Microstructural Geochronology E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Geophysical Monograph Series
• Sprache: Englisch

Seitenzahl: 1209

Veröffentlichungsjahr: 2017

Beschreibung

Microstructural Geochronology Geochronology techniques enable the study of geological evolution and environmental change over time. This volume integrates two aspects of geochronology: one based on classical methods of orientation and spatial patterns, and the other on ratios of radioactive isotopes and their decay products. The chapters illustrate how material science techniques are taking this field to the atomic scale, enabling us to image the chemical and structural record of mineral lattice growth and deformation, and sometimes the patterns of radioactive parent and daughter atoms themselves, to generate a microstructural geochronology from some of the most resilient materials in the solar system. * First compilation of research focusing on the crystal structure, material properties, and chemical zoning of the geochronology mineral archive down to nanoscale * Novel comparisons of mineral time archives from different rocky planets and asteroids and their shock metamorphic histories * Fundamentals on how to reconstruct and date radiogenic isotope distributions using atom probe tomography Microstructural Geochronology will be a valuable resource for graduate students, academics, and researchers in the fields of petrology, geochronology, mineralogy, geochemistry, planetary geology, astrobiology, chemistry, and material science. It will also appeal to philosophers and historians of science from other disciplines.

Leseprobe

Table of Contents

COVER

TITLE PAGE

CONTRIBUTORS

PREFACE

Part I: Chemical Microstructure/Zoning

1 Zircon as Magma Monitor

1.1. INTRODUCTION

1.2. THE SAMPLE SET

1.3. METHODS

1.4. RESULTS: CALCULATED ZIRCON K

DS

1.5. DISCUSSION AND IMPLICATIONS

1.6. IMPLICATIONS AND APPLICATIONS

1.7. CONCLUSIONS

ACKNOWLEDGEMENTS

REFERENCES

2 Petrology and Geochronology of Metamorphic Zircon

2.1. INTRODUCTION

2.2. HOW DOES METAMORPHIC ZIRCON FORM?

2.3. ANALYTICAL STRATEGIES

2.4. INCLUSION ASSEMBLAGES

2.5. WHAT DOES METAMORPHIC ZIRCON CHEMISTRY TELL US?

2.6. EXAMPLES

2.7. RECOMMENDATIONS

ACKNOWLEDGMENTS

REFERENCES

3 Origins of Textural, Compositional, and Isotopic Complexity in Monazite and Its Petrochronological Analysis

3.1. INTRODUCTION

3.2. ORIGINS AND APPLICATIONS OF COMPLEX ZONING TEXTURES IN MONAZITE

3.3. DIFFUSION IN MONAZITE

3.4. CASE STUDIES OF MONAZITE TEXTURE DEVELOPMENT IN NATURAL SYSTEMS

3.5. ISOTOPE DISTRIBUTION IN TEXTURALLY COMPLEX MONAZITE

3.6. EXPLOITING COMPOSITIONAL COMPLEXITY IN MONAZITE FOR GEOCHRONOMETRY AND ISOTOPE STUDIES

3.7. EXAMPLES AND APPLICATIONS OF LA‐ICP‐MS

3.8. CONCLUDING REMARKS

ACKNOWLEDGMENTS AND DATA

REFERENCES

4 Application of Single‐Shot Laser Ablation Split‐Stream Inductively Coupled Plasma Mass Spectrometry to Accessory Phase Petrochronology

4.1. INTRODUCTION

4.2. METHODS

4.3. SS‐LASS ANALYTICAL CONSIDERATIONS

4.4. APPLICATIONS

4.5. PETROCHRONOLOGY AT THE GRAIN‐SCALE

4.6. DISCUSSION AND SUMMARY

4.7. CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

5 Comparing Chemical Microstructures of Some Early Solar System Zircon from Differentiated Asteroids, Mars and Earth

5.1. INTRODUCTION

5.2. SAMPLES AND METHODS

5.3. RESULTS

5.4. DISCUSSION

5.5. CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

6 Crystallization of Baddeleyite in Basaltic Rocks from Mars, and Comparisons with the Earth, Moon, and Vesta

6.1. INTRODUCTION

6.2. METHODS FOR FINDING AND IMAGING BADDELEYITE

6.3. OCCURRENCES OF BADDELEYITE IN PLANETARY BASALTIC ROCKS

6.4. GENERALIZATIONS AND IMPLICATIONS

ACKNOWLEDGMENTS

REFERENCES

Part II: Orientation Microstructure

7 Strength and Deformation of Zircon at Crustal and Mantle Pressures

7.1. INTRODUCTION

7.2. METHODS

7.3. RESULTS

7.4. DISCUSSION

7.5. CONCLUSION

ACKNOWLEDGMENTS

REFERENCES

8 Role of Elastic Anisotropy in the Development of Deformation Microstructures in Zircon

8.1. INTRODUCTION

8.2. ELASTIC ANISOTROPY OF MINERALS

8.3. ZIRCON: PROPERTIES, DEFORMATION MECHANISMS, AND MICROSTRUCTURES

8.4. ELASTIC PROPERTIES OF ZIRCON

8.5. APPROACH AND METHODS

8.6. ELASTIC ANISOTROPY OF ZIRCON

8.7. DISCUSSION

8.8. CONCLUSIONS

ACKNOWLEDGMENTS

APPENDIX

REFERENCES

9 The Rietputs Formation in South Africa

9.1. INTRODUCTION TO DETRITAL SHOCKED MINERALS

9.2. GEOLOGICAL BACKGROUND

9.3. SAMPLES AND METHODS

9.4. RESULTS

9.5. DISCUSSION

ACKNOWLEDGMENTS

REFERENCES

10 Deciphering the Effects of Zircon Deformation and Recrystallization to Resolve the Age and Heritage of an Archean Mafic Granulite Complex

10.1. INTRODUCTION

10.2. REGIONAL GEOLOGY

10.3. RESULTS

10.4. DISCUSSION

10.5. CONCLUSIONS

ACKNOWLEDGMENTS

APPENDIX

REFERENCES

11 Alpha Recoil Loss of Pb from Baddeleyite Evaluated by High‐Resolution Ion Microprobe (SHRIMP II) Depth Profiling and Numerical Modeling

11.1. INTRODUCTION

11.2. METHODS

11.3. RESULTS

11.4. DISCUSSION

11.5. CONCLUSIONS

ACKNOWLEDGMENTS

APPENDIX

REFERENCES

12 Transmission Electron Microscope Imaging Sharpens Geochronological Interpretation of Zircon and Monazite

12.1. INTRODUCTION

12.2. SAMPLE PREPARATION

12.3. STRUCTURAL AND CHEMICAL EVIDENCE FOR NANO‐INCLUSIONS AFFECTING THE U‐TH‐PB SYSTEMATICS IN MONAZITE AND ZIRCON

12.4. NANOSCALE CONSTRAINS ON THE RESETTING MECHANISM OF U‐Th‐Pb SYSTEMS IN EXPERIMENTALLY ALTERED MONAZITE

12.5. NANO‐PETROCHRONOLOGY OF MONAZITE

12.6. CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

Part III: 3D Nanostructure

13 Detecting Micro‐ and Nanoscale Variations in Element Mobility in High‐Grade Metamorphic Rocks

13.1. INTRODUCTION

13.2. THE ISSUE OF REVERSELY DISCORDANT DATA

13.3. LOCATIONS WHERE ANCIENT Pb MOBILIZATION HAS BEEN IDENTIFIED

13.4. RECOGNIZING ANCIENT Pb MOBILIZATION

13.5. LEAD NANO‐INCLUSIONS AND THE FORMATION OF PB CLUSTERS

ACKNOWLEDGMENTS

REFERENCES

14 The Optimization of Zircon Analyses by Laser‐Assisted Atom Probe Microscopy

14.1. INTRODUCTION

14.2. MATERIALS AND METHODS

14.3. DATA

14.4. RESULTS AND DISCUSSION

14.5. CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

15 Atom Probe Tomography of Phalaborwa Baddeleyite and Reference Zircon BR266

15.1. INTRODUCTION

15.2. BACKGROUND

15.3. METHODS

15.4. RESULTS

15.5. DISCUSSION

15.6. CONCLUSION

REFERENCES

16 Uncertainty and Sensitivity Analysis for Spatial and Spectral Processing of Pb Isotopes in Zircon by Atom Probe Tomography

16.1. INTRODUCTION

16.2. SAMPLES AND METHODS

16.3. RESULTS AND DISCUSSION

16.4. CONCLUSIONS

ACKNOWLDGMENTS

REFERENCES

17 Complex Nanostructures in Shocked, Annealed, and Metamorphosed Baddeleyite Defined by Atom Probe Tomography

17.1. INTRODUCTION

17.2. GEOLOGICAL BACKGROUND AND SAMPLE SELECTION

17.3. APT METHODOLOGY

17.4. APT OF SHOCKED BADDELEYITE

17.5. FORMATION OF CHEMICAL NANOSTRUCTURES IN SHOCKED BADDELEYITE

17.6. IMPLICATIONS FOR TRACE ELEMENT AND ISOTOPE ANALYSIS OF BADDELEYITE

17.7. CONCLUSIONS

ACKNOWLEDGMENTS

REFERENCES

18 Best Practices for Reporting Atom Probe Analysis of Geological Materials

18.1. INTRODUCTION

18.2. REPORTING

REFERENCES

INDEX

END USER LICENSE AGREEMENT

List of Tables

Chapter 01

Table 1.1 Characteristics of Samples

Table 1.2 Estimated Zircon Kds from Zircon Rims or Surfaces

a

and Host Glasses

Table 1.3 Best fit Parameters for Curves Describing Relationship Between Kds and Ionic Radius [

Onuma et al.

