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Igneous Rocks II 8/24/2011
1
ERSC 3P21 - Brock University Greg Finn
ERSC 3P21
Igneous RocksNomenclature and Classification
ERSC 3P21 - Brock University Greg Finn
Introduction• Numerous means exist for classifying and
naming igneous rocks• As humans we feel the need to recognize and
categorize common or contrasting features in related things– Eg. animals or plants
• Kingdom, phylum, order, genera, class, species
• Systems of rock nomenclature and classification may reflect
• Genetic, textural, chemical or mineralogical features
ERSC 3P21 - Brock University Greg Finn
Genetic• Basic systems which classifies igneous
rocks ________________________________________
_____________
_____________
________________
________________
________________
•
•
Igneous Rocks II 8/24/2011
2
ERSC 3P21 - Brock University Greg Finn
Textural• Relies on the _____________________
____________________________________________
____________
____________
______________ - < 1 mm
______________ - 1-5 mm
______________ - > 5 mm
•• Specific textures may aid in classification
• eg.
ERSC 3P21 - Brock University Greg Finn
Chemical• Requires a _______________________
of the rock in order to classify it• This is not practical under field conditions,
where only a _________ and ________ are available
• Chemical classification has been proposed for ____________, a comparable scheme for ____________ is not available
• This leaves a system based on mineralogy
ERSC 3P21 - Brock University Greg Finn
Mineralogical• Requires only a _________ and ________
and the ability to ____________________ present in a rock
• System gaining acceptance and the one you will use is the result of several years work by the IUGS Subcommission on the Classification of Igneous Rocks, chaired by Alfred Streckeissen
• AKA – The Streckeissen Classification
Igneous Rocks II 8/24/2011
3
ERSC 3P21 - Brock University Greg Finn
Mineralogical• Based on Modal Mineralogy
– (MODE –
)
• A simple, field based system • Based on the percentages of:
• _____________ (____)• _________________ (____)• __________________ (____), and• _______________, eg. nepheline, leucite etc. (____)
– Subdivisions are dependant on the percentage of mafic minerals
ERSC 3P21 - Brock University Greg Finn
(1) If biotite is the dominant mafic mineral, constituting < 10%, the
rock is termed a Trondhjemite.
(3)The type of alkali feldspar
should be specified if
possible, e.g., Microcline
granite.
(4) The feldspathoid should be specified in each rock name; e.g., Nepheline
syenite
(2) With < 5% mafic minerals, the rock is anorthosite. With
>40% mafic minerals, it is typically gabbro. Rocks with
5-40% mafic minerals are either diorite or
leucodiorite, and require determination of the
plagioclase content with the limiting composition being
An50.
Q
P
F(4)
A(3)
90
60
20 35 65
10 50
90
90
Quartz-richgranitic rocks
Granite
Granodiorite
Tonalite (1)
Alka
li-fe
ldsp
ar g
rani
te
Percentage of Plagioclase
Perc
enta
ge o
f Qua
rtz
Quartzsyenite
Quartzmonzonite
Quartzmonzodiorite
or quartzmonzogabbro
Syenite Monzonite Monzodiorite ormonzogabbro
Alk-
feld
.qt
z sy
enite
Quartz diorite orquartz gabbro (2)
Diorite orgabbro
Foid-bearingsyenite
Foid-bearingmonzonite
Foid-bearingmonzodiorite ormonzogabbro
Foid-bearingdiorite orgabbro35 65
Foid-bearingalk-feldspar
syenite
Foidmonzosyenite
Foid monzodioriteor foid monzogabbro
Foidilite(as nephelinite, etc.)
Foid syenite
Foid
dio
rite
or fo
id g
abbr
o
Alk-feldsyenite
(file=iugsclas.ds4)
IUGS Classification of Igneous Rocks
From: Streckeisen, 1976)
ERSC 3P21 - Brock University Greg Finn
(1) If biotite is the dominant mafic mineral, constituting < 10%, the
rock is termed a Trondhjemite.
(3)The type of alkali feldspar
should be specified if
possible, e.g., Microcline
granite.
Q
PA(3)
90
60
20 35 65 90
Quartz-richgranitic rocks
Granite
Granodiorite
Tonalite (1)
Alka
li-fe
ldsp
ar g
rani
te
Percentage of Plagioclase
Perc
enta
ge o
f Qua
rtz
Quartzsyenite
Quartzmonzonite
Quartzmonzodiorite
or quartzmonzogabbro
Syenite Monzonite Monzodiorite ormonzogabbro
Alk-
feld.
qtz
syen
ite
Quartz diorite orquartz gabbro (2)
Diorite orgabbro
Alk-feldsyenite
(2) With < 5% mafic minerals, the rock is anorthosite. With
>40% mafic minerals, it is typically gabbro. Rocks with
5-40% mafic minerals are either diorite or
leucodiorite, and require determination of the
plagioclase content with the limiting composition being
An50.
