Discussion on Spot Size and Energy Density Effects on Zircon U-Pb Dating Precision

doi:10.19657/j.geoscience.1000-8527.2023.040

Abstract

Abstract:

LA-ICP-MS, an effective method for zircon U-Pb dating, is the most commonly used technology in geochronological studies. In the LA-ICP-MS zircon U-Pb dating process, the spot diameter and energy density are two important factors that can affect the dating precision. Zircon standard 91500 and GJ-1 are selected as both standards and unknown samples, respectively, and the effects of spot size and energy densities on the LA-ICP-MS U-Pb dating were determined. We aim to optimize the LA-ICP-MS zircon U-Pb dating method, improve the analysis accuracy, and provide reference for other laboratories to carry out similar research work. The results show that with fixed energy density when the ablation beam spot increases from 25 to 65 μm, the relative error (RE) between the measured age results and the recommended values of zircon 91500 and GJ-1 decreases continuously (RE=0.61%, 0.41%, 0.13%, and 0.08%, respectively), i.e., increasing the beam spot diameter can reduce RE and improve the dating precision. Under fixed beam spot diameter (35 μm) with energy density below or equal to 3.5 J/cm², as the energy density increases, the relative error between the measured age results and the recommended values gradually decreases (RE=8.69%, 3.48%, 3.95%, 4.16%, and 0.41%, respectively), and the dating precision gradually increases. However, when the energy density is over 3.5 J/cm², the energy density increase can lead to a significant increase in the denudation rate, and the fractionation effect in the depth direction increases greatly. The relative error between the measured ages and recommended values increases (RE=2.40% and 0.83%, respectively), and the dating precision decreases. Therefore, in the actual test, considering the sample size and the need to preserve the integrity of the sample, choosing reasonable energy density and beam spot size can effectively improve the dating precision.

Key words: zircon U-Pb dating, LA-ICP-MS, laser energy density, beam spot size, dating precision

CLC Number:

P597.3
P599

HU Ziqi, ZHANG Dexian, LIU Lei. Discussion on Spot Size and Energy Density Effects on Zircon U-Pb Dating Precision[J]. Geoscience, 2023, 37(03): 722-732.

