in the Tangyuan Formation the lowest part of the Badu Group, and display a transitional rela-
tionship with the surrounding leptynites, with a few granitic gneisses showing intrusive contacts
with the country rocks Hu et al., 1991. These rocks have undergone amphibolite facies meta-
morphism. The upper sequence, i.e. the Mamian- shan Group in Fujian and the Longquan Group
in Zhejiang, mainly comprise schists, meta-vol- canics, Fe-bearing quartzites and marbles. These
rocks have been metamorphosed to lower green- schist facies Hu et al., 1991; Jin et al., 1992.
Samples of amphibolite analyzed in this study were collected from two localities along road-cuts
in Tianjingping, Jianning County, NW Fujian and Zhulu, Longquan County, SW Zhejiang Fig. 1.
Samples from NW Fujian include LG24, LG28, LG29 and LG35 with chemical compositions of
transitional and alkali basalts Group 1, while those from SW Zhejiang include LB258, LB259,
LB2622, LB263, LB264 and LB265 with tholeiitic compositions Group 2, and one sample, LB261,
with transitional basalt composition similar to Group 1 samples. A 50 kg amphibolite sample
LG28, collected from NW Fujian yields a SHRIMP U – Pb zircon age of 1766 9 19 Ma
which is interpreted as the crystallization age for the protolith of the amphibolites Li, 1997a. This
zircon date provides the best estimate of the for- mation age of the Mayuan Group in NW Fujian.
Amphibolites in SW Zhejiang have not been di- rectly dated, but U – Pb zircon dates of 1832 9 80
Ma, 1870 9 36 Ma, 1889 9 95 Ma and 1975 9 80 Ma obtained by conventional U – Pb techniques
were reported for the granitic gneisses Hu et al., 1992; Gan et al., 1993, 1995. Because the granitic
gneisses are intrusive into the surrounding lep- tynites and amphibolites, the lowest part of the
Badu Group, their ages 1.8 – 1.98 Ga are sup- posed as minimum age for the Badu Group. It is
noted, however, that all the zircons from the granitic gneisses are highly discordant, and the
significance of the upper intercept ages of 1.8 – 1.98 Ga is equivocal. A precise
207
Pb
206
Pb age of 1743 9 8 Ma by evaporation techniques has been
reported for a pegmatite which intrudes the Tangyaun Formation Gan et al., 1995. This age
provides a minimum age for the amphibolites in SW Zhejiang. Geological and chronological data
therefore suggest that the amphibolites from NW Fujian and SW Zhejiang are likely contemporane-
ous, although the precise age of the SW Zhejiang amphibolites is not yet known.
3. Analytical methods
Major element oxides were determined using a Rigaku RIX 2000 X-ray fluorescence spectrome-
ter XRF at the Department of Geology, Na- tional Taiwan University. The analytical un-
certainties are generally better than 5 for most elements. The detailed analytical procedures for
major element analysis by XRF are described by Lee et al. 1997.
Trace elements were analyzed using a Perkin- Elmer Sciex ELAN 6000 inductively-coupled
plasma mass spectrometer ICP-MS at the Guangzhou Institute of Geochemistry, Chinese
Academy of Sciences. The detailed procedures for trace element analysis by ICP-MS are described
by Li 1997b. About 50 mg sample powders were dissolved in Teflon bombs using a HF + HNO
3
mixture. An internal standard solution containing the single element Rh was used to monitor drift in
mass response during counting. The international standard BCR-1 was chosen to calibrate element
concentrations of measured samples. In-run ana- lytical precision for most elements is less than 3,
whilst reproducibility is generally less than 5 see LB264 in Table 1. Trace elements are also
presented for basalt standard BHVO-1, and are generally in good agreement with compiled values
Govindaraju, 1994.
Nd isotopic compositions unspiked aliquots were determined using a multi-collector Finnigan
MAT-262 mass spectrometer operated in static multi-collector mode at the Research Center of
Geoscience, Chinese Academy of Sciences in Bei- jing. Sm and Nd concentrations spiked with
mixed
146
Nd –
149
Sm tracers were measured on a VG-354 mass spectrometer operated in dynamic
multi-collector mode at the Guangzhou Institute of Geochemistry. The
143
Nd
144
Nd ratio of the La Jolla standard and USGS basalt standard BCR-1
measured on this MAT-262 mass spectrometer
X .-
H .
Li et
al .
