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在U-Pb石地质年代学中最大限度地减少可变的下洞分离,通过LA-MC-ICP-MS在较小的点尺寸上进行

Saurabh Singhal^1,2, Sandeep Singh³, Dharmendra Singh²

¹Wadia Institute of Himalayan Geology, Dehradun, India.

Journal of mass spectrometry : JMS

|February 19, 2025

概括

这项研究优化了激光剥离感应合等离子体质谱法 (LA-ICPMS),以在小点尺寸上获得准确的U-Pb约会. 改进了方法,以最大限度地减少下洞分化 (DHF),以提高地质年代学中的精度.

科学领域:

地质时间学 (Geochronology)
同位素地球化学同位素地球化学
分析化学分析化学

背景情况:

激光除感应合等离子体质谱法 (LA-ICPMS) 和LA-MC-ICPMS是使用20-60μm点大小的已建立的土时间学方法.
复杂地划分的石需要U-Pb在较小的斑点大小,但减少的斑点大小增加下孔分化 (DHF).
增加的DHF会导致石颗粒与参考标准之间的差异,从而影响到年龄的准确性.

研究的目的:

开发和验证使用空间分辨率低于20微米的石精确的U-Pb测年.
为了研究和减轻低孔分成 (DHF) 在减少点大小的影响.
为了提高LA-MC-ICPMS的精度和准确性,用于高分辨率的地质年代应用.

主要方法:

测试了三个标准 (91500,GJ-1,Plešovice) 在 35,20,15 和 10 微米的点大小.
优化了激光和质谱调整,激光射击计数和切除时间,以最大限度地减少DHF.
采用静态除,并分析了掩盖除末期射击计数对精度的影响.

主要成果:

通过使用35-15μm斑点和150次激光射 (30秒) 的静态除,实现了<1.5%的精度和<2%的年龄偏移.
在10微米的点尺寸下,显著的DHF导致与参考标准相比4%的年龄偏移.
掩蔽射击计数提高了精度,75次激光射击产生1.4%的精度和1.6%的206Pb/238U年龄偏移.

结论:

优化的LA-MC-ICPMS方法使得在小于20微米的点尺寸下准确的U-Pb石测年法.
尽量减少激光射击数量和优化除参数可以有效地减少DHF并提高年龄的准确性.
在较小的点尺寸中,石DHF的高可变性仍然是影响优点分析数据的因素.

关键词:

在LA-MCICP-MS中使用.UPb地质年代学下洞分成部分的分成部分.齐尔康 (Zircon) 是一种的材料.

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