Ion microprobe U-Pb dating of monazite with Y S

Geochemical Journal, Vol. 40, pp. 597 to 608, 2006
Ion microprobe U-Pb dating of monazite with
about five micrometer spatial resolution
YUJI S ANO,1* NAOTO TAKAHATA ,1 Y UKIYASU TSUTSUMI2 and TOMOHARU MIYAMOTO 3
1
Center for Advanced Marine Research, Ocean Research Institute, The University of Tokyo,
Nakano-ku, Tokyo 164-8639, Japan
2
Department of Geology, The National Science Museum, Shinjuku-ku, Tokyo 169-0073, Japan
3
Department of Earth and Planetary Sciences, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan
(Received February 7, 2006; Accepted July 31, 2006)
We have developed 238U-206Pb and 207Pb- 206Pb dating method of monazite by using a Cameca NanoSIMS NS50 ion
microprobe. A ~4 nA O– primary beam was used to sputter a 5~7- µm-diameter crater and secondary positive ions were
extracted for mass analysis using a Mattauch-Herzog geometry. The multi-collector system was modified to simultaneously detect 140Ce +, 204Pb +, 206 Pb+, 238U16O+, and 238 U16O2+ ions. A mass resolution of 4100 at 1% peak height was attained with a flat peak top, while the sensitivity of Pb was about 4 cps/nA/ppm. A monazite from North-Central Madagascar with a U-Pb age of 524.9 ± 3.1 Ma (2σ ) obtained by thermal ionization mass spectrometry was used as a reference for
Pb+ /UO+ - UO2+/UO+ calibration. Based on the positive correlation, we have determined the 206Pb/238U ratios of samples.
207
Pb/ 206Pb ratios were measured by a magnet scanning with a single collector mode. Then 44 monazite grains extracted
from a sedimentary rock in Taiwan were analyzed. Observed ages were compared with the U-Th-Pb chemical ages by
electron microprobe. 238U-206 Pb ages agree well with those of the chemical ages except for some samples. The discrepancy may be due to an over-estimation of radiogenic Pb by the chemical method. 207Pb-206Pb ages also agree with the
chemical ages while there are a few discordant samples. Taking into account the concordant samples, there are three main
age groups, 230 Ma, 440 Ma and 1850 Ma of monazites. The age distribution suggests that the provenance of detrital
monazites is possibly the North China Craton or the Qinling-Dabie-Sulu zone between the North China and South China
blocks.
Keywords: SIMS, monazite, U-Pb age, Pb-Pb age, U-Th-Pb chemical age
suffers from elevated Hg backgrounds interfering at 204Pb
(Comspton, 1999). On the other hand, the advantages of
U-Th-Pb chemical dating using EMP are rapid analysis,
the lowest cost and excellent spatial resolution (spot size
3~5 µm) compared with SIMS method, while the major
drawback is a relatively low sensitivity of Pb and in case
of discordant sample, the chemical ages are only apparent ages.
The most powerful tool for precise in situ U-Th-Pb
dating is the SIMS method, although laser ablation multicollector inductively coupled plasma mass spectrometry
(LA-MC-ICPMS) may provide in the future an alternative technique. A pionier work of the SIMS U-Pb dating
was carried out by using an ARL machine (Hinthorne et
al., 1979). The commonest application of the SIMS U-Pb
dating has been on zircons with 20~30 µm scale using
the Sensitive High Resolution Ion MicroProbe (SHRIMP)
instrument built at the Australian National University
(Compston et al., 1984; Williams, 1998). The SIMS
method has been also extended to several minerals such
as monazite (DeWolf et al., 1993), perovskite (Ireland et
al., 1990), titanite (Kinny et al., 1994) and apatite (Sano
INTRODUCTION
In situ U-Th-Pb dating of accessory minerals such as
zircon, monazite and apatite has provided significant information on Earth Sciences, since the linkage between
the age, textures and petrology may quantify the dynamics of several geologic processes (Muller, 2003). There
are a few methods of in situ U-Th-Pb dating with ~30 µm
scale such as laser ablation inductively coupled plasma
mass spectrometry (LA-ICPMS: Hirata and Nesbitt, 1995;
Horn et al., 2000; Ballard et al., 2001), secondary ion
mass spectrometry (SIMS: Compston et al., 1984;
Whitehouse et al., 1997; Williams, 1998), and electron
microprobe (EMP: Suzuki and Adachi, 1991; Montel et
al., 1996). Among them, LA-ICPMS method has several
advantages such as easy to operate, less expensive and
smaller matrix effect than SIMS method. However it consumes more sample amount (worse depth resolution) and
*Corresponding author (e-mail: [email protected])
Copyright © 2006 by The Geochemical Society of Japan.
597
et al., 1999). Cameca ims-3f and ims-1270 instruments
were also applied to the U-Pb dating (Wiedenbeck and
Goswami, 1994; Schuhmacher et al., 1994; Tsunogae and
Yurimoto, 1995; Whitehouse et al., 1997). Recently,
NanoSIMS NS50 ion microprobe, with supreme lateral
resolution up to 0.05 µm has been develped by Cameca
(Hillion et al., 1993) and mostly applied to the field of
cosmochemistry (Nguyen and Zinner, 2004; Stadermann
et al., 2005), even though geochemical applications are
significantly less (Meibom et al., 2004; Stern et al., 2005;
Sano et al., 2005). It is desirable that the instrument would
apply to in situ U-Pb dating with its high lateral resolution.
We report here U-Pb dating of monazite samples with
various formation ages using a NanoSIMS NS50 instrument installed at Ocean Research Institute, The University of Tokyo. Experimental details of the ion microprobe
analysis at spot size of 5~7 µm are given. We assess the
accuracy and precision of the 238U-206Pb and 207Pb-206Pb
ages obtained this work as compared with those determined by the U-Th-Pb chemical dating using EMP at The
National Science Museum, Tokyo. Then we discuss the
provenance of monazites based on the concordant ages.
SAMPLES
Standard sample was derived from a large crystal of
monazite kept as one of Sakurai Mineral Collection at
The National Science Museum, Tokyo. It was collected
in North-Central Madagascar and said to be derived from
the Andriamena unit that experienced a thermal event at
530–500 Ma (Paquette et al., 2004). A sedimentary rock
sample (sandstone of Middle Miocene) was derived from
Chunhuangkeng Formation, Juifang Group in Western
foothills of Taiwan. Figure 1 shows the sampling site and
geologic province of Taiwan.
ANALYTICAL METHOD
Monazite grains were separated from their matrix of
sandstone using standard crushing and heavy-liquid techniques. The separated monazites were hand-picked and
then cast into epoxy resin discs together with standard
monazite grains. The monazites were polished until the
mid-sections of the grains were exposed. Final polishing
was with 0.25 µm diamond paste. After carbon coating,
major element compositions, U, Th, and Pb abundances
were analyzed by EMP (JOEL JCMA8800 at The National
Science Museum). Measurements were performed under
conditions of 15 kV accelerating voltage, 200 nA specimen current and about five micrometer spatial resolution
(see Fig. 2). Peak intensities of U, Th and Pb were derived from M α-line peaks using wavelength-dispersive
spectrometers with 100~300 second counting time.
598 Y. Sano et al.
°
°
°
22°N
100km
°E
°
°
Fig. 1. Sampling point of Middle Miocene sedimentary rock in
the Western foothills of Taiwan together with major geological
provinces.