IUGS Classification of Igneous Rocks
From: Streckeisen, 1976)
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Pl
OlPx
90
65
35
10 10
35
65
90
OlivineGabbronorite
Plag. bearing ultramafic rocks
Gabbronorite Troctolite
Anorthosite(plagioclasite) Anorthosite
Gabbroids
Ultramafic rocks
(leuco-)
(mela-)
Anorthosite
(leuco-)
(mela-)
Gabbroids
Ultramafic rocks
Pl
Px
65
35
10
90
Hbl1010
10
35
65
90
Gabbronorite
Anorthosite(plagioclasite)
Pyroxene -hornblende
gabbronorite
Hornblendegabbro
plag.-bearinghbl pyroxenite
plag.-bearingpx hornblendite
plag.-bearinghornblendite
plag.-bearingpyroxenite
Pl Pl
Opx Cpx
Gabbronorite
Plag.-bearing pyroxenites
GabbroNorite
(file=iugsclas.ds4)
Gabbroic rocksplagioclase +
pyroxene + olivine
Gabbroic rockscontaining hornblende
Gabbroic rocksplagioclase +
orthopyroxene +clinopyroxene
IUGS Classification of Mafic Igneous Rocks
From: Streckeisen, 1976)
ERSC 3P21 - Brock University Greg Finn
Chemistry of Igneous Rocks• The chemical composition of any sample
(igneous, metamorphic or sedimentary) is determined by analyzing a powder of the rocks
• The actual process is covered ERSC 3P31
ERSC 3P21 - Brock University Greg Finn
Chemistry of Igneous RocksThe composition of an igneous rock is
dependant on:1.2.3.4.
•5.
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Chemistry of Igneous Rocks• Generally three groups of elements are
analyzed when studying Igneous Rocks–––
ERSC 3P21 - Brock University Greg Finn
Chemistry of Igneous RocksMajor Elements
– 13 oxide components, reported in wt.%• SiO2 35-80 wt%• Al2O3 8-22 wt%• TiO2, Fe2O3, FeO, MnO, MgO, CaO 4-30 wt %• Na2O 1.5-8 wt%• K2O 0.5-8 wt%• H2O+,- Varies• P2O5 < 0.15 wt%• CO2 Varies
• Reported as percentages, the total should = 100%
ERSC 3P21 - Brock University Greg Finn
Periodic Table of the Elements
Major Elements
MgNaFeK Ca Ti Mn
Al Si PC
H
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Average chemical compositions (wt%) of common igneous rocksOxide Granite Granodiorite Diorite Syenite Anorthosite Gabbro BasaltSiO2 72.04 66.80 58.58 57.49 51.05 51.06 50.06TiO2 0.30 0.54 0.96 0.82 0.63 1.17 1.87Al2O3 14.42 15.99 16.98 17.23 26.57 15.91 15.94Fe2O3 1.22 1.52 2.55 3.05 0.99 3.10 3.90FeO 1.68 2.87 5.13 3.22 2.07 7.76 7.50MnO 0.05 0.08 0.12 0.13 0.05 0.12 0.20MgO 0.71 1.80 3.73 1.84 2.14 7.68 6.98CaO 1.82 3.92 6.66 3.54 12.76 9.88 9.70Na2O 3.69 3.77 3.60 5.48 3.18 2.48 2.94K2O 4.12 2.79 1.81 5.03 0.62 0.96 1.08P2O5 0.12 0.18 0.29 0.29 0.69 0.24 0.34
No. 2485 885 872 517 104 1451 3796Data from LeMaitre (1976)
ERSC 3P21 - Brock University Greg Finn
Minor or Trace Elements–
–
• Basalt – analyze for ___, ___, ___ but not ___, ___, ___, as these latter are not present in detectable amounts
• Granite pegmatite with lepidolite – analyze for ___, ___ and ___, but not ___, ___ and ___
Chemistry of Igneous Rocks
ERSC 3P21 - Brock University Greg Finn
Periodic Table of the Elements
Trace Elements
BeLi
CrRb Sr
Sc V
Pb
U
S
Th
Cs BaY Zr Nb Mo
Co Ni Cu Zn Ga
FCl
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Rare Earth Elements– REE or ______________, with atomic
number between ____ to ____–– Rare Earth Elements are important for
Chemistry of Igneous Rocks
ERSC 3P21 - Brock University Greg Finn
Periodic Table of the Elements
Rare Earth Elements
PrCe GdNd PmSm Eu Tb Ho ErDyLa Tm Yb Lu
ERSC 3P21 - Brock University Greg Finn
• Several aspects which historically have played and continue to play a role in the classification of Igneous rocks will also be considered––––
