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Zircon Group ABO 4

Zircon Group ABO 4. Presented by Joyleen Desai. Zircon Occurrences. Zircons are found in igneous, sedimentary, and metamorphic rocks They are found in mantle xenoliths, lunar rocks, meteorites, and tektites

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Zircon Group ABO 4

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  1. Zircon GroupABO4 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 • ZrSiO4I41/amd Z=4 • Naturally occurring dimorph • ZrSiO4I41/a Z=4 • High P polymorph • Scheelite structure ~11% more dense • Unknown in nature

  4. Zircon Structure Reference: Speer (1980)

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

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

  7. Thermal Expansion • The bulk thermal expansion coefficient (α) = 4-5 x 10-6/°C (25-1300°C) • Relatively insensitive to thermal shock

  8. Compression • Zircon has the highest bulk modulus (234 GPa) of any measured substance with tetrahedrally coordinated Si • Si bulk modulus = 230 + 40 GPa • Anonymously compressible • Zr bulk modulus = 280 + 40 GPa • Unusually incompressible • c axis ~ 70% more compressible than a

  9. Transformations

  10. Inclusion Chemistry

  11. 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

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