Multi-aliquot method for determining (U-Th)/He ages of hydrothermal hematite: Returning to Elba
Multi-aliquot method for determining (U-Th)/He ages of hydrothermal hematite: Returning to Elba
复制标题
确定热液赤铁矿 (U-Th)/He 年龄的多等分法：返回厄尔巴岛
DOI：
10.1016/j.chemgeo.2018.11.005
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发表时间：
2019
期刊：
影响因子：
3.9
通讯作者：
Hu Rui-Zhong
中科院分区：
文献类型：
--
作者：
Wu Li-Yan;Stuart Finlay M.;Di Nicola Luigia;Heizler Matthew;Benvenuti Marco;Hu Rui-Zhong
我们已经使用了多等分的方法，以获得精确的（U + Th）/He年龄的热液赤铁矿和评估在何种程度上，他从细粒赤铁矿的扩散和反冲造成的损失。意大利厄尔巴岛里奥马里纳矿的赤铁矿（n = 6）的（U + Th）/He年龄范围为5.36 ± 0.33 ~ 5.64 ± 0.11 Ma，加权平均年龄为5.53 ± 0.14Ma，等时线年龄为5.25 ± 0.20Ma。同源冰长石的~（39）Ar年龄谱较平坦，坪年龄（5.575 ± 0.008和5.583 ± 0.013 Ma）难以区分。另一个冰长石的光谱更为复杂，其年龄为5.64 ± 0.03 Ma。赤铁矿（U + Th）/He年龄与40 Ar/39 Ar年龄重叠，但精确度较低（2-6%对0.2-0.5%）。这表明，从复杂的细粒赤铁矿，无论是通过扩散和反冲，在原位放射性4 He的损失是微不足道的。该研究表明，多等分试样方法有可能可靠地提供精确和准确的氧化铁矿化年龄，没有遭受显着的结晶后热扰动。
We have used a multi-aliquot method to obtain precise (U + Th)/He ages of hydrothermal hematite and to assess the extent to which He loss from fine-grained hematite caused by diffusion and recoil. Hematite (n = 6) from the Rio Marina mine, Elba (Italy) yields (U + Th)/He ages that range from 5.36 ± 0.33 to 5.64 ± 0.11 Ma, giving a weighted mean age of 5.53 ± 0.14 Ma and an isochron age of 5.25 ± 0.20 Ma.40Ar/39Ar data from cogenetic adularia yield flat age spectra with analytically indistinguishable plateau ages (5.575 ± 0.008 and 5.583 ± 0.013 Ma). An additional adularia has a more complex spectrum and yields an interpreted age of 5.64 ± 0.03 Ma. The hematite (U + Th)/He ages overlap the40Ar/39Ar ages, albeit they are less precise (2–6% vs. 0.2–0.5%). This indicates that the loss of in situ radiogenic4He from complex fine-grained hematite, either by diffusion and recoil, is insignificant. The study shows that multi-aliquot method has the potential to reliably deliver precise and accurate ages for iron oxide mineralisation that has not suffered significant post-crystallisation thermal perturbation.