1. Presented by Joyleen Desai
Zircon Group ABO4
Presented by
Joyleen Desai

2. Zircon Occurrences
Zircons are found in igneous, sedimentary, and metamorphic rocks
They are found in mantle xenoliths, lunar rocks, meteorites, and tektites
Zircons can survive one or more cycles of erosion, sedimentary transport, diagenesis, and/or low grade metamorphism

3. Zircon Structure ZrSiO4 I41/amd Z=4 Naturally occurring dimorph
ZrSiO4 I41/a Z=4
High P polymorph
Scheelite structure ~11% more dense
Unknown in nature
Scheelite = CaWO4

4. Yellow = Zr, blue = Si

5. Zircon Structure Atom Site Multiplicity Positional Parameters
Site Symmetry Zr a 4
0, 3/4, 1/8
42m Si b
0, 3/4, 5/8 O h 16
0, x, z m
The atoms in zircon occupy special positions and the two positional parameters of the O atom are the only variables
Reference: Speer (1980)

6. Other Minerals Having the ABO4 Zircon Structure
Hafnon HfSiO4
Xenotime YPO4
Behierite (Ta,Nb)BO4
Thorite ThSiO4
Coffinite USiO4

7. Zircon Chemistry Elements substituting for Zr(A) and Si(B)
in zircon (ABO4)

8. Thermal Expansion
The bulk thermal expansion coefficient (α) = 4-5 x 10-6/°C ( °C)
Relatively insensitive to thermal shock

9. Compression
Zircon has the highest bulk modulus (234 GPa) of any measured substance with tetrahedrally coordinated Si
Si bulk modulus = GPa
Anonymously compressible
Zr bulk modulus = GPa
Unusually incompressible
c axis ~ 70% more compressible than a

10. Transformations

11. Inclusion Chemistry

12. Inclusions as Indicators of Early Earth Environments
Inclusions contained in igneous zircons typically reflect the parent melt
δ18O values of Hadean zircons indicate that oceans, continental crust, and a sedimentary cycling process were all present by 4.3 Ga
fO2 values can theoretically be determined via knowledge of the Fe3+/Fe2+ ratio