Zircon - ZrSiO4 • Monazite - (Ce,La,Th)PO4 • Xenotime ... part 3.pdfdata-point error ellipses...

Dating minerals that usually do not requirecorrection for initial (common) Pb

• Zircon - ZrSiO4

• Monazite - (Ce,La,Th)PO4

• Xenotime – YPO4

• Baddeleyite - ZrO2

Zircon

Zircon 91500Concordia age1060 ± 7 Ma (2 sigma)n = 120

TIMS ages:

207 235Pb/ U206 238Pb/ U age = 1065 ± 0.6 Ma (2 sigma)

age = 1062 ± 0.8 Ma (2 sigma)

206

238

Pb/

U

207 235Pb/ U

data point error ellipses are 1 sigma

1300

1200

900

1000

1100

800

0.22

0.20

0.18

0.16

0.14

0.121.0 1.4 1.8 2.2 2.6 3.0

Zircon 02123Concordia age295 ± 1 Ma (2 sigma)n = 117

206

238

Pb/

U

207 235Pb/ U

data point error ellipses are 1 sigma

380

340

260

220

0.06

0.05

0.04

0.030.1 0.2 0.3 0.4 0.5

300

TIMS age: 295 ± 1 Ma (2 sigma)

400 900 1400 1900 2400 2900400

900

1400

1900

2400

2900

NORDSIM Ma

LA

M I

CPM

S (M

UN

) Ma

Concordant U-Pb ages,error boxes are 1 sigma

DETRITAL ZIRCONSOs - Ulven Group, SW Norway

1 : 1

Comparison of techniques for U-Pb zircon dating

LA ICPMS

SIMS

0 25 50

Microns

Zircon crystal

SIMS10 - 20 micron spot size< 2 microns depthca 30 minutes per analysis0.5 - 5 % 2 sigma precision

LA ICPMS30 - 60 micron spot size10 - 20 microns depthca 4 minutes per analysis1 - 10 % 2 sigma precision

Comparison of techniques for U-Pb zircon dating

Isot

opic

rat

io

Cou

nts p

er se

cond

laser signal

206Pb/238U

208Pb/232Th

205T l/233U

0 50 150 200 250100

10 6

105

10 4

10 3

10 2

laser signal

M adagascar monazite

0 50 100 150 200

gas blk

1.2

1.41.61.8

0.02

0.06

0.10

0.14

" True value" (~555 M a)

0 50 100 150 200

50 100 150 200 250Data acquisition time (seconds) Data acquisition time (seconds)

205T l232T h

238U

206Pb

208Pb233U

R 0

Laser ablation time (seconds) Laser ablation time (seconds)

" True value" (~555 M a)

a.

R 0

b.

Monazite

Monazite U-Th-Pb dating requires a large dynamicrange of detector to accommodate signals

from % (232Th) to ppm (207Pb) analyte abundances

206Pb/238U

1 10 100 1000

208Pb/232Th

207Pb/235U

207Pb/206Pb

10

100

1

0.1Sensitivity 30 cps/ppm

Average count rates238U: 1.3*105235U: 1.7*103

232Th: 1.8*106

RSE% a.206Pb/238U

1 10 100 1000

208Pb/232Th

207Pb/235U

207Pb/206Pb

1

10

0.1



232Th: 1.8*107

RSE% b.

206Pb/238U

1 10 100 1000

208Pb/232Th

207Pb/235U

207Pb/206Pb

0.1

1

0.01



232Th: 1.8*109

RSE% c.

Monazite age Ma Monazite age Ma

Monazite age Ma

Precision vs. monazite age (SEM pulse counting)

Thailand

77 + 4 Ma(4 points)

0.04 0.08 0.12

0.013

0.011

0.012

0.010

0.014

68

76

84

1.7 1.9 2.10.15

0.160.17

9601000

10401080

11201160

1087 + 26 Ma(3 points)

1.5

Quebec0.62 0.70

565 + 16 Ma(9 points)

0.86

0.105

0.095

0.085

0.075

500

540580

620Madagascar

0.78

0.4 0.8 1.2 1.6 2.0 2.4

0.04

0.08

0.12

0.16

0.20

0.24

207Pb/235U

200

400

600

800

1000

1200

Error elipses are 1σmeasured 235Ucalculated 238U

206Pb/238U

Monazite (U measured as 235U)

0.4 0.8 1.2 1.6 2.0 2.4

0.04

0.08

0.12

0.16

0.20

0.24

207Pb/235U

200

400

600

800

1000

1200

0.5 0.6

0.7

0.09

0.08

0.07440

480520

560600

0.8

0.9

0.10

0.11

556 + 8 Ma(22 points)

Madagascar

1.75 1.85 1.95

0.18

0.17 1073 + 17 Ma

(7 points)

1060

10201040

1080

11201140

1100

Quebec

Thailand 76 + 5 Ma(4 points)

