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In situ location and U‐Pb dating of small zircon grains in igneous rocks using laser ablation-inductively coupled plasma-quadrupole mass spectrometry
Citation
Sack, PJ and Berry, RF and Meffre, S and Falloon, TJ and Gemmell, JB and Friedman, RM, In situ location and U‐Pb dating of small zircon grains in igneous rocks using laser ablation-inductively coupled plasma-quadrupole mass spectrometry, Geochemistry Geophysics Geosystems, 12, (April) pp. 1-23. ISSN 1525-2027 (2011) [Refereed Article]
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Copyright Statement
Copyright 2011 by the American Geophysical Union
Abstract
A new U‐Pb zircon dating protocol for small (10–50 mm) zircons has been developed using an automated
searching method to locate zircon grains in a polished rock mount. The scanning electron microscopeenergy‐
dispersive X ray spectrum‐based automated searching method can routinely find in situ zircon grains
larger than 5 mm across. A selection of these grains was ablated using a 10 mm laser spot and analyzed in an
inductively coupled plasma‐quadrupole mass spectrometer (ICP‐QMS). The technique has lower precision
(∼6% uncertainty at 95% confidence on individual spot analyses) than typical laser ablation ICP‐MS (∼2%),
secondary ion mass spectrometry (<1%), and isotope dilution‐thermal ionization mass spectrometry (∼0.4%)
methods. However, it is accurate and has been used successfully on fine‐grained lithologies, including
mafic rocks from island arcs, ocean basins, and ophiolites, which have traditionally been considered devoid
of dateable zircons. This technique is particularly well suited for medium‐ to fine‐grained mafic volcanic
rocks where zircon separation is challenging and can also be used to date rocks where only small amounts
of sample are available (clasts, xenoliths, dredge rocks). The most significant problem with dating small in
situ zircon grains is Pb loss. In our study, many of the small zircons analyzed have high U contents, and the
isotopic compositions of these grains are consistent with Pb loss resulting from internal a radiation damage.
This problem is not significant in very young rocks and can be minimized in older rocks by avoiding high‐
U zircon grains.
Item Details
| Item Type: | Refereed Article |
|---|---|
| Keywords: | U-Pb dating LA ICP-MS zircons |
| Research Division: | Earth Sciences |
| Research Group: | Geology |
| Research Field: | Geochronology |
| Objective Division: | Expanding Knowledge |
| Objective Group: | Expanding Knowledge |
| Objective Field: | Expanding Knowledge in the Earth Sciences |
| Author: | Sack, PJ (Mr Patrick Sack) |
| Author: | Berry, RF (Associate Professor Ron Berry) |
| Author: | Meffre, S (Dr Sebastien Meffre) |
| Author: | Falloon, TJ (Dr Trevor Falloon) |
| Author: | Gemmell, JB (Professor Bruce Gemmell) |
| ID Code: | 74867 |
| Year Published: | 2011 |
| Web of Science® Times Cited: | 12 |
| Deposited By: | Centre for Ore Deposit Research - CODES CoE |
| Deposited On: | 2011-12-14 |
| Last Modified: | 2012-04-19 |
| Downloads: | 1 View Download Statistics |
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