Radiation damage in zircon
Radiation damage in zircon
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DOI：
10.2138/am-2003-5-606
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发表时间：
2003-05
影响因子：
3.1
通讯作者：
C. Palenik;L. Nasdala;R. Ewing
中科院分区：
文献类型：
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作者：
C. Palenik;L. Nasdala;R. Ewing
斯里兰卡单一环带锆石具有从结晶到近无定形的一系列微观结构，这些微观结构是在2.1-10.1·1015 α衰变事件/ mg（0.16-0.47 dpa）剂量范围内辐射损伤的结果。使用光学显微镜、显微拉曼光谱、电子探针分析和透射电子显微镜在各种长度尺度下检查晶体中的区域。双折射率与剂量呈线性关系：双折射率= -4.71统计10 -18 /g·Dα + 4.86·10-2。通过显微拉曼光谱测定的B1 g（ν3）峰的半高宽（FWHM）测量值用于估计每个区域的辐射损伤程度。辐射剂量（U和Th浓度和样品年龄的基础上计算）与损害（从半高宽测量的B1 g（n3）峰）区域之间的关系是一致的结果，一套斯里兰卡单晶，这表明所有这些锆石晶体经历了类似的热历史。基于与被认为经历了最小退火的锆石晶体的比较（例如，根据计算的剂量，斯里兰卡锆石晶体累积的损害比预期的要少，这与以前的退火证据一致。为了估计斯里兰卡样品中退火的程度，等效损伤剂量（即，在未退火的样品中产生相同量的损伤所需的剂量），通过确定在未退火的锆石中产生等量损伤所需的损伤累积时间来计算给定的U和Th浓度。斯里兰卡锆石晶体（560 Ma）中的剂量与损伤关系相当于~375 Ma未退火锆石的剂量与损伤关系，这表明约三分之一的损伤已因退火而丧失。剂量-损伤关系符合损伤累积的直接撞击模型。透射电子显微镜显示分区的规模比可以识别的光学（<0.5 μm）和丰富的ZrO 2纳米粒子的存在下，在区域边界。
Abstract A single, zoned, Sri Lankan zircon exhibits a range of microstructures from crystalline to nearly amorphous that are the result of radiation damage over a dose range of 2.1-10.1·1015 α-decay events/ mg (0.16-0.47 dpa). The zones in the crystal were examined at a variety of length scales using optical microscopy, micro-Raman spectroscopy, electron microprobe analysis, and transmission electron microscopy. Birefringence varies linearly with dose: birefringence = -4.71·10-18 /g·Dα + 4.86·10-2. Full width at half maximum (FWHM) measurements of the B1g(ν3) peak, as determined by micro-Raman spectroscopy, were used to estimate the extent of radiation damage in each zone. The radiation dose (calculated on the basis of U and Th concentrations and sample age) vs. damage (from the FWHM measurements of the B1g(n3) peak) relationship among zones was consistent with results for a suite of Sri Lankan single crystals, suggesting that all of these zircon crystals have undergone a similar thermal history. Based on a comparison with zircon crystals that are considered to have undergone minimal annealing (e.g., lunar zircon), the Sri Lankan zircon crystals have accumulated less damage than is expected based on their calculated dose, consistent with previous evidence for annealing. To estimate the extent of annealing in Sri Lankan samples, an equivalent damage dose (i.e., the dose required to produce the same amount of damage in an unannealed sample) was calculated for a given U and Th concentration by determining the time of damage accumulation required to create an equivalent amount of damage in an unannealed zircon. The dose vs. damage relationship in Sri Lankan zircon crystals (560 Ma) is equivalent to that of a ~375 Ma unannealed zircon, suggesting that approximately one-third of the damage has been lost due to annealing. The dose vs. damage relationship is consistent with the direct impact model of damage accumulation. Transmission electron microscopy revealed zoning on a scale finer than could be identified optically (<0.5 μm) and the presence of abundant ZrO2 nano-particles at zone boundaries.