普通铅对LA-ICP-MS磷灰石U-Pb定年结果的影响及校正方法

罗涛; 王瀚林; 朱松柏; 卿丽媛; 胡兆初

doi:10.15898/j.ykcs.202404070079

普通铅对LA-ICP-MS磷灰石U-Pb定年结果的影响及校正方法

1.
中国地质大学(武汉)地质过程与矿产资源国家重点实验室，湖北武汉 430074
2.
中国石油塔里木油田公司克拉采油气管理区，新疆库尔勒 841000

基金项目: 国家自然科学基金项目(42373032)；湖北省自然科学基金项目(2024AFD372)

详细信息

作者简介:
罗涛，博士，副研究员，主要从事副矿物U-Th-Pb年代学和激光剥蚀电感耦合等离子体质谱机理研究。E-mail：luotao11@cug.edu.cn

中图分类号: O657.63；P597.3
计量
- 文章访问数: 204
- HTML全文浏览量: 92
- PDF下载量: 78
出版历程
- 收稿日期: 2024-04-06
- 修回日期: 2024-07-05
- 录用日期: 2024-07-10
- 网络出版日期: 2024-08-08
- 发布日期: 2024-08-06
- 刊出日期: 2025-01-30

Impacts of Common Lead on Apatite U-Pb Geochronology by LA-ICP-MS: Assessment and Correction Strategies

1.
State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Wuhan), Wuhan 430074, China
2.
PetroChina Tarim Oilfield Company, Korla 841000, China

摘要

摘要:
磷灰石是火成岩、变质岩和沉积岩中广泛分布的含铀矿物，开展磷灰石U-Pb年代学研究对揭示岩浆演化过程、示踪溯源等方面具有重要意义。激光剥蚀电感耦合等离子体质谱法(LA-ICP-MS)是开展磷灰石U-Pb年龄微区分析的重要手段之一。当前，基体匹配磷灰石U-Pb定年矿物标样缺乏和标样中不可避免的普通铅是制约LA-ICP-MS高精度磷灰石U-Pb年龄分析的主要瓶颈。本文对比研究了标样中普通铅对LA-ICP-MS磷灰石U-Pb定年结果的影响，采用含普通铅的磷灰石MAD作外标直接开展U-Pb年龄校正，获得的被测样品年龄会产生显著的系统偏差(最大约6%)；采用²⁰⁷Pb法或Tera-Wasserburg图解法先校正标样中普通铅，再利用校正后的数据进行元素分馏和仪器漂移校正则可获得准确的磷灰石U-Pb年龄，与推荐值偏差在2%以内。另一方面，为消除标样中普通铅对分析结果的影响，本文还采用水蒸气辅助激光剥蚀方法，实现以NIST612玻璃作为外标准确分析磷灰石U-Pb年龄，解决了磷灰石U-Pb定年微区分析高质量标样缺乏的难题。本研究通过对标样中普通铅进行预校正或采用非基体匹配分析，建立了高精度LA-ICP-MS磷灰石U-Pb定年新方法，将促进磷灰石U-Pb年代学在地球科学研究中的应用。
- 激光剥蚀电感耦合等离子体质谱法 /
- 磷灰石 /
- U-Pb定年 /
- 普通铅校正 /
- 非基体匹配分析
要点
(1)使用含普通铅的磷灰石标样MAD作外标，直接校正样品产生2.5%～6.0%的系统偏差。

(2)预先校正标样中普通铅(²⁰⁷Pb法或Tera-Wasserburg图解法)再进行样品Pb/U分馏校正可获得准确分析结果(偏差低于2.0%)。

(3)采用水蒸气辅助激光剥蚀法，以玻璃NIST612非基体匹配分析磷灰石MAD、Otter Lake和Durango可获得准确年龄，有效地避免标样中普通铅对分析结果的影响。

HIGHLIGHTS
(1) A systematic bias of 2.5% to 6.0% is observed when using the common lead-containing apatite standard MAD as an external standard for direct U-Pb calibration.

(2) Accurate results (with bias below 2.0%) can be obtained by correcting for common lead in the standard (using the ²⁰⁷Pb method or Tera-Wasserburg diagram method) prior to performing Pb/U elemental fractionation correction.

