Electron Probe Microanalysis of Monazite and Its Applications to U-Th-Pb Dating of Geological Samples

Abstract

Electron probe microanalysis (EPMA) dating of monazite has been developed over decades. However, limited by the detectability and analytical sensitivity of dating-related elements (Th, Pb, U and Y), the EPMA dating has been restricted to geological research. In this study, various probe currents, beam diameters and counting times have been utilized on a JEOL JXA-8230 electron microprobe to determine the optimal experimental conditions for measuring Th, Pb, U and Y in monazite. The optimal conditions are: (1) accelerating voltage is 15 kV; (2) probe current is 100 nA; (3) beam diameter is 1 μm; (4) the peak and background counting time of U and Pb are 200 and 100 s; and (5) the peak and background counting time of Th and Y are 100 and 50 s. We apply this method to monazite from garnet-bearing biotite gneiss in the Zanhuang area of the Central Orogenic Belt of the North China Craton. The PbO-ThO₂* isochron age calculated by EPMA data is 1 812±17 Ma (MSWD=2.06), which is similar to the weighted mean ²⁰⁷Pb/²⁰⁶Pb age (1 805±12 Ma, MSWD=1.07) obtained by LA-ICP-MS. This study suggests that EPMA dating of monazite as a powerful dating technique can be widely used in geochronological study.

Keywords

monazite / EPMA dating / garnet-bearing biotite gneiss / Zanhuang area / North China Craton / geochemistry

References

Allaz J M, Williams M L, Jercinovic M J, . Multipoint Background Analysis: Gaining Precision and Accuracy in Microprobe Trace Element Analysis. Microscopy and Microanalysis, 2019, 25(1): 30-46.

Amli R, Griffin W L. Microprobe Analysis of REE Minerals Using Empirical Correction Factors. American Mineralogist, 1975, 60: 599-606.

Ba J, Zhang L, He C, . Zircon and Monazite Ages Constraints on Devonian Magmatism and Granulite-Facies Metamorphism in the Southern Qaidam Block: Implications for Evolution of Proto- and Paleo-Tethys in East Asia. Journal of Earth Science, 2018, 29(5): 1132-1150.

Barth S, Oberli F, Meier M. Th-Pb versus U-Pb Isotope Systematics in Allanite from Co-Genetic Rhyolite and Granodiorite: Implications for Geochronology. Earth and Planetary Science Letters, 1994, 124(1/2/3/4): 149-159.

Bosse V, Villa I M. Petrochronology and Hygrochronology of Tectono-Metamorphic Events. Gondwana Research, 2019, 71: 76-90.

Braun I, Montel J M, Nicollet C. Electron Microprobe Dating of Monazites from High-Grade Gneisses and Pegmatites of the Kerala Khondalite Belt, Southern India. Chemical Geology, 1998, 146(1/2): 65-85.

Carpenter P K. EPMA Standards: The Good, the Bad, and the Ugly. Microscopy and Microanalysis, 2008, 14(S2): 530-531.

Cherniak D J, Pyle J M. Th Diffusion in Monazite. Chemical Geology, 2008, 256(1/2): 52-61.

Cherniak D J, Watson E B, Grove M, . Pb Diffusion in Monazite: A Combined RBS/SIMS Study. Geochimica et Cosmochimica Acta, 2004, 68(4): 829-840.

Cocherie A, Albarede F. An Improved U-Th-Pb Age Calculation for Electron Microprobe Dating of Monazite. Geochimica et Cosmochimica Acta, 2001, 65(24): 4509-4522.

Copeland P, Parrish R R, Harrison T M. Identification of Inherited Radiogenic Pb in Monazite and Its Implications for U-Pb Systematics. Nature, 1988, 333(6175): 760-763.

Corfu F. Differential Response of U-Pb Systems in Coexisting Accessory Minerals, Winnipeg River Subprovince, Canadian Shield: Implications for Archean Crustal Growth and Stabilization. Contributions to Mineralogy and Petrology, 1988, 98(3): 312-325.

Deng H, Kusky T M, Polat A, . Geochemistry of Neoarchean Mafic Volcanic Rocks and Late Mafic Dikes in the Zanhuang Complex, Central Orogenic Belt, North China Craton: Implications for Geodynamic Setting. Lithos, 2013, 175–176: 193-212.

Dutch R A. Monazite Chemical Dating via Electron-Probe Micro-Analysis. MESA Journal, 2009, 53: 34-40.

Engi M, Janots E, Rubatto D, . Rates of Metamorphism in Collisional Orogeny. Geochmica et Cosmochimica Acta, 2017, 72 72 A244.

Faure M. Electron-Microprobe Dating as a Tool for Determining the Closure of Th-U-Pb Systems in Migmatitic Monazites. American Mineralogist, 2005, 90(4): 607-618.

