1 Structure and Chemistry of Zircon and Zircon-Group
Minerals
Robert J. Finch, John M. Hanchar
INTRODUCTION ................................................. 1
STRUCTURE OF ZIRCON .......................................... 2
Cation polyhedra .......................................... 2
Interstitial sites ........................................ 3
ZIRCON-GROUP MINERALS ........................................ 4
Silicates ................................................. 7
Actinide silicates ........................................ 7
Phosphates ................................................ 8
Borates ................................................... 8
Vanadates ................................................. 8
Arsenates ................................................. 9
Chromates ................................................ 10
Related structures ....................................... 10
STRUCTURAL EFFECTS OF TEMPERATURE, PRESSURE AND
COMPOSITION ................................................. 13
Temperature .............................................. 13
Pressure ................................................. 14
Composition .............................................. 19
ACKNOWLEDGMENTS .......................................... 20
REFERENCES .................................................. 21
2 The Composition of Zircon and Igneous and Metamorphic
Petrogenesis
Paul W.O. Hoskin, Urs Schaltegger
INTRODUCTION ................................................ 27
Analytical techniques .................................... 28
ZIRCON AND IGNEOUS PETROGENESIS .......................... 29
Saturation, crystallization, occurrences and zoning of
igneous zircon ........................................... 29
Major-element composition of igneous zircon .............. 32
Trace-element composition of igneous zircon .............. 34
Zircon composition and investigations of igneous
processes ................................................ 42
Provenance-indicator studies using igneous zircon
composition .............................................. 43
ZIRCON AND METAMORPHIC PETROGENESIS ......................... 45
Textural characterization of metamorphic zircon .......... 45
The growth of new zircon during metamorphism and its
composition .............................................. 46
Solid-state recrystallization and dissolution-
reprecpitation of protolith zircon and compositional
changes .................................................. 48
HYDROTHERMAL ZIRCON ......................................... 52
CONCLUSIONS AND OUTLOOK ..................................... 54
ACKNOWLEDGMENTS ............................................. 55
REFERENCES .................................................. 55
3 Melt Inclusions in Zircon
J.B. Thomas, R.J. Bodnar, N. Shimizu, C.A. Chesner
INTRODUCTION ................................................ 63
PREVIOUS INVESTIGATIONS ..................................... 65
METHODOLOGY ................................................. 66
Petrography of melt inclusions hosted in zircon .......... 67
Heating and homogenization of crystalline melt
inclusions in zircon ..................................... 69
Major and trace element compositions of melt inclusions
in zircon ................................................ 69
DETERMINING ZIRCON/MELT TRACE ELEMENT PARTITION
COEFFICIENTS USING MELT INCLUSIONS IN ZIRCON ................ 72
Trace element partitioning data and interpretations ...... 72
Petrogenetic implications ................................ 77
Summary of trace element partitioning by the MIM
technique ................................................ 78
ARE MI COMPOSITIONS REPRESENTATIVE OF THE BULK MELT? ..... 79
Boundary layer effects ................................... 79
Re-equilibration of melt inclusions ...................... 81
Potential errors during homogenization and analysis ...... 82
FUTURE DIRECTIONS ........................................... 82
ACKNOWLEDGMENTS ............................................. 83
REFERENCES .................................................. 83
4 Zircon Saturation Thermometry
John M. Hanchar, E. Bruce Watson
INTRODUCTION ................................................ 89
ZIRCON SATURATION THERMOMETRY ............................ 90
Historical development ................................... 90
APPLICATIONS OF ZIRCON SATURATION THERMOMETRY ............... 96
Background ............................................... 96
Selected examples of studies that used zircon
saturation thermometry ................................... 97
CALCULATION OF ZIRCON SATURATION TEMPERATURES .............. 102
Considerations for using zircon saturation thermometry
with plutonic rocks ..................................... 102
Bulk sample or in situ analyses? ........................ 103
Calculation of M for geologic samples ................... 104
Worked example to determine M and Zr content and
zircon saturation temperature ........................... 105
SUMMARY .................................................... 109
ACKNOWLEDGMENTS ............................................ 110
REFERENCES ................................................. 110
5 Diffusion in Zircon
Daniele J. Cherniak, E. Bruce Watson
INTRODUCTION ............................................... 113
HISTORY—A BRIEF REVIEW OF BULK-RELEASE AND EARLY LOWER-
RESOLUTION DIFFUSION MEASUREMENTS .......................... 113