(3) Accurate U-Pb ages of apatite reference materials of MAD, Otter Lake, and Durango can be obtained through calibration against non-matrix-matched NIST612 glass using a water vapor-assisted laser ablation method, effectively mitigating the influence of common lead in standards on the analytical results.
Abstract:
Apatite is a widespread U-bearing mineral in igneous, metamorphic, and sedimentary rocks. U-Pb geochronology of apatite can provide significant information for constraining magmatic evolution processes and tracing provenance. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a crucial technique for in situ U-Pb age analysis of apatite. However, the lack of suitable matrix-matched apatite reference materials and the inevitable presence of common lead in reference materials are major obstacles restricting high-precision determination of apatite U-Pb ages. This study investigates the impact of common lead on LA-ICP-MS apatite U-Pb dating results. The significant systematic biases (6%−30%) in both measured lower intercept ages and initial lead compositions are observed when calibrating against MAD apatite without common lead correction. However, accurate apatite U-Pb ages (within 2% systematic bias) can be obtained by correcting for common lead in MAD using the ²⁰⁷Pb method or Tera-Wasserburg plot method prior to Pb/U fractionation calibration. Furthermore, a vapor-assisted laser ablation method is employed in conjunction with NIST612 glass as an external standard to accurately analyze apatite U-Pb ages. This non-matrix matched method eliminates the need to consider the influence of common lead in the reference materials. Novel high-precision LA-ICP-MS apatite U-Pb dating methods are established with both matrix-matched and non-matrix-matched analyses, which greatly promote the application of apatite U-Pb geochronology in Earth science. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202404070079.
- laser ablation inductively coupled plasma-mass spectrometry /
- apatite /
- U-Pb dating /
- common lead correction /
- non-matrix-matched analysis
BRIEF REPORT
Significance: Apatite is a ubiquitous accessory mineral occurring in diverse geological environments^[1]. It typically contains U ranging from a few to several hundred ppm or more^[2-3]. Consequently, apatite U-Pb dating is widely employed to constrain the timing of significant geological processes, including diagenesis, mineralization, and fossil formation^[4-8]. Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) is one of the important techniques for conducting in situ U-Pb age analysis of accessory minerals. Matrix-matched standards are crucial for obtaining accurate results in LA-ICP-MS U-Pb geochronology. However, apatite from diverse geological origins typically incorporates common lead, and the standards reported for in situ U-Pb geochronology of apatite likewise contain variable amounts of common lead. The measured Pb/U ratios are a mixture of radiogenic and common lead components when the apatite standards contain variable amounts of common lead. In previous apatite U-Pb geochronology studies, the ²⁰⁷Pb method was commonly employed to correct for common lead in MAD standards, which contain minimal common lead (approximately 1% age discordance). However, this approach is unsuitable for analyzing standards with higher common lead contents. As in situ U-Pb dating techniques for apatite continue to advance and the number of microanalysis laboratories expands, the availability of apatite MAD standards with low common lead content is diminishing. To obtain accurate and precise LA-ICP-MS apatite U-Pb results, different common lead correction methods (²⁰⁷Pb method or Tera-Wasserburg plot method) are performed to the apatite standard prior to Pb/U elemental fractionation correction in this study. Moreover, a water vapor-assisted method is proposed to determine accurate apatite U-Pb ages with NIST612 glass as the external standard. This non-matrix-matched analytical approach alleviates the lack of apatite U-Pb dating standards and effectively mitigates the impact of common lead in apatite standards on analytical results.
Methods: Experiments were performed with Agilent7900 quadrupole inductively coupled plasma-mass spectrometer (Agilent Technologies, Tokyo, Japan) coupled with a Coherent 193nm excimer nanosecond laser ablation system (Geolas HD, MicroLas Gttingen, Germany). Detailed experimental parameters are presented in Table 1. Apatite reference materials MAD, Durango, Otter Lake, and NIST612 glass were analyzed for U-Pb dating. For matrix-matched apatite U-Pb dating analysis, MAD was used as an external standard and Durango, and Otter Lake served as monitors to evaluate data accuracy. To obtain accurate and precise apatite U-Pb results, different common lead correction methods (²⁰⁷Pb method or Tera-Wasserburg plot method) were performed to the MAD standard prior to Pb/U elemental fractionation correction. The calibration procedures for the ²⁰⁷Pb method were as follows: (1) Subtract the background from the U and Pb signals for each measured MAD; (2) Perform common lead correction for each measured MAD; (3) Use the common lead-corrected MAD samples for Pb/U fractionation correction. These specific correction steps can be implemented using the VizualAge UComPbine function in the Iolite software. The principle of the Tera-Wasserburg plot method is based on the Tera-Wasserburg concordia diagram. The processes are as follows: (1) Calculate the intersection point of the discordia line constructed from all measured MAD with the X-axis of the Tera-Wasserburg concordia diagram; (2) Calculate the intersection point of the discordia line passing through the recommended age of the MAD standard with the X-axis. The ratio of these two intersection points is the Pb/U fractionation correction factor; (3) Correct the Pb/U ratios of unknown samples using the fractionation correction factor. The ²⁰⁷Pb/²⁰⁶Pb ratios of the unknown samples were directly corrected using a standard with homogeneous Pb isotopic composition (such as NIST glass). A water vapor-assisted method was proposed for non-matrix-matched apatite U-Pb age determination with approximately 4mg/min of water vapor introduced into the laser ablation cell. Apatite U-Pb ages were determined using NIST612 glass as the external standard.
Data and Results: The U-Pb age results of apatite Otter Lake and Durango by calibration against MAD without common lead correction are presented in Fig.2. The initial lead compositions of apatite standards are anchored with the Pb isotopic compositions from Stacey and Kramer’s model. The obtained lower intercept ages of Otter Lake and Durango show systemic bias of 2.5% and 6% relative to their reference ages, respectively. The results indicate that significant systematic biases in measured lower intercept ages are observed when calibrating against MAD apatite without common lead correction.
　　Fig.3 presents the U-Pb results for Otter Lake and Durango, calibrated against apatite MAD after common lead correction using the ²⁰⁷Pb method. The obtained lower intercept age for Otter Lake is less than 1% younger than the reference value. Moreover, the lower intercept age of Durango shows a deviation of −1.7% with the initial lead composition anchored in the Tera-Wasserburg concordia diagram. The results of Otter Lake and Durango using MAD as the external standard with common lead correction via the Tera-Wasserburg plot method are presented in Fig.4. The lower intercept ages of Otter Lake and Durango are 929.0±7.1Ma (2σ, MSWD=1.2) and 29.3±0.5Ma (2σ, MSWD=1.0), showing deviations of 1.7% and 6.6% from their recommended values, respectively. The larger deviation for Durango apatite may be attributed to its higher common lead content and the insufficient spread of the measured Pb/U ratios. Fig.5 shows the U-Pb results of apatite MAD, Otter Lake, and Durango using NIST612 glass as the external standard with the addition of water vapor within the laser ablation cell. The obtained lower intercept ages from the Tera-Wasserburg diagrams for apatite MAD, Otter Lake, and Durango are 474.7±2.7Ma (2σ, MSWD=1.6), 934.8±2.1Ma (2σ, MSWD=2.1), and 31.2±1.2Ma (2σ, MSWD=1.6), respectively. These ages show good consistency with their recommended values within the analytical uncertainties, respectively.

HTML全文

磷灰石是各种地质环境中广泛存在的副矿物^［1］，通常含有一定数量的铀(几μg/g到数百μg/g以上)^［2-3］，因此磷灰石U-Pb定年常用于限定成岩成矿和化石形成等重要地质作用时代^［4-8］。激光剥蚀电感耦合等离子体质谱(LA-ICP-MS)因其样品制备简单、分析效率高、可提供微区原位信息等优点^［9-11］，是开展副矿物U-Pb年龄微区分析的重要手段之一^{［4，12-14］}。对于LA-ICP-MS磷灰石U-Pb定年测定，Chew等^［12］于2011年采用激光线扫描剥蚀法联合溶液校正建立LA-ICP-MS磷灰石U-Pb定年方法，此后该技术在磷灰石U-Pb年龄微区分析中应用广泛^［15-19］。

