Chemical and oxygen isotope composition of gem-quality apatites: Implications for oxygen isotope reference materials for secondary ion mass spectrometry (SIMS)
Chemical and oxygen isotope composition of gem-quality apatites: Implications for oxygen isotope reference materials for secondary ion mass spectrometry (SIMS)
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DOI：
10.1016/j.chemgeo.2016.07.013
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发表时间：
2016-11
期刊：
影响因子：
3.9
通讯作者：
Yadong Sun;M. Wiedenbeck;M. Joachimski;C. Beier;Fabian Kemner;C. Weinzierl
中科院分区：
文献类型：
--
作者：
Yadong Sun;M. Wiedenbeck;M. Joachimski;C. Beier;Fabian Kemner;C. Weinzierl
过去，生物磷灰石的氧同位素比值(δ18O)已成为重建古环境条件的一种广泛使用的工具。二次离子质谱仪(SIMS)技术的不断改进使得在单个微化石样品中进行亚纳克域的原位δ18O分析成为可能；然而，这种方法需要用与样品的矩阵“相似”的标准物质(RMS)进行校准。在这里，我们评估了五种宝石级非生物成因磷灰石的来源，以评估它们作为SIMS RMS的潜力。结果表明，这些宝石级磷灰石均为低稀土氟化钙磷灰石，δ为18OVSMOW值在6.6%~11.4%‰之间。在单个矿床的晶体之间以及单个晶体内，δ18O的变化很大。杜兰戈磷灰石的晶间δ18O范围为4.4‰(6.6-11.0‰，N=9个晶体)。马达加斯加绿色磷灰石、马达加斯加一矿磷灰石和Ipira磷灰石的δ18O晶间变化分别为4.1‰(7.3-11.4‰，N=1.15晶体)、3.5‰(7.6-11.1‰，N=9.9晶体)和3.1‰(7.1-10.2‰，N=1111晶体)。南非蓝色磷灰石的晶间δ18O范围较小，仅为0.9‰(8.7-9.6‰，N=9.6晶体)，尽管这可能是一个人工制品，因为研究的样品数量有限。所研究晶体的晶内δ18O变化一般在0.8~1.8‰之间。然而，马达加斯加的几个宝石磷灰石晶体的δ18O变化在0.5RM以内，是最有希望的候选‰。宝石质量的非生物磷灰石可以作为均方根用于校准SIMS的δ18O分析，但这需要提前进行亚毫米尺度的均质测试。杜兰戈晶体在早期基于SIMS的研究中通常用作RMS，在δ18O中显示出明显的非均质性，通过气源同位素比质谱仪和大几何SIMS检测到的晶内变化范围为0.70-2‰。因此，杜兰戈磷灰石不能被认为适合于SIMS校准，需要寻找替代的参考材料。
Oxygen isotope ratios (δ18O) of biogenic apatite have become a widely used tool for reconstructing palaeoenvironmental conditions in the past. Ongoing improvements in secondary ion mass spectrometry (SIMS) technology have madein situδ18O analyses on sub-nanogram domains within single microfossil samples possible; however this method requires calibration with reference materials (RMs) with a matrix “similar” to that of the samples. Here we evaluated five sources of gem-quality, abiogenic apatites to assess their potentials as SIMS RMs. Our results show that all these gem-quality apatites are low-REEs calcium fluorapatites with δ18OVSMOWvalues between 6.6 and 11.4‰. Large variations in δ18O have been found for between crystals from a single deposit as well as within individual crystals. Durango apatite has an inter-crystal δ18O range of 4.4‰ (6.6–11.0‰,N= 9 crystals). Madagascar Green apatite, Madagascar 1st Mine apatite and Ipira apatite have inter-crystal variations in δ18O of 4.1‰ (7.3–11.4‰,N= 15 crystals), 3.5‰ (7.6–11.1‰,N= 9 crystals) and 3.1‰ (7.1–10.2‰,N= 11 crystals), respectively. South Africa Blue apatite has a smaller inter-crystal δ18O range of only 0.9‰ (8.7–9.6‰,N= 6 crystals), though this might be an artefact due to the restricted number of samples studied. Intra-crystal δ18O variations of studied crystals generally range from 0.8 to 1.8‰. However, several gem apatite crystals from Madagascar have minor δ18O variation within 0.5‰ and represent most promising candidate RM.Gem-quality abiogenic apatites can be used as RMs for calibrating SIMS δ18O analyses, however these require homogeneity testing at sub-millimetre scale in advance. Durango crystals, commonly used as RMs in earlier SIMS-based studies, display a conspicuous heterogeneity in δ18O, with intra-crystal variations ranging from 0.7 to 2‰ as detected by both gas source isotope ratio mass spectrometry and large geometry SIMS. Thus, Durango apatite cannot be considered as suitable for SIMS calibration and alternative reference materials need to be sought.