Figures/Tables 8

References 41

[1]	第五春荣. 电感耦合等离子质谱仪在地质样品测试中的应用:小秦岭太华群灰色片麻岩地球化学及锆石年代学[D]. 西安: 西北大学, 2005.
[2]	ZONG K Q, LIU Y S, GAO C G, et al. In situ U-Pb dating and trace element analysis of zircons in thin sections of eclogite: Refining constraints on the ultra high-pressure metamorphism of the Sulu terrane, China[J]. Chemical Geology, 2010, 269(3/4): 237-251. DOI URL
[3]	陈文, 万渝生, 李华芹, 等. 同位素地质年龄测定技术及应用[J]. 地质学报, 2011, 85(11): 1917-1947.
[4]	吴元保, 郑永飞. 锆石成因矿物学研究及其对U-Pb年龄解释的制约[J]. 科学通报, 2004, 49(16):1589-1604.
[5]	MARTINEZ M, BAUDELET M. Calibration strategies for elemental analysis of biological samples by LA-ICP-MS and LIBS-A review[J]. Analytical and Bioanalytical Chemistry, 2020, 412(1): 27-36. DOI
[6]	唐燕文, 谢玉玲, 李应栩, 等. 浙江安吉多金属矿区石英二长斑岩岩石化学特征和锆石U-Pb年龄及其地质意义[J]. 现代地质, 2012, 26(4): 647-655.
[7]	涂湘林, 张红, 邓文峰, 等. RESOlution激光剥蚀系统在微量元素原位微区分析中的应用[J]. 地球化学, 2011, 40(1):83-98.
[8]	陈有炘, 裴先治, 李瑞保, 等. 东昆仑造山带东段元古界小庙岩组的锆石U-Pb年龄[J]. 现代地质, 2011, 25(3): 510-521.
[9]	李献华, 柳小明, 刘勇胜, 等. LA-ICPMS锆石U-Pb定年的准确度:多实验室对比分析[J]. 中国科学(地球科学), 2015, 45(9): 1294-1303.
[10]	罗涛. LA-ICP-MS分析过程中ICP引起的元素分馏效应研究[D]. 武汉: 中国地质大学(武汉), 2015.
[11]	王家松, 许雅雯, 彭丽娜, 等. 应用激光拉曼光谱研究锆石LA-ICP-MSU-Pb定年中的α通量基体效应[J]. 岩矿测试, 2016, 35(5): 458-467.
[12]	周亮亮, 魏均启, 王芳, 等. LA-ICP-MS工作参数优化及在锆石U-Pb定年分析中的应用[J]. 岩矿测试, 2017, 36(4):350-359.
[13]	侯振辉. 激光剥蚀束斑大小及深度对锆石U-Pb定年准确度的影响[J]. 矿物岩石地球化学通报, 2020, 39(6):1067-1076.
[14]	WIEDENBECK M, HANCHAR J M, PECK W H, et al. Further characterisation of the 91500 zircon crystal[J]. Geostandards and Geoanalytical Research, 2004, 28(1): 9-39. DOI URL
[15]	王辉, 汪方跃, 关炳庭, 等. 激光能量密度对LA-ICP-MS分析数据质量的影响研究[J]. 岩矿测试, 2019, 38(6):609-619.
[16]	谭细娟, 郭超, 凤永刚, 等. 激光剥蚀系统气体流速变化对LA-ICP-MS锆石U-Pb定年精度的影响[J]. 岩矿测试, 2022, 41(4):554-563.
[17]	罗涛. LA-ICP-MS分析过程中元素分馏效应机理及其在副矿物U-Pb年代学中的应用研究[D]. 武汉: 中国地质大学(武汉), 2018.
[18]	KOCH J, WÄLLE M, PISONERO J, et al. Performance characteristics of ultra-violet fem to second laser ablation inductively coupled plasma mass spectrometry at -265 and - 200 nm[J]. Journal of Analytical Atomic Spectrometry, 2006, 21(9):932-940. DOI URL
[19]	TIEPOLO M. In situ Pb geochronology of zircon with laser ablation-inductively coupled plasma-sector field mass spectrometry[J]. Chemical Geology, 2003, 199(1/2):159-177. DOI URL
[20]	钟玉芳, 马昌前. 含U副矿物的地质年代学研究综述[J]. 地球科学进展, 2006, 21(4):372-382. DOI
[21]	HORSTWOOD M S A, KOŠLER J, GEHRELS G, et al. Community-derived standards for LA-ICP-MS U-(Th-)Pb geochrono-logy—Uncertainty propagation, age interpretation and data reporting[J]. Geostandards and Geoanalytical Research, 2016, 40(3):311-332. DOI URL
[22]	JACKSON S E, PEARSON N J, GRIFFIN W L, et al. The application of laser ablation-inductively coupled plasma-mass spectrometry to in situ U-Pb zircon geochronology[J]. Chemical Geology, 2004, 211(1/2):47-69. DOI URL
[23]	GWOZDZ R, HANSEN H J, RASMUSSEN K L. Stevns Klint fish clay (FC-1): Preparation of, and preliminary results for a candidate reference material[J]. Geostandards Newsletter, 2001, 25(1):159-166. DOI URL
[24]	SLÁMA J, KOŠLER J, CONDON D J, et al. Plešovice zircon—A new natural reference material for U-Pb and Hf isotopic microanalysis[J]. Chemical Geology, 2008, 249(1/2):1-35. DOI URL
[25]	BLACK L P, KAMO S L, ALLEN C M, et al. TEMORA 1:A new zircon standard for Phanerozoic U-Pb geochronology[J]. Chemical Geology, 2003, 200(1/2):155-170. DOI URL
[26]	李献华, 唐国强, 龚冰, 等. Qinghu(清湖)锆石:一个新的U-Pb年龄和O、Hf同位素微区分析工作标样[J]. 科学通报, 2013, 58(20):1954-1961.
[27]	柳小明, 高山, 第五春荣, 等. 单颗粒锆石的20 μm小斑束原位微区LA-ICP-MS U-Pb年龄和微量元素的同时测定[J]. 科学通报, 2007, 52(2):228-235.
[28]	吴石头, 杨岳衡, ROBERTS Nick M W, 等. 高灵敏度-单接收杯LA-SF-ICP-MS原位方解石U-Pb定年[J]. 中国科学(地球科学), 2022, 52(7):1375-1390.
[29]	沈安江, 胡安平, 程婷, 等. 激光原位U-Pb同位素定年技术及其在碳酸盐岩成岩-孔隙演化中的应用[J]. 石油勘探与开发, 2019, 46(6):1062-1074. DOI
[30]	刘勇胜, 胡兆初, 李明, 等. LA-ICP-MS在地质样品元素分析中的应用[J]. 科学通报, 2013, 58(36):3753-3769.
[31]	LIU Y S, HU Z C, LI M, et al. Applications of LA-ICP-MS in the elemental analyses of geological samples[J]. Chinese Science Bulletin, 2013, 58(32):3863-3878. DOI URL
[32]	FRYER B, JACKSON S, LONGERICH H. The design, operation and role of the laser-ablation microprobe coupled with an inductively coupled plasma-mass spectrometer (LAM-ICP-MS) in the earth sciences[J]. The Canadian Mineralogist, 1995, 33(2): 303-312.
[33]	JACKSON S E. Correction of fractionation in LA-ICP-MS elemental and U-Pb analysis[J]. Geochimica et Cosmochimica Acta, 2009, 73(13): A579.
[34]	POPOV D V, SPIKINGS R A, SCAILLET S. Diffusion and fluid interaction in Itrongay pegmatite (Madagascar): Evidence from in situ ⁴⁰Ar/³⁹Ar dating of gem-quality alkali feldspar and U-Pb dating of protogenetic apatite inclusions[J]. Chemical Geology, 2020, 556:119841. DOI URL
[35]	GEHRELS G E, VALENCIA V A, RUIZ J. Enhanced precision, accuracy, efficiency, and spatial resolution of U-Pb ages by laser ablation-multicollector-inductively coupled plasma-mass spectrometry[J]. Geochemistry, Geophysics, Geosystems, 2008, 9(3): Q03017.
[36]	GABOARDI M, HUMAYUN M. Elemental fractionation during LA-ICP-MS analysis of silicate glasses: Implications for matrix-independent standardization[J]. Journal of Analytical Atomic Spectrometry, 2009, 24(9):1188-1197. DOI URL
[37]	GERDES A, ZEH A. Combined U-Pb and Hf isotope LA-(MC-)ICP-MS analyses of detrital zircons: Comparison with SHRIMP and new constraints for the provenance and age of an Armorican metasediment in Central Germany[J]. Earth and Planetary Science Letters, 2006, 249(1/2):47-61. DOI URL
[38]	HIRATA T. Chemically assisted laser ablation ICP mass spectrometry[J]. Analytical Chemistry, 2003, 75(2): 228-233. PMID
[39]	JOCHUM K P, STOLL B, HERWIG K, et al. Validation of LA-ICP-MS trace element analysis of geological glasses using a new solid-state 193 nm Nd: YAG laser and matrix-matched calibration[J]. Journal of Analytical Atomic Spectrometry, 2007, 22(2):112-121. DOI URL
[40]	JOCHUM K P, WEIS U, STOLL B, et al. Determination of re-ference values for NIST SRM 610-617 glasses following ISO guidelines[J]. Geostandards and Geoanalytical Research, 2011, 35(4): 397-429. DOI URL
[41]	GÜNTHER D, HATTENDORF B. Solid sample analysis using laser ablation inductively coupled plasma mass spectrometry[J]. TrAC Trends in Analytical Chemistry, 2005, 24(3): 255-265. DOI URL

