Sample preparation for LAM work:

Grain mounts Thin sections

Grain separation via:Rock crushing, sieving,Heavy liquids,Magnetic separation andpicking. ThenMounting PolishingImaging by BSE or CL

Analyses by LAM

Imaging of individualgrains by BSE or CL.

Locate minerals in situusing SEM or opticalMicroscope.

Magnetic separator

Picking microscope

Mounting in epoxy rings

Polishing

Sample preparation

Daily/routine maintenance

To remove contamination, especially common Pb,from the surfaces of samples and standards,

ICP sample cone and skimmer cone,they are ultrasonically cleaned in nanopure water.

Periodically standards are re-polished toremove ablation pits and ablation residue

from sample surfaces.

Daily/routine maintenance

Ablation cell parts,ICP glass ware,

Tubing andsamples and standards

are all acid-washed (2M HNO3) andair-dried in a HEPA filtered

clean air hood.

Mineral standards.

• Need mineral standards of similar matrix as unknowns.

• Must be homogeneous and concordant.• Must contain reasonable amounts of

radiogenic Pb and U.• Large enough for long term LAM use.

Mineral standards.

• We presently have and use zircons that are: 295 Ma, 720 Ma, 1065 Ma and 1330 Ma.

• Monazites of 555 Ma and 2580 Ma.• Titanite of 520 Ma• Allanite 353 Ma• Rutile 934 Ma• Baddeleyite 2060 Ma

Other considerations:

Argon gas supply.Gas or liquid?

“Clean” acid and water for solution mixing.

Effect of laser wavelengthon the precision and accuracyof LA ICPMS U-Th-Pb data

0 200 400 600 800 1000

F2 (157 nm)

ArF (193 nm)NdYAG (213 nm)

NdYAG (266 nm)

NdYAGfundamental(1064 nm)

NdYAG (532 nm)

NdYAG

Excimer

Laser wavelength (nm)

2

4

6

8

Ener

gy o

f pho

tons

(eV)

NdYAG 266 nm NdYAG 213 nm

Some minerals, e.g. calcite, better ablatewith shorter UV wavelength

Jackson S.E. (2001): The Application of NdYAG lasers in LA-ICP-MS.In: Sylvester P.J. ed.: Laser ablation ICPMS in the Earth Sciences, MAC Short course 29, 29-46.

Zircon 91500266 nm NdYAGsingle laser pit

10 Hz, 0.35 mJ/pulse206Pb/238U: 11.72% 1σm207Pb/206Pb: 1.53% 1σm

Zircon 91500213 nm NdYAGsingle laser pit

10 Hz, 0.35 mJ/pulse206Pb/238U: 10.54% 1σm207Pb/206Pb: 2.31% 1σm

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 50 100 150 200 250 300Time (seconds)

206/238

207/206

je14b30

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 50 100 150 200 250 300Time (seconds)

206/238

207/206

je14b07

266 vs 213 nm NdYAG comparison

Zircon 91500266 nm NdYAG

100x100 µm raster10 Hz, 0.35 mJ/pulse

206Pb/238U: 0.52% 1σm207Pb/206Pb: 0.42% 1σm

Zircon 91500213 nm NdYAG

100x100 µm raster10 Hz, 0.35 mJ/pulse

206Pb/238U: 0.52% 1σm207Pb/206Pb: 0.56% 1σm

0

0.05

0.1

0.15

0.2

0.25

0.3

0 50 100 150 200 250 300Time (seconds)

209/205

207/235

206/238

207/206

205/237

je14b21

0

0.05

0.1

0.15

0.2

0.25

0.3

0 50 100 150 200 250 300Time (seconds)

209/205

207/235

206/238

207/206

205/237

je14b01

266 vs 213 nm NdYAG comparison

Zircon 91500TIMS age 1065 Ma

Zircon 02123TIMS age 295 Ma

266 vs 213 nm NdYAG comparison

Femtosecond lasers

ICP-MS time-dependent Pb and U intensities, and Pb/U ratios versus laser fluence. 800 nm Ti: Sapphire laser, 100 fs pulses at 10 Hz repetition rate, single spot.Russo et al., J. Anal. Atom. Spectrom. 2002, 17, 1072-1075.

