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Characterization of the zircon Ce anomaly for estimation of oxidation state of magmas: a revised Ce/Ce* method
Mineralogy and Petrology ( IF 1.4 ) Pub Date : 2019-08-29 , DOI: 10.1007/s00710-019-00682-y
Shihua Zhong , Reimar Seltmann , Hongying Qu , Yingxin Song

As a proxy of magmatic oxidation state, the accurate characterization of the Ce anomaly of zircon is of great significance since it can give important information for provenance studies of rocks as well as for exploration of intrusion-related mineral deposits. The magnitude of the zircon Ce anomaly has been traditionally described by Ce/Ce*, where Ce* is the theoretical Ce value derived from a chondrite-normalized rare earth element (REE) pattern. More recently, the Ce4+/Ce3+ method based on the lattice strain model has been proposed, since the latter method does not need La and Pr contents for zircon, both of which are commonly below the limit of detection and susceptible to contamination from melt/mineral inclusions. In this contribution we show that the Ce4+/Ce3+ method is confronted with some problems in practice and should be further improved. In contrast, by re-examining chondrite-normalized REE patterns of zircon, we find that Ce* can be estimated according to a logarithmic function curve without involvement of La and Pr contents. Application of this new method to zircon data from 11 giant to supergiant porphyry Cu deposits suggests this revised method as a more valid measure in evaluating magmatic oxidation state. The revised Ce/Ce* method is of particular importance for analyses where the provenance of the analyzed zircon is unknown or in question, since the method does not require knowledge of the melt composition.

中文翻译:

用于估计岩浆氧化态的锆石 Ce 异常特征:修正的 Ce / Ce * 方法

作为岩浆氧化态的代表,锆石Ce异常的准确表征具有重要意义,因为它可以为岩石物源研究以及与侵入相关的矿床勘探提供重要信息。锆石 Ce 异常的大小传统上用 Ce / Ce * 描述,其中 Ce * 是从球粒陨石归一化稀土元素 (REE) 模式得出的理论 Ce 值。最近,有人提出了基于晶格应变模型的 Ce4 + / Ce3 + 方法,因为后一种方法不需要锆石的 La 和 Pr 含量,这两种含量通常都低于检测限并且容易受到熔体污染/ 矿物包裹体。在这个贡献中,我们表明 Ce4 + / Ce3 + 方法在实践中面临一些问题,应该进一步改进。相反,通过重新检查锆石球粒陨石归一化的 REE 模式,我们发现可以根据对数函数曲线估算 Ce * ,而无需涉及 La 和 Pr 含量。将这种新方法应用于 11 个巨型到超巨型斑岩铜矿床的锆石数据表明,这种修改后的方法是评估岩浆氧化状态的更有效措施。修订后的 Ce / Ce * 方法对于分析锆石的来源未知或存在疑问的分析特别重要,因为该方法不需要了解熔体成分。将这种新方法应用于 11 个巨型到超巨型斑岩铜矿床的锆石数据表明,这种修改后的方法是评估岩浆氧化状态的更有效措施。修订后的 Ce / Ce * 方法对于分析锆石的来源未知或存在疑问的分析特别重要,因为该方法不需要了解熔体成分。将这种新方法应用于 11 个巨型到超巨型斑岩铜矿床的锆石数据表明,这种修改后的方法是评估岩浆氧化状态的更有效措施。修订后的 Ce / Ce * 方法对于分析锆石的来源未知或存在疑问的分析特别重要,因为该方法不需要了解熔体成分。
更新日期:2019-08-29
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