Hand-picked grains of the standard monazite were
dissolved by acid using standard chemical techniques and
separated by anion exchange resin after addition of selected isotope spikes. U and Pb abundances, and Pb isotopic compositions were measured by a thermal ionization mass spectrometer, TIMS (JEOL JMS05RB Mass
spectrometer at Kyushu University). Experimental details
were given elsewhere (Miyamoto and Yanagi, 1996).
Observed 238U-206Pb* and 235U-207Pb* ages are 531 ± 5
Ma (2σ) and 521 ± 4 Ma (2σ ), respectively. Taking into
account of error weighted average, the TIMS U-Pb age
of the standard monazite should be 524.9 ± 3.1 Ma (2σ).
After EMP measurements, the monazite mounts were
polished slightly to remove carbon coat and damaged
layer, and cleaned with petroleum spirit, detergent and
pure water to reduce surface contaminants and then gold
coated to dissipate charge during SIMS analysis. The samples were evacuated in the air-rock system of NanoSIMS
to reduce water absorbed onto the surface of the mount.
Using a critical illumination mode, a ~4 nA mass filtered
O– primary beam was used to sputter a 5~7 µm-diameter
crater (see Fig. 2b) and secondary positive ions were extracted for mass analysis using a Mattauch-Herzog ge-
Fig. 2. (a) Back-scattered electron image of sample No. 1 obtained by EMP where analyzed spot (~5 µm diameter) is shown.
(b) Optical photomicrograph of standard monazite where
analyzed spot (5~7 µm diameter) is shown. Because of primary
beam tunning to be the brightest in this study, the pit is triangular. Note that the spot sizes are comparable.
ometry. Before the actual analysis, the sample surface was
rastered by 10 µm square for 3 min in order to reduce the
contribution of surface contaminant Pb to the analysis.
There are two advantages of NanoSIMS over any conventional SIMS. First, co-axial signature of primary and
secondary beams makes short working distance of the
probe forming lens/extraction system giving smaller spot
size for a provided beam current with higher collection
efficiency. For example SHRIMP can produce ~1 nA of
mass filtered O– primary beam at 5 µm spot at maximum
(Terada, personal communication), while the primary
beam intensity of NanoSIMS is 4 times larger than that
of SHRIMP. Second, multi-collector system with a
Mattauch-Herzog geometry should cover wide range of
mass number. In case of calcite analysis, we can detect
26
Mg (a detector called EM#1 whose position is movable),
43
Ca (EM#2 movable), 88 Sr (EM#3 movable), 138 Ba
(EM#4 movable), 238U 16O (EM#5 fixed position) and
238 16
U O2 (LD fixed position) at the same time under static
magnetic field (Sano et al., 2005). In case of monazite
analysis, it is possible to detect Pb isotopes, UO and UO2
together with a matrix peak of Ce at the same time. Then
it is not necessary to scan the magnetic field from Ce to
UO2, which can reduce measurement time. There is a
drawback that the distance of ion beams at high mass
number after the magnet should become significantly
short by using NanoSIMS. For example, the distance between 204Pb+ and 206Pb+ at the focal plane is only 2 mm,
which makes impossible to detect them at the same time
by an original configuration of NanoSIMS. So we have
developed a dual collector system (EM#4 and 4b) to detect 204Pb+ and 206Pb + at the same time by two ion counting system located very closely. Difference in the sensitivity of EM#4 and EM#4b is calibrated by using 208Pb+
beam with a magnet scanning, which was 1.053 ± 0.003
at the time of experiment. In addition the position of EM#5
(fixed) was adjusted to collect 238U + beam when 238U16O+
beam could enter LD detector at the outermost position.
Then modified multi-collector system can detect 140Ce+
(Faraday cup), 204Pb + (EM#4) 206 Pb + (EM#4b), 238U +
(EM#5) and 238U16O + (LD) ions of monazite at the same
time. It is also possible to detect 146Nd+, 204Pb+, 206Pb +,
238 16 +
U O , and 238U 16O2+ ions simultaneously.
The entrance and exit slits (for Faraday cup,
EM#1~EM#5, and LD) were set to about 40 µm and 50
µm, respectively. A mass resolution of 4100 at 1% peak
height was attained to separate 206Pb+ from 143Nd31P 16O2+
with adequate flat topped peaks (see Fig. 3). 204Pb+ beams
are also discriminated from 172Yb16O2+ beams. The Pb
sensitivity =4 cps/1 nA/ppm Pb was obtained by an
intensitiy of 208Pb ion beam and abundance of Pb in the
standard monazite (Table 1), which is about 1/5 of Pb
sensitivity in zircon using SHRIMP instrument. Difference of sensitivity may be due to the fact that we use a O–
primary while the SHRIMP value is derived from O2–. In
addition the transmission of Pb ions at high mass resolution mode may be higher in SHRIMP than NanoSIMS,
even though we cannot calculate the difference precisely.
Taking into account of the 4 times bright primary beam
at 5~7 µm spot (see Fig. 2b), however, total performance
of NanoSIMS is equivalent with SHRIMP. It takes 6 min
including pre-analysis raster to complete single analysis
of 140Ce+, 204Pb +, 206Pb+, 238 U16O+, and 238U 16O2+ ions
with statistically enough counts (e.g., 206 Pb: 5 × 10 5
counts) by Nano-SIMS. Then the magnet was cyclically
peak-stepped through a series of mass numbers 204, 206,
Ion microprobe U-Pb dating of monazite 599
[c/s]
[c/s]
143 Nd 31 P 16 O +
2
206Pb +
141Pr 31 P 16 O +
2
172Yb16 O +
2
204 Pb +
174 Yb 16 O +
2
mass
mass
Fig. 3. Mass spectrum in the vicinity of m/e = 206 and 204 in a monazite standard. Mass resolution for 206Pb = 4100 at 1% peak
height. 206Pb + is well separated from 143Nd 31P16O 2+ with adequate flat topped peak. Tail of 172Yb 16O2+ is significantly small at
204
Pb+.
Table 1. Chemical compositions and U-Th-Pb chemical ages of standard monazite derived from Madagascar
P2 O5
(%)
La 2 O3
(%)
Ce 2 O3
(%)
Pr 2 O3
(%)
Nd2 O3
(%)
Sm2 O3
(%)
Gd2 O3
(%)
UO2
(%)
std-1
std-2
std-2
std-3
std-3
27.11
26.72
26.65
27.28
26.71
9.61
9.78
9.74
9.78
9.38
24.71
26.09
24.98
25.51
25.77
3.61
3.48
3.44
3.42
3.41
12.42
12.29
12.18
12.19
12.04
2.61
2.59
2.74
2.52
2.53
1.41
1.51
1.46
1.56
1.58
0.150
0.077
0.094
0.091
0.110
av.
26.89
9.66
25.41
3.47
12.22
2.60
1.50
0.104
ThO2
(%)
9.69
9.38
9.61
9.50
10.98
9.832
PbO
(%)
Chemical age
(Ma)
0.229
0.214
0.219
0.221
0.250
529.4 ± 18.4
524.6 ± 19.4
521.8 ± 18.8
531.2 ± 19.0
520.2 ± 16.4
0.227
525.2 ± 8.2
Errors are 2 σ.
and 207 to measure Pb isotopes by using EM#5 as a single collector mode. More precisely we detect 204Pb for
10 sec, 206Pb for 2 sec and 207Pb for 10 sec with 4 sec, 2
sec, and 2 sec of waiting time before measurements, respectively, in a single cycle. It takes about 14 min to carry
out the Pb isotope analysis by 28 cycles. Total time required for U-Pb dating procedure is about 20 min.