NIST 610 NIST 610

NIST 610NIST 610

Single collector magnetic sector data

1100

1080

1060

1040

1020

0.168

0.172

0.176

0.180

0.184

0.188

0.192

1.65 1.75 1.85 1.95

207Pb/235U

206 Pb

/238 U

Concordia Age = 1064 ± 4 Ma(2σ, decay-const. errs ignored)

data-point error ellipses are 68.3% conf.

Zircon 91500n = 10TIMS age 1065 Ma

Element 2, UP213, 10 Hz, 3 J/cm2, 40 µm beam diameter, line raster 10 µm/s

Multi collector magnetic sector data

Neptune, UP213, 10 Hz, 6 J/cm2, 60 µm beam diameter, line raster 10 µm/s

1110

1090

1070

1050

1030

0.170

0.174

0.178

0.182

0.186

0.190

1.65 1.75 1.85 1.95 2.05

207Pb/235U

206 Pb

/238 U

Concordia Age = 1063 ± 6 Ma(2σ, decay-const. errs ignored)

data-point error ellipses are 68.3% conf.

Zircon 91500n = 8TIMS age 1065 Ma

Multi collection strategies

L4 L3 L2 L1Ax

FAR H1 H2 H3 H4

205Tl 206Pb 207Pb 209Bi 220.5 237Np 238U221.5 222.5

L4 L3 L2 L1Ax

SEM H1 H2 H3 H4

200Hg 201Hg 202Hg

Staticall faradays

no com. Pb cor.

205Tl 206Pb 207Pb204Pb 221 237Np 238U222 223

205Tl 206Pb204Pb

203Tl201Hg 202Hg

Dynamicaxial SEMcom. Pb cor.

1)2)

3)

4)

17 % mass dispersion (e.g. Neptune)

Pros and cons of using quadrupoleand magnetic sector/multicollector ICPMS

for laser ablation U-Th-Pb dating

Limited in MC modeLargeMass rangeFaraday/SEM/DalySEMDetector type

Single/MultipleSingleDetector array

Low (magnet)High (electrostatic)

HighScanning speed (incl. settling time)

Flat-top“Gaussian”Peak shapeLowHighIon energy spread

Magnetic sectorQuadrupoleParameter

Pros and cons of using quadrupoleand magnetic sector/multicollector ICPMS

for laser ablation U-Th-Pb dating

Not possible on Faraday detectors, requires detection by channeltrons, SEM/Daly

Requires detection by SEM

Analysis of small samples

(spatial resolution)

Can measure 204Pb precisely

High 204Hg background

Low 204Pb intensityHigh 204Hg background

Common Pb correction using 204 method(where applicable)

Often is not apparent during the short acquisition

Often has to be corrected for

Laser-induced fractionation

Short (static acquisition)LongLength of analysis to achieve useful precision

Magnetic sectorQuadrupoleFeature

Bruguier O., Télouk P., Cocherie A., Fouillac A.M., Albarède F., 2001. Evaluation of Pb-Pb and U-Pb laser ablation ICP-MS zircon dating using matrix-matched calibration samples with a frequency quadrupled (266 nm) Nd-YAG laser. Geost Newslet 25:361-373

Cox R., Wilton D., Košler J., 2003. Laser ablation U-Th-Pb dating of zircon and allanite: an example of in-situ dating from the October Harbour granite, Central Coastal Labrador. Can. Mineral., 41, 273-291.

Fryer B.J., Jackson S.E., Longerich H.P., 1993. The application of laser ablation microprobe-inductively coupled plasma mass spectrometry (LAM-ICPMS) to in situ (U)-Pb geochronology. Chem. Geol. 109, 1-8.

Hirata T., Nesbitt R.W., 1995. U-Pb isotope geochronology of zircon: Evaluation of the laser probe-inductively coupled plasma mass spectrometry technique. Geochim. Cosmochim. Acta 59, 2491-2500.

Horn I., Rudnick R.L., McDonough W.F., 2000. Precise elemental and isotope ratio measurement by simultaneous solution nebulisation and laser ablation-ICP-MS: application to U-Pbgeochronology. Chem. Geol. 164, 281-301.

