How to Plot Ternary Diagrams
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Transcript of How to Plot Ternary Diagrams
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8/11/2019 How to Plot Ternary Diagrams
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How to plot ternary diagrams
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Ternary diagrams
Used to represent three variables
Very useful for geochemical and petrological
data
Often used as a means of classifying data and
rocks
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Ternary Diagrams
Suppose we have a hypothetical rock with the following
hypothetical minerals:
P 23.2%Q 25.2%
X 36%
Y 10.4%
Z 5.2%
Total 100%
Now suppose we want torepresent this rock just in terms
of the minerals X, Y & Z
How would we do this?
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Ternary Diagrams
First, we would have to normaliseour data to
just these three variables:
P 23.2%
Q 25.2%
X 36%
Y 10.4%
Z 5.2%
Total 100%
X 36
Y 10.4
Z 5.2
Total 51.6
So, we multiply each
by 100/51.6 = 1.94
X 70
Y 20
Z 10
Total 100
x 1.94 =
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Ternary
There are two methods for plotting this data
on a ternary diagram..
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Ternary Diagrams
Method 1
Use when ternary diagram
has grid lines
Each apex represents 100%of that component
The horizontal lines opposite
each apex
Count up from 0% for eachcomponent
E.G. 1,A 40 %
B 50 %
C 10 %
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Ternary Diagrams
Method 1
Use when ternary diagram
has grid lines
Each apex represents 100%of that component
The horizontal lines opposite
each apex
Count up from 0% for eachcomponent
E.G. 2,X 70 %
Y 20 %
Z 10 %
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Ternary Diagrams
Method 1
Use when ternary diagram
has grid lines
Each apex represents 100%of that component
The horizontal lines opposite
each apex
Count up from 0% for eachcomponent
E.G. 2,X 70 %
Y 20 %
Z 10 %
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Ternary Diagrams
Method 2Use when ternary diagram hasno grid lines (manyclassification diagrams)
Ratio the two smallestcomponents (100Y/(Y+Z)).Here, this equals 2000/30 =67%
This Y/Z ratio will remain thesame regardless of X. So draw a
line from the X apex to a Y:Zratio of 67% and plot where itcrosses the 70% X position
E.G. 2,X 70 %
Y 20 %
Z 10 %
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Ternary Diagrams - examples
We have a course-grained (plutonic)igneous rock with the followingmineral proportions:
Hornblende 10.4%
Pyroxene 5.2%
Quartz 29.8%
Alkali Feldspar 10.4%
Plagioclase Feldspar 44.2%
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Ternary Diagrams - examples
This particular classification diagramrequires that Quartz (Q), Alkali-feldspar (A) and Plagioclase Feldspar(P) make up a total >10%
Hornblende 10.4%
Pyroxene 5.2%Quartz (Q) 29.8%
Alkali Feldspar (A) 10.4%
Plagioclase Feldspar (P) 44.2%
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Ternary Diagrams - examples
This particular classification diagramrequires that Quartz (Q), Alkali-feldspar (A) and Plagioclase Feldspar(P) make up a total >10%
Hornblende 10.4%
Pyroxene 5.2%Quartz (Q) 29.8%
Alkali Feldspar (A) 10.4%
Plagioclase Feldspar (P) 44.2%
Now, how do we plot this data on
our ternary (classification)
diagram?
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Ternary Diagrams - examples
First, normaliseour data to just these three
variables:
Hbl 10.4%
Pyx 5.2%
Q 29.8 %
A 10.4%
P 44.2%
Total 100%
Q 29.8
A 10.4
P 44.2
Total 84.4
So, we multiply each
by 100/84.4 = 1.18
Q 35.2 %
A 12.3 %
P 52.5 %
Total 100
x 1.18 =
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Ternary Diagrams - examples
Q 35.2 %
A 12.3 %
P 52.5 %
Total 100 %
Q/A ratio = 100x35.2/(35.2+12.3)
= 74.1 %
GRANODIORITE
52.5% P74.1% Q/A