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Gradation in Silica Content• Referred to as _____ or ______, implying
a range of silica content• ______ > ____ wt% SiO2
• Granites ~ 72 wt% SiO2, granodiorites ~ 68 wt % SiO2
• _________ ____ - ____ wt% SiO2• Andesite ~ 57 wt% SiO2
• _______ ___ - ____ wt% SiO2• Basalts range from 48-50 wt% SiO2
• ________ < _____ wt% SiO2• Peridotites 41 to 42 wt% SiO2
ERSC 3P21 - Brock University Greg Finn
DescriptiveTerms
Acidic> 66 wt% SiO2
Intermediate52-66 wt% SiO2
Basic45-52 wt% SiO2
Ultrabasic< 45 wt% SiO2
Intrusive
Extrusive
Granite
Rhyolite
Diorite
Andesite
Gabbro
Basalt
Peridotite
Composition
MajorMinerals
MinorMinerals
Most CommonColour
QuartzPotassium FeldsparSodium Feldspar(plagioclase)
AmphiboleIntermediateplagioclasefeldspar
Calcium Feldspar(plagioclase)Pyroxene
OlivinePyroxene
MuscoviteBiotiteAmphibole
Pyroxene OlivineAmphibole
Calcium Feldspar(plagioclase)
Light coloured Medium gray or medium green
Dark grey to black
Very dark greento black
Aluminiumoxide 4%
Aluminiumoxide 16%
Aluminiumoxide 17%
Aluminium oxide 14%
Iron oxide 3%Iron oxide 8%
Ironoxide 11%
Ironoxide 12%
Magnesium oxide 1%Magnesium oxide 3%
Magnesium oxide 7%
Magnesiumoxide31%
Silica72%
Silica59%
Silica50%
Silica45%
Other 8%
Other16%
Other13%
Other 10%
Komatiite
Gradation in Silica Content
ERSC 3P21 - Brock University Greg Finn
Colour GradationFelsic Rocks
––
Mafic Rocks–
––
Ultrabasic vs ultramafic
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Olivine
Pyroxene
Amphibole
Quartz
PotassiumFeldspar
MuscoviteBiotite
Calcium-richPlagioclase
Sodium -richPlagioclase
Rhyolite
Granite
Andesite Basalt
Diorite Gabbro Peridotite
Felsic Intermediate Mafic Ultramafic
Colour of rock becomes increasingly dark
Increasing silica content
Increasing sodium and potassium content
Increasing calcium, iron and magnesium content
80
60
40
20
0
KomatiiteFGCG
Colour Gradation
ERSC 3P21 - Brock University Greg Finn
Silica SaturationMinerals present in igneous rocks can be divided
into two groups:1. Those which are ___________ with ______ or
a primary SiO2 mineral (tridymite, cristobalite etc.).
• minerals are ___________ with respect to Si,• e.g., ____________________.
2. Those which ______ _______ with a primary silica mineral.
• These are ______________ minerals• e.g.
ERSC 3P21 - Brock University Greg Finn
Silica Saturation• The occurrence of quartz with an
________________ mineral causes a reaction between the two minerals to form a ___________ mineral.2SiO2 + NaAlSiO4 ===> NaAlSi3O8
Q + ne ===> ab
SiO2 + Mg2SiO4 ===> 2MgSiO3
Q + ol ===> en
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Silica SaturationIncompatible Phases• Under magmatic conditions some
minerals react with free silica to form other, more silica-rich, minerals: These reactant minerals are said to be _______________ (with respect to SiO2).
• Other minerals are stable (can coexist) with free silica (generally in the form of quartz) and are said to be ___________(with respect to SiO2).
ERSC 3P21 - Brock University Greg Finn
Silica SaturationTypical reactions are:
2SiO2 + NaAlSiO4 =======> NaAlSi3O8
Q + ne =======> ab2SiO2 + KAlSiO4 =======> KAlSi3O8Q + ks =======> or
SiO2 + KAlSiO4 =======> KAlSi2O6
Q + ks =======> lcSiO2 + Mg2SiO4 =======> 2MgSiO3
Q + ol =======> en
ERSC 3P21 - Brock University Greg Finn
Silica SaturationShand (1927) proposed the following list of minerals, subdivided on the basis of silica
saturation and/or undersaturation.