Horstwood M.S.A., Foster G.L., Parrish R.R., Noble S.R., Nowell G.M., 2003. Common-Pb corrected in situ U–Pb accessory mineral geochronology by LA-MC-ICP-MS. J. Anal. Atom. Spectr. 18, 837-846.

Jackson S.E., Longerich H.P., Horn I., Dunning G.R., 1996. The application of laser ablation microprobe (LAM)-ICP-MS to in situ U-Pb zircon geochronology. J. Conf. Abstr. 1, 283.

Jeffries T.E., Fernandez-Suarez J., Corfu F., Gutierrez G., 2003. Advances in U-Pb geochronology using a frequency quintupled Nd:YAG based laser ablation system (λ = 213 nm) and quadrupole based ICP-MS. J. Anal. Atom. Spectr. 18, 847-855.

Ketchum J.W..F, Jackson S..E, Culshaw N.G., Barr S.M., 2001. Depositional and tectonic setting of thePaleoproterozoic Lower Aillik Geoup, Makkovik Province, Canada: evolution of a passive margin – foredeep sequence based on petrochemistry and U-Pb (TIMS and LAM-ICP-MS) geochronology. Precam Res 105:331-356

Košler J., Tubrett M., Sylvester P., 2001. Application of laser ablation ICPMS to U-Th-Pb dating of monazite. Geost. Newslet. 25, 375-386.

Košler J., Fonneland H., Sylvester P., Tubrett M., Pedersen R.B., 2002. U-Pb dating of detrital zircons for sediment provenance studies – a comparison of laser ablation ICPMS and SIMS techniques. Chemical Geology, 182, 605-618.

Košler J., Sylvester P.J., 2003. Present trends and the future of zircon in geochronology: laser ablation ICPMS. In: Hanchar J.M. and Hoskin P.W.O. (eds), Zircon. Reviews in Mineralogy & Geochemistry, vol 53, 243-275.

Li X., Liang X., Sun M., Guan H., Malpas J.G., 2001. Precise 206Pb/238U age determination on zircons by laser ablation microprobe-inductively coupled plasma-mass spectrometry using continuous linear ablation. Chem. Geol. 175, 209-219.

Longerich H.P., Fryer B.J., Strong D.F., 1987. Determination of lead isotope ratios by inductively coupled plasma-mass spectrometry (ICP-MS). Spectrochim. Acta 42B, 39-48.

Ludwig K.R., 1999. IsoplotEx v. 2.6. Berkeley Geochronological Center Special Publication no. 1a.Machado N., Gauthier G., 1996. Determination of 207Pb/206Pb ages on zircon and monazite by laser

ablation ICPMS and application to a study of sedimentary provenance and metamorphism in southeastern Brazil. Geochim. Cosmochim. Acta 60, 5063-5073.

Machado N., Simonetti A., 2001. U-Pb dating and Hf isotopic composition of zircon by laser ablation-MC-ICP-MS. In: Sylvester P. (ed.): Laser ablation ICPMS in the Earth Sciences - Principles and Applications, MAC short course 29, 185-202.

Parrish R.R., Nowell G., Noble S.R., Horstwood M., Timmerman H., Shaw P., Bowen I.J., 1999. LA-PIMMS: A New Method of U-Th-Pb Geochronology Using Micro-Sampling Techniques. J. Conf. Abst. 4, 799.

Tiepolo M., 2003. In situ Pb geochronology of zircon with laser ablation–inductively coupled plasma–sector field mass spectrometry. Chem. Geol., 199, 159-177.

Tiepolo M., Bottazzi P., Palenzona M., Vannucci R., 2003. A laser probe coupled with ICP-double-focusing sector-field mass spectrometer for in situ analysis of geological samples and U-Pb dating of zircon. Can. Mineral. 41, 259-272.

Willigers B.J.A., Baker J.A., Krogstad E.J., Peate D.W., 2002. Precise and accurate in situ Pb-Pb dating of apatite, monazite, and sphene by laser ablation multiple-collector ICP-MS. GeochimCosmochim Acta 66:1051-1066