Red Earth, Green Glass, and Compositional Data: A New Procedure for Solid-State Elemental Characterization, Source Discrimination, and Provenience Analysis of Ochres
Red Earth, Green Glass, and Compositional Data: A New Procedure for Solid-State Elemental Characterization, Source Discrimination, and Provenience Analysis of Ochres
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DOI：
10.1007/s10816-020-09448-9
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发表时间：
2020-02-22
影响因子：
2.3
通讯作者：
Taylor, Alexander H.
中科院分区：
文献类型：
--
作者：
Zipkin, Andrew M.;Ambrose, Stanley H.;Taylor, Alexander H.
赭石是一种自然形成的富铁的土壤和岩石，以及氧化铁矿物，它们的颜色来自含铁的生色团，适合用作颜料。在过去的二十年里，对考古赭石的起源研究已经从一个只有专家才感兴趣的稀有项目发展成为考古科学中公认和预期的一部分。要区分赭石的来源并确定考古颜料的来源，最有效的方法是多元素表征或“元素指纹”。在这项研究中，我们使用了一种以前没有在赭石考古中使用的样品制备方法，并结合了激光烧蚀-电感耦合等离子体质谱(LA-ICP-MS)和电子探针显微分析(EPMA)的元素指纹图谱。我们提出了一种用于固态分析的硼酸锂(LiBO)熔融样品的程序，该程序优化了与OERE一起使用，并为许多专业和学生考古学家面临的预算和实验室设备限制而设计。这项方法开发研究是更广泛的项目“Olkaria：肯尼亚的赭石景观--人类学研究和氧化铁考古”的一部分，该项目的部分目的是确定肯尼亚裂谷所有已知的赭石地质来源的元素组成。利用LiBO Fusion制备的Olkaria工程样品子集，用LA-ICPMS和EPMA进行了测量，成功地区分了六种地质赭石来源和一种商用氧化铁颜料样品。我们对这一数据集支持证据假设的能力，与使用相同样品的整个奥克雷的中子活化分析(NAA)数据所做的来源判别分析相比，是有利的。LiBO熔融提供了潜在的解决方案，解决了使用束流技术对赭石进行固态分析的一些批评，包括由于矿物学不均一性、表面地形变化、存在自由水和化学结合水以及缺乏与基质匹配的标准参考物质所引起的问题。我们还讨论了将成分数据分析最佳做法应用于人道协调厅的挑战，重点是四舍五入的零替换和多元正态问题，并强调了这一领域仍需完成的工作。
Ochres are a diverse category of naturally occurring iron-enriched earths and rocks, as well as iron oxide minerals, that derive their color from iron-containing chromophores and are suitable for use as pigments. Over the last two decades, provenience studies of archaeological ochres have grown from a rarity largely of interest only to specialists to an accepted and expected part of the archaeological science panoply. The most effective approach to distinguishing among sources of ochre and assigning archaeological pigments to their origin is multi-elemental characterization or "elemental fingerprinting." In this study, we coupled a sample preparation method not previously used in ochre archaeometry with elemental fingerprinting by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) and Electron Probe MicroAnalysis (EPMA). We present a procedure for lithium borate (LiBo) fusion of samples for solid-state analysis, optimized for use with ochres, and designed for the budget and laboratory equipment constraints faced by many professional and student archaeologists. This method development research is part of the broader project "OLKARIA: Ochre Landscapes of Kenya - Anthropological Research and Iron-oxide Archaeometry," which seeks in part to characterize the elemental composition of all known geologic ochre sources in the Kenya Rift Valley. Using a subset of project OLKARIA samples prepared by LiBo fusion and measured with LA-ICP-MS and EPMA, we successfully distinguished among six geologic ochre sources and a sample of commercially available iron oxide pigment. Our ability to uphold the Provenience Postulate for this data set compared favorably with source discrimination analyses done using data from Neutron Activation Analysis (NAA) of whole ochre for the same samples. LiBo fusion presents potential solutions to some criticisms of solid-state analysis of ochre using beam techniques, including issues arising from mineralogical heterogeneity, variable surface topography, the presence of free and chemically bound water, and the lack of matrix-matched standard reference materials. We also address the challenges of applying compositional data analysis best practices to ochre with an emphasis on the issues of rounded zero replacement and multivariate normality and highlight the work that remains to be done in this area.