, 1968;

Blundy and Wood

, 1994] for Samples from This Study and from

Colombini et al.

[2011],

Bachmann et al.

[2005], and

Sano et al.

[2002]

Table 1.4 Comparison of Kds for Three MSH Samples, Calculated Using Eruption‐Age Zircon Surfaces Versus Conventional Rim Analyses

Table 1.5 Kd Versus Ti in Zircon (ppm) Correlations

Chapter 05

Table 5.1 Occurrence, Sizes, and Chemistry of Zircon Grains in Achondrites

Table 5.2 Actinide Concentrations, Raman Spectral Characteristics and Calculated Alpha Dose of Selected Zircon Grains

Table 5.3 Raman Shift and FWHM of Selected Zircon Grains

Chapter 06

Table 6.1 Summary of bulk Zr contents, baddeleyite size and frequency, oxygen fugacity, and Zr content of ilmenite in selected shergottites

Chapter 08

Table 8.1 X‐Ray Diffraction Peak Attributes and α‐Dose of Zircon Samples 1, 2, and 3 from

Özkan

[1976].

Chapter 09

Table 9.1 Locations of Rietputs Formation Samples Analyzed in this Study

Table 9.2 EBSD Analysis Conditions

Table 9.3 Summary of Shocked Minerals Identified in Rietputs Formation Samples

Table 9.4 SHRIMP‐RG U‐Th‐Pb Isotopic Data for Rietputs Formation Detrital Shocked Zircon Grains

Table 9.5 SHRIMP‐RG U‐Th‐Pb Isotopic Data for Rietputs Formation Detrital Shocked Monazite Grains

Chapter 10

Table 10.1 SHRIMP U‐Pb Results

Table 10.2 SHRIMP Trace Element Results

Chapter 11

Table 11.1 General Operating Conditions

Table 11.2 Estimated Average Recoil Distances

Table 11.3 Calculated Pb Loss for Tabular Baddeleyite Crystals

Chapter 13

Table 13.1 d‐Spacing of Analyzed Pb Nanospheres Compared with Published Values for Native Pb and PbS

Chapter 14

Table 14.1 Adjustable Parameters for a Laser‐Assisted Atom Probe Data Acquisition, with Indicative Values Provided for Each

Table 14.2 An Example of a “Decomposition Matrix” for APM Analysis of Zircon

Table 14.3 Comparison with SIMS and LA‐ICP‐MS Data

Table 14.4 Suitable APM Acquisition Conditions for the 91500 Zircon Standard, Using the CAMECA LEAP 4000X HR Instrument

Chapter 15

Table 15.1 The Published Composition of the Phalaborwa Baddeleyite and the Composition Measured in this Study Classified by the Confidence Level of the Identification

Table 15.2 The Published Composition of Zircon BR266 and the Composition Measured in this Study Classified by the Confidence Level of the Identification

Chapter 16

Table 16.1 Summary of EBSD Acquisition and Analysis

Table 16.2 APT Data Acquisition Settings and Run Summary (For Summary of Terms, see

Blum et al

. [chapter 18, this volume])

Table 16.3 Summary of SIMS U‐Pb and APT Pb Isotope Data

Chapter 17

Table 17.1 Nanostructurally Subdivided Chemical Composition of Microtip R60_146506

Chapter 18

Table 18.1 Example Atom Probe Tomography Data Acquisition Settings and Data Summary

List of Illustrations

Chapter 01

Figure 1.1 Compilation of zircon‐melt Kds from the literature. The gray field represents the range of Kds calculated in this study. (a) Studies of experimental zircon [

Watson

, 1980;

Thomas et al.

, 2002;

Luo and Ayers

, 2009;

Burnham and Berry

, 2012;

Trail et al.

, 2012;

Taylor et al.

, 2015]. (b) Studies of natural zircon [

Nagasawa

, 1970;

Mahood and Hildreth

, 1983;

Fujimaki

, 1986;

Bea et al.

, 1994;

Bachmann et al.

, 2005;

Sano et al.

, 2002;

Rubatto and Hermann

, 2007;

Reid et al.

, 2011;

Nardi et al.

, 2013;

Padilla and Gualda

, 2016].

Figure 1.2 Zircons from MSH. White bar is 50 µm. (a) Scanning electron image of a polished zircon with adhering glass. SHRIMP analysis pits shown in the core and rim. (b) Cathodoluminescence image of the polished zircon interior shown in (a). (c) Scanning electron image of a zircon pressed into Indium. The circle indicates the location of a SHRIMP analysis of the “surface” composition.

Figure 1.3 Estimated Kds based on zircon surfaces (MSH) and conventional rims in cross section (others). CREC, Colorado River Extensional Corridor, AZ‐NV, USA.

Figure 1.4 Elemental ratios in zircon versus ratios in glass. (a) Zr/Hf (1.34 = mean ratio Zr/Hf

zircon

/Zr/Hf

glass

); (b) Th/U (Th/U

zircon

/Th/U

glass

 = 0.1 and 0.3 shown for reference); (c) Sm/Lu

zircon

/Sm/Lu

glass

versus Lu Kd, with linear correlation; and (d) Dy/Lu Lu

zircon

/Dy/Lu

glass

versus Lu Kd, with linear correlation.

Figure 1.5 (a and b) Onuma diagrams for REE for two Icelandic samples. Top portion of the diagrams shows partition coefficient versus ionic radius for our data (circles); solid line represents best fit curve using the lattice‐strain model of

Blundy and Wood

[1994]. Filled circles are included in the calculation of the best fit curves, while open circles are ignored for best fit procedure. Bottom diagram shows residuals between measured and best fit values for each element, with elements included or excluded in best fit calculation indicated by different crosses. Best fit curve fits the included data very well. Note that Eu and Ce are not expected to follow the best fit curve due to the coexistence of two valence states. Extrapolation of the best fit curve to La shows that expected partition coefficients for La are very low, resulting in very low concentrations of La in zircon; measured values are much higher than expected, and probably reflect the presence of small inclusions. This same problem also affects Nd, but to a much lower extent. See text for details. (c) Onuma diagram for REE showing best‐fit curves for data from this study and select data from the literature. Best fit curve for the data from

Bachmann et al.

[2005] is based only on Sm, Dy, Er, and Yb due to the lack of data for Tb, Ho, Tm, and Lu. Note that best fit curves are mostly subparallel, and they vary by more than an order of magnitude, particularly for the HREE. Some of the data for MSH show a distinctively steeper slope (more enriched in HREE over LREE).

Figure 1.6 Calculated zircon‐melt Kds for the three Mount St. Helens samples. Kds calculated from surface analyses are represented by closed symbols, and Kds calculated from conventional rim analyses are represented by open symbols.

Figure 1.7 Kds

zircon/melt

versus melt (glass) composition parameters. Only Lu Kd versus SiO

2

shows any correlation. (a) U Kd versus SiO

2

; (b) Lu Kd versus SiO

2

; (c) U Kd versus M [

Watson and Harrison

, 1983]; (d) Lu Kd versus M; (e) U Kd versus FM [

Ryerson and Watson

, 1987]; (f) Lu Kd versus FM; (g) U Kd versus A/CNK (molecular Al

2

O

3

/(CaO + Na

2

O + K

2

O)); (h) Lu Kd versus A/CNK; (i) Lu Kd versus NBO/

T

[Mysen et al., 1985]; and (j) U Kd versus NBO/

T

.

Figure 1.8 Comparisons of temperature‐related quantities in zircon and coexisting melt (glass), with correlations. (a) Zr concentration in glass (ppm) versus calculated zircon saturation temperature [

Boehnke et al.

, 2013; based on glass compositions]; (b) Ti concentration in zircon rim or surface (ppm) versus calculated zircon saturation temperature; and (c) Zr concentration in glass (ppm) versus Ti concentration in zircon rim or surface (ppm).

Figure 1.9 Kds

zircon/melt

versus 1/calculated zircon saturation temperature [

Boehnke et al.

, 2013; based on glass compositions]. (a) U Kd; (b) Th Kd; (c) Nb Kd; (d) Y Kd; (e) Hf Kd; (f) Nd Kd; (g) Sm Kd; (h) Eu Kd; (i) Gd Kd; (j) Tb Kd; (k) Dy Kd; (l) Ho Kd; (m) Er Kd; (n) Tm Kd; (o) Yb Kd; and (p) Lu Kd.

