Improved dissolution and chemical separation methods for Lu-Hf garnet chronometry
Research output: Contribution to journal › Journal article › Research › peer-review
Garnet-based Lu-Hf geochronology using conventional (HF-HNO3) dissolution methods may be compromised by full or partial digestion of Hf-rich zircon inclusions. This study integrates two complimentary methods to substantially reduce zircon digestion while assuring complete digestion of garnet and sample-spike equilibration. Handpicked garnet fractions are heat treated to >1000°Cinan evacuated silica glass ampoule to anneal zircon inclusions and then dissolved with 12 M HCl at 210°C and cold 28 M HF. Analyses of heat-treated garnet (and their high-temperature breakdown products orthopyroxene-spinel-quartz) from Gore Mountain, New York, demonstrate the method is capable of complete dissolution of garnet and routinely achieving sample-spike equilibration. Independent analyses of annealed and unannealed zircons dissolved by HCl- cold HF demonstrate the benefit of heat treatment prior to dissolution. Analyses of zircon-rich garnets from peletic paragneisses of Labrador, Canada, show the potential of this method by returning Lu-Hf ratios commensurate with the degree of heat treatment. Finally, a complementary chemical separation method for Lu and Hf is presented that supports analysis of garnet by MC-ICP-MS.
Original language | English |
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Article number | Q04005 |
Journal | Geochemistry, Geophysics, Geosystems |
Volume | 7 |
Issue number | 4 |
Number of pages | 9 |
ISSN | 1525-2027 |
DOIs | |
Publication status | Published - 2006 |
Externally published | Yes |
- Bboric acid, Garnet, Geochronology, HCl dissolution, Hf isotopes, Lu-Hf
Research areas
ID: 333881792