由于磷灰石中铀含量通常较低^［3］，采用激光微束分析时进样量少，其Pb/U分析精度是首要考虑的问题。Thomson等^［20］采用激光剥蚀联用MC-ICP-MS分析，分别用法拉第杯接收²³⁸U、²³²Th、²⁰⁸Pb、²⁰⁷Pb和²⁰⁶Pb，在激光剥蚀束斑65μm时获得的磷灰石标准样品MAD的²⁰⁶Pb/²³⁸U单点分析精度为4%～40%(2SD)。Chew等^［21］采用四极杆电感耦合等离子体质谱开展磷灰石U-Pb年龄分析，在剥蚀束斑50μm时获得的Durango磷灰石²⁰⁶Pb/²³⁸U单点分析精度为8%～10% (2SD)，而在束斑130μm时才达到满足激光分析要求的精度(约2%)。因此，开展激光微区磷灰石U-Pb定年分析时，评估仪器灵敏度对分析精度的影响是获得准确精密分析结果的基础。另一方面，磷灰石在结晶过程中矿物晶格中可能混入Pb元素，此类Pb不由U、Th等放射性衰变产生，即初始铅或普通铅^［4］。不同成因的磷灰石普遍含有普通铅，已报道的用于磷灰石U-Pb定年微区分析的标准样品也均含有不同程度的普通铅^［20-21］。U-Pb定年分析标样需具有均匀的²⁰⁶Pb/²³⁸U和²⁰⁷Pb/²⁰⁶Pb比值，当磷灰石标样中有不同含量的普通铅时，标样实测的²⁰⁶Pb/²³⁸U和²⁰⁷Pb/²⁰⁶Pb比值是其放射性成因比值和不同含量普通铅的混合信息，若直接用于Pb/U分馏和仪器漂移校正，则会对磷灰石样品的定年结果和初始铅组成造成影响。前人开展磷灰石U-Pb定年分析时均采用基体匹配的磷灰石MAD^［20］作外标校正分析未知样品年龄，研究者多采用²⁰⁷Pb法先对MAD进行普通铅校正^［16］。由于MAD标样普通铅含量低(约1%的年龄不谐和)^［20］，采用²⁰⁷Pb法可获得准确的分析结果，但该方法不适用于普通铅含量较高的标样分析。随着磷灰石原位U-Pb定年技术的发展和微区分析实验室数量的增加，低普通铅磷灰石MAD逐渐缺乏。为获得准确的激光微区U-Pb定年结果，因此需要对磷灰石标样中普通铅校正方法进行系统研究和开发非基体匹配分析方法。对当前特定副矿物U-Pb年龄微区分析高质量标样极度匮乏的问题，部分学者尝试开发了非基体匹配分析方法^［4］。如以储量丰富、不含普通铅的锆石标样校正分析榍石^［22］和金红石^［23］等。Luo等采用水蒸气辅助激光剥蚀方法实现以锆石或NIST玻璃作为外标分析榍石^［13］、独居石^［13］、磷钇矿^［13］、氟碳铈矿^［24］以及黑钨矿^［25］等副矿物的U-Th-Pb年龄。采用非基体匹配分析方法，不仅可以有效地解决基体匹配标样缺乏的问题，也可一定程度地避免标样中普通铅组成对分析结果造成的偏差。

因此，针对当前激光微区磷灰石U-Pb定年分析时标样中普通铅影响分析结果准确度和精密度等问题，本文将定量评估分析灵敏度对磷灰石U-Pb定年分析精度的影响，对比研究磷灰石标样中普通铅组成对分析结果造成的偏差；尝试建立磷灰石非基体匹配分析方法以消除普通铅对分析结果的影响，建立了准确的高精度激光微区磷灰石U-Pb定年新方法。

1. 实验部分

1.1 实验仪器

本实验在中国地质大学(武汉)地质过程与矿产资源国家重点实验室进行，采用Agilent 7900四极杆等离子体质谱仪(Agilent Technology，Tokyo，Japan)联合相干公司的193nm准分子纳秒激光(GeoLas HD，MicroLas Göttingen，Germany)。详细的实验参数列于表1。

表 1 LA-ICP-MS磷灰石U-Pb定年实验仪器参数

Table 1. Instrumental parameters for LA-ICP-MS U-Pb dating of apatite.

LA参数	GeoLas HD 193nm准分子激光
波长	193nm
激光能量密度	10J/cm²
剥蚀频率	5Hz
剥蚀时间	50s
背景时间	20s
He流速	650mL/min
束斑直径	60～90μm
ICP-MS参数	Agilent 7900型
等离子体功率	1400W
样品气	0.86L/min
检测元素	²⁹Si，⁴²Ca，⁴⁹Ti，⁵¹V，⁸⁹Y，⁹³Nb，¹³⁹La，¹⁴⁰Ce， ¹⁴¹Pr，¹⁴⁶Nd，¹⁴⁷Sm，¹⁵¹Eu，¹⁵⁷Gd，¹⁵⁹Tb，¹⁶³Dy， ¹⁶⁵Ho，¹⁶⁶Er，¹⁶⁹Tm，¹⁷³Yb，¹⁷⁵Lu，¹⁷⁹Hf，¹⁸¹Ta， ²⁰¹Hg，²⁰⁴Pb，²⁰⁶Pb，²⁰⁷Pb，²⁰⁸Pb，²³²Th，²³⁸U

下载: 导出CSV

| 显示表格

1.2 实验样品和分析方法

MAD磷灰石来自于马达加斯加的“1st Mine Discovery”。ID-TIMS年龄测试出两个年龄486±0.85Ma和474.25±0.41Ma，Th/U值约为15～30。MAD磷灰石是目前激光微区磷灰石U-Pb年龄分析常用的外标^［2，26］，本研究中基体匹配分析实验也采用MAD作为年龄校正标样。Durango磷灰石产于墨西哥杜兰戈市的露天铁矿中，磷灰石的形成与长英质侵入体有关，产出于火山口的两个熔结凝灰岩之间^［27］，同时结晶的四个单晶透长-歪长石的⁴⁰Ar-³⁹Ar年龄为31.44±0.18Ma (2SD) ^［27］。Durango磷灰石由于年轻且U含量较低，Pb同位素难以准确测定，在测试中需要采用大束斑测量，并固定初始铅组成，或分析较大范围区域从而获得更为广泛的Pb/U组成分布^［21］。Otter Lake磷灰石产于加拿大魁北克省，该地区的岩石经历了多期构造活动，产自该地区的磷灰石样品通常呈深绿色-棕色长六角棱柱体，对同一磷灰石晶体使用溶液法测试其铅同位素，在²⁰⁷Pb/²⁰⁴Pb-²⁰⁶Pb/²⁰⁴Pb图解中获得的等时线年龄为913±7Ma (2SD，MSWD=0.24)，该年龄作为Otter Lake磷灰石推荐年龄被广泛采用^{［21，28］}。为解决基体匹配标样缺乏的问题，研究者们常采用美国国家标准与技术研究所(NIST)的合成玻璃NIST610、NIST612或NIST614^［29］作为U-Pb年龄分析时的外标校正仪器分馏和信号漂移^{［13，30-32］}，本研究选用U含量与磷灰石较为相当的NIST612玻璃作为非基体匹配分析时的外部校正标样。数据处理采用Iolite软件^［33］和Excel程序，U-Pb谐和图由Isoplot R软件绘制^［34］。