RESULTS AND DISCUSSION
Table 1 lists chemical compositions and U-Th-Pb
chemical ages of standard monazite grains from NorthCentral Madagascar. Individual EMP chemical ages are
600 Y. Sano et al.
calculated from the U, Th and Pb concentrations assuming that unradiogenic Pb in the monazite is negligible and
that no partial Pb loss occurred since its initial crystallisation or last complete resetting (closed system evolution). Then the chemical ages should be considered as
apparent ages. The weighted mean of five measurements
is 525.2 ± 8.2 Ma (2σ), which agrees well with the TIMS
U-Pb age of 524.9 ± 3.1 Ma, and is consistent with a thermal event that affected the sample at 530-500 Ma
(Paquette et al., 2004).
Table 2 shows chemical compositions and U-Th-Pb
chemical ages of 44 monazite grains extracted from a
sedimentary rock in Taiwan. The chemical ages are refered
Table 2. Chemical compositions and U-Th-Pb chemical ages of monazite samples extracted from a sedimentary rock in Taiwan
No.
P2 O5
(%)
La 2 O3
(%)
Ce 2 O3
(%)
Pr 2 O3
(%)
Nd2 O3
(%)
Sm2 O3
(%)
Gd2 O3
(%)
UO2 #
(%)
ThO2 #
(%)
PbO#
(%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
29.2
29.7
29.5
28.6
29.5
28.6
28.8
29.2
29.7
27.7
29.2
29.7
29.4
28.7
28.1
29.4
30.2
29.3
27.7
30.0
30.1
23.8
30.2
29.7
30.0
29.1
30.0
29.4
29.2
30.5
30.4
28.3
30.2
29.6
29.1
29.9
27.2
29.3
26.2
28.3
29.1
28.7
28.6
27.8
12.8
14.9
13.6
12.7
14.5
12.6
14.6
14.1
16.0
13.1
15.1
14.8
14.4
15.3
14.9
13.7
13.3
15.1
15.0
13.8
13.5
14.0
14.7
13.9
15.1
18.8
19.0
13.8
14.7
15.6
16.1
11.8
14.2
15.3
15.3
14.1
14.7
14.3
21.5
16.1
14.6
12.8
16.4
16.4
23.0
25.4
28.0
26.9
28.0
26.0
27.6
26.1
30.3
29.1
29.4
25.3
27.7
28.8
28.8
29.3
26.4
30.0
28.3
25.8
26.4
24.1
25.9
28.7
28.4
31.3
32.7
28.0
29.7
28.6
29.7
27.0
27.4
29.3
31.3
28.8
28.1
28.4
29.0
29.8
27.5
28.4
29.8
29.1
2.51
2.85
3.29
3.25
3.20
3.05
3.15
2.98
3.14
3.51
3.16
2.73
2.93
3.12
3.16
3.48
2.97
3.58
2.96
3.16
3.00
2.51
3.01
3.48
3.22
3.34
3.43
3.26
3.16
2.88
3.20
3.65
3.05
3.11
3.41
2.98
2.95
2.99
2.46
3.23
3.03
3.10
3.06
3.09
9.51
9.47
11.78
11.98
10.78
10.01
11.20
10.68
10.74
11.90
10.74
9.30
10.22
10.29
10.95
11.87
10.55
12.18
9.76
10.52
11.11
7.85
10.65
11.90
11.18
10.15
11.86
11.33
10.55
10.19
10.61
12.96
10.47
10.64
11.44
10.37
9.70
10.70
6.78
10.74
10.21
10.62
10.08
10.28
2.63
1.23
1.92
1.67
1.80
1.57
1.68
1.46
1.63
1.30
1.48
1.65
1.61
1.29
1.55
1.47
1.95
1.93
1.23
1.78
1.89
0.70
1.65
2.23
1.52
1.03
0.84
1.53
1.66
1.63
1.57
1.45
1.68
1.60
1.66
1.87
0.91
1.79
0.44
1.15
1.90
1.76
1.45
1.07
2.89
1.32
1.83
0.89
1.47
1.20
1.14
1.23
1.56
0.64
0.92
1.38
1.35
0.89
1.23
0.78
1.77
1.33
1.06
1.47
1.93
0.41
1.39
1.63
1.16
0.54
0.44
0.86
1.01
1.31
1.19
0.63
1.45
1.12
1.29
1.62
0.40
1.59
0.10
0.38
1.64
1.08
0.94
0.73
0.933
1.15
0.466
0.363
0.632
0.593
0.261
0.305
0.221
0.457
0.256
1.74
0.288
0.964
0.282
0.282
1.37
0.489
0.391
0.959
0.989
0.581
0.645
0.693
0.636
0.126
0.03
0.44
1.042
0.594
0.656
0.309
0.809
0.653
0.298
0.724
0.366
0.708
0.302
0.594
0.999
0.412
0.297
0.314
10.82
6.54
5.67
9.40
5.14
10.95
5.56
7.19
2.43
9.34
5.98
5.07
7.13
6.17
6.78
7.09
7.31
3.58
9.02
6.33
5.50
18.77
4.61
4.06
5.03
3.23
0.12
8.36
7.88
3.41
2.98
9.43
4.48
6.31
4.72
7.03
11.20
6.96
9.83
6.15
4.67
10.10
6.26
7.75
0.144
0.787
0.544
0.775
0.066
0.952
0.496
0.611
0.046
0.821
0.512
0.863
0.255
0.092
0.130
0.596
0.214
0.424
0.721
0.786
0.729
1.520
0.550
0.554
0.585
0.017
0.026
0.603
0.113
0.458
0.110
0.829
0.601
0.085
0.420
0.757
0.376
0.630
0.097
0.642
0.096
0.064
0.086
0.177
Chemical age #
(Ma)
245 ± 14
1761 ± 21
1821 ± 30
1820 ± 22
208 ± 28
1813 ± 18
1883 ± 35
1824 ± 27
244 ± 63
1869 ± 21
1847 ± 33
1783 ± 19
770 ± 25
225 ± 21
401 ± 26
1851 ± 28
435 ± 17
1937 ± 41
1726 ± 22
1922 ± 23
1915 ± 24
1887 ± 47
1829 ± 12
1883 ± 32
2022 ± 34
124 ± 56
1938 ± 30
1530 ± 22
244 ± 18
1927 ± 39
485 ± 38
1974 ± 22
1911 ± 30
243 ± 24
1816 ± 38
1915 ± 23
767 ± 17
1642 ± 23
218 ± 19
1909 ± 27
249 ± 25
125 ± 18
280 ± 28
508 ± 23
#
Tsutsumi et al. (2004).
Errors are 2 σ.
from the other work (Tsutsumi et al., 2004). Generally
sample monazites have higher La, U and P2O5 abundances
than those of standard, while Nd concentrations are contrary. Observed chemical ages vary significantly from 124
Ma to 2022 Ma, even though they are apparent ages.