激光参数	设定值	ICP-MS参数	设定值
激光源	TelydyneCetac HE Photon Machines Excimer	ICP-MS系统	Analytik Jena Plasma Quant MS Elite
波长	193 nm	功率	1400 W
脉冲宽度	20 ns	等离子冷却气(Ar)流速	13.5 L/min
激光束	均值化平顶光束	辅助气(He)流速	0.850 L/min
脉冲能量	0.01~0.1 mJ	样品传输气(He)流速	0.250 L/min
能量密度	3.5 J/cm²(仪器配1~12 J/cm²)	样品传输气(Ar)流速	0.90 L/min
焦点	表面	扫描模式	峰跳跃模式,1点/峰
光栅扫描速度	5 Hz	获取模式	时间分辨率分析
激光束直径	35 μm(仪器配置1~180 μm)	分析持续时间	70 s(20 s背景,30 s 信号,20 s冲洗)

激光参数	设定值	ICP-MS参数	设定值
激光源	TelydyneCetac HE Photon Machines Excimer	ICP-MS系统	Analytik Jena Plasma Quant MS Elite
波长	193 nm	功率	1400 W
脉冲宽度	20 ns	等离子冷却气(Ar)流速	13.5 L/min
激光束	均值化平顶光束	辅助气(He)流速	0.850 L/min
脉冲能量	0.01~0.1 mJ	样品传输气(He)流速	0.250 L/min
能量密度	3.5 J/cm²(仪器配1~12 J/cm²)	样品传输气(Ar)流速	0.90 L/min
焦点	表面	扫描模式	峰跳跃模式,1点/峰
光栅扫描速度	5 Hz	获取模式	时间分辨率分析
激光束直径	35 μm(仪器配置1~180 μm)	分析持续时间	70 s(20 s背景,30 s 信号,20 s冲洗)