Precambrian
Research
102 2000
251 –
262
Table 1 Major and trace element analyses of the amphibolites from the Cathaysia Block, SE China
Standard Group 2B
Group 2A Group 1
LB258 LB259
LB262 LB263
LB264 LB264
b
LB265 BHVO-1
Sample LG24
LG28 LG29
LG35 LB261
46.18 50.21
47.74 48.46
47.08 49.03
47.23 SiO
2
47.87 47.28
47.50 48.47
2.56 1.82
2.42 1.76
2.20 2.13
1.50 1.43
2.21 2.28
TiO
2
2.22 13.64
15.92 15.92
15.19 15.84
16.08 Al
2
O
3
16.78 17.90
16.31 16.11
17.02 14.93
12.18 13.88
15.67 13.20
12.70 13.73
14.45 13.37
S Fe
2
O
3
13.86 13.05
0.17 0.20
0.26 0.22
0.20 0.18
0.22 0.23
0.19 0.21
0.20 MnO
8.08 5.22
5.28 3.87
6.02 MgO
5.93 4.48
5.08 5.71
5.28 5.25
8.96 10.01
9.59 8.86
9.96 9.47
9.58 7.33
CaO 7.94
7.81 7.91
3.31 4.08
2.67 2.97
3.01 3.40
2.98 2.83
3.90 3.39
2.88 Na
2
O 1.04
1.06 0.92
0.78 1.04
1.27 1.08
1.53 1.00
1.30 1.36
K
2
O 0.24
0.21 0.22
0.17 0.13
0.22 0.13
0.33 P
2
O
5
0.31 0.28
0.31 99.08
99.15 98.30
99.48 99.08
99.20 98.01
98.70 99.05
99.02 98.70
Total 57
51 48
37 52
Mg c
a
51 44
48 49
48 50
309 236
295 357
233 223
205 259
184 320
V 146
165 143
689 78.7
379 543
362 165
546 522
539 292
36.5 58.1
28.0 Cr
245 38.0
195 224
168 62.2
231 220
236 125
64.0 74.0
70.8 Ni
42.9 20.4
43.0 59.0
46.6 45.3
40.4 82.7
59.8 9.8
46.5 Rb
32.5 28.1
315 448
221 257
282 244
235 236
265 410
739 535
442 Sr
28.6 26.7
45.6 33.3
38.7 46.7
29.9 30.3
32.4 30.8
22.3 26.9
29.1 Y
158 131
140 147
90.5 89.6
159 90.1
Zr 181
216 179
140 191
18.4 17.4
7.93 9.72
8.30 7.67
3.76 3.85
3.63 20.4
Nb 17.1
15.9 16.4
1.50 1.27
2.50 2.25
1.78 1.80
2.85 2.87
5.82 0.11
4.80 Cs
3.66 1.75
155 469
90.9 100
110 89.6
87.2 83.4
144 144
623 401
380 Ba
8.96 11.5
9.94 8.20
4.20 4.14
La 4.74
17.6 16.0
15.2 17.7
17.1 20.1
22.8 26.9
24.0 20.8
12.2 12.1
42.0 13.3
42.7 39.5
Ce 40.7
42.0 35.8
5.28 5.81
3.70 3.49
3.35 3.14
1.95 1.99
2.22 5.65
4.29 5.56
5.40 Pr
20.9 25.0
18.9 15.2
16.4 15.1
9.93 10.1
11.0 25.6
19.8 23.2
23.2 Nd
5.48 4.34
4.90 4.96
3.41 3.45
4.97 3.62
5.62 6.48
5.56 Sm
6.21 4.90
1.91 2.40
1.81 1.59
1.67 1.83
1.35 1.33
1.54 2.15
1.89 2.09
1.95 Eu
5.11 6.73
6.52 5.43
6.31 6.43
4.85 4.68
4.95 6.44
4.87 5.99
5.51 Gd
1.20 0.92
1.09 1.26
0.82 0.79
0.89 0.90
Tb 0.99
0.91 0.94
0.75 1.02
7.40 Dy
5.79 5.95
6.74 7.41
5.43 5.53
5.25 5.42
4.35 5.34
5.13 4.77
1.61 1.23
1.46 1.77
1.17 1.13
1.05 1.23
1.16 1.01
Ho 1.03
1.06 0.84
2.94 3.13
4.44 3.47
3.97 4.98
3.31 3.20
3.47 2.70
2.29 2.81
2.72 Er
0.42 0.43
0.68 0.49
0.60 0.75
0.49 0.52
0.51 0.32
0.31 0.38
0.39 Tm
4.23 3.22
3.65 4.67
3.12 3.08
2.64 3.29
Yb 2.06
2.37 2.41
1.98 2.65
0.62 0.48
0.53 0.72
0.47 0.48
0.50 0.30
Lu 0.39
0.28 0.35
0.33 0.41
3.86 3.06
3.38 3.81
2.15 2.10
3.88 2.37
4.25 4.56
5.40 Hf
4.54 3.12
1.05 0.99
0.50 0.61
0.47 0.44
0.21 0.22
0.21 1.24
0.89 0.93
1.15 Ta
1.16 Th
1.36 2.00
0.63 0.78
0.29 0.30
0.39 1.16
1.26 1.70
1.54 2.61
0.99 0.34
0.10 0.25
0.20 0.19
0.08 0.44
0.62 U
0.67 0.32
0.56 1.88
a
Mg c = 100 MgMg+Fe
2+
, assuming Fe
2
O
3
FeO+Fe
2
O
3
= 0.20.
b
Duplicate analysis.
Fig. 2. Classification of amphibolites rocks from Cathaysia Block Winchester and Floyd, 1976, 1977. a ZrTiO
2
versus NbY; b TiO
2
versus ZrP
2
O
5
; c NbY versus ZrP
2
O
5
.
4. Results