Table 3 lists 238U 16O+/140Ce+, 238U16O2+/238U16O+, and
206
Pb+/ 238U 16O+ ratios of the standard monazite obtained
by NanoSIMS within successive three days. In this work
Pb is emitted almost entirely as Pb + while formed
UO2+:UO+:U + are 10:10:1. Generally in SIMS U-Pb dating, Pb+/UO+ could differ as much as a factor two for a
target of constant Pb/U ratio (Willaims, 1998; Sano et
al., 1999). However it is possible to determine a correction factor as a function of UO2+/UO+ for calculating Pb/
U ratio from the Pb+/UO+, which was well documented
in titanite and perovskite using SHRIMP (Ireland et al.,
Ion microprobe U-Pb dating of monazite 601
U1 6 O/1 4 0 Ce (×10– 3 )
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
4.10
4.22
4.54
4.21
4.21
4.37
4.20
4.12
4.62
4.02
4.29
4.44
5.23
4.31
4.58
4.49
4.49
4.54
4.46
4.42
4.48
4.47
4.48
4.22
4.19
4.33
4.61
4.75
4.61
4.80
5.40
5.13
4.83
4.75
4.82
4.76
4.30
4.37
4.46
4.91
5.72
238
Pb/238U 16O
0.30
U1 6 O2 /2 3 8 U1 6 O
206
Pb/2 3 8 U1 6 O
1.145 ± 0.003
1.108 ± 0.004
1.135 ± 0.005
1.111 ± 0.002
0.980 ± 0.002
0.999 ± 0.003
1.066 ± 0.002
1.020 ± 0.003
1.071 ± 0.004
1.086 ± 0.003
1.036 ± 0.003
1.082 ± 0.003
1.169 ± 0.005
1.008 ± 0.003
0.944 ± 0.002
1.105 ± 0.003
1.204 ± 0.002
1.287 ± 0.003
1.327 ± 0.003
1.199 ± 0.003
1.238 ± 0.004
1.249 ± 0.003
1.251 ± 0.003
1.194 ± 0.003
1.108 ± 0.003
1.053 ± 0.004
1.320 ± 0.003
1.265 ± 0.004
1.217 ± 0.003
1.029 ± 0.003
0.943 ± 0.005
0.900 ± 0.002
1.008 ± 0.003
1.093 ± 0.003
1.125 ± 0.003
1.170 ± 0.002
0.879 ± 0.002
0.902 ± 0.002
0.818 ± 0.003
0.759 ± 0.003
0.821 ± 0.005
0.215 ± 0.001
0.201 ± 0.001
0.195 ± 0.002
0.200 ± 0.001
0.163 ± 0.001
0.168 ± 0.001
0.193 ± 0.001
0.180 ± 0.001
0.190 ± 0.001
0.199 ± 0.001
0.183 ± 0.001
0.205 ± 0.001
0.222 ± 0.002
0.176 ± 0.002
0.161 ± 0.001
0.204 ± 0.001
0.228 ± 0.001
0.251 ± 0.001
0.257 ± 0.001
0.214 ± 0.001
0.225 ± 0.001
0.224 ± 0.001
0.224 ± 0.001
0.221 ± 0.001
0.195 ± 0.001
0.178 ± 0.001
0.263 ± 0.001
0.262 ± 0.001
0.239 ± 0.001
0.177 ± 0.001
0.147 ± 0.002
0.167 ± 0.001
0.186 ± 0.001
0.204 ± 0.001
0.213 ± 0.001
0.222 ± 0.001
0.154 ± 0.001
0.158 ± 0.001
0.136 ± 0.001
0.114 ± 0.001
0.110 ± 0.001
Errors are 2 σ.
0.25
Pb/238U16O
238
206
206
Table 3. 238U 16O/140Ce, 238U16O2/238U16O and
ratios of the standard monazite
0.20
0.15
0.10
0.7
0.8
0.9
1.0
238 16
1.1
238
U O2/
1.2
1.3
1.4
16
U O
Fig. 4. A correlation diagram between Pb+/UO + and UO 2+/
UO+ ratios of standard monazite. Errors are portrayed at two
sigma level. A dotted line shows best fit by a simple linear regression (y = ax + b), where a = 0.252 and b = –0.0777.
206Pb/204 Pb
18.0
17.6
17.2
16.8
16.4
207
Pb/204Pb
16.4
16.0
1990; Kinny et al., 1994). Williams et al. (1996) reported
that the Pb/U calibration curve for monazite is a Pb+/U + UO +/U + power law with exponent 2. On the other hand
we decide to use Pb+/UO+ - UO2+/UO+ calibration since
the U+ ion beam is significantly weak and Pb+/U+ ratio is
errorneous. Figure 4 shows the correlation between observed secondary Pb +/UO+ and UO2+/UO + ratios. It is
noted that the variation of Pb/UO ratios is up to a factor
three, which is larger than those of previsou works
(Willaims, 1998; Sano et al., 1999). This may be due to
the wide variation of U concentrations (see Table 1).
However the mechanism is not well understood. In order
602 Y. Sano et al.
15.6
15.2
14.8
Fig. 5. Repeated measurements of 206 Pb/204Pb and 207Pb/204 Pb
ratios in NIST SRM610 glass. Mass discriminations are significantly small, +0.1 ± 2.6‰ for 206Pb/204 Pb and –1.5 ± 2.6‰
for 207 Pb/204Pb, within experimental error margins.
Table 4.
204
Pb/206Pb and
204
207
Pb/ 206Pb ratios of the standard monazite
Pb/2 0 6 Pb
207
Pb*/2 0 6 Pb
f2 0 6
207
Pb*/2 0 6 Pb*
207
Pb*/2 0 6 Pb* age
1
2
3
4
5
6
7
8
9
10
11
12
13
14
0.000331 ± 0.000039
0.000235 ± 0.000026
0.000208 ± 0.000012
0.000388 ± 0.000068
0.000246 ± 0.000018
0.000121 ± 0.000011
0.000491 ± 0.000073
0.000281 ± 0.000015
0.000168 ± 0.000017
0.000137 ± 0.000010
0.000140 ± 0.000011
0.000141 ± 0.000013
0.000101 ± 0.000009
0.000129 ± 0.000012
0.0611 ± 0.0014
0.0617 ± 0.0016
0.0612 ± 0.0015
0.0632 ± 0.0020
0.0615 ± 0.0016
0.0597 ± 0.0021
0.0654 ± 0.0015
0.0618 ± 0.0014
0.0599 ± 0.0024
0.0595 ± 0.0013
0.0599 ± 0.0012
0.0599 ± 0.0008
0.0601 ± 0.0008
0.0601 ± 0.0011
0.0059
0.0042
0.0037
0.0069
0.0044
0.0022
0.0088
0.0050
0.0030
0.0024
0.0025
0.0025
0.0018
0.0023
0.0563
0.0583
0.0581
0.0575
0.0579
0.0579
0.0582
0.0577
0.0574
0.0575
0.0579
0.0579
0.0586
0.0582
463 ± 54
541 ± 59
535 ± 55
511 ± 75
528 ± 59
527 ± 78
538 ± 55
519 ± 52
508 ± 89
510 ± 49
526 ± 45
524 ± 30
553 ± 30
537 ± 41
av.