CATIONS .................................................... 114
РЬ ......................................................... 115
Substitutional processes involving Pb ................... 118
Diffusion systematics of trivalent cations .............. 119
Substitutional processes for trivalent cations .......... 122
Tetravalent cations ..................................... 123
Cation diffusion in zircon—a general summary ............ 125
OXYGEN DIFFUSION ........................................... 126
Experimental results .................................... 126
Diffusion mechanisms .................................... 128
IMPLICATIONS AND APPLICATIONS OF DIFFUSION FINDINGS ........ 129
Diffusive fractionation ................................. 129
Closure temperatures .................................... 129
The preservation of zoning in zircon .................... 130
Pbloss .................................................. 132
Preservation of oxygen isotope signatures ............... 134
18O/16O retention in zircon cores and rims .............. 135
Retention at rim and core centers during cooling ........ 138
FUTURE DIRECTIONS .......................................... 139
ACKNOWLEDGMENTS ............................................ 139
REFERENCES ................................................. 139
6 Historical Development of Zircon Geochronology
Donald W. Davis, Ian S. Williams, Thomas E. Krogh
INTRODUCTION ............................................... 145
PRELUDE .................................................... 146
ISOTOPIC DATING OF ZIRCON — 1955 TO 1973 ................... 148
ADVANCES IN TECHNIQUE — 1973 TO 1982 ....................... 154
RESOLUTION OF THE PB LOSS PROBLEM — 1982 TO THE PRESENT .... 159
Further advances in ID-TIMS methods ..................... 159
The Sensitive High-Resolution Ion Micro-Probe
(SHRIMP) ................................................ 164
The zircon evaporation method ........................... 171
Other developments ...................................... 171
THE LEGACY OF ZIRCON DATING ................................ 171
ACKNOWLEDGMENTS ............................................ 173
REFERENCES ................................................. 173
7 Zircon U-Th-Pb Geochronology by Isotope Dilution -
Thermal Ionization Mass Spectrometry (ID-TIMS)
Randall R. Parrish, Stephen R. Noble
INTRODUCTION ............................................... 183
METHODS AND DATA PRESENTATION .............................. 184
Background .............................................. 184
Evolution of analytical methods ......................... 184
Mass spectrometry ....................................... 187
Advances in chemical procedures and tracers ............. 187
Standards, reproducibility, corrections, errors, and
presentation ............................................ 190
OTHER METHODS OF ID OR TIMS ................................ 191
Pb evaporation (TIMS but no ID) ......................... 191
ID-PIMMS (ID but no TIMS) .................................. 191
THE MAPPING OF U-TH-PB DATA ONTO DIAGRAMS .................. 192
Age equations ........................................... 192
Wetherill Concordia diagram ............................. 192
Теrа-Wasserburg diagram ................................. 194
Isochron diagram ........................................ 194
The interpreted age of crystallization .................. 194
ZIRCON DATING APPLICATIONS AND U-TH-PB SYSTEMATICS ......... 195
High precision dating of igneous zircon across the
scope of geological time ................................ 195
Difficulties with igneous U-Pb zircon geochronology ..... 199
Dating of metamorphic zircon ............................ 200
Baddeleyite-zircon reactions in coronitic gabbro ........ 200
Growth of zircon in granulites and upper amphibolite
facies rocks ............................................ 200
Metamorphic growth of zircon in amphibolite facies ...... 201
The dating of zircon in eclogite and other UHP rocks .... 203
Th and Pa chemical partitioning in zircon and its
implications ............................................ 204
Other examples where ID-TIMS data has proved
effective ............................................... 207
SUMMARY .................................................... 210
ACKNOWLEDGMENTS ............................................ 210
REFERENCES ................................................. 210
8 Considerations in Zircon Geochronology by SIMS
Trevor R. Ireland, Ian S. Williams
INTRODUCTION ............................................... 215
SELECTED APPLICATIONS ...................................... 216
Oldest zircon in the solar system ....................... 216
Development of fractionated lunar crust ................. 217
The oldest-known terrestrial rocks ...................... 218
Detrital-zircon age spectra ............................. 218
Analysis of thin rims and near-surface concentration
gradients (depth profiles) .............................. 219
The youngest zircons .................................... 219
Timescale ............................................... 219
INSTRUMENTAL AND ANALYTICAL APPROACHES ..................... 220
SHRIMP ..................................................... 221
Cameca 1270 ............................................. 221
Operational comparison .................................. 222
ZIRCON ANALYSIS ............................................ 222
