Abstract In this study, we provide a microsampling method that determines the Cu isotopic composition of copper-bearing minerals using the microdrill sampling and MC-ICP-MS measurement. Eleven different natural copper minerals were sampled with microdrill and analyzed using MC-ICP-MS after digestion for half an hour on a 140 °C hot plate without chromatography. The Cu isotope results were calibrated using the standard sample bracketing combined with NIST 994 Ga as the internal standard. Cu isotope compositions of the same sample processed with chromatography were also determined to verify the accuracy of this method. Results have shown that δ65Cu of all sample solutions with or without chromatography are overlapped and the deviations between them are less than 0.04‰, indicating this method is applicable to most natural copper-bearing minerals. All the microdrill-sampled copper minerals were directly digested without chemical purification, thus potential matrix elements, including metal cations and some anions, still existed in the solutions. The matrix effects of metal cations and anions were systematically investigated in this study. Results have shown that the δ65Cu deviations are less than 0.05‰ within the uncertainty when the concentration ratios of matrix elements Zn, Fe, Ni, Al, Sb, and Co/Cu + S were less than 2, Ti/Cu + S ≤ 0.8, and Mn/Cu + S ≤ 0.5. This method has the merits of saving time and reagents, low background, good accuracy and reliability as well as improved spatial resolution. It is easier to achieve in most isotope laboratories compared to other microsampling methods such as laser ablation method.

中文翻译：

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使用微钻和 MC-ICP-MS 准确测定含铜矿物中的铜同位素组成

摘要 在本研究中，我们提供了一种微量采样方法，该方法使用微钻采样和 MC-ICP-MS 测量来确定含铜矿物的 Cu 同位素组成。使用微钻对 11 种不同的天然铜矿物进行采样，并在 140 °C 热板上消解半小时后使用 MC-ICP-MS 进行分析，无需色谱法。使用标准样品括号法和 NIST 994 Ga 作为内标对 Cu 同位素结果进行校准。还测定了用色谱法处理的同一样品的 Cu 同位素组成，以验证该方法的准确性。结果表明，无论有无色谱，所有样品溶液的δ65Cu均存在重叠，两者之间的偏差均小于0.04‰，表明该方法适用于大多数天然含铜矿物。所有微钻采集的铜矿物均未经化学纯化直接消化，因此溶液中仍存在潜在的基质元素，包括金属阳离子和一些阴离子。本研究系统地研究了金属阳离子和阴离子的基体效应。结果表明，当基体元素Zn、Fe、Ni、Al、Sb和Co/Cu+S的浓度比小于2，Ti/Cu+S≤0.8时，δ65Cu偏差在不确定度范围内小于0.05‰ , 和 Mn/Cu + S ≤ 0.5。该方法具有省时省试剂、本底低、准确度和可靠性好、空间分辨率提高等优点。与激光烧蚀法等其他微量采样方法相比，在大多数同位素实验室中更容易实现。