0.000180
0.0611
0.0040
0.0578
528 ± 13
Errors are 2 σ.
to describe the positive correlation between the Pb/UO
and UO 2/UO ratios, a simple linear regression with R =
0.971 is more appropriate than the quadratic relation with
R = 0.898. Thus we take the simple linear regression as
follow:
(Pb+/UO+)obs = a(UO2+/UO+)obs + b
where obs is the observed ratio, and a and b are constant.
Best fit shows a = 0.252 and b = –0.0777. We can determine the 206Pb/ 238U ratio of unknown sample based on
the following equation:
206
Pb/238U
= A × (206Pb+/238UO+)sample/{a(UO 2+/UO+)sample + b}
where constant A is determined by repeated measurements
of the standard.
Figure 5 shows repeated measurements of Pb isotopes
in NIST SRM 610 glass. Based on the data, isotopic mass
discriminations of 206Pb/ 204Pb and 207Pb/204Pb ratios are
+0.1 ± 2.6‰ and –1.5 ± 2.6‰, respectively. Stern et al.
(2005) have measured Pb isotopes of SRM Pb metals and
zirconolite and suggested that the mass discrimination is
undetectable. Thus we did not make any corrections for
the instrumental isotopic mass discrimination of Pb isotopes by using NanoSIMS. Table 4 lists observed 204Pb/
206
Pb and 207Pb/ 206Pb ratios together with common 206Pb
fraction (f206), 207Pb*/ 206Pb* ratio (where “*” denotes radiogenic) and 207Pb*-206Pb* age of standard monazite
from North-Central Madagascar. Generally subtraction of
common Pb from measured Pb is required to estimate the
accurate age (Williams, 1998). In this study a measured
204
Pb/206Pb ratio, (204Pb/206Pb)obs was used for the cor-
rection of common Pb, (204Pb/206Pb)com whose isotopic
composition were assumed by a two-stage evolution
model (Stacey and Kramers, 1975). Then “f206” deonotes
(204Pb/ 206Pb)obs/(204Pb/206Pb)com. As is shown in Table 4,
the weighted mean of 14 measurements is 528 ± 13 Ma
(2σ), which is consistent with the TIMS U-Pb age of 524.9
± 3.1 Ma (2σ). Thus the standard sample shows its concordant signature.
Table 5 lists observed 204Pb/206Pb, 207Pb/ 206Pb, 206Pb/
238
U ratios, and 238U-206Pb* and 207Pb*-206Pb* ages of 44
monazite grains extracted from a sedimentary rock in
Taiwan. Error of the 206Pb/238U ratio is estimated by the
counting statistics of 206Pb and 238U and the external reproducibility of the relation between Pb+/UO+ and UO2+/
UO+ ratios in measuring standard monazite, which was
propagated to the individual sample measurements based
on the equation above. Data reduction are following as
SHRIMP is doing in Hiroshima (Sano et al., 2000). Common Pb correction was made as following the way of
standard monazite. The 238U- 206Pb* and 207Pb*- 206Pb*
ages vary significantly from 128 Ma to 1986 Ma and 61
Ma to 1910 Ma, respectively. There is a general agreement between the 238 U-206Pb* and 207 Pb*-206Pb* ages
except for No. 1 and 5.
Figure 6 shows the comparison between the U-Th-Pb
chemical ages measured by EMP (Tsutsumi et al., 2004)
and 238U- 206Pb* ages obtained from pits in close proximity on the same monazite grain from a sedimentary rock
in Taiwan by using Nano-SIMS. Except for some samples such as No. 4, 19, 38 and 44, excellent agreement
between the EMP chemical ages and NanoSIMS 238U206
Pb* ages is evident within experimental error. This
means that the both U-Th-Pb chemical and NanoSIMS
238
U- 206Pb* ages are reliable. Outliers such as No. 4, 19,
Ion microprobe U-Pb dating of monazite 603
Table 5.
samples
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
204
Pb/ 206Pb, 207Pb/206Pb, 206Pb/ 238U ratios, and 238U- 206Pb* and 207Pb*-206Pb* ages of monazite
204
Pb/2 0 6 Pb
0.002018 ± 0.000056
0.000110 ± 0.000016
0.000083 ± 0.000006
0.000245 ± 0.000017
0.000465 ± 0.000033
0.000280 ± 0.000018
0.000037 ± 0.000005
0.000505 ± 0.000030
0.000547 ± 0.000062
0.000081 ± 0.000005
0.002822 ± 0.000144
0.000024 ± 0.000002
0.000408 ± 0.000026
0.000181 ± 0.000017
0.001380 ± 0.000125
0.000211 ± 0.000019
0.000064 ± 0.000006
0.000039 ± 0.000005
0.000116 ± 0.000010
0.000782 ± 0.000033
0.000021 ± 0.000002
0.000524 ± 0.000024
0.000023 ± 0.000002
0.000024 ± 0.000002
0.000024 ± 0.000002
0.002528 ± 0.000301
0.000079 ± 0.000016
0.000138 ± 0.000011
0.000218 ± 0.000017
0.000026 ± 0.000002
0.001005 ± 0.000033
0.000261 ± 0.000022
0.000018 ± 0.000002
0.000353 ± 0.000025
0.000092 ± 0.000007
0.000279 ± 0.000043
0.000211 ± 0.000012
0.000085 ± 0.000006
0.003067 ± 0.000251
0.000033 ± 0.000003
0.000158 ± 0.000014
0.001364 ± 0.000115
0.000914 ± 0.000074
0.000947 ± 0.000083
207
Pb/2 0 6 Pb
0.1401 ± 0.0164
0.1152 ± 0.0013
0.1135 ± 0.0018
0.0949 ± 0.0035
0.1152 ± 0.0099
0.1153 ± 0.0008
0.1133 ± 0.0028
0.1157 ± 0.0016
0.0531 ± 0.0015
0.1183 ± 0.0008
0.1425 ± 0.0087
0.0974 ± 0.0027
0.0668 ± 0.0011
0.0508 ± 0.0007
0.0676 ± 0.0034
0.1145 ± 0.0013
0.0555 ± 0.0011
0.1175 ± 0.0012
0.1122 ± 0.0008
0.1225 ± 0.0061
0.1140 ± 0.0012
0.1212 ± 0.0026
0.1138 ± 0.0011
0.1149 ± 0.0008
0.1172 ± 0.0018
0.0642 ± 0.0087
0.1124 ± 0.0020
0.1115 ± 0.0008
0.0517 ± 0.0010
0.1158 ± 0.0008
0.0612 ± 0.0025
0.1155 ± 0.0017
0.1151 ± 0.0009
0.0532 ± 0.0011
0.1133 ± 0.0009
0.1145 ± 0.0026
0.0672 ± 0.0009
0.1097 ± 0.0015
0.0786 ± 0.0047
0.1129 ± 0.0008
0.0544 ± 0.0021
0.0525 ± 0.0032
0.0574 ± 0.0022
0.0610 ± 0.0019
206
Pb/2 3 8 U
0.0433 ± 0.0033
0.3164 ± 0.0252
0.3335 ± 0.0265
0.2705 ± 0.0223
0.0358 ± 0.0027
0.3124 ± 0.0028
0.3348 ± 0.0247
0.3007 ± 0.0265
0.0348 ± 0.0239
0.3398 ± 0.0028
0.2990 ± 0.0269
0.3177 ± 0.0227
0.1413 ± 0.0252
0.0368 ± 0.0112
0.0704 ± 0.0029
0.3405 ± 0.0055
0.0718 ± 0.0270
0.3505 ± 0.0057
0.2764 ± 0.0278
0.3023 ± 0.0219
0.3383 ± 0.0239
0.3095 ± 0.0268
0.3498 ± 0.0244
0.3458 ± 0.0277
0.3609 ± 0.0274
0.0253 ± 0.0287
0.3198 ± 0.0020
0.2886 ± 0.0255