Pb isotopes ............................................. 223
Correction for common Pb ................................ 224
U/Pb calibration ........................................ 225
OTHER MINERALS ............................................. 227
Monazite ................................................ 227
Xenotime ................................................ 227
Apatite (+whitlockite) .................................. 227
Titanite ................................................ 228
Baddeleyite ............................................. 228
Rutile .................................................. 228
Perovskite .............................................. 228
Allanite ................................................ 228
DATA ANALYSIS .............................................. 229
Analytical uncertainties ................................ 230
207Pb/206Pb ratio ....................................... 230
U-Pb ratio .............................................. 230
Standards ............................................... 231
Data assessment ......................................... 233
COMPARISON OF DIFFERENT ANALYTICAL SESSIONS ................ 234
FUTURE DEVELOPMENTS ........................................ 236
ACKNOWLEDGMENTS ............................................ 238
REFERENCES ................................................. 238
9 Present Trends and the Future of Zircon in Geochronology:
Laser Ablation ICPMS
Jan Košler, Paul J. Sylvester
INTRODUCTION ............................................... 243
LASER ABLATION ............................................. 244
Laser principles ........................................ 244
Laser ablation system ................................... 245
Interaction of laser radiation with solid samples ....... 246
Choice of laser ablation parameters ..................... 247
INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY ............ 249
Inductively coupled plasma as ion source ................ 249
Quadrupole ICPMS ........................................ 250
Magnetic sector ICPMS ................................... 251
Time-of-flight ICPMS .................................... 252
Mass discrimination (bias) and fractionation of
isotopes and elements ................................... 252
DATING OF ZIRCON BY LASER ABLATION ICPMS ................... 253
Past studies of U-Pb zircon dating by laser ablation
ICPMS ................................................... 254
Elemental fractionation of Pb and U and methods of
correction .............................................. 254
Sampling strategies ..................................... 256
Spatial resolution ...................................... 257
Correction for instrument mass bias (standardization) ... 258
Correction for initial common-Pb ........................ 260
Precision and accuracy .................................. 261
Strategies for data acquisition and reduction ........... 262
LASER ABLATION ICPMS DATING IN PRACTICE .................... 264
Laser ablation ICPMS dating of zircon for sedimentary
provenance studies ...................................... 264
Dating magmatic events by laser ablation ICPMS .......... 265
Application of laser ablation ICPMS to fission track
dating of zircon ........................................ 266
In situ dating of accessory minerals by laser ablation
ICPMS ................................................... 268
FUTURE PROSPECTS OF LASER ABLATION ICPMS DATING ............ 269
Quadrupole vs. magnetic sector and single- vs. multi-
collector comparisons ................................... 270
New applications in laser ablation ICPMS dating of
zircon .................................................. 271
ACKNOWLEDGMENTS ............................................ 271
REFERENCES ................................................. 271
10 Detrital Zircon Analysis of the Sedimentary Record
Christopher
M. Fedo, Keith N. Sircombe, Robert H. Rainbird
INTRODUCTION ............................................... 277
STATISTICS AND METHODOLOGY OF SAMPLING ..................... 278
Sampling ................................................ 278
Sample preparation ...................................... 279
Analysis ................................................ 280
Data display ............................................ 281
Interpretation .......................................... 282
AGE OF STRATIGRAPHIC SUCCESSIONS ........................... 284
Maximum age and age bracketing .......................... 284
Direct depositional ages ................................ 286
Disconformity recognition ............................... 287
PROVENANCE ANALYSIS ..................................... 288
Petrographic and petrologic ............................. 288
Geochemistry ............................................ 288
Fission track (FT) ...................................... 289
Geochronology ........................................... 289
PALEOGEOGRAPHIC AND TECTONIC RECONSTRUCTIONS ............... 293
Introduction ............................................ 293
Initial studies—Shaler Supergroup ....................... 294
Regional studies—northern Cordillera .................... 294
Regional studies—central Cordillera ..................... 294
Siberia ................................................. 295
Scotland ................................................ 295
A cryptic Grenvillian foreland basin in the U.S.