Figure 1.10 Kds

zircon/melt

versus Zr concentration in melt (glass). (a) U Kd; (b) Th Kd; (c) Nb Kd; (d) Nd Kd; (e) Sm Kd; (f) Dy Kd; (g) Yb Kd; and (h) Lu Kd.

Figure 1.11 Kds

zircon/melt

versus Ti concentration in zircon rim or surface (ppm) with correlations. (a) U Kd; (b) Th Kd; (c) Nb Kd; (d) Y Kd; (e) Hf Kd; (f) Ce Kd; (g) Nd Kd; (h) Sm Kd; (i) Eu Kd; (j) Gd Kd; (k) Dy Kd; (l) Tb Kd; (m) Ho Kd; (n) Er Kd; (o) Tm Kd; (p) Yb Kd; and (q) Lu Kd.

Figure 1.12 Trace element compositions of MSH model melts, based on application of new Ti‐dependent Kds to conventional SHRIMP analysis of polished zircon interiors, including cores and rims, from three samples (SHL21Z, SHL26Z, and SHL34Z). (a) Model melt U (ppm) versus model melt Th (ppm) and (b) model melt Zr/Hf versus model melt Th/U.

Figure 1.13 REE model melt/chondrite patterns for Mount St. Helens, based on application of Ti‐dependent Kds to conventional SHRIMP analysis of polished zircon interiors, including cores and rims. Pr and Pm, shown in parentheses, were not analyzed for any samples, and Tb, Ho, Tm only for some. Missing elements are calculated as midpoints between elements of adjacent atomic number. (a–c) Model melt REE patterns for samples SHL21Z, SHL26Z, and SHL34Z, respectively. The solid black line represents the median model melt composition for each sample. The dashed black line represents the average glass composition of each sample.

Figure 1.14 Zircon age versus model melt trace element ratios for Mount St. Helens, based on application of new, Ti‐dependent Kds to conventional SHRIMP analysis of polished zircon interiors, including cores and rims. Zircon ages from U‐Th and U‐Pb SHRIMP analyses. (a) Th/U and (b) Zr/Hf. The gray bar represents chondritic Zr/Hf [

Ahrens and Erlank

, 1969;

Hoskin and Schaltegger

, 2003]; (c) Sm/Lu.

Chapter 02

Figure 2.1 Mechanisms of zircon growth in metamorphic rocks. (a) At low grades, metamict zircon may recrystallize or dissolve and reprecipitate either within a crystal (upper images) or as overgrowths on other crystals (lower images).(b) With increasing temperature, Zr contents of major and minor minerals increase. With decreasing temperature and/or retrograde dissolution, Zr is liberated and may form zircon. Sketches of natural rocks modified from

Degeling et al.

[2001] and

Ewing et al.

[2013]. (c) High Zr solubility in melts means that zircon dissolves during partial melting and reprecipitates during cooling. Sketch of leucosome zircon from

Brouand et al.

[1990]. (d) Ostwald ripening reflects the instability of small grains relative to large grains, due to high surface free energy contributions to total free energy in small grains.

Figure 2.2 (a) Simplified petrogenetic grid for a metapelitic composition showing that the mode of zircon should decrease during prograde metamorphism and increase during retrograde metamorphism, especially if melting reactions are crossed. “Alpine,” “WGR,” and “CC” indicate representative P‐T paths experienced by UHP rocks in the Alps, HP rocks in the Western Gneiss Region, and expected paths for models of continent‐continent collision. (b–g) Main reservoirs of Zr along the P‐T paths delineated in Figure 2.2a, showing decreases in the amount of zircon during prograde metamorphism and increases during retrograde metamorphism, as balanced against the Zr content of garnet, rutile, and melt. Zircon reservoir in mafic compositions shown for reference along the same P‐T paths.

Figure 2.3 (a) Theoretical calculations scaled from

Miyazaki

[1996] of the efficacy of Ostwald ripening for zircon over different timescales, contoured for the product of Zr diffusivity (

D

, m

2

/s), Zr concentration (

C

, mol/m

3

), and porosity (Φ, dimensionless). This, flat, labeled lines imply no significant change to grain size; inclined lines imply Ostwald ripening. Thin, flat, labeled lines indicate the maximum grain size that would experience ripening on timescales of 1–10 Ma for a particular value of

D

 · 

C

 · Φ. For example, if

D

 · 

C

 · Φ = 10

−19

(multiple converging lines), grains with initial radii of ~2μm, 1 µm, 0.4 µm, and 0.2 µm would show slight Ostwald ripening on timescales of ~1 Ma, ~100 ka, ~10 ka, and ~1 ka, respectively, and would coarsen to grain sizes of ~3 µm on timescales of 1–10 Ma. Smaller grains could show coarsening with smaller values of

D

 · 

C

 · Φ. (b) Calculations of minimum grain size of zircon that would show Ostwald ripening in water‐saturated rocks (lower thick lines) and anatectic rocks (upper thick lines). Ostwald ripening appears ineffective in water‐saturated rocks of low solute content (only the smallest grains at the highest temperatures), but appears inevitable in anatectic rocks.

Figure 2.4 (a) Sketch of a CL image of zircon from Rhodope, Greece, showing multiple zones with different ages. Spots are locations of SIMS analyses; numbers are preferred ages in Ma for different zones.(b) Schematic of a typical data stream, including raw count rate and isotope ratios. Initial data are not reliable until sputtering or ablation stabilizes. (c) Schematic of depth profiling method: crystal surface is exposed in a flat mount and progressively sputtered (SIMS) or ablated (LA‐ICP‐MS), collecting age information with depth. Depth profiling data using single‐shot method on two Himalayan zircons reveal ca. 18 Ma, 1–1.5 µm thick rims that overgrew ca. 514 Ma cores. Outermost analyses had high common Pb and were not plotted.

Figure 2.5 Sketches of textural relationships between zircon and other minerals, demonstrating the utility of retaining textural context for interpreting zircon ages and chemistry. Circles and ellipses represent locations of SIMS U‐Pb analyses. (a and b) Zircon textures from high‐temperature gneisses, Rogaland, Norway.(a) Zircon (gray tones) partially enclosed in titaniferous magnetite. The outer zircon rim is Y‐ and P‐enriched and contains a xenotime inclusion. (b) Zircon (labeled gray tones) intergrown with magnetite, with a retrograde garnet corona (M3) that developed on magnetite and encloses zircon. The zircon shows an inherited core and multiple rim generations formed through growth and/or recrystallization. Inherited cores (ca. 1050–1020 Ma) are rimmed by multiple zircon generations. Zircon mantles give estimates for M1 (ca. 1015 Ma, locally partially reset). Zircon rims are intergrown with or occur inside M2 minerals (ca. 940–930 Ma), while those rimmed by M3 minerals give ages down to ca. 908 Ma. (c) Zircon, locally rimmed by monazite and included in intergrowths of garnet and apatite, from a late‐crystallized partial melt. Trace element compositions suggest zircon growth in a more HREE‐enriched melt compared to the HREE‐depleted garnet [

Kelly

, unpublished data].

Figure 2.6 Simplified P‐T diagram delineating main metamorphic facies and key mineral reactions. Zircons that grow in a specific facies or mineral stability field may be expected to harbor inclusions diagnostic of that facies or field. P‐T paths of several UHP terranes illustrate how different paths cross different mineral stability fields.For facies and reaction boundaries, see sources in

Liou et al.

[1998] and

Kohn

[2014]. Mineral abbreviations: Ab, albite; And, andalusite; Coe, coesite; Dia, diamond; Gph, graphite; Jd, jadeite; Ky, kyanite; Qtz, quartz; and Sil, sillimanite. Facies abbreviations: Am, amphibolite; Amp‐Ec, amphibole eclogite; BS, blueschist; Dry‐Ec, dry eclogite; EA, epidote amphibolite; Ep‐Ec, epidote eclogite; GS, greenschist; HPG, high‐pressure granulite; LPG, low‐pressure granulite; and Lws‐Ec, lawsonite eclogite.

Figure 2.7 (a) Schematic diagram illustrating general trends of chondrite‐normalized, absolute REE concentrations in metamorphic zircon. Ce* refers to the positive Ce anomaly, and Eu* refers to the negative Eu anomaly. See text for full explanation. (b) Empirical studies of high‐temperature and high‐pressure metamorphic rocks where

values appear to increase with increasing atomic number. R02:

Rubatto

[2002]; R03:

Rubatto and Hermann

[2003b]; H03:

Hermann and Rubatto

[2003]; B06:

Buick et al.

[2006]. (c) Empirical studies of zircon in high‐ and ultrahigh‐temperature metamorphic rocks where

values appear to show essentially no dependence on atomic number. SH01:

Harley et al.

