerals, flows through the sediment and some of these minerals precipitate on the grain

surfaces. With enough time, this intergranular material effectively glues the sediment

together into a cohesive solid- a sedimentary rock.

CLASTIC SEDIMENTARY ROCK

THE ULTIMATE SOURCE of sediment is FROM OLDER ROCKS that

are exposed to the surface and are weathered and broken intosmaller pieces. These pieces may be CARRIED AWAY A STREAM,

bulldozed by a GLACIER, or picked up by the WIND as their

SEDIMENT LOAD. Ultimately these sediments are DEPOSITED and

may CONSOLIDATE into A COHESIVE MASS that we callCLASTIC or fragmental sedimentary rock. These rocks DO NOT

HAVE THE INTERLOCKING CRYSTAL CHARACTERISTICS of

igneous rocks. Clastic rocks are COMPOSED OF BROKEN UP

PIECES OF PREEXISTING ROCKS AND MINERALS. We can

further IDENTIFY these rocks based on THE SIZE OF THE

FRAGMENTS THAT THEY ARE COMPOSED.

MAXIMUM GRAIN SIZE: fine, medium, coarse

GRAIN SHAPE: angular, rounded

SORTING: well-sorted, poorly-sortedWell-sorted,

angular

Poorly sorted

Mixture of sand

& gravel with

Rounded fragments

MAXIMUM GRAIN SIZE fi di

GRAIN SHAPE R d d A l

GRAIN SHAPE: Rounded, Angular

SORTING W ll S t d P l S t d

SORTING: Well Sorted, Poorly Sorted

SORTING W ll S t d P l S t d

SORTING: Well Sorted, Poorly Sorted

EXAMPLES

CLASSIFICATION OF CLASTIC SEDIMENTARY

ROCKS BY TEXTURE

TEXTURE ROCK TYPE

coarse, rounded Conglomerate

coarse, angular Breccia

medium Sandstone

fine Siltstone, Mudstone,

Claystone, or Shale

ROCKS BY TEXTURE

Classification of Sandstones by Composition

COMPOSITION ROCK TYPE

Pure Quartz Sand quartz sandstone

Sand Which Includes at arkosic sandstone

Least 20% Feldspar

Sand Which Includes at lithic sandstone

Least 20% Rock Fragments

Sand and Fine Matrix graywacke sandstone

CLASSIFICATION OF BIOLOGIC & CHEMICAL

SEDIMENTARY ROCKS BY TEXTURE

COMPOSITION ROCK TYPE

calcite (may also contain some mud) limestone

plant remains coal or peat

silica chert

halite rock salt

gypsum rock gypsum

METAMORPHISM

• includes processes which

change the minerals and

texture of rock withoutmelting it

• caused by changes inpressure, changes in

temperature, and/or fluids

THE TERM METAMORPHIC is derived from the Latin term

meaning, "CHANGE OF FORM". These rocks have been

ALTERED while in THEIR SOLID STATE as a response to

the environment. Extreme circumstances of PRESSUREAND TEMPERATURE, or an introduction of certain

chemicals, can cause the existing rocks minerals to

RECRYSTALLIZE, and they may even become different

minerals all together. It is important that you realize thatthe ROCK REMAINS IN ITS SOLID STATE. Once a rocks

minerals are melted, and then recrystallize, the new

material will be igneous.

CAUSES OF METAMORPHISM

PRESSURE

- different minerals are stable at different pressures

- changing the pressure can cause the types of minerals

present in a rock to change

CONFINING PRESSURE (LITHOSTATIC PRESSURE)- equal pressure in all directions

- increased confining pressure can cause minerals with

more compact (denser) structures to form

DIRECTED PRESSURE- pressure which is greater in a specific direction

- may cause folding or cause mineral to grow with a

specific orientation

TEMPERATURE

- different minerals are stable at different temperatures

- changing the temperature can cause the types of minerals

present in a rock to change

HYDROTHERMAL FLUIDS

(mostly water and/or carbon dioxide plus dissolved material)

- can change the overall chemical composition of a rock by

adding or removing material- many important ore deposits have been formed by this

metamorphic process

TYPE OF METAMORPHIC ROCKS

CLASSIFICATION OF METAMORPHIC ROCKS

A FOLIATED :This is determined by the presence of

minerals that are aligned parallel to each other. This

results in a layered appearance.

A NONFOLIATED metamorphic rock generally consists of

equaldimensional grains.

A rock can also be IDENTIFIED BY ITS METAMORPHICGRADE.

FOLIATED METAMORPHIC ROCKS

- foliation refers to a preferred orientation of mineral grains

found in some metamorphic rocks

- metamorphic rocks which have a preferred orientation of mineral grains are called foliated metamorphic rocks

- the preferred orientation is the result of directed

pressure

NON-FOLIATED METAMORPHIC ROCKS

- lack a preferred orientation of mineral grains

SEDIMENTARY TO METAMORPHIC

The following is a very general progression from

sedimentary rock to metamorphic rock based primarily on

pressure

SURFACE MUD5 km DEEP SHALE (sedimentary)

10 km DEEP SLATE (low grade metamorphic)

15 km DEEP SCHIST (Garnet appears)

20 km DEEP GNEISS (high grade metamorphic)25 km DEEP HORNFELS (Cordierite appears)

Shale Slate PhylliteSchist

Sandstone

Quarzite

Limestone

Marble

TYPES OF FOLIATED METAMORPHIC ROCKS

TEMPERATURE

TYPES OF NON- FOLIATED METAMORPHIC ROCKS

QUARTZITE - composed primarily of quartz (REGIONAL)

MARBLE - composed mostly of calcite and/or dolomite

HORNFELS - variable composition

SKARN - contains mostly calcite and/or dolomite with garnet

TYPES OF NON FOLIATED METAMORPHIC ROCKS

TYPES OF NON- FOLIATED METAMORPHIC ROCKS

OTHERS METAMORPHIC ROCKS

MYLONITE- formed in the deepest parts of fault zones

MIGMATITE

- formed when a rock begins to partially melt- represents the transition between metamorphic and

igneous rock

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