2. 结果与讨论

2.1 信号强度对分析精度的影响

U-Pb定年的测试精度取决于U和Pb的信号强度，而信号强度与样品中U、Pb的含量及进样量有关。由于含普通铅矿物的U-Pb年龄需要对其进行普通铅校正，因此对于磷灰石U-Pb定年来说，除了关注Pb/U的分析不确定度外，还需注意Pb/Pb的分析不确定度。而U-Pb体系中的比值精度主要取决于低含量元素的信号强度。图1展示了在不同激光条件下同时测试磷灰石参考物质MAD和Durango获得U-Pb年龄的内部不确定度与Pb信号强度的关系。对于²⁰⁶Pb/²³⁸U，当²⁰⁶Pb计数达到6000cps时，其不确定度可以缩小到2%；当²⁰⁶Pb计数超过6000cps时，其不确定度下降变缓，超过20000cps时可以达到～1%的不确定度。对于²⁰⁷Pb/²⁰⁶Pb，其不确定度主要取决于含量更低的²⁰⁷Pb的信号强度，因此其不确定度较²⁰⁶Pb/²³⁸U相比偏高。当²⁰⁷Pb计数为～600cps时，其不确定度可以达到～5%，随后缓慢降低，直到～2400cps时达到～2%的水平。从图1还可以看到，对于年轻的样品Durango，由于其Pb含量过低，U-Pb年龄的内部精度始终较低。

图 1 ²⁰⁶Pb/²³⁸U和²⁰⁷Pb/²⁰⁶Pb年龄精度随Pb信号强度的变化

(a)²⁰⁶Pb/²³⁸U年龄；(b) ²⁰⁷Pb/²⁰⁶Pb年龄。

Figure 1. The precision of ²⁰⁶Pb/²³⁸U and ²⁰⁷Pb/²⁰⁶Pb ages varing with Pb signal intensity: (a) ²⁰⁶Pb/²³⁸U age; (b) ²⁰⁷Pb/²⁰⁶Pb age.

下载: 全尺寸图片幻灯片

2.2 磷灰石U-Pb年龄基体匹配分析

副矿物U-Pb定年测试一般采用标样、样品间插分析以校正元素分馏和仪器漂移。而当外部校正标样中含一定程度普通铅时，需要先对标样进行普通铅扣除，使用经过校正后的Pb/U比值对未知样品进行校正。本研究对比了磷灰石MAD作外标时直接校正和选用不同方法进行普通铅校正后对待测样品分析结果的影响。

2.2.1 磷灰石MAD直接校正结果

如图2展示在不对标样MAD进行普通铅校正情况下，直接用其校正监控样品的结果。对于Otter Lake，在不固定普通铅组成得到的Tera-Wasserburg谐和图交点年龄与推荐值的偏差在1%内，但是初始铅组成与推荐值产生了较大偏差，偏低36%；固定Tera-Wasserburg谐和图普通铅组成(²⁰⁷Pb/²⁰⁶Pb=0.9，由地球铅同位素演化模型^［35］确定)，交点年龄偏差为2.5%。对于Durango磷灰石，在不固定初始铅组成(²⁰⁷Pb/²⁰⁶Pb=0.84)得到的Tera-Wasserburg谐和图交点年龄偏差达到了30%，初始铅组成与推荐值产生了较大偏差，偏低60%；固定Tera-Wasserburg谐和图普通铅组成，交点年龄偏差为6%。研究结果表明使用含普通铅的磷灰石标样作为外标时，若不对其进行普通铅校正，最终获得的被测样品年龄和初始铅组成均会产生较大的系统偏差。

图 2 使用磷灰石MAD作为外标直接校正获得的磷灰石样品U-Pb年龄

(a) 磷灰石Otter Lake，不固定初始铅同位素；(b) 磷灰石Otter Lake，固定初始铅同位素；(c) 磷灰石Durango，不固定初始铅同位素；(d) 磷灰石Durango，固定初始铅同位素。

Figure 2. U-Pb ages results obtained by calibrating with apatite MAD as the external standard: (a) Apatite Otter Lake, without anchored initial Pb isotopic composition; (b) Apatite Otter Lake, with anchored initial Pb isotopic composition; (c) Apatite Durango, without anchored initial Pb isotopic composition; (d) Apatite Durango, with anchored initial Pb isotopic composition.

下载: 全尺寸图片幻灯片

2.2.2 ²⁰⁷Pb法普通铅校正结果

对含普通铅的标准样品，常需对标样进行普通铅校正，再采用经过校正后的各标样对未知样品进行元素分馏和仪器漂移校正^［4］。本研究选用²⁰⁷Pb法先对磷灰石标样MAD进行校正^［4］，其校正原理和操作步骤简述如下。用于分馏校正的磷灰石标样中含普通铅时，需先对标样中普通铅进行校正。

若采用²⁰⁷Pb法校正：(a)先对每个标样测试点的U、Pb信号扣除背景；(b)对每个标样测试点进行普通铅校正，计算公式如下所示。

$$ ^{206}\mathrm{P}\mathrm{b}_{\mathrm{r}}=^{206}\mathrm{P}\mathrm{b}_{\mathrm{m}}\times(1-\mathrm{\mathit{f}}_{206}) $$

(1)

$$ ^{207}\mathrm{P}\mathrm{b}_{\mathrm{r}}=^{207}\mathrm{P}\mathrm{b}_{\mathrm{m}}-^{206}\mathrm{P}\mathrm{b}_{\mathrm{m}}\times\left(^{207}\mathrm{P}\mathrm{b}/^{206}\mathrm{P}\mathrm{b}\right)_{\mathrm{c}}\times f_{206} $$

(2)

$$ \mathit{\mathrm{\mathit{f}}}_{206}=\frac{\left(^{207}\mathrm{Pb}/^{206}\mathrm{Pb}\right)_{\mathrm{m}}-\left(^{207}\mathrm{Pb}^*/^{206}\mathrm{Pb}^*\right)}{\left(^{207}\mathrm{Pb}/^{206}\mathrm{Pb}\right)_{\mathrm{c}}-\left(^{207}\mathrm{Pb}^*/^{206}\mathrm{Pb}^*\right)} $$

(3)

式中：²⁰⁶Pb_r为普通铅校正后的瞬时²⁰⁶Pb信号；²⁰⁶Pb_m为测试的瞬时²⁰⁶Pb信号；²⁰⁷Pb_r为普通铅校正后的瞬时²⁰⁷Pb信号；²⁰⁷Pb_m为测试的瞬时²⁰⁷Pb信号；(²⁰⁷Pb/²⁰⁶Pb)_m为测试的²⁰⁷Pb/²⁰⁶Pb比值(²⁰⁷Pb/²⁰⁶Pb)_c为初始的²⁰⁷Pb/²⁰⁶Pb比值。