mid-continent ........................................... 296
Rodinian paleogeography ................................. 296
IMPLICATIONS FOR EARLIEST EARTH HISTORY .................... 297
SUMMARY ................................................. 297
ACKNOWLEDGMENTS ............................................ 298
REFERENCES ................................................. 298
11 High-Precision U-Pb Zircon Geochronology and the
Stratigraphic Record
Samuel A. Bowring, Mark D. Schmitz
INTRODUCTION ............................................... 305
THE GEOLOGIC TIME SCALE .................................... 307
Proxies for radiometric geochronology:
chemostratigraphy ....................................... 307
GEOCHRONOLOGICAL TECHNIQUES ............................. 308
Measurement uncertainty ................................. 310
Common Pb correction .................................... 311
Tracer calibration and interlaboratory comparison ....... 312
U decay constants ....................................... 312
INTERMEDIATE DAUGHTER PRODUCT DISEQUILIBRIA ................ 313
GEOLOGICAL COMPLEXITY AND OPEN SYSTEM BEHAVIOR ............. 313
Crystal inheritance and Pb-loss ......................... 313
Resolving a geological "age" from a large population
of zircon dates ......................................... 314
Sample selection and analytical strategies .............. 315
THE NEOPROTEROZOIC-CAMBRIAN TRANSITION .................. 316
Triassic-Jurassic boundary .............................. 318
THE END-PERMIAN EXTINCTION ................................. 320
SUMMARY .................................................... 322
ACKNOWLEDGMENTS ............................................ 323
REFERENCES ................................................. 323
12 Lu-Hf and Sm-Nd isotope systems in zircon
Peter D. Kinny, Roland Maas
INTRODUCTION ............................................... 327
THE Lu-Hf ISOTOPE SYSTEM IN NATURE ......................... 327
Hafnium as a geochemical tracer ......................... 328
HF ISOTOPES IN ZIRCON ................................... 329
Measurement techniques .................................. 331
Studies of magmatic zircons ............................. 331
Studies of detrital zircon .............................. 332
Studies of metamorphic zircon ........................... 334
Studies of mantle zircons ............................... 334
Concluding remarks: Lu-Hf isotopes and zircon ........... 335
Sm-Nd ISOTOPE STUDIES OF ZIRCON ......................... 335
REE patterns of zircon .................................. 336
Sm-Nd mineral dating of zircon .......................... 336
Inherited Nd ............................................ 338
Concluding remarks: Sm-Nd isotopes and zircon ........... 338
OUTLOOK .................................................... 339
ACKNOWLEDGMENTS ............................................ 339
REFERENCES ................................................. 339
13 Oxygen Isotopes in Zircon
John W. Valley
INTRODUCTION ............................................... 343
ANALYSIS OF δ18O IN ZIRCON ................................. 343
Laser fluorination ...................................... 343
Ion microprobe .......................................... 343
Standards ............................................... 344
ZIRCON SAMPLE PREPARATION .................................. 345
Mechanical separation of zircons ........................ 346
Selection of zircons .................................... 346
Imaging zircons ......................................... 348
OXYGEN ISOTOPE FRACTIONATION IN ZIRCON ..................... 348
OXYGEN DIFFUSION RATE IN ZIRCON ............................ 349
ASSIMILATION VS. FRACTIONAL CRYSTALLIZATION ................ 352
MANTLE ZIRCONS ............................................. 354
PRE-CAMBRIAN ZIRCONS ....................................... 355
Archean granitoids ...................................... 355
Volcanogenic massive sulfide deposits ................... 357
Hadean detrital zircons ................................. 358
Mid-Proterozoic ......................................... 359
CRUSTAL GROWTH AND MATURATION .............................. 363
Superior vs. Grenville province ......................... 363
Evolution of magmatic δ18O through time ................. 364
ULTRA-HIGH PRESSURE ECLOGITES, DAB IE AND SULU ............. 365