0.0385 ± 0.0229
0.3469 ± 0.0030
0.0695 ± 0.0275
0.3141 ± 0.0054
0.3438 ± 0.0249
0.0393 ± 0.0273
0.3140 ± 0.0031
0.3395 ± 0.0249
0.1304 ± 0.0268
0.2568 ± 0.0103
0.0343 ± 0.0209
0.3226 ± 0.0027
0.0361 ± 0.0256
0.0201 ± 0.0029
0.0379 ± 0.0016
0.0725 ± 0.0030
f2 0 6
0.0312
0.0017
0.0013
0.0040
0.0073
0.0043
0.0006
0.0079
0.0085
0.0012
0.0445
0.0004
0.0072
0.0033
0.0257
0.0033
0.0012
0.0006
0.0018
0.0121
0.0003
0.0081
0.0004
0.0004
0.0004
0.0389
0.0012
0.0021
0.0040
0.0004
0.0188
0.0040
0.0003
0.0066
0.0014
0.0043
0.0037
0.0013
0.0474
0.0005
0.0029
0.0209
0.0140
0.0176
238
U- 2 0 6 Pb* age
(Ma)
265 ± 21
1768 ± 141
1852 ± 147
1537 ± 127
225 ± 18
1745 ± 139
1860 ± 148
1682 ± 135
220 ± 18
1883 ± 150
1619 ± 129
1777 ± 141
846 ± 67
232 ± 18
428 ± 34
1883 ± 95
446 ± 27
1935 ± 133
1570 ± 79
1684 ± 92
1877 ± 88
1725 ± 68
1932 ± 98
1913 ± 103
1985 ± 114
158 ± 11
1786 ± 131
1630 ± 93
243 ± 14
1918 ± 103
425 ± 35
1753 ± 89
1903 ± 130
247 ± 18
1757 ± 134
1876 ± 76
787 ± 59
1471 ± 88
210 ± 17
1801 ± 131
228 ± 13
128 ± 9
238 ± 20
443 ± 40
207
Pb*- 2 0 6 Pb* age
(Ma)
1846 ± 252
1860 ± 21
1838 ± 29
1456 ± 73
1781 ± 162
1825 ± 13
1845 ± 44
1780 ± 27
297 ± 110
1915 ± 13
1695 ± 157
1569 ± 51
634 ± 42
218 ± 40
510 ± 196
1826 ± 252
395 ± 21
1910 ± 29
1811 ± 73
1831 ± 159
1859 ± 162
1865 ± 13
1857 ± 44
1874 ± 27
1909 ± 110
76 ± 13
1822 ± 157
1793 ± 51
257 ± 42
1886 ± 40
485 ± 196
1831 ± 21
1877 ± 45
281 ± 18
1833 ± 14
1811 ± 98
746 ± 20
1775 ± 42
248 ± 18
1839 ± 13
288 ± 28
61 ± 212
320 ± 32
534 ± 14
Errors are 2 σ.
38 and 44 are all located below the dotted line (Fig. 6),
suggesting that the discrepancy may be due to an overestimation of radiogenic Pb by the chemical method, since
it is assumed that common Pb in the monazite is negligibly small. If the common Pb was incorporated at the time
of initial crystallization, there would be a negative correlation between the extent of discrepancy and the observed
age of grain. However this is not the case. Common Pb
604 Y. Sano et al.
may also be trapped in the grain after crystallization during geological time. The mechanism of incorporation is
not easy to assess since we have selected the analyzed
spot as non-metamicted state by using EMP.
Figure 7 shows the comparison between the U-Th-Pb
chemical ages (Tsutsumi et al., 2004) and 207Pb*-206Pb*
ages obtained by Nano-SIMS. Generally the chemical
ages are consistent with 207Pb*-206Pb* ages, even though
NANO-SIMS Pb-Pb (Ma)
2500
2000
#5
#1
1500
#12
#4
1000
#13
500
0
500
1000
1500
2000
2500
Chemical age (Ma)
Fig. 6. The comparison between U-Th-Pb chemical ages and
NanoSIMS 238U-206Pb* ages obtained from pits in close proximity on the same monazite grain from a sedimentary rock in
Taiwan. Errors are portrayed at two sigma level.
there is larger discrepancy than the comparison with 238U206
Pb* ages. For example, No. 1 and 5 indicate significantly older 207Pb*-206Pb* ages than the chemical ages,
suggesting discordant signature (probably partial Pb loss
due to recent thermal events). Outliers such as No. 4, 12,
and 13 may again be attributable to common Pb incorporation. However the 238U-206Pb* ages of No. 12 and 13
are comparable to those of chemical ages. Common Pb
incorporation as well as discordant signature may occur
in these samples, which makes its explanation difficult.
Figure 8 shows a Tera-Wasserburg U-Pb monazite
concordia diagram for the sedimentary rock in Taiwan.
Most grains indicate a concordant signature except for
two samples No. 1 and 5 which may have a recent Pb
loss. It is noted that there are three main age groups, 232
± 12 Ma, 436 ± 11 Ma and 1848 ± 57 Ma of concordant
monazite grains, even though the oldest group (1848 ±
57 Ma) may be composed of few sub-groups. Geological
province of Taiwan is relatively simple with five major
blocks (Western foothills, Hsuehshan Range, Backbone
Range, Eastern Central Range and Coastal Range) located
from west to east (Fig. 1). Western foothills where the
sample rock was collected is mainly composed of clastic
rocks of neritic signature between Miocene and Quaternary. A cumulative probability of the monazite ages is
similar to those of monazite ages in sandstone from the
mouth of the Chang Jiang (Yangtze river), which flows
on the Yangtze craton (Tsutsumi et al., 2004). Based on
the bulk chemical compositions, however, most
sandstones are considered to be derived from the North
China Platform (Tsutsumi et al., 2004).
Fig. 7. The comparison between U-Th-Pb chemical ages and
NanoSIMS 207Pb*-206Pb* ages obtained from pits in close proximity on the same monazite grain from a sedimentary rock in
Taiwan. Errors are portrayed at two sigma level.
Fig. 8. Terra-Wasserburg U-Pb monazite concordia diagrams
for the sedimentary rock in Taiwan. Errors are portrayed at
two sigma level. Dotted curve indicates concordant ages.
Taking into account observed age groups (232 ± 12
Ma, 436 ± 11 Ma and 1848 ± 57 Ma), one may assess the
provenance of detrital monazites. There are two main
blocks characterized by distinctive geological epoch in
China; the North China and the South China blocks. The
South China block is subdivided into two units: Yangtze
carton to the northwest and Cathaysia block to the southIon microprobe U-Pb dating of monazite 605
east. Geochronology of the Fuping Complex revealed that
there is Archean to Paleoproterozoic magmatic arc system that has been subsequently tectonically disrupted and
juxtaposed during the collision of the eastern and western North China blocks at similar to 1850 Ma, which resulted in the final assembly of the North China Craton
(Zhao et al., 2002; Guan et al., 2002). Recently Liu et al.