0.0780.070

0.011

0.010

0.086

6872

7680

84

Error elipses are 1σmeasured 238Ucalculated 235U

206Pb/238U

Monazite (U measured as 238U)

0.052 0.054

0.176

0.1701020

1040

11201100

1072 + 7 Ma(8 points)

10601080

0.056

Quebec

0.02 0.04

0.04

0.08

0.12

0.16

0.20

0.24

208Pb/232Th

200

400

600

800

1000

1200

0.06

0.025

560 + 5 Ma(4 points)0.092

0.088

0.084 520

540

560

Madagascar0.096

0.027

580

Thailand

76 + 1 Ma(3 points)

0.0380.034

0.011

0.010

72

7680

0.042

0.012

Error elipses are 1σmeasured 238Uand 232Th

206Pb/238U

Monazite (measured 235U and 232Th)

Monazite – dual SEM mode

232Th ~ 9 * 109 cps (analog)207Pb ~2.5 * 103 cps (pulse counting)

Element 2, UP213, 20Hz, 2 J/cm2, 8 µm spot, line raster 10 µm/s

600

580

560

540

520

500

0.078

0.082

0.086

0.090

0.094

0.098

0.012 0.016 0.020 0.024 0.028 0.032 0.036 0.040

208Pb/232Th

206 Pb

/238 U

Concordia Age = 556.1 ± 5.9 Ma(2σ, decay-const. errs ignored)

MSWD (of concordance) = 0.052,Probability (of concordance) = 0.82

data-point error ellipses are 68.3% conf.600

580

560

540

520

500

0.078

0.082

0.086

0.090

0.094

0.098

0.56 0.60 0.64 0.68 0.72 0.76 0.80 0.84 0.88

207Pb/235U20

6 Pb/23

8 U

Concordia Age = 556.1 ± 5.5 Ma(2σ, decay-const. errs ignored)

MSWD (of concordance) = 0.018,Probability (of concordance) = 0.89

data-point error ellipses are 68.3% conf.

Madagascar monaziteTIMS age 555 Ma

Madagascar monaziteTIMS age 555 Ma

0 25 50microns

SIMS5-15 micron spot size< 0.3 micron depthca 20 minutes per analysis0.3-1 % 2 sigma precision

Laser ablation ICPMSca 20 micron raster pits2-3 micron depthca 4 minutes per analysis1-3 % 2 sigma precision

ID TIMSalmost the whole grainseveral days per analysis0.01-0.5 % 2 sigma precision

Comparison of techniques for Th-Pb monazite dating

370

350

330

310

0.044

0.048

0.052

0.056

0.060

0.064

0.34 0.36 0.38 0.40 0.42 0.44

207Pb/235U

206 Pb

/238 U

TIMS age336+/-1 Ma

LA ICPMS age206/238 337+/-10 Ma207/235 342+/-8 Ma

Svratka RiverBohemian Massif data-point error ellipses are 1σ

No common Pb correction required

Xenotime

2500

2300

2100

1900

1700

1500

0.15

0.25

0.35

0.45

0.55

2 4 6 8 10

207Pb/235U

206 Pb

/238 U

LA ICPMS ageIntercept age 2055+/-56

TIMS age2060+/-2.1

data-point error ellipses are 1σ

No common Pb correction required

Baddeleyite

PhalaborwaSouth Africa

• Titanite - CaTiSiO4

• Allanite - (Ce,Ca,Y)2(Al,Fe)3(SiO4)3(OH)• Rutile – TiO2

Dating minerals that usually requirecorrection for initial (common) Pb

Common Pb correction

Mass

Abundance 238U

206Pb

207Pb

208Pb

204Hg

204Pb

232Th

Common (initial) PbRadiogenic PbParent isotopes

235U

The stable, non-radiogenic 204Pb is used to subtract a corresponding amount of common Pb from the 206Pb, 207Pb and 208Pb.

High and varying background levels of Hg (204)in most ICP-MS instruments result in large uncertainties in the 204 Pb correction and large uncertainties in the corrected ratios.

Common Pb correction using 204Pb isotope

Common Pb correction using232Th/238U, 208Pb and estimated age

Mineral is concordant.

Assumed model of common Pb composition e.g. Stacey & Kramers (1975) is valid.

Assumptions:

Th and U in analysed area is undisturbed.

No Pb has been lost.