Saturated (+Q)all feldsparsall pyroxenesall amphibolesmicasfayalite (Fe-rich olivine)spessartine Mn3Al2(SiO4)3almandine Fe3Al2(SiO4)3sphenezircontopazmagnetiteilmeniteapatite
Undersaturated (-Q)leucitenephelinesodalite cancriniteanalciteforsterite (Mg-rich olivine)melanite (Ti garnet)andradite Ca3(Fe,Ti)2(SiO4)3pyrope Mg3Al2(SiO4)3perovskitemelilitecorundumcalcite
Undersaturated and saturated minerals can coexist stably under magmatic conditions, but quartz, tridymite and cristobalite can only coexist stably with saturated minerals. For example Q + ne is an impossible igneous assemblage, so is Q + ol (Mg - rich), but Q + ol (Fe- rich) is stable.
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Silica SaturationThe saturation concept can also be applied
to rocks• ________________ - contains primary
silica mineral• ______________ - contains neither
quartz nor an unsaturated mineral• ____________ - contains unsaturated
minerals
ERSC 3P21 - Brock University Greg Finn
Alumina Saturation• Independent of the silica saturation• Alumina saturation is based on the 1:1
alkali:alumina ratio of _________ and _____________ (ne, lc, ks).
• Any excess or deficiency in alumina in a rock is reflected in the mineralogy.
• Four classes of alumina saturation are employed:
ERSC 3P21 - Brock University Greg Finn
Alumina Saturation1. Peraluminous - Al2O3 > (CaO + Na2O + K2O)
––
2. Metaluminous - Al2O3 < (CaO + Na2O + K2O) but Al2O3 > (Na2O + K2O).
––
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Alumina Saturation3. Subaluminous - Al2O3 = (Na2O + K2O)
••
4. Peralkaline - Al2O3 < (Na2O + K2O) and rarely Al2O3 < K2O
•
••
ERSC 3P21 - Brock University Greg Finn
• Two additional types of analysis are useful in examining igneous rocks
• ________________– requires __________________
• ________________– requires __________________
ERSC 3P21 - Brock University Greg Finn
Modal Analysis• Produces an ___________________________________________________________________________________________
• Methods of analysis are:1.
2.
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Modal Analysis3.POINT COUNT
–
–
ERSC 3P21 - Brock University Greg Finn
Modal Analysis3. POINT COUNT (Continued) Advantages
–
––
Disadvantages–––
ERSC 3P21 - Brock University Greg Finn
Modal Analysis Results for DDH 70011 DEPTH (M) SAMPLE # GR QTZ MICRO PLAG EPI ACT AMP CHL BIO SPH AP OP
329.00 70011-1 50.90 6.10 0.00 23.30 2.50 1.30 0.90 9.20 2.50 0.00 0.30 2.80
364.00 70011-2 66.00 8.40 0.00 11.40 4.00 1.10 0.00 6.80 0.00 1.00 0.10 1.20
435.00 70011-4 68.40 2.80 0.00 16.10 5.90 1.20 0.20 3.40 0.00 0.00 0.00 1.90
457.00 70011-6 70.50 4.40 0.00 9.70 9.00 1.90 0.10 0.80 0.00 0.00 0.00 3.20
521.00 70011-7 63.90 3.70 0.00 15.50 7.40 0.10 0.00 6.10 0.00 0.00 0.20 3.10
537.00 70011-8 62.20 7.30 0.00 11.80 12.60 1.10 0.00 2.90 0.00 0.00 0.00 0.90
540.30 70011-9 63.60 3.70 0.00 14.50 7.50 1.00 0.00 5.80 0.00 0.00 0.00 4.00
541.00 70011-10 59.70 5.00 0.00 17.90 7.40 1.10 0.00 5.60 0.00 0.20 0.20 2.90
572.00 70011-11 64.70 3.30 0.00 13.80 8.80 0.20 0.00 4.80 0.10 0.40 0.00 2.30
627.00 70011-12 69.80 2.80 0.00 13.10 7.40 0.70 0.00 3.60 0.00 0.00 0.10 2.50
628.00 70011-13 67.50 6.80 0.00 11.80 6.80 0.50 0.10 3.40 0.00 0.00 0.00 2.50
