A Synthetic Haematite Reference Material for LA‐ICP‐MS U‐Pb Geochronology and Application to Iron Oxide‐Cu‐Au Systems,Geostandards and Geoanalytical Research

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A Synthetic Haematite Reference Material for LA‐ICP‐MS U‐Pb Geochronology and Application to Iron Oxide‐Cu‐Au Systems
Geostandards and Geoanalytical Research ( IF 2.7 ) Pub Date : 2020-10-17 , DOI: 10.1111/ggr.12365
Liam Courtney‐Davies ₁ , Sarah E. Gilbert ₂ , Cristiana L. Ciobanu ₁ , Simon R. Tapster ₃ , Marcus W. Richardson ₄ , Nigel J. Cook ₅ , Benjamin P. Wade ₂ , Max R. Verdugo‐Ihl ₁ , Kathy Ehrig ₆ , Daniel J. Condon ₃

Affiliation

In both nature and synthetic experiments, the common iron oxide haematite (α‐Fe₂O₃) can incorporate significant amounts of U into its crystal structure and retain radiogenic Pb over geological time. Haematite is a ubiquitous component of many ore deposit types and, therefore, represents a valuable hydrothermal mineral geochronometer, allowing direct constraints to be placed on the timing of ore formation and upgrading. However, to date, no suitable natural haematite reference material has been identified. Here, a synthetic haematite U‐Pb reference material (MR‐HFO) is characterised using LA‐ICP‐MS and ID‐TIMS. Centimetre‐scale ‘chips’ of synthesised α‐Fe₂O₃ were randomly microsampled via laser ablation‐extraction and analysed using ID‐TIMS. Reproducible U/Pb and Pb/Pb measurements were obtained across four separate chips (n = 13). Subsequently, an evaluation of the suitability MR‐HFO in constraining U‐Pb data via LA‐ICP‐MS is presented using a selection of natural samples ranging from Cenozoic to Proterozoic in age. The MR‐HFO normalised U‐Pb ratios are more concordant and ages more accurate versus the same LA‐ICP‐MS spot analyses normalised to zircon reference material, when compared with independently acquired ID‐TIMS data from the same natural haematite grains. Results establish MR‐HFO as a suitable reference material for LA‐ICP‐MS haematite U‐Pb geochronology.

中文翻译：

用于LA‐ICP‐MS U-Pb年代学的合成赤铁矿参考材料及其在氧化铁-Cu-Au系统中的应用

在这两种性质和合成的实验中，将共同的氧化铁赤铁矿（α-的Fe ₂ ö ₃）可以结合显著量U形成其晶体结构和过地质时间保留放射性铅。赤铁矿是许多矿床类型中普遍存在的成分，因此，它是一种有价值的热液矿物时计，可以直接限制成矿和提质的时间。然而，迄今为止，尚未鉴定出合适的天然赤铁矿参考物质。在这里，使用LA‐ICP‐MS和ID‐TIMS对合成的赤铁矿U‐Pb参考材料（MR‐HFO）进行了表征。合成的厘米刻度“芯片”的α-Fe ₂ ö ₃通过激光消融提取随机取样，并使用ID-TIMS进行分析。在四个独立的芯片（n = 13）上获得了可重现的U / Pb和Pb / Pb测量值。随后，使用年龄从新生代到元古代的一系列自然样本，对通过LA-ICP-MS约束U-Pb数据的MR-HFO的适用性进行了评估。与从同一天然赤铁矿晶粒中独立获取的ID-TIMS数据相比，MR-HFO归一化U-Pb比率与归一化为锆石参考材料的同一LA-ICP-MS斑点分析相比更加一致，且年龄更准确。结果确定MR-HFO作为LA-ICP-MS赤铁矿U-Pb地球年代学的合适参考材料。

更新日期：2020-10-17

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