1800

1400

1000

600

2000.0

0.1

0.2

0.3

0.4

0 1 2 3 4 5 6

207Pb/235U

206 Pb

/238 U


Uncorrected data

Titanite, LAC - Norway

440

480

560

0.065

0.075

0.085

0.095

0.50 0.54 0.58 0.62 0.66 0.70 0.74 0.78

207Pb/235U

206 Pb

/238 U

TIMS age520+/-5 Ma

LA ICPMS age206/238 504+/-13 Ma207/235 516+/-16 Ma


Applied common Pb correction is based on 208

Titanite, LAC - Norway

250

350

450

550

0.01

0.03

0.05

0.07

0.09

0.0 0.4 0.8 1.2 1.6 2.0

207Pb/235U

206 Pb

/238 U

Uncorrected data


Allanite – Blansky les, Bohemian Massif


420

380

340

300

260

0.035

0.045

0.055

0.065

0.075

0.25 0.35 0.45 0.55

207Pb/235U

206 Pb

/238 U

σ

LA ICPMS age206/238 343+/-13 Ma207/235 337+/-16 Ma

TIMS age353+/-6 Ma

Sm/Nd mineral-WRdata-point error ellipses are 1σ


460

420

380

340

300

260

2200.03

0.04

0.05

0.06

0.07

0.08

0.0 0.4 0.8 1.2 1.6 2.0

207Pb/235U

206 Pb

/238 U




1020

980940

900

860

820

780

0.12

0.14

0.16

0.18

1.1 1.3 1.5 1.7207Pb/235U

206 Pb

/238 U

LA ICPMS age206/238 959+/-29 Ma207/235 942+/-25 Ma

TIMS age934+/-4 Ma



Rutile – Manicouagan, Quebec

Protolith ages of granitic gneisses (Bohemian Massif)206 238Pb/ U

207 235Pb/ U

620

580

540

500

460

420

a.

Měděnec (Sphinx)augen gneiss

Concordia age524 ± 10 Ma (2 )σConcordia age524 ± 10 Ma (2 )σ

0.45 0.55 0.65 0.75 0.85

0.07

0.08

0.09

0.10

0.11

0.06

207 235Pb/ U

620

580

540

500

460

420

St Catherineaugen gneiss

’s dome

Concordia age480 ± 10 Ma (2 )σ

0.07

0.08

0.09

0.10

0.11

0.06

206 238Pb/ U

0.45 0.55 0.65 0.75 0.85 0.95

660c.

Košler J. et al. (2004): Eur. J. Mineral., 16

Hi 262 Hi 262

Hi 262

20 µm

20 µm

20 µm

Monazite crystal in Monazite crystal in sillimanitesillimanitematrixmatrix

BSE BSE

BSE

In-situ monazite dating in High Himalayan gneisses

100 µm

100 µm 100 µm

100 µm

Kfs

Sil

Sil

Bt

Sil

Bt

MzMz

Mz

Mz

Hi-292

Hi-262Hi-262

Hi-262

Sedimentary provenance using detrital zircon ages

Fonneland H.C., et al. (2004): Onshore and offshore provenance studies; a key to understanding the depositionof deep marine sandstones in the Norwegian Sea.- Sedimentary Geology (in press)

Sedimentary provenance – Norwegian SeaPotential source areas:

0 300 km

Paleozoic and olderplatform deposits

(exposed/inferred)NArchaean Domain

Gothian andSveconorwegianDomain (1750-900Ma)CaledonianFoldbelt (see Fig. 2)

TransscandinavianGranite-Porphyry Belt(1750-1500Ma)

Svecofennian Domain(2000-1750Ma)

Proterozoic Domain

East Greenland foldbelt:wide age range, from Tertiaryto Archaean.

Norwegian landmass:Mainly ages from 900-1750 Ma.

Can the age differences between potential sources be detected in the offshore sediments?

Detrital zircon signatures of the potential sources

0 400 800 1200 1600 2000 2400 2800 3200Ma

Home ForlandAlbianN = 63

GulelvAptianN = 103

A)

B)

Agat Field N = 114

Ma200 600 1000 1400 1800 2200 2600 3000

East Greenland (Laurentian)signature: wide age range and asignificant Archaean component.

Norwegian (west Baltic)signature: narrow age range, ages mainly within 900-1700Ma.

Detrital zircon Pb/Pb ages – Ormen - Lange Dome

SpringarFM.

NiseFM.

KvitnosFM.

LysingFM.

UpperLangeFM.

Blodøks skifer

LowerLange

FM.

LyrFM.

SpekkFM.

Maastricht.

Campanian

Santonian

Coniacian

Turonian

Cenoman.

Albian

Aptian

Barremian

Hauterivian

Valanginian

Ryazanian Sandstein

Karbonater

LithologyLithostr atigraphyAge

Marin skifer og silt

6305/1-1T2,3651-3654m

6305/1-1T2,2618,6m6305/1-1T2,2614,5m

6305/5-1,2789,7m

6305/1-1T2,2569,5m6305/5-1,2736m6305/7-1,2939m

65

70

75

80

85

90

95

100

105

110

115

120

125

130

135

140

PaleoceneTang FM.