685.00 70011-14 72.30 3.50 0.00 10.20 4.50 0.70 0.00 5.00 0.30 0.10 0.00 3.30
779.00 70011-16 67.40 3.10 0.00 15.10 7.20 0.80 0.00 3.50 0.00 0.10 0.00 2.80
837.00 70011-17 71.90 3.30 0.00 9.80 12.00 0.70 0.00 1.10 0.10 0.80 0.10 0.10
865.00 70011-18 64.20 6.20 0.00 12.30 7.90 3.30 0.00 4.50 0.00 0.40 0.30 0.90
935.00 70011-19 74.90 1.10 0.00 9.20 4.10 1.00 0.00 7.50 0.00 0.60 0.00 1.50
952.00 70011-20 69.00 3.90 0.00 7.70 6.60 3.60 0.30 7.00 0.00 0.40 0.30 1.10
1039.00 70011-22 59.20 4.60 0.00 14.40 4.40 1.90 1.60 11.50 0.10 0.70 0.40 1.30
1052.00 70011-23 50.00 4.80 0.00 23.60 5.30 2.30 0.20 11.60 0.30 0.70 0.20 0.90
1078.00 70011-24 61.10 4.90 0.00 14.00 3.70 2.00 0.10 9.20 2.70 1.20 0.30 0.90
1086.60 70011-25 55.90 4.40 0.00 24.70 3.50 1.20 0.40 8.30 0.20 0.50 0.20 0.50
1117.50 70011-26 54.60 6.40 0.00 18.90 3.70 3.80 0.50 7.80 2.20 1.50 0.10 0.60
1021.25 70011-27 56.50 4.30 0.00 18.80 5.90 2.50 0.50 8.20 1.20 1.40 0.10 0.60
1128.00 70011-28 49.80 4.10 0.00 20.90 5.20 4.00 0.50 12.70 0.00 0.70 0.10 1.90
1147.25 70011-29 59.20 3.60 0.00 18.10 2.30 4.00 0.10 11.30 0.00 1.00 0.20 0.20
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
0 2 0 4 0 6 0 8 0 1 0 00
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0
2 5 0 0
3 0 0 0
3 5 0 0
4 0 0 0
4 5 0 0
5 0 0 0
Variation in modal mineralogy for samples from DDH 70011, collared in Wisner Township. The location of the drill hole is shown in Figure 2.
Granophyre + Quartz + Microcline
Plagioclase
Opaques + Apatite + Sphene
Biotite + Amphibole + Clinopyroxene
Epidote + Actinolite + Chlorite
MODAL PER CENT
VE
RTI
CAL
DE
PTH
, IN
FEE
T, B
ELO
W S
UR
FAC
E
ERSC 3P21 - Brock University Greg Finn
Normative Analysis or NORM• NORM –
• The original purpose for the norm was essentially ___________. An elaborate classification scheme based on the normative mineral percentages was proposed.
• The classification groups together rocks of ______ _____ ______________ irrespective of their actual mineralogy.
• Various types of NORMs have been proposed - CIPW, Niggli, Barth with each having specific advantages and/or disadvantages.
ERSC 3P21 - Brock University Greg Finn
Normative Analysis or NORM• The CIPW norm, originally proposed in 1919, was
very elegant and based on a number of simplifications:
1.
2.
3.
4.
• Since CIPW introduced in ______ several other normative calculations have been suggested– e.g. Niggli norm, Barth mesonorm. The latter is used for
granitic rocks.
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
ERSC 3P21 - Brock University Greg Finn
NORM for average granite composition used earlier
ERSC 3P21 - Brock University Greg Finn
NORM for average basalt composition used earlier
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
Presenting Chemical Data
• Now that we have analyzed the samples of interest how can we present the results in a succinct and coherent manner
ERSC 3P21 - Brock University Greg Finn
Variation Diagrams• An objective of any research program
involving chemical analysis of rocks is to describe and display chemical variations within the rocks for simplicity and to facilitate condensing information
• The best way of accomplishing this is through graphical means