Faure M, Cocherie A, Gache J, . Middle Carboniferous Intracontinental Subduction in the Outer Zone of the Variscan Belt (Montagne Noire Axial Zone, French Massif Central): Multimethod Geochronological Approach of Polyphase Metamorphism. Geological Society, London, Special Publications, 2014, 405(1): 289-311.

Geisler T, Schleicher H. Improved U-Th-total Pb Dating of Zircons by Electron Microprobe Using a Simple New Background Modeling Procedure and Ca as a Chemical Criterion of Fluid-Induced U-Th-Pb Discordance in Zircon. Chemical Geology, 2000, 163(1/2/3/4): 269-285.

Goldstein J I, Williams D B, Cliff G. Quantitative X-Ray Analysis, 1986

Jercinovic M J. Analytical Perils (and Progress) in Electron Microprobe Trace Element Analysis Applied to Geochronology: Background Acquisition, Interferences, and Beam Irradiation Effects. American Mineralogist, 2005, 90(4): 526-546.

Jercinovic M J, Williams M L, Lane E D. In-situ Trace Element Analysis of Monazite and Other Fine-Grained Accessory Minerals by EPMA. Chemical Geology, 2008, 254(3/4): 197-215.

Jiao H S, Li X T. Scanning Electron Microscope Energy Dispersive Spectrometer and Wave Dispersive Spectrometer Analysis Technology, 2011, Changchun: Northeast Normal University Press

Konečný P, Kusiak M A, Dunkley D J. Improving U-Th-Pb Electron Microprobe Dating Using Monazite Age References. Chemical Geology, 2018, 484: 22-35.

Kusky T M, Polat A, Windley B F, . Insights into the Tectonic Evolution of the North China Craton through Comparative Tectonic Analysis: A Record of Outward Growth of Precambrian Continents. Earth-Science Reviews, 2016, 162: 387-432.

Lee J K W, Williams I S, Ellis D J. Pb, U and Th Diffusion in Natural Zircon. Nature, 1997, 390(6656): 159-162.

Liu S W, Liu C H, Li Q G, . EPMA Th-U-Pb Monazite Dating of Zhongtiao and Luliang Precambrian Metamorphic Complexes. Earth Science Frontiers, 2007, 14(1): 64-74.

Liu S W, Shu G M, Pan Y M, . Electron Probe Monazite Dating and the Metamorphic AGE of Wutai Group. Geological Journal of China Universities, 2004, 10(3): 356-363.

Liu S W, Zhao G C, Wilde S A, . Th-U-Pb Monazite Geochronology of the Luliang and Wutai Complexes: Constraints on the Tectonothermal Evolution of the Trans-North China Orogen. Precambrian Research, 2006, 148(3/4): 205-224.

Liu Y S, Hu Z C, Gao S, . In-Situ Analysis of Major and Trace Elements of Anhydrous Minerals by LA-ICP-MS without Applying an Internal Standard. Chemical Geology, 2008, 257(1/2): 34-43.

Ludwig K. Users Manual for Isoplot/Ex: A Geochronological Toolkit for Microsoft Excel, 2000.

Montel J M, Foret S, Veschambre M, . Electron Microprobe Dating of Monazite. Chemical Geology, 1996, 131(1/2/3/4): 37-53.

Montel J M, Kato T, Enami M, . Electron-Microprobe Dating of Monazite: The Story. Chemical Geology, 2018, 484: 4-15.

Montel J-M, Kornprobst J, Vielzeuf D. Preservation of Old U-Th-Pb Ages in Shielded Monazite: Example from the Beni Bousera Hercynian Kinzigites (Morocco). Journal of Metamorphic Geology, 2001, 18(3): 335-342.

Parrish R R. U-Pb Dating of Monazite and Its Application to Geological Problems. Canadian Journal of Earth Sciences, 1990, 27(11): 1431-1450.

Qiao G B, Wu Y Z. Geochronology, Petrogenesis and Tectonic Significance of Quanshuigou Pluton from Southeastern West Kunlun Mountain in Xinjiang, China. Earth Science, 2018, 43(12): 4283-4299.

Qiu K F, Yang L Q. Genetic Feature of Monazite and Its U-Th-Pb dating: Critical Considerations on the Tectonic Evolution of Sanjiang Tethys. Acta Petrologica Sinica, 2011, 27(9): 2721-2732.

Reed S J B. Optimization of Wavelength Daspersive X-Ray Spectrometry Analysis Conditions. Journal of Research of the National Institute of Standards and Technology, 2002, 107 6 497

Reed S. Wavelength Dispersive Spectrometry: A Review. X-Ray Spectrometry in Electron Beam Instruments, 1995, Berlin: Springer, 221-238

Rhede D, Wendt I, Forster H J. A Three-Dimensional Method for Calculating Independent Chemical U/Pb- And Th/Pb-Ages of Accessory Minerals. Chemical Geology, 1996, 130(3/4): 247-253.

