Ion microprobe U-Pb dating of monazite with about five micrometer spatial resolution
Ion microprobe U-Pb dating of monazite with about five micrometer spatial resolution
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DOI：
10.2343/geochemj.40.597
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发表时间：
2006-12
影响因子：
0.8
通讯作者：
Y. Sano;N. Takahata;Y. Tsutsumi;T. Miyamoto
中科院分区：
文献类型：
--
作者：
Y. Sano;N. Takahata;Y. Tsutsumi;T. Miyamoto
铅的灵敏度约为4cps/nA/ppm。用热电离质谱法测得的马达加斯加中北部独居石的U-Pb年龄为524.9 ± 3.1Ma（2σ），作为Pb ~+ /UO ~+ -UO ~（2+）/UO ~+刻度的参考。根据正相关关系，我们测定了样品的~（206）Pb/~（238）U比值。207 Pb/ 206 Pb比通过具有单收集器模式的磁体扫描来测量。然后分析了从台湾沉积岩中提取的44个独居石颗粒。并与电子探针U-Th-Pb化学年龄进行了比较。238 U- 206 Pb年龄除个别样品外，与化学年龄基本一致。这种差异可能是由于化学方法高估了放射成因铅。207 Pb- 206 Pb年龄也与化学年龄一致，但也有少数样品不一致。考虑到一致的样品，有三个主要的年龄组，230 Ma，440 Ma和1850 Ma的独居石。年龄分布表明，碎屑独居石的物源可能是华北陆块或华北陆块与华南陆块之间的秦岭-大别-苏鲁带。
tained with a flat peak top, while the sensitivity of Pb was about 4 cps/nA/ppm. A monazite from North-Central Madagascar with a U-Pb age of 524.9 ± 3.1 Ma (2σ) obtained by thermal ionization mass spectrometry was used as a reference for Pb + /UO + - UO2 + /UO + calibration. Based on the positive correlation, we have determined the 206 Pb/ 238 U ratios of samples. 207 Pb/ 206 Pb ratios were measured by a magnet scanning with a single collector mode. Then 44 monazite grains extracted from a sedimentary rock in Taiwan were analyzed. Observed ages were compared with the U-Th-Pb chemical ages by electron microprobe. 238 U- 206 Pb ages agree well with those of the chemical ages except for some samples. The discrepancy may be due to an over-estimation of radiogenic Pb by the chemical method. 207 Pb- 206 Pb ages also agree with the chemical ages while there are a few discordant samples. Taking into account the concordant samples, there are three main age groups, 230 Ma, 440 Ma and 1850 Ma of monazites. The age distribution suggests that the provenance of detrital monazites is possibly the North China Craton or the Qinling-Dabie-Sulu zone between the North China and South China blocks.