• Any element or oxide may be chosen as the X-axis value, resulting in a similar set of diagrams
ERSC 3P21 - Brock University Greg Finn
Variation Diagrams• Oldest method is the ________ or ______
diagram (first proposed in _____), which plots the data as _______ or _________ against other _______ or _________
• A Harker diagram uses SiO2 as abscissa (X-axis), as it is generally the _______ _________ oxide and exhibits the greatest range in value within a suite of rocks being considered
Igneous Rocks II 8/24/2011
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ERSC 3P21 - Brock University Greg Finn
12
13
100.00
0.32
0.21
3.05
6.61
3.28
0.92
0.20
4.06
2.03
17.1
1.00
61.22
13
13
12
100.00
0.38
0.24
2.87
7.07
3.33
0.76
0.22
1.21
5.09
17.14
0.68
61.01
12
11
11
99.00
0.46
0.46
1.43
6.47
4.83
1.57
0.24
4.18
4.13
16.96
1.40
56.87
11
10
10
100.00
0.32
0.52
2.22
6.33
5.20
1.73
0.22
5.32
3.23
17.13
1.61
56.17
10
9
9
100.00
0.51
0.38
1.64
6.11
7.49
2.67
0.26
4.60
5.51
16.09
2.29
52.45
9
4
7
100.00
0.33
0.26
1.28
4.89
8.84
3.31
0.24
9.14
1.71
16.83
3.08
50.09
8
6
6
100.00
0.26
0.23
1.35
4.96
8.84
3.50
0.23
9.14
1.79
16.90
2.98
49.82
7
7
8
100.19
0.89
0
1.98
1.66
4.98
7.77
4.31
0.22
8.12
2.20
16.33
2.73
49.00
6
8
4
100.00
0.68
0.39
1.28
5.97
9.04
4.67
0.22
5.04
5.51
16.01
2.82
48.37
5
3
3
100.67
0.83
0
0.89
1.49
4.63
9.30
4.82
0.20
6.89
4.64
16.32
3.30
47.36
4
2
2
99.94
0.74
0
0.98
1.46
3.81
10.11
5.14
0.20
3.02
9.26
15.47
3.92
45.83
3
1
1
99.9
0.68
0
1.15
1.23
3.17
10.72
5.58
0.20
8.36
4.06
15.08
3.93
45.74
2
5
5
98.91
0.85
0
0.97
1.19
4.95
8.91
5.07
0.22
8.84
3.64
15.24
3.52
45.51
1
Na2OCaO
TotalP2O5H2O-H2O+K2O
Na2OCaOMgOMnOFeO
Fe2O3Al2O3TiO2SiO2
Within province chemical variation, oxide results given in weight percent, for volcanic rocks from the Hanish-Zukur Islands, Red Sea (data from Gass et al. 1973)
The samples 1 thru 13 are arranged by increasing SiO2 content
ERSC 3P21 - Brock University Greg Finn
1
2
3
SiO2
TiO2
44 48 52 56 60 64
5
10FeO + Fe2O3
15
16
17Al2O3
123
SiO2
44 48 52 56 60 64
K2O
2
4
6
Na2O
3
6
9 CaO
2
4MgO
Harker plots of the Hanish-Zukur data
12 3
45 6
7 8
910 11
1213
ERSC 3P21 - Brock University Greg Finn
12
13
100.00
0.32
0.21
3.05
6.61
3.28
0.92
0.20
4.06
2.03
17.1
1.00
61.22
13
13
12
100.00
0.38
0.24
2.87
7.07
3.33
0.76
0.22
1.21
5.09
17.14
0.68
61.01
12
11
11
99.00
0.46
0.46
1.43
6.47
4.83
1.57
0.24
4.18
4.13
16.96
1.40
56.87
11
10
10
100.00
0.32
0.52
2.22
6.33
5.20
1.73
0.22
5.32
3.23
17.13
1.61
56.17
10
9
9
100.00
0.51
0.38
1.64
6.11
7.49
2.67
0.26
4.60
5.51
16.09
2.29
52.45
9
4
7
100.00
0.33
0.26
1.28
4.89
8.84
3.31
0.24
9.14
1.71
16.83
3.08
50.09
8
6
6
100.00
0.26
0.23
1.35
4.96
8.84
3.50
0.23
9.14
1.79
16.90
2.98
49.82
7
7
8
100.19
0.89
0
1.98
1.66
4.98
7.77
4.31
0.22
8.12
2.20
16.33
2.73
49.00
6
8
4
100.00
0.68
0.39
1.28
5.97
9.04
4.67
0.22
5.04
5.51
16.01
2.82
48.37
5
3
3
100.67
0.83
0
0.89
1.49
4.63
9.30
4.82
0.20
6.89
4.64
16.32
3.30
47.36
4
2
2
99.94
0.74
0
0.98
1.46
3.81
10.11
5.14
0.20
3.02
9.26
15.47
3.92
45.83
3
1
1
99.9
0.68
0
1.15
1.23
3.17
10.72
5.58
0.20
8.36
4.06
15.08
3.93
45.74
2
5
5
98.91
0.85
0
0.97
1.19
4.95
8.91
5.07
0.22
8.84
3.64
15.24
3.52
45.51
1
Na2OCaO
TotalP2O5H2O-H2O+K2O
Na2OCaOMgOMnOFeO
Fe2O3Al2O3TiO2SiO2