[2001]; K05:

Kelly and Harley

[2005]; TH04:

Hokada and Harley

[2004]; W03:

Whitehouse and Platt

[2003]; RG: Rauer Group,

Kelly

[unpublished data]; SW: Stillwell Hills,

Kelly

[unpublished data]; BR: Brattstrand Bluffs,

Kelly

[unpublished data]. Data cover a range of peak temperature conditions and metasedimentary rock (therefore partial melt) compositions. (d) Experimentally derived

. The experimental data of

Rubatto and Hermann

[2007] show increasing

with increasing atomic number and imply a decreasing preference for the HREE in zircon with increasing temperatures (garnet compositions also vary from

X

Grs

 = 0.22 at 800°C to

X

Grs

 = 0.08 at 1000°C). Experimental data of

Taylor et al.

[2015] show relatively flat

and no temperature dependence; garnet is Ca‐absent.

Figure 2.8 (a) Sketches of BSE and CL images of zircon grains from the Kokchetav massif [

Hermann et al.

, 2001;

Katayama et al.

, 2001] and the Dabie‐Sulu orogen [

Zhang et al.

, 2006, 2009;

Liu and Liou

, 2011], illustrating different generations of zircon and their inclusions. Numbers reflect approximate ages in Ma. For Sulu zircon, thin lines indicate internal zoning of relict, magmatic, Proterozoic cores (“Prot.”). Cryptic dissolution and reprecipitation of zircon cores along cracks during metamorphism has allowed Proterozoic cores to now harbor ca. 220 Ma eclogite‐facies minerals [so‐called pseudo‐inclusions:

Gebauer et al.

, 1997]. For Dabie zircon, thin lines indicate internal zoning of metamorphic zircon, arguably mimicking matrix textures. Scale bars are all 100 µm. (b) P‐T diagram illustrating ranges of P‐T conditions over which distinctive inclusion assemblages are thought to have been entrapped for Kokchetav and Dabie‐Sulu rocks. Mineral abbreviations: Ab, albite; And, andalusite; Coe, coesite; Dia, diamond; Gph, graphite; Grt, garnet; Jd, jadeite; Ky, kyanite; Omp, omphacite; Qtz, quartz; Rt, rutile; and Sil, sillimanite. Facies abbreviations: Am, amphibolite; Amp‐Ec, amphibole eclogite; BS, blueschist; Dry‐Ec, dry eclogite; EA, epidote amphibolite; Ep‐Ec, epidote eclogite; GS, greenschist; HPG, high‐pressure granulite; LPG, low‐pressure granulite; and Lws‐Ec, lawsonite eclogite.

Figure 2.9 Integration of textural, U‐Pb, and trace element data to constrain high‐temperature metamorphic processes. Shaded dots in images correspond with shaded trace element patterns. (a to f) Texturally constrained analysis of zircon and garnet from a metasedimentary migmatite from the LGB, Fennoscandian shield, Finland. (a) BSE image of zircon (see Fig. 2.9c) partially enclosed by garnet. (b) Y element map of euhedral garnet showing Y‐enriched rims. (c) BSE image of zoned zircon within a garnet edge: round, bright cores are rimmed by darker mantles and rims that have planar banding and sector zoning. Outer rims are commonly euhedral. (d) BSE image of a zoned zircon from a leucosome domain, with well‐developed euhedral rims. (e) Chondrite‐normalized REE compositions of zircon and garnet: GC, garnet cores; GR, garnet rims; ZC, zircon cores; and ZR, zircon rims. Data normalized using the chondrite values of

Anders and Grevasse

[1989]. (f)

values for analyses of the Lapland migmatite zircon and garnet. ZC, ZR, and GC as for Figure 2.9e, G‐IR represents measured garnet rim values as proximal to the grain boundary as possible by ion microprobe; G‐OR represents garnet compositions as extrapolated from Y zoning measured by electron microprobe. Both

are ~1. (g) Equilibration of HREE compositions in zircon during garnet‐present UHT metamorphism in a paragneiss. Detrital magmatic zircon (Z‐Detr.) is locally recrystallized (Z‐Rx; dark zones and domains of blurred oscillatory zoning in zircon cores) with HREE patterns progressively depleted toward compositions similar to that in zircon grown from anatectic melt (Z‐An) and garnet (Grt).

Figure 2.10 Links between zircon growth and metamorphic fluid production.(a) Zircon contains Permian igneous cores, with two stages of zircon overgrowth in Si‐poor rocks, and one‐stage of zircon overgrowth in Si‐rich rocks. Oxygen isotope values for igneous cores are ca. 3.5‰ higher than metamorphic overgrowths. Z1, first stage overgrowth; Z2, second stage overgrowth, and ZC, zircon core. (b) REE patterns are steep for protolith cores and first‐stage overgrowths for Si‐poor rocks. Progressive growth of garnet (“Grt‐growth”) and consequent fractionation of HREE develops flat or even negatively sloped HREE patterns in later zircon overgrowths. GC, garnet core and GR, garnet rim. In low‐Si rocks, Z1 contains inclusions of phlogopite (Phl), whereas in high‐Si rocks, Z1 contains inclusions of phengite (Phn) and talc (Tlc). (c) P‐T diagram showing proposed P‐T path and key reactions for low‐Si rock. Z1 formed when garnet mode was low, in the phlogopite‐stable field. Modeling of Lu fractionation combined with phase equilibrium modeling allows P‐T conditions of different zircon compositions to be inferred (dots). These points cluster around the phlogopite‐out and talc‐out reactions, which are major water‐producing reactions in these rocks.

Chapter 03

Figure 3.1 Compilation of monazite textures. (a and b) Monazites from Lamoille Canyon, Ruby Mountains, Nevada, showing complex patchy zoning suggesting a history of dissolution‐reprecipitation reactions. (c) Oscillatory zoned monazite from Lamoille Canyon, Ruby Mountains, Nevada, suggesting igneous crystallization. (d–g) Complexly zoned monazites from the East Humboldt Range, NV showing complex patchy internal zoning showing sharp curvilinear boundaries suggesting a history of dissolution reprecipitation reactions. (h) BSE image of monazite from the Sveconorwegian Province of Norway showing multiple subdomains that are interpreted to be the result of variations in pore fluid [

Bingen and van Breemen

, 1998]. (i) NanoSIMS map of

89

Y in monazite from the Central Slovakia Volcanic Field showing higher resolution than typical electron microprobe mapping [

Didier et al.

, 2015]. (j) BSE image of “satellite” monazites surrounding monazite, fluorapatite, and allanite [

Finger et al.

, 2016]. (k) Yttrium‐map of monazite from the Western Gneiss Region of Norway showing four domains resulting from recrystallization [

Kylander‐Clark et al.

, 2013]. (l) Thorium map of monazite from northern Saskatchewan showing overgrowths of monazite representing shearing [

Williams and Jercinovic

, 2002]. (m) Uranium map of monazite from Saskatchewan showing patchy compositional zoning that corresponds to age zonation [

Mahan et al.

, 2006b].

Figure 3.2 Simplified geologic map of the Ballachulish Igneous Complex and its thermal aureole showing the spatial relationships that enable comparison of monazite in different compositions at equivalent temperatures.

Figure 3.3 BSE images of monazites from the contact metamorphosed, regional garnet‐grade, metasedimentary rocks surrounding the Ballachulish Igneous Complex. Monazites from the Appin Phyllite (a–d) are typically small, discrete, and anhedral at lower temperatures. Monazites from the Creran Succession (e–h) show a decrease in grain size and abundance as temperature increases. Monazites from the Ballachulish Slate‐Appin Quartzite Transition Series (i–l) showing a decrease in size and becoming more rounded as temperature increases. Monazites from the Levin Schist (m–p) are typically subhedral to euhedral, and show little variability in grain size as the pluton is approached. Temperatures are from

Pattison and Harte

[1997],

Pattison and Harte

[2001], and

Pattison and Harte

[1988].

Figure 3.4 Element maps of monazites from the thermal aureole of the Ballachulish Igneous Complex. All maps show Th Mα except F that shows Nd Lα. (a–d) Monazite from the Creran Succession at temperatures <550°C (a and b), 585–640°C (c), and 640–650°C (d). Monazites show an increasing abundance of Th in the cores as temperature increases. (e and f) Monazite from the Appin Phyllite (670–720°C) showing patchy zoning. (e) shows a high Th patchy core, with a lower Th, patchy mantle, separated by a sharp curvilinear boundary. (f) shows patchy zoning Nd distributed throughout a grain. (g and h) Monazite from the Chaotic Zone (Levin Schist; 660–680°C) showing scalloped sharp boundary textures and internal zonation. (g and h) show an increase in Th toward the rims of the grain.