(2004) reported that zircon U-Pb ages of 418–427 Ma of
olivine pyroxenite from Hannuoba could be records of
the subduction of Mongolia oceanic crust under the North
China Craton. On the other hand, Li (1997) suggested
that the Paleoproterozoic basement rocks in Cathaysia
block were most likely formed at 1.77 Ga through
cratonization by granite formation. And then, the basement rocks were covered by anorogenic magmatic rocks
dated at ca. 850–750 Ma (e.g., Li et al., 2005). The Yangtze craton has a Late Archean to Paleoproterozoic core
surrounded mostly by younger orogenic belts which are
characterized by igneous activities about 800 Ma U-Pb
zircon (Li, X.-H. et al., 2003; Li, Z. X. et al., 2003). The
700–800 Ma U-Pb zircon ages also observed in the
ultrahigh-pressure metamorphic unit of the Dabie Shan,
eastern China (Schmid et al., 2003; Bryant et al., 2004).
From the Qinling-Dabie-Sulu zone which formed between
North China and South China blocks, detrital zircons with
about 400 Ma U-Pb ages are derived in Carboniferous
sedimentary rocks (Li et al., 2004), and Triassic zircon
with 220–250 Ma U-Pb ages are also found in Ultra High
Pressure metamorphism (Hacker et al., 1998). Li et al.
(2004) suggested that the detrital zircon were supplied
from the southern margin of North China block.
Observed age groups (436 ± 11 Ma and 1848 ± 57
Ma) agree well with those of the North China Craton,
suggesting that these detrital monazites were derived from
the craton. The youngest age group (232 ± 12 Ma) may
be related to Triassic syn-collisional monzogranites, possibly representing the collision of the Central Asian
Orogenic Belt with the North China Craton and final closure of the Paleo-Asian Ocean (Zhang et al., 2004). However, zircons with U-Pb ages of 1700–1900 Ma and 700–
800 Ma were also found in South China block. The Chang
Jiang flows on the Yangtze craton along the QinlingDabie-Sulu zone, which is another source of zircons with
400 Ma and 220–250 Ma U-Pb ages. This area is an alternative provenance for western foothills sediments in Taiwan.
CONCLUSIONS
A pilot study of NanoSIMS 238U*-206Pb* and 207Pb*Pb* dating of monazite samples with various formation ages has been reported here. After taking the Pb+/
UO + and UO 2+/UO + calibration, we obtain consistent
238
U- 206Pb* ages at 5~7 µm pits, which agree with the U206
606 Y. Sano et al.
Th-Pb chemical ages from spots in close proximity on
the same monazite grains by using EMP. The 207Pb*206
Pb* ages are also comparable with the chemical ages
while there are a few discordant samples. U-Pb dating is
routinely undertaken by the IDTIMS method as well as
SHRIMP instrument. However, in cases where the
monazite grains are smaller than 10 µm or the textural
context of the grains are significantly complex, then it is
possible to use NanoSIMS to obtain accurate and reasonably precise U-Pb ages. For instance based on the U-Pb
age distribution of 44 monazite grains extracted from a
sedimentary rock in Taiwan, the provenance of detrital
monazites is attributed to either North China Craton or
Qinling-Dabie-Sulu zone between North China and South
China blocks.
Acknowledgments—We appreciate K. Yokoyama for providing a standard monazite; K. Terada and R. A. Stern for helpful
comments and discussion. Earlier version of the paper was reviewed by an anonymous referee. Constructive comments by
H. Yurimoto and P. W. O. Hoskin were useful to revise the manuscript.
REFERENCES
Ballard, J. R., Palin, J. M., Williams, I. S., Campbell, I. H. and
Faunes, A. (2001) Two ages of porphyry intrusion resolved
for the super-giant Chuquicamata copper deposit of northern Chile by ELA-ICP-MS and SHRIMP. Geology 29, 383–
386.
Bryant, D. L., Ayers, J. C., Gao, S., Miller, C. F. and Zhang, H.
F. (2004) Geochemical, age, and isotopic constraints on the
location of the Sino-Korean/Yangtze Suture and evolution
of the Northern Babie Complex, east central China. Geol.
Soc. Amer. Bull. 116, 698–717.
Compston, W. (1999) Geological age by instrumental analysis:
the 29th Hallimond Lecture. Mineral. Mag. 63, 297–311.
Compston, W., Williams, I. S. and Meyer, C. E. (1984) U-Pb
geochronology of zircons from lunar breccia 73217 using a
sensitive high mass-resolution ion microprobe. Proceedings
of the Fourteenth Lunar and Planetary Science Conference,
Part two, J. Geophys. Res. B89(Suppl.), 525–534.
DeWolf, C. P., Belshaw, N. and O’Nions, R. K. (1993) A metamorphic history from micron-scale 207Pb/206Pb chronometry of Archean monazite. Earth Planet. Sci. Lett. 120, 207–
220.
Guan, H., Sun. M., Wilde, S. A., Zhou, X. H. and Zhai, M. G.
(2002) SHRIMP U-Pb zircon geochronology of the Fuping
Complex: implications for formation and assembly of the
North China Craton. Precam. Res. 113, 1–18.
Hacker, B. R., Ratschbacher, L., Webb, L., Ireland, T., Walker,
D. and Shuwen, D. (1998) U/Pb zircon ages constrain the
architecture of the ultrahigh-pressure Qinling-Dabie
Orogen, China. Earth Planet. Sci. Lett. 161, 215–230.
Hillion, F., Daigne, B., Girard, F., Slodzian, G. and
Schuhmacher, M. (1993) A new high performance instrument: The Cameca Nano-SIMS 50. Secondary Ion Mass
Spectrometry: SIMS IX. Proceedings of the 9th International
Conference on Secondary Ion Mass Spectrometry
(Benninghoven, A., Nihei, Y., Shimizu, R. and Werner, H.
W., eds.), 254–257.
Hinthorne, J. R., Andersen, C. A., Conrad, R. L. and Lovering,
J. F. (1979) Single-grain 207 Pb/ 206 Pb and U/Pb age
determinations with a 10 µm spatial resolution using the
ion microprobe mass analyser (IMMA). Chem. Geol. 25,
271–303.
Hirata, T. and 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., Rundnick, R. L. and McDonough, W. F. (2000) Precise elemental and isotope ratio determination by simultaneous solution nebulization and laser ablation-ICP-MS:
application to U-Pb geochronology. Chem. Geol. 164, 281–
301.
Ireland, T. R., Compston, W., Williams, I. S. and Wendt, I.
(1990) U-Th-Pb systematics of individual perovskite grains
from the Allende and Murchison carbonaceous chondrites.
Earth Planet. Sci. Lett. 101, 379–387.
Kinny, P. D., McNaughton, N. J., Fanning, C. M. and Maas, R.
(1994) 518 Ma sphene (titanite) from the Khan pegmatite,
Namibia, southwest Africa: a potential ion-microprobe
standard. Abstracts of the Eighth International Conference
on Geochronology, Cosmochronology and Isotope Geology
(Lanphere, M. A., Dalrymple, G. B. and Turrin, B. D., eds.),
U.S. Geological Survey Circular 1107, 171 pp.
Li, R., Li, S., Jin, F., Wan, Y. and Zhang, S. (2004) Provenance
of Carboniferous sedimentary rocks in the northern margin
of Dabie Mountains, central China and the tectonic significance: constraints from trace elements, mineral chemistry
and SHRIMP dating of zircons. Sediment. Geol. 166, 245–
264.
