ESC 211 Final Exam Likely Questions

Tectosilicates

Framework silicates with all oxygens shared in a 3D network

Si:O ratio tectosilicates

1:2

Effect of shared oxygens

Creates open framework structure

Cation accommodation tectosilicates

Large cations K Na Ca fit easily

Density tectosilicates

Low specific gravity

Quartz density

~2.65

Silica polymorphs

Same chemical formula SiO2 different crystal structures

Quartz

Low temperature stable SiO2

Tridymite

Intermediate temperature SiO2

Cristobalite

High temperature SiO2

Polymorphism

Same composition different structure

Phase diagram

Graph of phase stability vs temperature and pressure

Solidus

Boundary below which system is fully solid

Liquidus

Boundary above which system is fully liquid

Solvus

Boundary separating solid solution from exsolution

Phase stability controls

Temperature pressure composition

Feldspar group

Most abundant crustal minerals tectosilicates

Feldspar composition

Aluminosilicates with K Na Ca

Orthoclase Or

KAlSi3O8

Albite Ab

NaAlSi3O8

Anorthite An

CaAl2Si2O8

Alkali feldspar

Solid solution between Or and Ab

Plagioclase feldspar

Solid solution between Ab and An

Plagioclase series order

Albite Oligoclase Andesine Labradorite Bytownite Anorthite

Coupled substitution

Substitution maintaining charge balance

Example coupled substitution

Ca2+ + Al3+ replaces Na+ + Si4+

Reason for coupled substitution

Maintain electrical neutrality

Mixing gap

Range where solid solution unstable

Exsolution

Unmixing into two phases on cooling

Perthite

K feldspar host with albite lamellae

Feldspathoids

Silica poor feldspar-like minerals

Feldspathoid silica relation

Lower silica than feldspar

Feldspathoids with quartz

Do not occur together

Feldspathoid environment

Alkali rich silica poor igneous rocks

Leucite

KAlSi2O6 feldspathoid

Zeolites

Hydrous tectosilicates with open frameworks

Zeolite property

Contain water in structure

Carbonates

Minerals with CO3^2- group

Carbonate structure

C4+ bonded to three O2-

Calcite

CaCO3 common carbonate

Aragonite

High pressure polymorph of CaCO3

Dolomite

CaMg(CO3)2 carbonate

Carbonate occurrence limestone

Mostly calcite or aragonite

Carbonate diagenesis

Limestone alters to dolomite or ankerite

Marble

Metamorphosed limestone or dolostone

Carbonatite

Igneous rock containing calcite

Calcite vs aragonite

Stability depends on pressure temperature

Halides

Minerals with halogen anions

Halite

NaCl

Sylvite

KCl

Fluorite

CaF2

Sulphates

Minerals with SO4^2- group

Gypsum

CaSO4·2H2O hydrated sulphate

Anhydrite

CaSO4 बिना water

Barite

BaSO4

Celestite

SrSO4

Native elements

Minerals of single element

Native element groups

Metals semi-metals non-metals

Examples native elements

Gold sulfur carbon

Oxides

Minerals with oxygen anions

Oxide groups

X2O XO XY2O4

Spinel structure

XY2O4 with mixed valence cations

Hydroxides

Minerals containing OH-

Sulphides

Minerals with S2- anion

Sulphide formula

MpXr

Sulphide metals

Fe Zn Pb etc

Sulfur role

Acts as anion S2-

Igneous rock minerals main

Olivine pyroxene amphibole mica feldspar quartz

Igneous accessory minerals

Apatite titanite zircon

QAPF classification

Uses Quartz Alkali feldspar Plagioclase Feldspathoid

QAPF use

Classify igneous rocks

Gabbro composition

Pyroxene and plagioclase

Granite composition

Quartz alkali feldspar plagioclase

Pegmatite

Very coarse grained igneous rock

Aplite

Fine grained felsic igneous rock

Pegmatite association

Associated with granite

Pegmatite zoning

Border wall intermediate core zones

Pegmatite formation

Late stage crystallization from melt

Sedimentary rocks types

Clastic carbonate chemical organic evaporite volcaniclastic

Clastic rocks percentage

80-85 percent

Carbonate rocks percentage

10-15 percent

Sedimentary controls

Source weathering transport deposition diagenesis

Maturity sediment

Degree of stability and reworking

Sorting

Uniformity of grain size

Rounding

Smoothness of grains

Mineral stability

Resistance to weathering

Sandstone classification

Based on texture and mineralogy

Chemical sediments

Precipitated from solution

Examples chemical sediments

Calcite evaporites banded iron formation

Clastic vs chemical

Clastic from fragments chemical from precipitation

Metamorphic facies

Set of mineral assemblages

Metamorphic grade

Intensity of metamorphism

Index minerals

Indicate metamorphic conditions

Progressive metamorphism

Change in minerals with increasing grade

Foliation

Alignment of minerals under الضغط

Slate

Fine foliated metamorphic rock

Schist

Medium foliated metamorphic rock

Gneiss

Coarse foliated metamorphic rock

Non foliated rocks

Lack mineral alignment

Hornfels

Contact metamorphic rock