期刊
CHEMICAL GEOLOGY
卷 261, 期 3-4, 页码 244-260出版社
ELSEVIER
DOI: 10.1016/j.chemgeo.2008.06.019
关键词
Lu-Hf isotopes; Pb isotopes; Zircon; Laser ablation; Greenland; Himalayas
资金
- Natural Environment Research Council [NE/D008891/2] Funding Source: researchfish
- NERC [NE/D008891/2] Funding Source: UKRI
The in situ Lu-Hf isotope analysis of zircon by laser ablation has emerged as a high-calibre tool for tackling magmatic and crustal evolution. The strength of the approach lies with the ability to target specific zircon growth domains identified by imaging, and thus to unravel polyphase crystallisation histories. However, due to the volume of material being sampled during analysis there remains the possibility of ablation-induced mixing between Hf from domains of different age. Inaccurate Hf isotope ratios and spurious geological interpretations could result. One approach to this problem involves dating the same volume of material analysed for Hf isotopes by concurrently measuring Pb-207/Pb-206 ratios during ablation [Woodhead,J.D., Hergt,J.M.. Shelley, M., Eggins, S., Kemp, R. 2004. Zircon Hf-isotope analysis with an excimer laser, depth profiling, ablation of complex geometries, and concomitant age estimation. Chemical Geology 209,121-135.]. This paper explores the viability of this dual analysis by investigating complex zircons from three different geological contexts, detrital zircons in sedimentary rocks, inherited zircons in granites, and zircons in metamorphosed Eo-Archaean TTG gneisses from Greenland. The implications of the Greenland data for Archaean crustal evolution are discussed in the light of published solution zircon Hf isotope datasets from these gneisses. A case study of detrital zircons from modern river sands in the Himalayas highlights the potential of the technique for providing a rapid, cost-effective picture of crustal evolution that should complement regional bulk rock studies. (C) 2008 Elsevier B.V. All rights reserved.
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