(c)经过普通铅校正后的各标样点再用于Pb/U分馏校正。具体校正步骤可在Iolite软件^［33］中的VizualAge UComPbine功能实现。

图3展示了MAD经过普通铅校正后分析磷灰石Otter Lake和Durango的结果。对于Otter Lake，在不固定普通铅组成得到的Tera-Wasserburg谐和图交点年龄偏差为−1.5%，普通铅组成与推荐值的偏差为−10%；固定Tera-Wasserburg谐和图普通铅组成，交点年龄偏小于1%。对于Durango磷灰石，在不固定普通铅组成得到的Tera-Wasserburg谐和图交点年龄偏差为−31.4%，普通铅组成与推荐值偏差为−45.4%；固定Tera-Wasserburg谐和图普通铅组成，交点年龄偏差为−1.7%。磷灰石标样MAD先经过普通铅校正，后校正获得的磷灰石Otter Lake和Durango年龄与其推荐值相比偏差均在±2%以内，达到了目前国际上激光剥蚀微区分析磷灰石U-Pb定年的普遍水平^{［16，21，36-37］}。

图 3 使用²⁰⁷Pb法校正MAD普通铅后获得的磷灰石样品的U-Pb年龄

Figure 3. U-Pb age results obtained after prior correction for common Pb in MAD with ²⁰⁷Pb method: (a) Apatite Otter Lake, without anchored initial Pb isotopic composition; (b) Apatite Otter Lake, with anchored initial Pb isotopic composition; (c) Apatite Durango, without anchored initial Pb isotopic composition; (d) Apatite Durango, with anchored initial Pb isotopic composition.

下载: 全尺寸图片幻灯片

2.2.3 Tera-Wasserburg图解法普通铅校正结果

²⁰⁷Pb法假定样品的²⁰⁶Pb/²³⁸U和²⁰⁷Pb/²³⁵U年龄谐和，其数学校正原理可在Tera-Wasserburg图解上清晰呈现^［4］。因此有学者采用标样测试点构筑的不一致线在Tera-Wasserburg图解下交点与其推荐值之比进行未知样品的分馏校正^［4，32］。其操作步骤为：①分别计算出由所有测试点构筑的不一致线与X轴的交点；②计算经过标样推荐年龄的不一致线与X轴的交点，两交点比值即为Pb/U分馏校正系数；③将该系数乘以待测样品的Pb/U比值便得到待测样品经过校正后的Pb/U比值，而未知样品的²⁰⁷Pb/²⁰⁶Pb比值则由Pb同位素组成均匀的标样(如NIST玻璃)直接校正获得。

图4展示了使用Tera-Wasserburg图下交点法校正得到的结果。将未经普通铅校正的磷灰石MAD测试点固定上交点于0.87(由地球铅同位素演化模型^［35］确定)，其不一致线与X轴的交点为18.33，将MAD推荐年龄(475Ma)^［20］也投入图中，得到经过推荐年龄的不一致线与X轴的交点为14.14 (图4a)，将两者的比值(0.79)校正到磷灰石Otter Lake和Durango各测试点(图4中b，c)，最终得到的Tera-Wasserburg谐和图交点年龄分别为929.0±7.1Ma (2σ，MSWD=1.2)和29.3±0.5Ma(2σ，MSWD=1.0)，与其各自推荐值偏差分别为1.7%和6.6%。磷灰石Durango的结果呈现较大偏差，可能是由于其普通铅含量较高，分析获得的Pb/U比值不够分散，因此其下交点年龄出现较大偏差。这也说明为获得准确的分析结果，采用Tera-Wasserburg图解校正法时，分析样品需有较大范围的Pb/U比值。

图 4 Tera-Wasserburg图解法校正获得磷灰石U-Pb年龄

Figure 4. U-Pb ages of apatite obtained by Tera-Wasserburg concordia correction method: (a) MAD; (b) Otter Lake; (c) Durango.

(a) MAD; (b) Otter Lake; (c) Durango。

下载: 全尺寸图片幻灯片

2.3 磷灰石U-Pb年龄非基体匹配分析

水蒸气辅助激光剥蚀法现已广泛应用于榍石、独居石、磷钇矿和氟碳铈矿等副矿物U-Th-Pb年龄的非基体匹配分析^［4，13］。为避免标样中普通铅对分析结果造成的影响，本研究也采用水蒸气辅助激光剥蚀方法，以NIST612玻璃作为外标，校正磷灰石MAD、Otter Lake和Durango的U-Pb年龄。水蒸气引入方法在本团队以往研究中已有详细介绍^{［4，13，24］}，本研究通过在剥蚀池前引入4.0mg/min水蒸气，选用NIST612玻璃作为外标直接校正磷灰石标样，分析结果如图5所示。磷灰石MAD、Otter Lake和Durango在Tera-Wasserburg图解下交点年龄分别为474.7±2.7Ma (2σ，MSWD=1.6)、934.8±2.1Ma(2σ，MSWD=2.1)和31.2±1.2Ma (2σ，MSWD=1.6)，与其推荐值均在误差范围内一致。

图 5 以NIST612玻璃作为外标分析获得的磷灰石U-Pb年龄

Figure 5. U-Pb ages of apatite obtained by using NIST612 glass as the external standard: (a) MAD; (b) Otter Lake; (c) Durango.

(b) MAD; (b) Otter Lake; (c) Durango。

下载: 全尺寸图片幻灯片

2.4 不同分析方法结果对比

本研究为获得准确的磷灰石U-Pb年龄，分别采用磷灰石MAD和NIST612玻璃作为外标校正分析，并对比了²⁰⁷Pb法和Tera-Wasserburg图解法对MAD标样中普通铅的校正结果(表2)。由于测试所得磷灰石Otter Lake和Durango的Pb/U比值较为集中，且含较高程度普通铅，此处仅列出固定普通铅时计算的年龄结果。磷灰石MAD作为外标直接校正时，固定初始铅组成，获得的Otter Lake下交点年龄与推荐值的偏差为2.5%；Durango磷灰石的下交点年龄与推荐值的偏差为6%。使用²⁰⁷Pb法先对磷灰石标样MAD进行普通铅校正，获得的Otter Lake和Durango的交点年龄与其推荐值的偏差分别为0.03%和1.7%。采用Tera-Wasserburg图解法校正MAD中普通铅后获得的Otter Lake和Durango的交点年龄与其推荐值的偏差分别为1.7%和6.6%，其中Durango的结果呈现较大偏差，可能因为分析点的Pb/U比值不够分散，获得的Tera-Wasserburg图解下交点有较大偏离导致。以NIST612玻璃作为外标，测试的磷灰石MAD、Otter Lake和Durango在Tera-Wasserburg图解下交点年龄分别为474.7±2.7Ma(2σ，MSWD=1.6)、934.8±2.1Ma(2σ，MSWD=2.1)和31.2±1.2Ma(2σ，MSWD=1.6)，与其推荐值的偏差分别为0.1%、2.3%和0.8%。虽然本研究中采用²⁰⁷Pb法和Tera-Wasserburg图解法都可以获得磷灰石Otter Lake和Durango准确的U-Pb年龄，但在标样普通铅含量较高时，采用²⁰⁷Pb法可能会存在过校正或校正不足的情况，造成样品年龄偏差，因此²⁰⁷Pb法适用于普通铅含量较低的标样校正；而Tera-Wasserburg图解法需要测试标样的Pb/U比值分散程度较大，构筑不一致线以获得准确的下交点，因此Tera-Wasserburg图解法适用于标样Pb/U比值分散程度较大的情况，应用范围广，但操作较为复杂。采用水蒸气辅助激光剥蚀非基体匹配分析，可避免标样中普通铅对分析结果的影响，同时有效地克服磷灰石标样匮乏的瓶颈。

