期刊
CHEMICAL GEOLOGY
卷 259, 期 3-4, 页码 218-229出版社
ELSEVIER
DOI: 10.1016/j.chemgeo.2008.11.004
关键词
U-Pb geochronology; Zircon; LA-ICP-MS
资金
- NSF [EAR 0443387, 0732436]
U-Pb zircon geochronology is hampered by problems acquiring meaningful geologic ages on zoned grains that retain isotope signatures from multiple growth or thermal events. We present a new method using laser ablation-multicollector-inductively coupled plasma-mass spectrometry to overcome complications associated with intricately zoned zircon crystals through in situ sampling of zircon volumes as small as 12-14 mu m in diameter by 4-5 mu m in depth (<3 ng of zircon). Using Channeltron multipliers to monitor Pb intensities in conjunction with a total ion counting method and errors calculated as function of the number of counts, the small-volume technique reproduced published ages on eight Mesoproterozoic-Cretaceous secondary zircon standards precise and accurate within 2%, and an age similar to 1 Ma too young on a Oligocene-aged grain. Two initial applications of the small-volume technique - the detrital zircon provenance of fine-grained mudstones and shales and the creation of zircon U-Pb age maps to investigate the detrital and metamorphic history of a granulite-facies paragneiss - demonstrate the utility of this technique to a variety of geologic problems and confirm the viability of laser ablation-multicollector-inductively coupled plasma-mass spectrometry as a tool for high spatial resolution U-Pb geochronology. Published by Elsevier B.V.mu
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