Figure 3.5 Comparison of optical and electron microbeam imaging techniques and monazite maps obtained by quadrupole LA‐ICP‐MS using a 5 µm diameter crater. The EPMA X‐ray maps show qualitative intensity data whereas the LA‐ICP‐MS approach provides a means to easily map true concentrations based on internal standardization to

31

P. In addition to important elements like Th and U, the LA‐ICP‐MS is sensitive enough even at 5 µm resolution to detect HREE and other trace elements. Subtle variations in Eu anomaly or HREE fractionation can be mapped out. Laser ablation inductively coupled plasma mass spectrometry maps were acquired with an 8 µm diameter 193 nm laser crater scanned at 4 µm/s and pulsed at 10 Hz with a fluence of 3 J/cm

2

. The ICP‐MS analyte list comprised 18 elements with quadrupole dwell times set to yield a total scan time (including dead time and settling time) of 0.5 s. These conditions produced scan lines of limited depth (~2 µm) allowing the grain to be quickly resurfaced prior to spot analyses for U‐Th‐Pb geochronology. White circles in

89

Y map show the locations where U‐Pb ages were obtained using 10 µm laser craters after re‐polishing of the thin section. Monazite in the same rock was analyzed by SHRIMP‐RG by

McFarlane

[2006] so this offers the chance to compare the reproducibility and precision of LA Q‐ICP MS relative to the ion microprobe data set. The grain was analyzed and the data reduced using three different standards: GSC‐1853, 44069, and Thompson Mine.

Figure 3.6 In situ U‐Pb data for the monazite overgrowth shown in Fig. 3.5 reduced offline in Iolite3 using three different monazite standards to illustrate the effect of subtle matrix mismatches on the final ratios and the effect on propagated error ellipses of better (Thompson Mine) versus poorer (44069) counting statistics on the standard used. The accuracy of the data can be tested by comparing values for two standards calibrated against the other or by comparing values obtained independently on unknown monazite using SHRIMP RG [

McFarlane

, 2006]. The difference in the geometry of the error ellipses between SHRIMP RG and LA‐ICP‐MS data reflects the much better counting statistics for

207

Pb by ion microprobe compared to Q‐LA‐ICP‐MS. The SHRIMP RG data was standardized using Thompson Mine monazite; reverse discordance reflects a bias from standard‐sample matrix‐mismatch.

Figure 3.7 Data from monazite in equigranular banded gneiss sampled in Lamoille Canyon. (a) Histogram showing three periods of monazite growth (90, 70–80, and 30–40 Ma). (b) Weighted average plot showing four distinct age populations between 30 and 40 Ma. (c) Y versus Th/U plot of analyses between 30 and 40 Ma for sample RD‐19A showing geochemical distinction between the four age populations observed. (d) RM‐26 Mnz 30 Th‐Mα map showing a high Th core and low Th rim. (e) RM‐26 Mnz 12 Th‐Mα map showing sector zoning. (f) RD‐31 Mnz 13 Th‐Mα map showing patchy internal zonation and a high Th rim. (g) RD‐19A Mnz 19 Th‐Mα map showing patchy zoning. (h) RD‐19A Mnz 13 Th‐Mα map showing patchy zoning. (i) RM‐26 Mnz 21 Th‐Mα map showing patchy zoning. (j) RD‐31 Mnz 14 Y‐Lα map showing patchy zoning. (k) Chondrite normalized REE patterns for Mnz 30 from RM‐26. Note that analyses have overlap in the LREE and MREE but diverge at Ho where the HREE are more abundant in the 90 Ma analyses. (l) Chondrite normalized REE patterns for Mnz 12 from RM‐26. Analyses have overlap in the LREE and MREE but diverge at Ho where the HREE are more abundant in the 90 Ma analyses. (m) Chondrite normalized REE patterns for Mnz 13 from RD‐31. Analyses have overlap in the LREE and MREE but diverge in the HREE. The 70 Ma analyses have higher HREE than the 30–40 Ma analyses. (n) Chondrite normalized REE patterns for Mnz 19 from RD‐19A. Analyses have overlap in the LREE and MREE but diverge in the HREE. The 90 Ma analyses have lower HREE than the 30–40 Ma analyses. (o) Chondrite normalized REE patterns for Mnz 13 from RD‐19A. Analyses have overlap in the LREE and MREE but diverge in the HREE. The 90 Ma analyses have lower HREE than the 30–40 Ma analyses. Monazite was analyzed by LASS at University of California Santa Barbara using methods modified from

Kylander‐Clark et al.

[2013], using a spot size of 8 µm. Data for U, Th, Pb, P, Ca, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu was collected; processed; and reduced using Iolite [

Paton et al.

, 2011].

Figure 3.8 Monazite images and data from Reading Prong monazite‐xenotime gneiss. (a) Back‐scattered electron image of a large monazite used for study. Highlighted box is shown in B. (b) (La/Lu)

CN

map, produced using Q‐LA‐ICPMS, overlain on reflected light optical image showing the location of 23 µm LASS‐spots along two traverses. Crater pits in neighboring xenotime are also visible. (c) Plot of

206

Pb/

238

U ages (Ma) (diamonds) and (La/Lu)

CN

(dots) showing correlation between young U‐Pb ages and domains of elevated (La/Lu)

CN

. (d) Plot of

206

Pb/

238

U and (La/Lu)

CN

for traverse B. (e) Concordia plot for monazite illustrating the three main age components identified within the grain.

Figure 3.9 Sm‐Nd isotopic data monaizte from Reading Prong. (a) Plot of

ε

Nd

(940 Ma)

for both travereses on the monazite used in this study. (b) Plot of

147

Sm/

144

Nd for transects A and B showing some isotopic variation, but showing most anlayses have a

147

Sm/

144

Nd ratio of approximately 0.145. (c) Isochron composed of monazite and xenotime anlayses yeilding an age of 938 ± 9 Ma for monazite + xenotime and an age of 940 ± 44 Ma for xenotime alone.

Chapter 04

Figure 4.1 (a) Single laser pulses simultaneously were fed into a multicollector‐ICP‐MS to measure U/Th‐Pb isotopes and a quadrupole‐ICP‐MS to measure trace elements. (b) The signal peaks resulting from each laser pulse are distinct and separated by several seconds of background collection. (c) The peaks are integrated to measure total counts and calibrated against a matrix‐matched reference material at the corresponding downhole depth. (d) The total depth, signal intensity, and resolution of the 1D, 2D, and 3D data are controlled by the number of laser shots, spot size, and fluence of the laser.

Figure 4.2 Integration, dwell, and sweep times affect the fidelity of the resulting single pulse of data. Increasing any one of these parameters in turn increases the discretization of the transient signal peak, which results in both over‐ and underestimation of the total counts from a single laser pulse. (a) An example of the modeled data shows the excess error associated with different levels of subsampling discretization, or increasing the total sweep time (Eq. 4.1), was determined by modeling this behavior using a random start time that was offset between arrival of the signal peak and instrument measurement times. (b) A plot of percent excess error versus dwell time illustrates the relationship shown in (a). Increasing the number of measured elements results in a longer effective dwell time (or sweep time; Eq. 4.1) and increases the additional error nonlinearly. The red lines indicate the minimum or default dwell times for common ICP‐MS instruments. This relationship demonstrates the advantage of splitting the analyte stream to two ICP‐MS instruments rather than mass sweeping on a single instrument for U‐Pb isotopic and/or trace element analysis.

Figure 4.3 Example application of SS‐LASS to resolving the age and composition of a thin rim domain in zircon from the Himalaya. (a) A “conventional” LASS profile in which the laser is pulsed at 4Hz, resulting in a ~0.5 µm s

−1

ablation rate. (b and c) illustrate two different SS‐LASS profiles through the outer rim on the same crystal as (a). Locations of analyses are labeled on the upper right image of the scanning electron microscope (SEM) image. Location of conventional profile is on underside of the pictured crystal.

Figure 4.4 Example application of SS‐LASS to identifying inclusions within accessory phases in zircon from Wyoming. Plane polarized light images of zircon crystal show position of inclusion (location is arrowed in images) ~1 µm beneath the exposed surface. Main plot shows trace element concentration and isotopic age data as a function of depth. Tera‐Wasserburg concordia plot, at right, for all individual laser pulses. The dashed line shows the

207

Pb‐corrected lower intercept for the three blue ellipses, which was anchored at a Stacey and Kramer single‐stage Pb value for 50 Ma for the upper intercept.

Figure 4.5 Isotopic and elemental concentration data for GJ‐1 secondary reference zircon run concurrently with detrital zircons (see Fig. 4.6). Percentage deviation is relative to the values published in

Liu et al.

[2010].

Figure 4.6 Kernel density estimate (KDE) and trace element variation diagrams for SS‐LASS detrital zircon data (

n

 = 500, data <10% discordant) from an alluvial sand in western Cameroon. Trace element variation diagrams are shaded by date. KDE plot generated using Density Plotter software v.2.4 [

Vermeesch

, 2012].

Figure 4.7 (a)

Stearns et al.

[2016] applied the SS‐LASS technique to titanite and observed ~8 Ma span of the U‐Pb dates colored by depth (blue, shallow; red, deep) (a) and variation of the Zr, Pb, U, and Th concentrations (b) over similar length scales that resembled re‐equilibration by lattice diffusion. Experiments predict that Pb‐Zr and U‐Th should begin diffusing at similar temperatures (similar activation energies) but move different distances owing to different diffusivities resulting in predictably different profiles (b and c; profiles are linear in erf

−1

space). Counter to a lattice‐diffusion controlled profile, each element varies at the same distance (or share the same slope in erf

−1

space). (d)

Stearns et al.