Li, W.-X., Li, X.-H. and Li, Z.-X. (2005) Neoproterozoic bimodal magmatism in the Cathaysia Block of South China
and its tectonic significance. Precam. Res. 136, 51–66.
Li, X.-H. (1997) Timing of the Cathaysia Block formation:
Constraints from SHRIMP U-Pb zircon geochronology.
Episode 20, 188–192.
Li, X.-H., Li, Z.-H., Ge, W., Zhou, H., Li, W., Liu, W. and
Wingate, M. T. D. (2003) Neoproterozoic granitoids in South
China: crustal melting above a mantle plume at ca. 825 Ma?
Precam. Res. 122, 45–83.
Li, Z. X., Li, X. H., Kinny, P. D., Wang, J., Zhang, S. and Zhou,
H. (2003) Geochronology of Neoproterozoic syn-rift
magmatism in the Yangtze Craton, South China and correlations with other continents: evidence for a mantle
superplume that broke up Rodinia. Precam. Res. 122, 85–
109.
Liu, Y. S., Yuan, H. L., Gao, S., Hu, Z. C., Wang, X., Liu, X. M.
and Lin, W. L. (2004) Zircon U-Pb ages of olivine
pyroxenite xenolith from Hannuoba: Links between the 97–
158 Ma basaltic underplating and granulite-facies metamorphism. Chinese Sci. Bull. 49, 1055–1062.
Meibom, A., Cuif, J., Hillion, F., Constantz, B. R., JuilletLeclerc, A., Dauphin, Y., Watanabe, T. and Dunbar, R. B.
(2004) Distribution of magnesium in coral skeleton.
Geophys. Res. Lett. 31, L23306.
Miyamoto, T. and Yanagi, T. (1996) U-Pb dating of detrital zircons from the Sangun metamorphic rocks, Kyushu, Southwest Japan: An evidence for 1.9–2.0 Ga ganite emplacement in the provenance. Geochem. J. 30, 261–271.
Montel, J. M., Foret, S., Veschambre, M., Nicollet, N. and Provost, A. (1996) Electron microprobe dating of monazite.
Chem. Geol. 131, 37–53.
Muller, W. (2003) Strengthening the link between
geochronology, textures and petrology. Earth Planet. Sci.
Lett. 206, 237–251.
Nguyen, A. N. and Zinner, E. (2004) Discovery of ancient silicate stardust in a meteorite. Science 303, 1496–1499.
Paquette, J., Goncalves, P., Devouard, B. and Nicollet, C. (2004)
Micro-drilling ID-TIMS U-Pb dating of single monazites:
A new method to unravel complex poly-metamorphic
evolutions. Application to the UHT granulites of
Andriamena (North-Central Madagascar). Contrib. Mineral.
Petrol. 147, 110–122.
Sano, Y., Oyama, T., Terada, K. and Hidaka, H. (1999) Ion microprobe U-Pb dating of apatite. Chem. Geol. 153, 249–
258.
Sano, Y., Hidaka, H., Terada, K., Shimizu, H. and Suzuki, M.
(2000) Ion microprobe U-Pb zircon geochronology of the
Hida gneiss: Finding of the oldest minerals in Japan.
Geochem. J. 34, 135–153.
Sano, Y., Shirai, K., Takahata, N., Hirata, T. and Sturchio, N.
C. (2005) Nano-SIMS analysis of Mg, Sr, Ba and U in natural calcium carbonate. Analy. Scvi. 21, 1091–1097.
Schmid, R., Romer, R. L., Franz, L., Oberhansi, R. and
Martinotti, G. (2003) Basement-cover sequences within the
UHP unit of the Dabie Shan. J. Metamor. Geol. 21, 531–
538.
Schuhmacher, M., de Chambost, E., McKeegan, K. D., Harrison,
T. M. and Migeon, H.-N. (1994) In situ U/Pb dating of zircon with the Cameca IMS 1270. Proceedings of the 11th
SIMS Conference (Benninghoven, A. et al., eds.), 919–922,
Wiley, New York.
Stacey, J. S. and Krammer, J. D. (1975) Approximation of terrestrial lead isotope evolution by a two-stage model. Earth
Planet. Sci. Lett. 26, 207–221.
Stadermann, F. J., Croat, T. K., Bernatowicz, T. J., Amari, S.,
Messenger, S., Walker, R. M. and Zinner, E. (2005) Supernova graphite in the NanoSIMS: Carbon, oxygen and titanium isotopic compositions of a spherule and its TiC subcomponents. Geochim. Cosmochim. Acta 69, 177–188.
Stern, R. A., Fletcher, I., Rasmussen, B., McNaughton, N. and
Griffin, B. (2005) Ion microprobe (NanoSIMS 50) Pb-isotope geochronology at <5 µ m scale. Int. J. Mass Spectr.
244, 125–134.
Suzuki, K. and Adachi, M. (1991) Precambrian provenance and
Silurian metamorphism of the Tsubonosawa paragneiss in
the South Kitakami terrane, Northeast Japan, revealed by
Th-U-total Pb chemical isochron ages of monazite, zircon
and xenotime. Geochem. J. 25, 309–328.
Tsunogae, T. and Yurimoto, H. (1995) Single zircon U-Pb
geochronology of the Limpopo Belt by secondary ion mass
spectrometry. Geochem. J. 29, 197–205.
Tsutsumi, Y., Lee, C.-S., Shen, J.-S., Lan, C.-Y. and Yokoyama,
Ion microprobe U-Pb dating of monazite 607
K. (2004) Detrital minerals in Tertiary and Quatternary
sandstones in Taiwan. Abstract of Annual Meeting of the
Mineralogical Society of Japan, 2004, 255 pp. (in Japanese).
Whitehouse, M. J., Claesson, S., Sunde, T. and Vestin, J. (1997)
Ion microprobe U-Pb zircon geochronology and correlation
of Archaean gneisses from the Lewisian Complex of
Gruinard Bay, northwestern Scotland. Geochim.
Cosmochim. Acta 61, 4429–4438.
Wiedenbeck, M. and Goswami, J. N. (1994) High precision
207
Pb/206Pb zircon geochronology using a small ion microprobe. Geochim. Cosmochim. Acta 58, 2135–2141.
Williams, I. S. (1998) U-Th-Pb geochronology by ion microprobe. Reviews in Economic Geology 7, 1–35.
608 Y. Sano et al.
Williams, I. S., Buick, I. S. and Cartwright, I. (1996) An extended episode of early Mesoproterozoic metamorphic fluid
flow in the Reynolds Range, central Australia. J. Metamor.
Geol. 14, 29–47.
Zhang, Y. B., Wu, F. Y., Wilde, S. A., Zhai, M. G., Lu, X. P. and
Sun, D. Y. (2004) Zircon U-Pb ages and tectonic implications of ‘Early paleozoic’ granitoids at Yanbian, Jilin Province, northeast China. Island Arc 13, 484–505.
Zhao, G. C., Wilde, S. A., Cawood, P. A. and Sun, M. (2002)
SHRIMP U-Pb zircon ages of the Fuping Complex: Implications for late Archean to Paleoproterozoic accreation and
assembly of the North China Craton. Amer. J. Sci. 302, 191–
226.