Electron Probe Microanalysis of Monazite and Its Applications to U-Th-Pb Dating of Geological Samples
Electron Probe Microanalysis of Monazite and Its Applications to U-Th-Pb Dating of Geological Samples
复制标题
独居石电子探针微量分析及其在地质样品U-Th-Pb定年中的应用
DOI：
10.1007/s12583-019-1020-8
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发表时间：
2019-10
影响因子：
3.3
通讯作者：
Fu Dong
中科院分区：
文献类型：
--
作者：
Ning Wenbin;Wang Junpeng;Xiao Deng;Li Fenfang;Huang Bo;Fu Dong
独居石的电子探针测年技术已经发展了几十年。但由于受测年元素（Th、Pb、U和Y）的可探测性和分析灵敏度的限制，EPMA测年一直局限于地质研究。在JEOL JXA-8230电子探针上，通过改变探针电流、电子束直径和计数时间，确定了独居石中Th、Pb、U和Y的最佳测量条件。最佳条件为：（1）加速电压15 kV，探针电流100 nA，束径1 μm，U和Pb的峰和本底计数时间分别为200和100 s，Th和Y的峰和本底计数时间分别为100和50 s。本文将此方法应用于华北中部造山带赞皇地区含石榴子石黑云母片麻岩中的独居石。独居石的电子探针测年结果为1812 ±17 Ma（MSWD=2.06），与LA-ICP-MS测年结果的加权平均值（1805 ±12 Ma，MSWD=1.07）相近。
Electron probe microanalysis (EPMA) dating of monazite has been developed over decades. However, limited by the detectability and analytical sensitivity of dating-related elements (Th, Pb, U and Y), the EPMA dating has been restricted to geological research. In this study, various probe currents, beam diameters and counting times have been utilized on a JEOL JXA-8230 electron microprobe to determine the optimal experimental conditions for measuring Th, Pb, U and Y in monazite. The optimal conditions are: (1) accelerating voltage is 15 kV; (2) probe current is 100 nA; (3) beam diameter is 1 μm; (4) the peak and background counting time of U and Pb are 200 and 100 s; and (5) the peak and background counting time of Th and Y are 100 and 50 s. We apply this method to monazite from garnet-bearing biotite gneiss in the Zanhuang area of the Central Orogenic Belt of the North China Craton. The PbO-ThO2* isochron age calculated by EPMA data is 1 812±17 Ma (MSWD=2.06), which is similar to the weighted mean207Pb/206Pb age (1 805±12 Ma, MSWD=1.07) obtained by LA-ICP-MS. This study suggests that EPMA dating of monazite as a powerful dating technique can be widely used in geochronological study.
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影响因子：
3.9
作者：
I. Williams;W. Compston;B. Chappell
通讯作者：
I. Williams;W. Compston;B. Chappell
影响因子：
3.1
作者：
A. Cocherie;E. B. Mezeme;O. Legendre;-C.;Mark Fanning;M. Faure;P. Rossi
通讯作者：
A. Cocherie;E. B. Mezeme;O. Legendre;-C.;Mark Fanning;M. Faure;P. Rossi
影响因子：
2.8
作者：
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通讯作者：
P. Carpenter
影响因子：
5.3
作者：
STEIGER, RH;JAGER, E
通讯作者：
JAGER, E
影响因子：
3.9
作者：
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通讯作者：
P. Konečný;M. Kusiak;D. Dunkley