[2016] favored a recrystallization mechanism and were then able to calculate a

T‐t

path and cooling rate (°C/Myr

−1

) for the metamorphic titanite.

Figure 4.8 Example SS‐LASS 2D maps and trace element variation diagrams of a zoned zircon crystal. Pre‐analysis CL image for reference. Each spot represents the average of three individual pulses of the laser, with the map consisting of 180 individual spots. Labels C1 and C2 are core regions discussed in text. Maps rendered using matrix gridding and 2D Delaunay triangulation algorithm in Paraview v. 4.2.0.

Figure 4.9 Example SS‐LASS 3D maps, trace element variation diagrams, and statistical analysis of a zoned Himalayan monazite crystal. (a) Diagram illustrating the position of each spot analysis. The resulting maps consist of 14,526 individual laser pulses. Note 2× vertical exaggeration. A, B‐B′, and C′ represent lines of section displayed in panel (a). (b) 3D isotopic date and trace element concentration/ratio maps and cross sections. Maps and cross‐sections are rendered in Paraview v. 4.2.0. (c) Cross‐correlation plot colored by the Pearson correlation coefficient for monazite data used to generate the maps. The Pearson correlation coefficient is a measure of the linear correlation between the two data types. Red indicates a strong positive linear correlation, magenta indicates a strong negative linear correlation, and green indicates no linear correlation between the data. (d) Histograms offer an alternative means to visualize the data. (e) Visual representation of different age domains identified within monazite crystal.

Chapter 05

Figure 5.1 BSE mosaic images of all investigated eucrite samples and one martian regolith breccia, that is, NWA 7906, paired with NWA 7475 not shown here. Zircon (Zrn) locations are highlighted. Note that two polished thin sections of Jonzac were investigated, both of which are zircon‐bearing. PS = polished section. Scale bars are 2 mm each.

Figure 5.2 Exemplary zircon grains from basaltic eucrites. (a–c) Low brightness BSE‐ and corresponding CL images indicate planar growth banding and sector zoning of magmatic origin, observed in some of the analyzed grains, whereas (d) some grains do not exhibit zoning. Scale bars are 2 µm each.

Figure 5.3 Eucrite zircon grains showing differences in microstructures. (a and b) BSE images showing petrographic context and texture of a zircon crystal (Zrn) from Camel Donga with preserved igneous texture in the core, followed by a monochromatic CL image (c). The mineral assemblage in (a) include Cpx/Opx = clino‐ and orthopyroxene, SiO

2

 = silica polymorph, and Pl = plagioclase. (d and e) BSE and CL images following polishing of the same grain for EBSD analysis, that is, band contrast map in (f). Zircon from NWA 1000 with limited/patchy zonation is observed in (g–i) BSE, CL, and EBSD band contrast, respectively. All scale bars are 2 µm, except (a) which is 20 µm.

Figure 5.4 A unique zircon assemblage in the HaH 286 eucrite, forming a skeletal aggregate composed of zoned ~5 µm‐grains that are intergrown with ilmenite, as seen by (a and b) BSE‐ and CL imaging, (c) EBSD band contrast mapping, and (d) EBSD phase mapping (zircon in red, in the online version).

Figure 5.5 Examples of zircon grains from martian regolith breccia. (a) Left to right: BSE, CL (RGB + UV), and EBSD band contrast map of a zircon from NWA 7906 showing structural variability from crystalline (bright in CL and EBSD) to metamict (black in CL and EBSD); (b) BSE and CL (RGB + UV) images of a magmatic zircon from NWA 7906 indicating a relatively homogenous chemical microstructure; (c) another zircon example from NWA 7475 that preserved magmatic sector zoning; (d) zircon from NWA 7475 which has banding as observed in CL (RGB + UV); and (e) bi‐mineralic clast of zircon from NWA 7475, zircon surrounded and intergrown with K‐feldspar and exhibiting sector zoning. Scale bars are 2 µm.

Figure 5.6 Images and color‐coded maps of zircon grains in the NWA 7475 martian regolith breccia. (a and b) BSE images. Note that in (a) the grain exhibit partial porosity on a sub‐micron scale. The grid in the center of the left side inside the grain is damage induced by laser irradiation during Raman mapping, due to the grain’s initial porosity. (c and d) Corresponding hyperspectral CL images indicating sector zoning in (c) and domains with broad band zoning indicative of magmatic zircon in (d). Note that zoning in CL‐active impurity ions (i.e., REE

3+

) correlate with domains of sub‐micron scale porosity. (e and f) Raman maps, indicating structural zoning due to varying degree of radiation damage on a micron scale within the grain as obtained by varying FWHMs of the ν

3

(SiO

4

) band. Note that in (f) Raman map shows structural zoning which is not observed in BSE image. (g and h) Hyperspectral PL maps visualizing radiation damage based on the broadening of the Dy

3+

emission sublevel near 17.200 cm

–1

. (i) and (j) EBSD band contrast maps for each grain showing areas with structure (white) and metamict region (black). Scale bars are 2 µm each.

Figure 5.7 Example of the complex chemical microstructure of one of the oldest terrestrial zircon grains from Jack Hills, Western Australia, containing an igneous core crystallized at 4.38 Ga surrounded by an igneous rim that grew at 3.40 Ga [

Valley et al.

, 2015]. (a) SE image showing topography of polished surface, inclusions of quartz (dark, arrow 1) and xenotime (arrow 2), crosscutting fractures infilled with zircon (arrow 3) and/or quartz (arrow 4), as well as ion microprobe analysis pit (arrow 5); (b) CL image (colored in the online version) showing oscillatory planar growth banding, inclusions of quartz (red, arrow 1) and xenotime (green, arrow 2), crosscutting fractures infilled with zircon (black, arrow 3) and/or quartz (red, arrow 4), as well as ion microprobe analysis pit (arrow 5); and (c) EBSD band contrast image showing grayscale variations in crystallinity correlated with more and less actinide rich (and partially metamict) igneous bands, inclusions of quartz (no response, arrow 1) and xenotime (arrow 2), crosscutting fractures infilled with zircon (no signal due to metamictization, arrow 3) and/or quartz (no response, arrow 4), as well as ion microprobe analysis pit (no response due to beam damage of surface, arrow 5). Scale bar is 100 µm.

Figure 5.8 Representative Raman spectra of zircon grains (a) in the NWA 7475 martian regolith breccia and (b) the eucrites NWA 1000 and Camel Donga revealing decreased Raman shifts and increased broadening of the ν

3

(SiO

4

) stretching bands with increasing radiation damage, relative to synthetic ZrSiO

4

. Variable Raman spectra in Camel Donga zircon, that is, Zrn 1 (1b) correspond to areas with high CL‐ (spectra Zrn 1‐1f) and low (dark) CL‐emission (spectra Zrn 1‐1a).

Figure 5.9 Plot of the FWHM of the ν

3

(SiO

4

) Raman band (representing the degree of radiation damage) against the calculated self‐irradiation dose for zircon grains in the NWA 7475 martian regolith breccia, and Cachari, HaH 286, Jonzac, and NWA 1000 eucrite basalts. Error bars represent an assumed 10% uncertainty. Note that only grains with U and Th concentrations above the EPMA detection limits are plotted here. For comparison, zircon data from the unbrecciated, unmetamorphosed NWA 5073 eucrites, further discussed in

Roszjar et al.

[2011], are shown in black.

Figure 5.10 Plots of the Raman shift against the FWHM of the ν

3

(SiO

4

) stretching band analyzed in zircon crystals from (a) the paired martian regolith breccias NWA 7906/7475 and (b) Cachari, Camel Donga, HaH 286, Jonzac, and NWA 1000 eucrite basalts. Note that martian zircon plot below the spectral trend defined by variably radiation‐damaged terrestrial zircon [data from

Nasdala et al.,

2005, and references therein]. Eucrite zircon grains mostly follow the trend of progressive radiation damage, except for zircon derived from NWA 1000, few grains from HaH 286, and Camel Donga.

Chapter 06

Figure 6.1 Representative microbaddeleyite grains from a post‐impact intracontinental basalt dyke from the center of the Vredefort Dome in the Kaapvaal craton, South Africa, shown in secondary electron imaging (a and c) and CL (b and d). Grain in (a and b) is shown in the same view; included grain is an apatite‐group mineral. External form and internal CL zoning of the same grain are shown in (c) and (d), respectively.

Figure 6.2 Map of baddeleyite grains in Zagami (USNM 6545‐2), obtained using the Particle Search method, superimposed with dots on BSE (a) and red dots on Si X‐ray (b) images. Boundary between the DML and NZ is shown in both. Note the occurrence of baddeleyite within or near Si‐rich mesostasis pockets especially in the DML (b), and the association of baddeleyite with Fe‐Ti oxides in both lithologies.