Scharer U, Allegre C J. Uranium-Lead System in Fragments of a Single Zircon Grain. Nature, 1982, 295(5850): 585-587.

Smith H A, Giletti B J. Lead Diffusion in Monazite. Geochimica et Cosmochimica Acta, 1997, 61(5): 1047-1055.

Steiger R H, Jager E. Subcommission on Geochronology: Convention on the Use of Decay Constants in Geo- And Cosmochronology. Earth and Planetary Science Letters, 1977, 36(3): 359-362.

Suzuki K, Adachi M. Denudation History of the High T/P Ryoke Metamorphic Belt, Southwest Japan: Constraints from CHIME Monazite Ages of Gneisses and Granitoids. Journal of Metamorphic Geology, 1998, 16(1): 23-37.

Suzuki K, Adachi M, Tanaka T. Middle Precambrian Provenance of Jurassic Sandstone in the Mino Terrane, Central Japan: Th-U-Total Pb Evidence from an Electron Microprobe Monazite Study. Sedimentary Geology, 1991, 75(1/2): 141-147.

Suzuki K, Kato T. CHIME Dating of Monazite, Xenotime, Zircon and Polycrase: Protocol, Pitfalls and Chemical Criterion of Possibly Discordant Age Data. Gondwana Research, 2008, 14(4): 569-586.

Tang A, Li G L, Su Y, . EMPA Chemical U-Th-Pb Dating of Uraninite in Ziyunshan Granite, Centre Jiangxi Province. Earth Science, 2017, 42(3): 378-388.

Trap P, Faure M, Lin W, . The Zanhuang Massif, the Second and Eastern Suture Zone of the Paleoproterozoic Trans-North China Orogen. Precambrian Research, 2009, 172(1/2): 80-98.

Trap P, Faure M, Lin W, . Syn-Collisional Channel Flow and Exhumation of Paleoproterozoic High Pressure Rocks in the Trans-North China Orogen: The Critical Role of Partial-Melting and Orogenic Bending. Gondwana Research, 2011, 20(2/3): 498-515.

Wang J P, Kusky T, Polat A, . A Late Archean Tectonic Mélange in the Central Orogenic Belt, North China Craton. Tectonophysics, 2013, 608: 929-946.

Wang J P, Kusky T, Wang L, . Structural Relationships along a Neoarchean Arc-Continent Collision Zone, North China Craton. Geological Society of America Bulletin, 2017, 129(1/2): 59-75.

Wang J P, Li X W, Ning W B, . Geology of a Neoarchean Suture: Evidence from the Zunhua Ophiolitic Mélange of the Eastern Hebei Province, North China Craton. GSA Bulletin, 2019.

Williams I S, Compston W, Chappell B W. Zircon and Monazite U-Pb Systems and the Histories of I-Type Magmas, Berridale Batholith, Australia. Journal of Petrology, 1983, 24(1): 76-97.

Williams M L, Jercinovic M J, Mahan K H, . Electron Microprobe Petrochronology. Reviews in Mineralogy and Geochemistry, 2017, 83(1): 153-182.

Williams M L, Jercinovic M J, Terry M P. Age Mapping and Dating of Monazite on the Electron Microprobe: Deconvoluting Multistage Tectonic Histories. Geology, 1999, 27 11 1023

Xiao L L, Jiang Z S, Wang G D, . Metamorphic Reaction Textures and Metamorphic P-T-t Loops of the Precambrian Zanhuang Metamorphic Complex, Hebei, North China. Acta Petrologica Sinica, 2011, 27(4): 980-1002.

Xiao L L, Liu F L, Chen Y. Metamorphic P-T-t Paths of the Zanhuang Metamorphic Complex: Implications for the Paleoproterozoic Evolution of the Trans-North China Orogen. Precambrian Research, 2014, 255: 216-235.

Yao L. Research and Application of Electron Probe Analysis Methods for Low Content and Trace Elements: [Dissertation], 2008, Changchun: Jilin University

Yao L, Tian D, Lian X R. Progress in Background Subtraction and Spectral Interference Correction in Electron Probe Microanalysis. Rock and Mineral Analysis, 2008, 27(1): 49-54.

Zhang W L, Wang R C, . Principles and Application of Electron Probe Chemical Dating Method for Accessory Minerals. Geological Review, 2003, 49(3): 253-260.

Zhang X, Yang S Y, Zhao H, . Effect of Beam Current and Diameter on Electron Probe Microanalysis of Carbonate Minerals. Journal of Earth Science, 2019, 30(4): 834-842.

Zhao Y L, Liu Y J, Li W M, . Detrital Zircon LA-ICP-MS U-Pb Age of Late Carboniferous to Early Permian Sandstones in Central Great Xing’an Range and Its Geological Significance. Earth Science, 2018, 43(6): 2055-2075.

Zhou J X. Electron Probe Analysis, 1988, Beijing: Geological Publishing House, 105-120.