样品名称	束斑直径 (μm)	能量密度 (J/cm²)	标样为91500		标样为GJ-1
样品名称	束斑直径 (μm)	能量密度 (J/cm²)	²⁰⁶Pb/²³⁸U 年龄(Ma)	与推荐值相对误差RE(%)	²⁰⁶Pb/²³⁸U 年龄(Ma)	与推荐值相对误差RE(%)
91500	25	3.5	1062.6±4.5	0.01	1073.7±4.7	0.95
	35	3.5	1063.8±2.3	0.02	1071.0±3.4	0.70
	50	3.5	1063.1±2.2	0.05	1064.5±2.3	0.09
	65	3.5	1063.0±1.8	0.06	1059.9±2.0	0.35
	35	1.5	1062.1±6.9	0.14	1176.5±1.8	10.61
	35	2.0	1062.8±2.3	0.08	1079.8±4.2	1.49
	35	2.5	1065.0±2.9	0.12	1094.7±5.0	2.93
	35	3.0	1063.0±2.1	0.06	1096.7±3.9	3.11
	35	3.5	1063.8±2.3	0.02	1071.0±3.4	0.70
	35	4.0	1063.0±1.9	0.06	1088.9±3.5	2.38
	35	4.5	1061.6±2.6	0.19	1078.4±2.6	1.40
GJ-1	25	3.5	598.1±2.2	0.61	600.7±1.9	0.20
	35	3.5	599.4±1.5	0.41	600.6±1.5	0.21
	50	3.5	602.7±1.0	0.13	600.8±1.0	0.17
	65	3.5	601.4±1.0	0.08	600.9±0.9	0.16
	35	1.5	549.6±1.6	8.69	600.5±1.8	0.23
	35	2.0	580.9±0.9	3.48	600.7±1.5	0.20
	35	2.5	578.1±1.1	3.95	601.0±1.2	0.15
	35	3.0	576.8±0.8	4.16	600.8±1.3	0.18
	35	3.5	599.4±1.5	0.41	600.6±1.5	0.21
	35	4.0	587.4±0.7	2.40	600.9±1.3	0.16
	35	4.5	596.9±1.2	0.83	601.0±1.0	0.15

样品名称	束斑直径 (μm)	能量密度 (J/cm²)	标样为91500		标样为GJ-1
样品名称	束斑直径 (μm)	能量密度 (J/cm²)	²⁰⁶Pb/²³⁸U 年龄(Ma)	与推荐值相对误差RE(%)	²⁰⁶Pb/²³⁸U 年龄(Ma)	与推荐值相对误差RE(%)
91500	25	3.5	1062.6±4.5	0.01	1073.7±4.7	0.95
	35	3.5	1063.8±2.3	0.02	1071.0±3.4	0.70
	50	3.5	1063.1±2.2	0.05	1064.5±2.3	0.09
	65	3.5	1063.0±1.8	0.06	1059.9±2.0	0.35
	35	1.5	1062.1±6.9	0.14	1176.5±1.8	10.61
	35	2.0	1062.8±2.3	0.08	1079.8±4.2	1.49
	35	2.5	1065.0±2.9	0.12	1094.7±5.0	2.93
	35	3.0	1063.0±2.1	0.06	1096.7±3.9	3.11
	35	3.5	1063.8±2.3	0.02	1071.0±3.4	0.70
	35	4.0	1063.0±1.9	0.06	1088.9±3.5	2.38
	35	4.5	1061.6±2.6	0.19	1078.4±2.6	1.40
GJ-1	25	3.5	598.1±2.2	0.61	600.7±1.9	0.20
	35	3.5	599.4±1.5	0.41	600.6±1.5	0.21
	50	3.5	602.7±1.0	0.13	600.8±1.0	0.17
	65	3.5	601.4±1.0	0.08	600.9±0.9	0.16
	35	1.5	549.6±1.6	8.69	600.5±1.8	0.23
	35	2.0	580.9±0.9	3.48	600.7±1.5	0.20
	35	2.5	578.1±1.1	3.95	601.0±1.2	0.15
	35	3.0	576.8±0.8	4.16	600.8±1.3	0.18
	35	3.5	599.4±1.5	0.41	600.6±1.5	0.21
	35	4.0	587.4±0.7	2.40	600.9±1.3	0.16
	35	4.5	596.9±1.2	0.83	601.0±1.0	0.15