表 2 不同测量条件下获得的磷灰石Tera-Wasserburg谐和图下交点年龄与推荐值的偏差

Table 2. Deviations of Tera-Wasserburg values and recommended values for apatite U-Pb age obtained under different measurement conditions.

激光条件	外标	普通铅校正方法	分析样品	Tera-Wasserburg谐和图下交点年龄与推荐值的偏差(%)
60μm，5Hz	MAD	无普通铅校正	Otter Lake	2.5
60μm，5Hz	MAD	无普通铅校正	Durango	6.0
60μm，5Hz	MAD	²⁰⁷Pb	Otter Lake	0.03
60μm，5Hz	MAD	²⁰⁷Pb	Durango	1.7
60μm，5Hz	MAD	Tera-Wasserburg图解法	Otter Lake	1.7
60μm，5Hz	MAD	Tera-Wasserburg图解法	Durango	6.6
60μm，5Hz	NIST612	无普通铅校正	MAD	0.1
			Otter Lake	2.3
			Durango	0.8

下载: 导出CSV

| 显示表格

3. 结论

系统评价了磷灰石标样中不可避免的普通铅组成对U-Pb定年分析结果的影响。采用磷灰石MAD作外标直接开展U-Pb年龄分析，获得的被测样品年龄和初始铅组成均会产生显著的系统偏差(6%)。分别采用²⁰⁷Pb法或Tera-Wasserburg图解法校正标样中普通铅，再使用校正后结果进行元素分馏和仪器漂移校正，最终获得准确的磷灰石U-Pb年龄，测试值与推荐值的相对偏差在2%误差范围内。此外，为完全消除标样中普通铅的影响，本文通过在剥蚀池前引入4.0mg/min水蒸气，实现了以NIST612玻璃作为外标校正磷灰石MAD、Otter Lake和Durango的U-Pb年龄。该方法简单有效，可以缓解激光微区磷灰石U-Pb定年分析高质量标样匮乏的难题。

本文通过建立基体匹配和非基体匹配分析方法，有效地解决了磷灰石U-Pb定年分析时标样中普通铅对分析结果的影响，成功实现磷灰石U-Pb定年准确分析。未来研究仍需加强低普通铅磷灰石U-Pb定年标准样品研制，促进非基体匹配磷灰石U-Pb定年方法的推广，为磷灰石U-Pb年代学在地球科学研究中的应用提供支撑。

致谢：感谢审稿人对本文提出的宝贵修改建议。

图 1 ²⁰⁶Pb/²³⁸U和²⁰⁷Pb/²⁰⁶Pb年龄精度随Pb信号强度的变化

(a)²⁰⁶Pb/²³⁸U年龄；(b) ²⁰⁷Pb/²⁰⁶Pb年龄。

Figure 1. The precision of ²⁰⁶Pb/²³⁸U and ²⁰⁷Pb/²⁰⁶Pb ages varing with Pb signal intensity: (a) ²⁰⁶Pb/²³⁸U age; (b) ²⁰⁷Pb/²⁰⁶Pb age.

下载: 全尺寸图片幻灯片

图 2 使用磷灰石MAD作为外标直接校正获得的磷灰石样品U-Pb年龄

下载: 全尺寸图片幻灯片

图 3 使用²⁰⁷Pb法校正MAD普通铅后获得的磷灰石样品的U-Pb年龄

下载: 全尺寸图片幻灯片

图 4 Tera-Wasserburg图解法校正获得磷灰石U-Pb年龄

Figure 4. U-Pb ages of apatite obtained by Tera-Wasserburg concordia correction method: (a) MAD; (b) Otter Lake; (c) Durango.

(a) MAD; (b) Otter Lake; (c) Durango。

下载: 全尺寸图片幻灯片

图 5 以NIST612玻璃作为外标分析获得的磷灰石U-Pb年龄

Figure 5. U-Pb ages of apatite obtained by using NIST612 glass as the external standard: (a) MAD; (b) Otter Lake; (c) Durango.

(b) MAD; (b) Otter Lake; (c) Durango。

下载: 全尺寸图片幻灯片

表 1 LA-ICP-MS磷灰石U-Pb定年实验仪器参数

Table 1 Instrumental parameters for LA-ICP-MS U-Pb dating of apatite.

LA参数	GeoLas HD 193nm准分子激光
波长	193nm
激光能量密度	10J/cm²
剥蚀频率	5Hz
剥蚀时间	50s
背景时间	20s
He流速	650mL/min
束斑直径	60～90μm
ICP-MS参数	Agilent 7900型
等离子体功率	1400W
样品气	0.86L/min
检测元素	²⁹Si，⁴²Ca，⁴⁹Ti，⁵¹V，⁸⁹Y，⁹³Nb，¹³⁹La，¹⁴⁰Ce， ¹⁴¹Pr，¹⁴⁶Nd，¹⁴⁷Sm，¹⁵¹Eu，¹⁵⁷Gd，¹⁵⁹Tb，¹⁶³Dy， ¹⁶⁵Ho，¹⁶⁶Er，¹⁶⁹Tm，¹⁷³Yb，¹⁷⁵Lu，¹⁷⁹Hf，¹⁸¹Ta， ²⁰¹Hg，²⁰⁴Pb，²⁰⁶Pb，²⁰⁷Pb，²⁰⁸Pb，²³²Th，²³⁸U

下载: 导出CSV

表 2 不同测量条件下获得的磷灰石Tera-Wasserburg谐和图下交点年龄与推荐值的偏差

Table 2 Deviations of Tera-Wasserburg values and recommended values for apatite U-Pb age obtained under different measurement conditions.