Figure 6.3 Typical baddeleyite (bdl) occurrences in Zagami. (a) Euhedral baddeleyite grain from the DML (section UH218) enclosed within titanomagnetite (tmt) which is rimmed by fayalite (fa), adjacent to maskelynite (mk) and Si‐rich mesostasis (me). (b) Grain associated with ilmenite (ilm) and pigeonitic pyroxene (pyx) enclosed within Si, Al, and K‐rich mesostasis (me) within the DML (USNM 6545‐2). (c) Baddeleyite grain within a late‐stage melt pocket (UH233), occurring at margin of pyrrhotite (po) in contact with coarse fayalite‐rich mesostasis. (d) Two baddeleyite grains within NZ (USNM 6545‐2), found at the margin of pyx and Si‐rich me containing needles of chlorapatite (ap).

Figure 6.4 Pyroxene compositions closely associated with baddeleyite in Zagami DML (a) and late‐stage melt pocket (LSMP) (b). Data for Zagami DML and LSMP from

McCoy et al.

[1999] and this study. Open symbols represent pyroxene compositions adjacent to an identified baddeleyite grain. Fayalitic olivine compositions are also plotted with similar symbology (e.g., fayalite compositions shown with upward filled triangles are associated with pyroxene compositions shown with upward open triangles). Symplectite composition in (b) is recast as a pyroxene as described in text. Also shown is the approximate boundary of the “forbidden zone” of pyroxene crystallization at 1 bar pressure, after

Lindsley

[1983].

Figure 6.5 Map of baddeleyite occurrences in NWA 3171 obtained using the BSE‐EDS feature mapping method.

Figure 6.6 Examples of baddeleyite (bdl) occurrences in NWA 3171 including (a) with Fe‐Ti oxides and Fe‐rich pyroxene (pyx) within maskelynite (mk); and (b) in a late‐stage melt pocket in association with SiO

2

‐rich mesostasis (me), chlorapatite (ap), and titanomagnetite (tmt). Abbreviations as in previous figures. (c) Pyx compositions in NWA 3171, including those found adjacent to bdl occurrences (open symbols). Pyx compositions associated with the bdl in (a) are shown with circles; those associated with the bdl in (b) are shown with diamonds. Also shown is the approximate boundary of the “forbidden zone” of pyroxene crystallization at 1 bar pressure, after

Lindsley

[1983].

Figure 6.7 Typical baddeleyite occurrence in the Los Angeles martian basalt, adjacent to three‐phase symplectite (symp), merrillite (mr), pyroxene (pyx: lighter gray = pigeonite; darker gray = augite), and maskelynite (mk). Other, smaller baddeleyite grains are found in the Si‐rich mesostasis (me) nearby, although most bright phases are pyrrhotite.

Figure 6.8 Representative baddeleyite (bdl) occurrences in NWA 1460 including (a) within symplectite (symp)‐containing mesostasis (me) and (b) at the boundary between ferroan pyroxene (pyx) and maskelynite (mk). (c) Pyx compositions in NWA 1460, including those found adjacent to bdl occurrences (open symbols). Pyx compositions associated with the bdl in (a) are shown with diamonds; those associated with the bdl in (b) are shown with squares, and may represent pyroxferroite. Symplectite composition in (c) is recast as a pyx as described in text. Also shown is the approximate boundary of the “forbidden zone” of pyx crystallization at 1 bar pressure, after

Lindsley

[1983]. An occurrence of bdl at the junction of pyx, mk, and merrillite (mr) with symplectite (symp) nearby is shown in (d); the corresponding CL image for this grain is given in (e).

Figure 6.9 Representative baddeleyite (bdl) occurrences in QUE 9401. (a) Overview showing fa‐rich mesostasis interstitial to maskelynite (mk), pyroxene (pyx) and merrillite (mr) in which bdl grains tend to be found. (b) Detail of elongate bdl grain from (a) adjacent to Fe‐rich augite (pyx), pyrrhotite (po), and mesostasis (me), which is here nearly pure SiO

2

. (c) Detail of several bdl grains in SiO

2

mesostasis (me) with associated ilmenite (ilm), fayalite (fa), and Fe‐rich augite (pyx). (d) Pyx compositions in QUE 94201 after

McSween et al.

[1996; gray field], and those found adjacent to bdl in (b and c) (open symbols). Also shown is the approximate boundary of the “forbidden zone” of pyroxene crystallization at 1 bar pressure, after

Lindsley

[1983].

Figure 6.10 Baddeleyite (bdl) occurrences in NWA 5298. (a) Map of bdl occurrences in NWA 5298 obtained using the BSE‐EDS feature mapping method. (b) Example occurrence showing bdl grains at the boundary between mesostasis (me) containing titanomagnetite (tmt), and vesicular plagioclase melt (vpm). (c) Representative relationships between bdl, symplectite, fractured and granular clinopyroxene (pyx), shock melt (sm), and vpm.

Figure 6.11 Map of baddeleyite occurrences in Dhofar 019 obtained using the BSE‐EDS feature mapping method.

Figure 6.12 (a) Representative baddeleyite (bdl) occurrence in LAR 06319, found enclosed in ilmenite (ilm), adjacent to merrillite (mr) and interstitial to maskelynite (mk) and pyroxene (pyx). (b) Pyx compositions in LAR 06319 after

Peslier et al.

[2010]; those found adjacent to bdl in (a) are shown in open squares. Also shown is the approximate boundary of the “forbidden zone” of pyx crystallization at 1 bar pressure, after

Lindsley

[1983].

Figure 6.13 Single known baddeleyite (bdl) occurrence in NWA 1068/1110, found enclosed in ilmenite (ilm), within pyroxene (pyx) adjacent to maskelynite (mk) and the rim of an olivine (ol) phenocryst. Note the presence of some terrestrial alteration in mk (center) and pyx (lower left).

Figure 6.14 Single known baddeleyite (bdl) occurrence in Chassigny, found within a melt inclusion in olivine, with associated ilmenite (ilm) and magnetite (mt).

Figure 6.15 (a) Map of baddeleyite (bdl) occurrences in the NWA 2200 lunar breccia obtained using the BSE‐EDS feature mapping method. (b) Example of a bdl grain in a context BSE image. Detail of bdl grain in BSE (c) and CL (d). Note weak planar zoning in the CL image, suggesting that the grain is a crystal clast of a much larger igneous grain.

Figure 6.16 BSE images of baddeleyite (bdl) occurrences in NWA 773, showing (a) inclusion within ilmenite (ilm) or (b) at ilmenite grain boundaries, with associated plagioclase (pl), an apatite‐group mineral (ap), pyroxene (pyx), and olivine (ol).

Figure 6.17 (a) Map of baddeleyite (bdl) occurrences in the NWA 1000 eucrite obtained using the BSE‐EDS feature mapping method. (b) Bdl grain at the boundary between pyroxene (pyx) and plagioclase (pl), associated with Si‐rich mesostasis (me); the light gray phase is likely fayalitic olivine (fa). (c) Bdl grain associated with me in contact with pl. Three‐phase symplectite (symp) is present within nearby pyx.

Figure 6.18 Examples of baddeleyite (bdl) occurrences with corresponding CL. A bdl grain from the NWA 7257 basaltic shergottite in secondary electron (a) and CL (b). A bdl grain from the NWA 7475 martian breccia in secondary electron (c) and CL (d).

Chapter 07

Figure 7.1 Schematic angle‐dispersive X‐ray diffraction in a radial geometry. The polycrystalline sample is confined under nonhydrostatic conditions between the two diamond anvils.

σ

1

and

σ

3

are radial and axial stress, respectively. 2

θ

is a diffraction angle. A monochromatic X‐ray beam passes through the gasket with the direction of the incoming beam, orthogonal to the diamond axis and the data collected on an imaging plate orthogonal to the incoming beam. Note that the diffracted X‐ray rings are circular for an unstrained sample, whereas individual rings (lattice planes) become elliptical, with eccentricity proportional to compression. Any concentrations in X‐ray intensity around the circumference of the ring are used to calculate lattice preferred orientation (texture), under load, of the population of thousands of ~1–10 µm zircon fragments in the cell.

Figure 7.2 Geometry for a given

ψ

angle between the diffracting plane normal

ñ

and the maximum stress axis

S

,

d

m

(

hkl

) is a measured

d

‐spacing function of the Miller indices

h

,

k

, and

l

. When

ψ

 = 90

°

, the diffracting plane is orthogonal with the maximum stress axis

S

; thus,

d

m

(

hkl

) is minimum. When

ψ

 = 0

°

, the diffracting plane is aligned with the maximum stress axis

S

; thus,

d

m

(

hkl

) is maximum.

Figure 7.3 Equation of state of zircon at

ψ

 = 0°, 54.7°, and 90°. The solid curves are fits to the third‐order Burch‐Murnaghan equation of state (see section 7.2) and dashed curve is a fit to the third‐order Birch‐Murnaghan equation of state above 11 GPa. Open stars are from

Ono et al.