Ma

6305/1-1T2

N = 94

D)Pa leocene

6305/ 1-1T2

N = 67

E)Maastr ichtian

6305/1-1T2

N = 87

F)Maastrichtian

6305/1-1T2

N = 168

G)Coniacian

200 600 1000 1400 1800 2200 26003000Ma

N = 89

6305/7-1A)Paleocene

N = 88

630 5/5-1B)Paleocene

N= 89

6305/5-1C)Maastrichtian

200 600 100014001800220026003000Ma

Norway

Sweden

68

65

62

O

O

O

5O 10O

Tertiary

Cretacous

Carb.-Jur.

Basement

Caledonian granites

High-grade paragneisses

Devonian

Neoprot.-Ord. sed.

Caledonian Nappes

Basement (Gothian)

Approximately boundaryof Sveconorwegiandeformation and intrusions (Tucker et. al., 1990).

Basement (Gothian andSveconorwegian)

Sample location

Basin area

Platform/Terrace/High

Reconstruction of sedimentary sources

Maastrichtian

Campanian

Santonian

Coniacian

Turonian

Cenomanian

Paleocene

SpringarFM.

NiseFM.

KvitnosFM.

LysingFM.

UpperLange

FM.

Blodøks FM.

LowerLange

FM.

LyrFM.

SpekkFM.

Sandstone

Limestone

Li thologyLithostrat igraphy

Shale and silt

Tang FM.

Ma

Albian

Aptian

Barremian

Hauterivian

Valanginian

Ryazanian

Age

65

70

75

80

85

90

95

100

105

110

115

120

125

130

135

140

Greenland

Norway

Greenland

Norway

Ormen Lange-Dome

Helland Hansen Arch

Dønna Terrace

Gjallar Ridge

Ormen Lange-Dome

Nyk High

A)

B)

Cenomanian-Campanian

Maastrichtian-Paleocene

PRINCIPLES OF FT DATING

• Fission-track (FT) analysis isa geochronological method basedon natural decay of uranium byspontaneous fission.

• The FT ages are derived fromcounted number of spontaneous fission tracks present in the minerallattice, known decay constant for spontaneous fission and frommeasured concentration of 238Uobtained from the proportion ofinduced fission-tracks afterirradiation with thermal neutronsin a nuclear reactor.

Surface Confined

A

BC

A

BC

Thermal neutronirradiation, induced fissiontracks register in detector

Induced tracks etchedonly in detector

Grain mount showingspontaneous tracks inthe individual grains

External detector showinginduced tracks defininggrain outlines

Mirrorimage

Plan view ofseveral crystals

Accumulation ofspontaneousfission tracks

Polished sectionthrough crystal

Spontaneous tracksetched

External micadetector attached

A

BC

A

BC



Grain mount showingspontaneous tracks inthe individual grains

External detector showinginduced tracks defininggrain outlines

Mirrorimage

Plan view ofseveral crystals

+= 1gln1AGE d

i

s ζρρρ

λλ αα

λα

ρs ρi

ζ, ρd

density ofspontaneous tracks

density ofinduced tracks

parameters of neutron flux

rate of 238U α decay

geometry factor

Conventional FT age calculation

Surface Confined

A

BC

A

BC




Polished sectionthrough crystal


External micadetector attached

A

BC


Polished sectionthrough crystalMEASURE Hf CONCENTRATION


COUNT SPONTANEOUS TRACKS

MEASURE 238U CONCENTRATIONBY LA ICPMS

Conventional vs LA fission track dating

150 200 250 300 350150

200

250

300

350

LA ICPMS FT age (Ma)1 :

1

Con

vent

iona

l FT

age

(Ma)

Conv. FT 231 + 13 MaLA ICPMS FT 238 + 12 Ma

errors are 1 sigma

JGM-29

Conventional FT 218 + 15 MaLA ICPMS FT 214 + 9 Ma

errors are 1 sigma

150 200 250 300 350LA ICPMS FT age (Ma)

150

200

250

300

350

Con

vent

iona

l FT

age

(Ma)

JGM- 31

1 : 1

Results of conventional and LA FT dating of zircons

Svojtka M., Košler J. (2002): Fission-track dating of zircon by laser ablation ICPMS.Geochim. Cosmochim. Acta AC 66 (15A): A756.

+= 1gln1AGE d

i

s ζρρρ

λλ αα

410 2 3 55

10

15

20

σρs/σρi

Tota

l age

unc

erta

inty

% ρs~ρiNs~Ni

Uncert. due to ρs, ρd and ζ

Uncrt.dueto ρi

Analytical uncertainties - FT

Zircon - ZrSiO4 • Monazite - (Ce,La,Th)PO4 • Xenotime ... part 3.pdfdata-point error ellipses...

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Transcript of Zircon - ZrSiO4 • Monazite - (Ce,La,Th)PO4 • Xenotime ... part 3.pdfdata-point error ellipses...