激光条件	外标	普通铅校正方法	分析样品	Tera-Wasserburg谐和图下交点年龄与推荐值的偏差(%)
60μm，5Hz	MAD	无普通铅校正	Otter Lake	2.5
60μm，5Hz	MAD	无普通铅校正	Durango	6.0
60μm，5Hz	MAD	²⁰⁷Pb	Otter Lake	0.03
60μm，5Hz	MAD	²⁰⁷Pb	Durango	1.7
60μm，5Hz	MAD	Tera-Wasserburg图解法	Otter Lake	1.7
60μm，5Hz	MAD	Tera-Wasserburg图解法	Durango	6.6
60μm，5Hz	NIST612	无普通铅校正	MAD	0.1
			Otter Lake	2.3
			Durango	0.8

下载: 导出CSV

参考文献(37)

[1]	Abdullin F, Solé J, Solari L, et al. Single-grain apatite geochemistry of Permian–Triassic granitoids and Mesozoic and Eocene sandstones from Chiapas, Southeast Mexico: Implications for sediment provenance[J]. International Geology Review, 2016, 58(9): 1132−1157. doi: 10.1080/00206814.2016.1150212
[2]	Krestianinov E, Amelin Y, Neymark L A, et al. U-Pb systematics of uranium-rich apatite from adirondacks: Inferences about regional geological and geochemical evolution, and evaluation of apatite reference materials for in situ dating[J]. Chemical Geology, 2021, 581: 120417. doi: 10.1016/j.chemgeo.2021.120417
[3]	Li Q L, Li X H, Wu F Y, et al. In-situ SIMS U-Pb dating of phanerozoic apatite with low U and high common Pb[J]. Gondwana Research, 2012, 21(4): 745−756. doi: 10.1016/j.gr.2011.07.008
[4]	罗涛, 胡兆初. 激光剥蚀电感耦合等离子体质谱副矿物 U-Th-Pb 定年新进展[J]. 地球科学, 2022, 47(11): 4122−4144. Luo T, Hu Z C. Recent advances in U-Th-Pb dating of accessory minerals by laser ablation inductively coupled plasma mass spectrometry[J]. Earth Science, 2022, 47(11): 4122−4144.
[5]	Pochon A, Poujol M, Gloaguen E, et al. U-Pb LA-ICP-MS dating of apatite in mafic rocks: Evidence for a major magmatic event at the Devonian—Carboniferous boundary in the Armorican Massif (France)[J]. American Mineralogist, 2016, 101(11): 2430−2442. doi: 10.2138/am-2016-5736
[6]	Morrison J L, Kirkland C L, Fiorentini M, et al. An apatite to unravel petrogenic processes of the Nova-Bollinger Ni-Cu magmatic sulfide deposit, Western Australia[J]. Precambrian Research, 2022, 369: 106524. doi: 10.1016/j.precamres.2021.106524
[7]	Rochín-Bañaga H, Davis D W, Schwennicke T. First U-Pb dating of fossilized soft tissue using a new approach to paleontological chronometry[J]. Geology, 2021, 49(9): 1027−1031. doi: 10.1130/G48386.1
[8]	Rochín-Bañaga H, Davis D W. Insights into U-Th-Pb mobility during diagenesis from laser ablation U-Pb dating of apatite fossils[J]. Chemical Geology, 2023, 618: 121290. doi: 10.1016/j.chemgeo.2022.121290
[9]	罗涛, 卿丽媛, 刘金雨, 等. 激光剥蚀电感耦合等离子体质谱法测定碳酸盐矿物中元素组成[J]. 岩矿测试, 2023, 42(5): 996−1006. Luo T, Qing L Y, Liu J Y, et al. Accurate determination of elemental contents in carbonate minerals with laser ablation inductively coupled plasma-mass spectrometry[J]. Rock and Mineral Analysis, 2023, 42(5): 996−1006.
[10]	Lv N, Bao Z A, Chen K Y, et al. Accurate determination of Cu isotopes in bronze by fsLA-MC-ICP-MS[J]. Atomic Spectroscopy, 2023, 44(6): 418−426. doi: 10.46770/AS.2023.282
[11]	Liu H, Feng Y, Li M, et al. Further characterization of four natural ilmenite reference materials for in situ Fe isotopic analysis[J]. Atomic Spectroscopy, 2023, 44(6): 409−417. doi: 10.46770/AS.2023.281
[12]	Chew D M, Sylvester P J, Tubrett M N. U-Pb and Th-Pb dating of apatite by LA-ICPMS[J]. Chemical Geology, 2011, 280(1−2): 200−216. doi: 10.1016/j.chemgeo.2010.11.010
[13]	Luo T, Hu Z, Zhang W, et al. Water vapor-assisted “universal” nonmatrix-matched analytical method for the in situ U-Pb dating of zircon, monazite, titanite, and xenotime by laser ablation-inductively coupled plasma mass spectrometry[J]. Analytical Chemistry, 2018, 90(15): 9016−9024. doi: 10.1021/acs.analchem.8b01231
[14]	Zhang W, Zhao S, Sun J, et al. Late Mesozoic tectono-thermal history in the south margin of Great Xing’an Range, NE China: Insights from zircon and apatite (U-Th)/He ages[J]. Journal of Earth Science, 2022, 33(1): 36−44. doi: 10.1007/s12583-021-1537-5
[15]	Chew D M, Spikings R A. Apatite U-Pb thermochronology: A review[J]. Minerals, 2021, 11(10): 1095. doi: 10.3390/min11101095
[16]	Apen F E, Wall C J, Cottle J M, et al. Apatites for destruction: Reference apatites from Morocco and Brazil for U-Pb petrochronology and Nd and Sr isotope geochemistry[J]. Chemical Geology, 2022, 590: 120689. doi: 10.1016/j.chemgeo.2021.120689
[17]	Duan L J, Zhang L L, Zhu D C, et al. Apatite MAP-3: A new homogeneous and low common lead natural reference for laser in situ U-Pb dating and Nd isotope analysis[J]. Journal of Analytical Atomic Spectrometry, 2023, 38(7): 1478−1493. doi: 10.1039/D2JA00405D
[18]	Abdullin F, Solari L, Solé J, et al. On LA-ICP-MS U-Pb dating of unetched and etched apatites[J]. Geochronology, 2020, 2020: 1−23.
[19]	Lana C, Gonçalves G O, Mazoz A, et al. Assessing the U-Pb, Sm‐Nd and Sr‐Sr isotopic compositions of the Sumé apatite as a reference material for LA‐ICP‐MS analysis[J]. Geostandards Geoanalytical Research, 2022, 46(1): 71−95. doi: 10.1111/ggr.12413
[20]	Thomson S N, Gehrels G E, Ruiz J, et al. Routine low-damage apatite U-Pb dating using laser ablation-multicollector-ICPMS[J]. Geochemistry, Geophysics, Geosystems, 2012, 13(2): 1−23.
[21]	Chew D, Petrus J, Kamber B. U-Pb LA-ICPMS dating using accessory mineral standards with variable common Pb[J]. Chemical Geology, 2014, 363: 185−199. doi: 10.1016/j.chemgeo.2013.11.006
[22]	Storey C, Smith M, Jeffries T. In situ LA-ICP-MS U-Pb dating of Metavolcanics of Norrbotten, Sweden: Records of extended geological histories in complex titanite grains[J]. Chemical Geology, 2007, 240(1−2): 163−181. doi: 10.1016/j.chemgeo.2007.02.004
[23]	Hou Z, Xiao Y, Shen J, et al. In situ rutile U-Pb dating based on zircon calibration using LA-ICP-MS, geological applications in the Dabie Orogen, China[J]. Journal of Asian Earth Sciences, 2020, 192: 104261. doi: 10.1016/j.jseaes.2020.104261
[24]	Luo T, Zhao H, Zhang W, et al. Non-matrix-matched analysis of U-Th-Pb geochronology of Bastnäsite by laser ablation inductively coupled plasma mass spectrometry[J]. Science China: Earth Sciences, 2021, 64(4): 667−676. doi: 10.1007/s11430-020-9715-1
[25]	Luo T, Deng X, Li J, et al. U-Pb geochronology of wolframite by laser ablation inductively coupled plasma mass spectrometry[J]. Journal of Analytical Atomic Spectrometry, 2019, 34(7): 1439−1446. doi: 10.1039/C9JA00139E
[26]	Paul A N, Spikings R A, Chew D, et al. The effect of intra-crystal uranium zonation on apatite U-Pb thermo-chronology: A combined ID-TIMS and LA-MC-ICP-MS study[J]. Geochimica et Cosmochimica Acta, 2019, 251: 15−35. doi: 10.1016/j.gca.2019.02.013
[27]	McDowell F W, McIntosh W C, Farley K A. A precise ⁴⁰Ar-³⁹Ar reference age for the durango apatite (U-Th)/He and fission-track dating standard[J]. Chemical Geology, 2005, 214(3−4): 249−263. doi: 10.1016/j.chemgeo.2004.10.002
[28]	Thompson J, Meffre S, Maas R, et al. Matrix effects in Pb/U measurements during LA-ICP-MS analysis of the mineral apatite[J]. Journal of Analytical Atomic Spectrometry, 2016, 31(6): 1206−1215. doi: 10.1039/C6JA00048G
[29]	Jochum K P, Weis U, Stoll B, et al. Determination of reference values for NIST SRM610−617 glasses following ISO guidelines[J]. Geostandards and Geoanalytical Research, 2011, 35(4): 397−429. doi: 10.1111/j.1751-908X.2011.00120.x
[30]	Mcfarlane C R M. Allanite U-Pb geochronology by 193nm LA-ICP-MS using NIST610 glass for external calibration[J]. Chemical Geology, 2016, 438: 91−102. doi: 10.1016/j.chemgeo.2016.05.026
[31]	Miyajima Y, Saito A, Kagi H, et al. Incorporation of U, Pb and rare earth elements in calcite through crystallisation from amorphous calcium carbonate: Simple preparation of reference materials for microanalysis[J]. Geostandards Geoanalytical Research, 2021, 45(1): 189−205. doi: 10.1111/ggr.12367
[32]	Roberts N M, Rasbury E T, Parrish R R, et al. A calcite reference material for LA‐ICP‐MS U‐Pb geochronology[J]. Geochemistry, Geophysics, Geosystems, 2017, 18(7): 2807−2814. doi: 10.1002/2016GC006784
[33]	Paton C, Woodhead J D, Hellstrom J C, et al. Improved laser ablation U-Pb zircon geochronology through robust downhole fractionation correction[J]. Geochemistry, Geophysics, Geosystems, 2010, 11(3): Q0AA06.
[34]	Vermeesch P. Isoplot R: A free and open toolbox for geochronology[J]. Geoscience Frontiers, 2018, 9(5): 1479−1493. doi: 10.1016/j.gsf.2018.04.001
[35]	Stacey J, Kramers J. Approximation of terrestrial lead isotope evolution by a two-stage model[J]. Earth and Planetary Science Letters, 1975, 26(2): 207−221. doi: 10.1016/0012-821X(75)90088-6
[36]	Schaltegger U, Schmitt A, Horstwood M. U‐Th‐Pb zircon geochronology by ID-TIMS, SIMS, and laser ablation ICP-MS: Recipes, interpretations, and opportunities[J]. Chemical Geology, 2015, 402: 89−110. doi: 10.1016/j.chemgeo.2015.02.028
[37]	赵令浩, 詹秀春, 曾令森, 等. 磷灰石LA-ICP-MS U-Pb定年直接校准方法研究[J]. 岩矿测试, 2022, 41(5): 744−753. Zhao L H, Zhan X C, Zeng L S, et al. Direct calibration method for LA-HR-ICP-MS apatite U-Pb dating[J]. Rock and Mineral Analysis, 2022, 41(5): 744−753.