[2004] and open circles are from

van Westrenen et al.

[2004]. The inset shows data plotted as a normalized pressure (

F

) versus Eulerian finite strain (

f

). The horizontal line suggests the pressure derivative

 = 4. The error bars show potential variations from the obtained values in this study.

Figure 7.4 (a) Ratios of differential stress to shear modulus for zircon and differential stress supported by each individual plane of zircon at pressure to 32 GPa (b). Polynomial fits were applied to each plane at <20 GPa, above 20 GPa linear fit is applied. Solid lines represent fits before phase transition, and dashed lines represent data after phase transition. The error bars show potential variations from the obtained values but are smaller than the symbols.

Figure 7.5 IPFs obtained from Rietveld analysis showing texture development along (001) at different pressures. Texture was fit in MAUD with the E‐WIMV model and fixed fiber (cylindrical) symmetry. Intensity scale, in m.r.d. is shown to the right of each figure. ND denotes normal direction to the pole figure. The scale was normalized to get comparable values (m.r.d.).

Figure 7.6 Sample A. (a) EBSD orientation map (IPF) of zircon crystallographic orientation normal to the sample surface. Microtwin is labeled. Note that color change in many grains indicating finite crystal‐plastic deformation (up to 30°). Black areas correspond to the areas with no EBSD data available. (b) Pole figure with the density contour of axes distribution along {001} shows weak texture parallel to sample normal (direction of maximum stress).

Figure 7.7 (a) A subset of an EBSD map of sample A (compressed to 20 GPa), highlighting one of the larger zircon grains containing microtwin lamellae (indicated with white arrow). The host zircon is colored according to which of its crystallographic axis is normal to the surface, in this case the

c

axis. The zircon within the microtwin domains is colored by degrees of misorientation relative to the red crosshair symbol. The blue to green color shift corresponds to a misorientation of 8°, whereas host grain is misoriented up to 16°. (b) Pole figures representing the main zircon and its microtwin domains. Note that the pole colors correspond to the colors in panel A. The microtwin zircon exhibits the typical 65° of misorientation about the <110> in the host zircon. The shared crystal‐plastic deformation of host zircon and microtwin domains is demonstrated by the asterism of pole populations. This suggests that microtwins formed at relatively low pressures and within the zircon stability field (see text for discussion).

Figure 7.8 (a) EBSD map of zircon and reidite from Sample B (compressed to 32 GPa). Note that black areas correspond to non‐indexing pressure medium from experiment or epoxy mounting medium. Zircon is colored according to crystal axis normal to the sample surface. Reidite grains are colored aqua (see inset for color‐code). Note color shifts within many individual zircon grains indicating crystal‐plastic strain. (b) Contoured pole plots of zircon and reidite {001} poles. Note that the zircon {001} poles plot close to the center indicating texture parallel to sample normal (direction of maximum stress). The lower stereonet shows the poles to reidite {001} plotting on the periphery, lying randomly within the plane parallel to zircon {001} and normal to the direction of maximum stress.

Figure 7.9 Average differential stress as a function of pressure for different mantle phases up to 32 GPa. Zircon [this study]; olivine [

Uchida et al.

, 1996]; majorite [

Kavner et al

., 2000]; ringwoodite [

Kavner and Duffy

, 2001]; Mg‐perovskite [

Merkel et al.

, 2006]; Ca perovskite [

Shieh et al.

, 2004]; and grossular [

Kavner

, 2007]. Polynomial or linear fits are applied to the data. The plot shows that zircon has the lowest differential stress. The error bars show potential variations from the obtained values.

Chapter 08

Figure 8.1 Conceptual diagrams of elasticity moduli and their directional anisotropy in crystals. (a) Young’s modulus,

E

, is a measure of longitudinal stiffness, and defines the slope on a plot of normal stress (

σ

n

) versus normal strain (

ε

n

). A scalar value for

E

can be plotted for any crystallographic direction as a color‐coded pole plot. (b) Shear modulus,

G

, is a measure of stiffness in shear, and defines the slope on a plot of shear stress (

σ

s

) versus normal strain (

ε

s

). Any given plane contains directional differences in

G

. The minimum scalar value (

G

min

) and maximum scalar value (

G

max

) for any plane can be plotted as two separate color‐coded pole plots, respectively. (c) Poisson’s ratio,

ν

, is the ratio of lateral strain to longitudinal strain, and is positive in most materials. Perfectly compressible materials have

ν

 = 0, whereas negative

ν

can occur in some crystalline solids, and is a property known as auxeticity. The minimum scalar value (

ν

min

) and maximum scalar value (

ν

max

) for planes in any orientation can be plotted in the same way as for

G

. (d) Hypothetical scenarios that relate elastic moduli to failure controlled by (i) critical yield strain, (ii) critical yield stress, (iii) yield as a function of stress and strain.

Figure 8.2 A lunar zircon grain that preserves two sets of {100}‐parallel planar deformation bands (PDBs). (a) SE image. (b and c) EBSD maps colored for crystallographic disorientation from reference point (red cross). (d) Pole figure of data shown in (c). Lower hemisphere projection in the

x‐y‐z

reference frame of the EBSD map. (e) Schematic pole figure in the crystal reference frame showing the relationship between PDBs and causative dislocation slip system. The alignment of the disorientation axis along the PDB plane is consistent with a tilt boundary geometry resulting from {100} <010> slip.

Figure 8.3 A detrital shocked zircon grain sourced from the Vredefort impact structure, South Africa, with four sets of shock twin lamellae. (a) EBSD map colored for crystallographic orientation (IPF color scheme). Twins shown in red. (b) Schematic pole figure in the crystal reference frame showing the four possible twin variants in zircon. (c) Schematic pole figure showing key features of the twin mode

K

1

{112}

η

1

 <111> in zircon.

Figure 8.4 A zircon grain from the Ries impact structure, Germany, preserving a set of reidite lamellae. (a) CL image. Dark concentric growth zones have higher U and Th contents and higher levels of radiation damage than the pale domains. Reidite is non‐luminescent. (b) BSE image. (c) EBSD map colored for crystallographic orientation phase. White dashed lines delimit dark CL zones in (a). (d) Raman spectra from spots 1 and 2 shown in (c). (e) Schematic pole figure in the crystal reference frame showing orientation relationship between host zircon (black symbols) and reidite (green symbols). The other seven possible reidite orientation variants are shown by gray symbols.

Figure 8.5 Plots of the anisotropy of elastic moduli

E

,

G

max

,

G

min

,

ν

max

, and

ν

min

in zircon as 3D visualizations (top row) and lower hemisphere equal area projections (subsequent rows). Poles to significant planes in zircon are shown on top left projection. Gray spheres in the 3D plots are the calculated VRH averages of each attribute. Strength of anisotropy (A) and VRH averages for each attribute are shown below pole plots. O&J’78 = non‐metamict Australian grain data,

Özkan and Jamieson

[1978]; O’76 = data for varying degrees of radiation damage, grains 1–3,

Özkan

[1976]; and H’84 = metamict zircon data,

Hearmon

[1984].

Figure 8.6 (a) Variation of

E

in specific directions in zircon. (b) Variation of

G

in <111> along {112}. (c) Variations in elastic moduli anisotropy strength.

Figure 8.7 Plots to show the anisotropy of

E

,

G

, and

ν

along specific planes in zircon as a function of direction in that plane. Colors show values for zircon with different levels of radiation damage.

Figure 8.8 Lower hemisphere equal area projections of the anisotropy of

E

,

G

max

,

G

min

,

ν

max

, and

ν

min

in zircon as a function of pressure in the range 1 atm to 24 GPa. Poles to significant planes in zircon are shown on top left projection.

Figure 8.9 (a) Variation of

E

in specific directions in zircon as a function of pressure in the range 1 atm to 24 GPa. (b) Variation of

G

in <111 > along {112} as a function of pressure. (c) Elastic moduli anisotropy strength as a function of pressure.

Figure 8.10 Plots to show the anisotropy of

E

,

G

, and

ν

along specific planes in zircon as a function of direction in that plane. (a) Projection of (001). (b) Projection of (100). (c) Projection of (110). (d) Projection of (112). Colors show values for zircon at different pressures.

Figure 8.11 Energy factors calculated for two slip systems in zircon as a function of radiation damage using an approach detailed in

Reddy et al

. [2007] and elasticity calculated from data in

Özkan

[1976].

Figure 8.12 Energy factors calculated for two slip systems in zircon as a function of pressure using an approach detailed in

Reddy et al

. [2007] and elasticity calculated from data in

Dutta and Mandal

[2012a].

Chapter 09

Figure 9.1 Regional geological setting. (a) Map showing features of the Kaapvaal craton in southern Africa. (b) Vaal River basin showing location of Rietputs Formation and samples analyzed in this study. Alluvium sites from

Cavosie et al.

[2010] and

Erickson et al.

[2013a]. L, Lesotho; S, Swaziland; and Z, Zimbabwe.