FELSIC VOLCANISM, WESTERN UNITED STATES .................... 365
Low δ18O-rhyolites, Yellowstone ......................... 365
Timber Mountain / Oasis Valley Caldera Complex .......... 368
Bishop Tuff, Long Valley caldera ........................ 370
PHANEROZOIC GRANITES ....................................... 371
British Tertiary Igneous Province ....................... 371
Mesozoic and Cenozoic granites of the western United
States .................................................. 374
A-type granites, northeastern China ..................... 377
Cenozoic granitoids of the Antarctic Peninsula .......... 377
Fe-oxide melt in syenitic xenoliths ..................... 378
Magmatic epidote-bearing granitoids ..................... 378
ACKNOWLEDGMENTS ............................................ 380
REFERENCES ................................................. 380
14 Radiation Effects in Zircon
Rodney C. Ewing, Alkiviathes Meldrum, LuMin Wang,
William J. Weber, L. René Corrales
INTRODUCTION ............................................... 387
EXPERIMENTAL RESULTS ....................................... 389
Bulk properties ......................................... 390
Long range order ........................................ 392
Short-range order ....................................... 398
Recovery of radiation damage ............................ 400
MODELS OF DAMAGE ACCUMULATION .............................. 405
Temperature ............................................. 406
Ion mass and energy ..................................... 410
COMPUTER SIMULATION OF DEFECT FORMATION AND RADIATION
DAMAGE ..................................................... 411
Intrinsic and extrinsic defect energies ................. 412
Threshold displacement energies ......................... 413
Collision cascades ...................................... 414
UNRESOLVED RESEARCH ISSUES ................................. 418
ACKNOWLEDGMENTS ............................................ 420
REFERENCES ................................................. 420
15 Spectroscopic methods applied to zircon
Lutz Nasdala, Ming Zhang, Ulf Kempe, Gerard Panczer,
Michael Gaft, Michael Andrut, Michael Plötze
INTRODUCTION ............................................... 427
LUMINESCENCE SPECTROSCOPY OF ZIRCON ........................ 428
Cathodoluminescence of zircon ........................... 428
Laser-induced time-resolved photoluminescence of
zircon .................................................. 435
VIBRATIONAL SPECTROSCOPY OF ZIRCON ......................... 438
Infrared absorption spectroscopy of zircon .............. 438
Raman spectroscopy of zircon ............................ 443
OTHER SPECTROSCOPIC TECHNIQUES ............................. 449
Electronic absorption spectroscopy ...................... 449
Mössbauer spectroscopy .................................. 455
Electron paramagnetic resonance ......................... 455
Other spectroscopic methods ............................. 459
ACKNOWLEDGMENTS ............................................ 460
REFERENCES ................................................. 460
16 Atlas of Zircon Textures
Fernando Corfu, John M. Hanchar, Paul W.O. Hoskin, Peter
Kinny
INTRODUCTION ............................................... 469
ZIRCON IMAGING .......................................... 470
MORPHOLOGY OF ZIRCON .................................... 472
ZONING TEXTURES IN IGNEOUS ZIRCON .......................... 476
XENOCRYSTIC CORES .......................................... 478
SUBSOLIDUS MODIFICATIONS AND GROWTH OF ZIRCON .............. 480
Late-magmatic phenomena ................................. 480
Medium to high temperature metamorphism ................. 481
High-pressure metamorphism .............................. 486
HYDROTHERMAL ZIRCON ........................................ 487
KIMBERLITIC AND MANTLE-RELATED ZIRCON ...................... 488
IMPACT-RELATED TEXTURES .................................... 489
FRACTURING ................................................. 489
ALTERATION ................................................. 491
INCLUSIONS, INTERGROWTHS AND OVERGROWTHS OF ZIRCON AND
OTHER MINERALS ............................................. 493
CONCLUDING REMARKS ......................................... 494
ACKNOWLEDGMENTS ............................................ 495
REFERENCES ................................................. 495
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