施引文献

资源附件(1)

其他相关附件
- 本文图文摘要
  10.15898-j.ykcs.202404070079-GA1 点击下载

图(5) / 表(2)

计量

文章访问数: 204
HTML全文浏览量: 92
PDF下载量: 78
被引次数: 0

1. 实验部分
1.1 实验仪器
1.2 实验样品和分析方法
2. 结果与讨论
2.1 信号强度对分析精度的影响
2.2 磷灰石U-Pb年龄基体匹配分析
2.2.1 磷灰石MAD直接校正结果
2.2.2 207Pb法普通铅校正结果
2.2.3 Tera-Wasserburg图解法普通铅校正结果
2.3 磷灰石U-Pb年龄非基体匹配分析
2.4 不同分析方法结果对比
3. 结论

1. 实验部分
1.1 实验仪器
1.2 实验样品和分析方法
2. 结果与讨论
2.1 信号强度对分析精度的影响
2.2 磷灰石U-Pb年龄基体匹配分析
2.2.1 磷灰石MAD直接校正结果
2.2.2 ²⁰⁷Pb法普通铅校正结果
2.2.3 Tera-Wasserburg图解法普通铅校正结果
2.3 磷灰石U-Pb年龄非基体匹配分析
2.4 不同分析方法结果对比
3. 结论

参考文献(37)

施引文献

资源附件(1)

普通铅对LA-ICP-MS磷灰石U-Pb定年结果的影响及校正方法

作者简介: 罗涛，博士，副研究员，主要从事副矿物U-Th-Pb年代学和激光剥蚀电感耦合等离子体质谱机理研究。E-mail：luotao11@cug.edu.cn

计量

出版历程