In situ U–Pb SIMS (IN-SIMS) micro-baddeleyite dating of mafic rocks: Method with examples
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- 作者：Kevin R. Chamberlain ; Axel K. Schmitt ; Susan M. Swapp ; T. Mark Harrison ; Norbert Swoboda-Colberg ; Wouter Bleeker ; Tony D. Peterson ; Charles W. Jefferson ; Andrei K. Khudoley
- 关键词：Baddeleyite ; U– ; Pb geochronology ; Secondary ionization mass spectrometry (SIMS)
- 刊名：Precambrian Research
- 出版年：2010
- 出版时间：1 December 2010
- 年：2010
- 卷：183
- 期：3
- 页码：379-387
- 全文大小：1933 K
文摘
An in situ U–Pb SIMS (IN-SIMS) method to date micro-baddeleyite crystals as small as 3 μm is presented with results from three samples that span a variety of ages and geologic settings. The method complements ID-TIMS geochronology by extending the range of dateable crystals to sizes smaller than can be recovered by physical separation. X-ray mapping and BSE imaging are used to locate target grains in thin section, followed by SIMS analysis on a CAMECA ims 1270, using the field aperture in the transfer column to screen out ions from host phases. Internal age precisions for the method are anticipated to range from 0.1 % for Precambrian rocks to 3–7 % for Phanerozoic rocks. Results establish a 2689 ± 5 Ma age for mafic dikes in the Wyoming craton, USA, a 1540 ± 30 Ma age for a subaerial lava flow from the Thelon Basin of northern Canada, and a 457 ± 34 Ma age for mafic dikes in the platform sequence of southeastern Siberia. The method is ideal for relatively non-destructive dating of small samples such as extraterrestrial rocks and precious terrestrial samples.