Within province chemical variation, oxide results given in weight percent, for volcanic rocks from the Hanish-Zukur Islands, Red Sea (data from Gass et al. 1973)
The samples 1 thru 13 are arranged by increasing SiO2 content
Igneous Rocks II 8/24/2011
18
ERSC 3P21 - Brock University Greg Finn
12
13
100.00
0.32
0.21
3.05
6.61
3.28
0.92
0.20
4.06
2.03
17.1
1.00
61.22
13
13
12
100.00
0.38
0.24
2.87
7.07
3.33
0.76
0.22
1.21
5.09
17.14
0.68
61.01
12
11
11
99.00
0.46
0.46
1.43
6.47
4.83
1.57
0.24
4.18
4.13
16.96
1.40
56.87
11
10
10
100.00
0.32
0.52
2.22
6.33
5.20
1.73
0.22
5.32
3.23
17.13
1.61
56.17
10
9
9
100.00
0.51
0.38
1.64
6.11
7.49
2.67
0.26
4.60
5.51
16.09
2.29
52.45
9
4
7
100.00
0.33
0.26
1.28
4.89
8.84
3.31
0.24
9.14
1.71
16.83
3.08
50.09
8
6
6
100.00
0.26
0.23
1.35
4.96
8.84
3.50
0.23
9.14
1.79
16.90
2.98
49.82
7
7
8
100.19
0.89
0
1.98
1.66
4.98
7.77
4.31
0.22
8.12
2.20
16.33
2.73
49.00
6
8
4
100.00
0.68
0.39
1.28
5.97
9.04
4.67
0.22
5.04
5.51
16.01
2.82
48.37
5
3
3
100.67
0.83
0
0.89
1.49
4.63
9.30
4.82
0.20
6.89
4.64
16.32
3.30
47.36
4
2
2
99.94
0.74
0
0.98
1.46
3.81
10.11
5.14
0.20
3.02
9.26
15.47
3.92
45.83
3
1
1
99.9
0.68
0
1.15
1.23
3.17
10.72
5.58
0.20
8.36
4.06
15.08
3.93
45.74
2
5
5
98.91
0.85
0
0.97
1.19
4.95
8.91
5.07
0.22
8.84
3.64
15.24
3.52
45.51
1
Na2OCaO
TotalP2O5H2O-H2O+K2O
Na2OCaOMgOMnOFeO
Fe2O3Al2O3TiO2SiO2
Within province chemical variation, oxide results given in weight percent, for volcanic rocks from the Hanish-Zukur Islands, Red Sea (data from Gass et al. 1973)
The samples 1 thru 13 are arranged by increasing SiO2 content
Order of analyses if sorted by decreasing CaO content
ERSC 3P21 - Brock University Greg Finn
12
13
100.00
0.32
0.21
3.05
6.61
3.28
0.92
0.20
4.06
2.03
17.1
1.00
61.22
13
13
12
100.00
0.38
0.24
2.87
7.07
3.33
0.76
0.22
1.21
5.09
17.14
0.68
61.01
12
11
11
99.00
0.46
0.46
1.43
6.47
4.83
1.57
0.24
4.18
4.13
16.96
1.40
56.87
11
10
10
100.00
0.32
0.52
2.22
6.33
5.20
1.73
0.22
5.32
3.23
17.13
1.61
56.17
10
9
9
100.00
0.51
0.38
1.64
6.11
7.49
2.67
0.26
4.60
5.51
16.09
2.29
52.45
9
4
7
100.00
0.33
0.26
1.28
4.89
8.84
3.31
0.24
9.14
1.71
16.83
3.08
50.09
8
6
6
100.00
0.26
0.23
1.35
4.96
8.84
3.50
0.23
9.14
1.79
16.90
2.98
49.82
7
7
8
100.19
0.89
0
1.98
1.66
4.98
7.77
4.31
0.22
8.12
2.20
16.33
2.73
49.00
6
8
4
100.00
0.68
0.39
1.28
5.97
9.04
4.67
0.22
5.04
5.51
16.01
2.82
48.37
5
3
3
100.67
0.83
0
0.89
1.49
4.63
9.30
4.82
0.20
6.89
4.64
16.32
3.30
47.36
4
2
2
99.94
0.74
0
0.98
1.46
3.81
10.11
5.14
0.20
3.02
9.26
15.47
3.92
45.83
3
1
1
99.9
0.68
0
1.15
1.23
3.17
10.72
5.58
0.20
8.36
4.06
15.08
3.93
45.74
2
5
5
98.91
0.85
0
0.97
1.19
4.95
8.91
5.07
0.22
8.84
3.64
15.24
3.52
45.51
1
Na2OCaO
TotalP2O5H2O-H2O+K2O
Na2OCaOMgOMnOFeO
Fe2O3Al2O3TiO2SiO2
Within province chemical variation, oxide results given in weight percent, for volcanic rocks from the Hanish-Zukur Islands, Red Sea (data from Gass et al. 1973)
The samples 1 thru 13 are arranged by increasing SiO2 content
Order of analyses if sorted by increasing Na2O content
ERSC 3P21 - Brock University Greg Finn
Harkerdiagram
forCraterLake
Figure 8-2. Harker variation diagram for 310 analyzed volcanic rocks from Crater Lake (Mt. Mazama), Oregon Cascades. Data compiled by Rick Conrey (personal communication).
For large datasets, graphical methods are preferred.
Igneous Rocks II 8/24/2011
19
ERSC 3P21 - Brock University Greg Finn
Fractionation Indices• No genetic link can be inferred from Harker
diagrams, i.e. that the lowest SiO2 sample represents the original or first liquid
• To attempt to discern a genetic link between analyses in a given suite of rocks various fractionation indices have been developed
• These indices are not realistic, but provide a first approximation to discerning a genetic link between samples
ERSC 3P21 - Brock University Greg Finn
Fractionation IndicesMgO Index•
•
0 20MgO (wt%)0
10
Oxi
de (w
t%)
ERSC 3P21 - Brock University Greg Finn
Fractionation IndicesMg-Fe Ratios•
• Involve a ratio of Mg to Fe:–––
0 1.0Mg/Mg+Fe0
10
Oxi
de (w
t%)
Igneous Rocks II 8/24/2011
20
ERSC 3P21 - Brock University Greg Finn
Fractionation IndicesNormative Ab/Ab+An•
•
••
ERSC 3P21 - Brock University Greg Finn
Fractionation IndicesSolidification Index• SI= 100MgO/(MgO+FeO+Fe2O3+Na2O+K2O)• When applied to _______, the SI is similar to
the Mg/Fe ratio, due to the ______________• As fractionation progresses, the residual
liquids become ________ in _______, thus Na2O and K2O contents offset the Mg-Fe index
• For _______ rocks, SI is high• For _______ rocks, SI is low
ERSC 3P21 - Brock University Greg Finn
0.00
1.00
2.00
3.00
4.00
5.00
6.00
4.00 8.00 12.00 16.00 20.00 24.00
Solidification Index
12 13 11 10 98 7
65 4 3
21
SI = (100*MgO)/(MgO+FeO+Fe2O3+Na2O+K2O)
2
4 MgO
SiO244 48 52 56 60 64
12 131110
98
7654
32
1 Data from Hanish-Zukur Islands
Igneous Rocks II 8/24/2011
21
ERSC 3P21 - Brock University Greg Finn
Fractionation IndicesDifferentiation Index• DI = normative Q+Or+Ab+Ne+Ks+Lc• Based on _____________ analysis• For mafic rocks
– DI is ______, as the minerals used are ______ in the NORM
• For felsic rocks– DI is ______, as the minerals in these rocks are
_________ in the NORM
ERSC 3P21 - Brock University Greg Finn
Triangular Variation Diagrams• The previous diagrams each essentially employ
two variables• It is possible to graphically present data such
that 3 chemical parameters are represented• Two diagrams used
– AFM– Na2O-K2O-CaO
• Big disadvantage is that the absolute values of the analysis are not readily evident, as they must be ratioed to plot on the diagram
ERSC 3P21 - Brock University Greg Finn
AFM
• Used mainly for _______ rocks, as MgO and FeO are abundant in these lithologies
• A = Na2O + K2O• F = FeO (+ Fe2O3)• M = MgO
5101530
17%33%50%
100%
Igneous Rocks II 8/24/2011
22
ERSC 3P21 - Brock University Greg Finn
AFM
http://www.unb.ca/courses/nsusak/geol2602/lec21/
FeO
Na2O+K2O MgO
ERSC 3P21 - Brock University Greg Finn
CaO-Na2O-K2O
• Used mainly for _______ rocks, as these three oxides are abundant in these lithologies
• Simple ratio of either weight percent of atomic proportions are used to calculate the data points
ERSC 3P21 - Brock University Greg Finn
CaO-Na2O-K2O
Alteration and
weathering
NormalTrend
http://www.unb.ca/courses/nsusak/geol2602/lec21/
Na2O
CaO K2O
Igneous Rocks II 8/24/2011
23
ERSC 3P21 - Brock University Greg Finn