Geochronological research of the Lincang Batholith is one key scientific problem to discuss the tectonic evolution of the Tethys. Two granitic specimens were selected from the Mengku-Douge area in the Lincang Batholith to perform the LA-ICPMS Zircon U-Pb dating based on thorough review of petrological, geochemical, and geochronological data by the former scientists. Rock-forming age data of biotite granite specimen from Kunsai is about 220 Ma, the Norian age. However, the west sample from Mengku shows 230 Ma, the Carnian age. The later intrusion in Kunsai area located east to the Mengku area shows directly their uneven phenomena in both space and time and may indirectly reflect the space difference of the contraction-extension transformation period of the deep seated faults. Considering the former 40Ar/39Ar data and the outcrop in Mengku, the Lincang Batholith should have experienced one tectonic exhumation and regional subsidence cycle. The regional subsidence cycle has close relations to the expansion of the Meso Tethys.
The Sanjiang-Indochina region is one key area to study the evolution of the Tethys [
Map of plate tectonics and ore-forming metals in the southern Sanjiang and Indochina peninsula. (a) Scope of Tethys and zone divisions; (b) research area and distribution of major metals: (1) Changning-Menglian-Chiangmai PaleoTethys Suture (time and space after [
Regional map of Indian Period and research locality in western Yunnan. The distribution of metal deposits also indicates that there is an important boundary along the Lincang Granite Batholith. Stereographic maps of lower hemisphere projection indicating the initial occurrence of Lincang granite Batholith are also plotted in the regional map. L, S, Q refer to joints parallel to the initial foliation, parallel to the flow direction but upright to the initial foliation, upright to both the flow direction and initial foliation. Orientation of shear fractures can be generated by local stress system of the Batholith with emplacements [
The Lingcang Batholith was divided into three lithologic intervals by previous authors, the Xiaojie, Lincang, and Menghai intervals (Figure
The Lingcang Batholith was proposed to form in a passive continental margin according to geochemical research [
Isotopic age data for the Lincang Batholite in the earlier stage.
Lithologic section | Lithology | Measured objects and methods | Dating results, Ma | Sample positions | Testers and the time |
---|---|---|---|---|---|
Xiaojie | Granite porphyry | Whole-rock (Rb-Sr) |
|
Laomaocun | Zhang et al., 2006 [ |
Xiaojie | Monzonitic granite | Whole-rock (87Sr/86Sr) | 279 | Yun County | Chen, 1991 [ |
Lincang | Biotite granite | Biotite (40Ar/39Ar) |
|
Near the Lancangjiang River | Dai et al., 1986 [ |
Lincang | Monzonitic granite | Whole-rock (Rb-Sr) | 279 | Lincang | Chen, 1991 [ |
Lincang | Medium-grained equigranular granodiorite | Whole-rock (Rb-Sr) | 263.8 | Milestone along Lincang-Mengku road 327–387 km | Zhang et al., 1990 [ |
Lincang | Unequal-sized biotite granite | Whole-rock (Rb-Sr) | 193 | Shangyun-Xiaotang | Zhang et al., 1990 [ |
Lincang | Monzonitic granite | Whole-rock (Rb-Sr) |
|
Lincang | Liu et al., 1989 [ |
Menghai | Monzonitic granite | Whole-rock (87Sr/86Sr) | 279 | Menghai | Chen, 1991 [ |
Menghai | Monzonitic granite | Biotite (Rb-Sr) | 256 | Menghai | Wang, 1984 [ |
But there are also some understanding differences on the crystallization period and evolution time of the Lincang Batholith. Many predecessors discussed mineral diagenesis and tectonic evolution through traditional data [
Therefore, the formation and evolution of the Lincang Batholith is still the key to discuss the regional tectonic evolution of the Baoshan and Lanping-Simao-Indochina block. In this study, we conducted petrographic analysis of the Lincang Batholith and provide new LA-ICP-MS U-Pb data in order to constrain the tectonic evolution of the Batholith. We discuss these results of dating in the context of regional tectonic evolution.
The U-Pb zircon age dating of monzonitic granite samples selected from the Mengku-Douge research area in Lincang segment (Figures
Geological sketch map in Mengku-Douge area (revised after [
The biotite monzonitic granite samples were selected from the Kunsai quarries to the east of Quannei-Douge migmatite rock belt (Figures
Geochronological research of granite sample KS-2. (a) Position photo of the biotite monzonitic granite sample in the field of Kunsai Quarry. (b) The zircon grows together with the microcline CPL. (c) The microstructure of complete recrystallized quartz indicates the rock once experienced high-greenschist facies of deformation, CPL. (d) One biotite crystal is folded, PPL. (e) Magmatic zircon is shown by the SEM cathodoluminescence (CL) image. The circled area is deduced to form during the crystallization of granite and is just the measured area by laser-ICPMS (f) Zircon La-ICPMs U-Pb dating figure, and the average age is about 220 Ma.
The monzonitic granite sample MK-4 is selected from the Mengku East Quarry at the eastern side of the Mengku Town in the Shuangjiang County, which separates Jurassic red clastic rocks with one bedding bottom granitic conglomerate by the paleo-weathering crust in between (Figures
Geochronological research of the granite sample MK-4. (a) Position photo of the biotite monzonitic granite sample in a field Quarry of east Mengku. (b) Granitic intrusion (lower left) and its fossil weathering were cleavaged. (c) The red detrital material of terrigenous origin, Huakaizuo Formation in Jurassic, was normal gradational. (d) Granitic intrusions are selected as sample. (e) The micro characteristics of MK-4 and the zircon setting are shown. The zircon grains are associated with quartz and plagioclase and have been degraded by some weathering process, CPL, (f) Magmatic zircon is shown by the SEM cathodoluminescence (CL) image. The circled area is deduced to form during the crystallization of granite and is just the measured area by laser-ICPMS. (g) Zircon La-ICPMs U-Pb dating figure, and the average age is about 245 Ma.
As shown in Figure
U-Pb isotopic dating for the single grain Zircon from granite of Kunsai.
No. | 207Pb/206Pb | 207Pb/235U | 206Pb/238U | 208Pb/232Th | 207Pb/206Pb | 207Pb/235U | 206Pb/238U | 208Pb/232Th | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
|
A77 | 0.05789 | 0.00231 | 0.25961 | 0.00949 | 0.03251 | 0.00089 | 0.01383 | 0.00076 | 526 | 38 | 234 | 8 | 206 | 6 | 278 | 15 |
A78 | 0.05188 | 0.00244 | 0.23562 | 0.00953 | 0.03294 | 0.00079 | 0.01035 | 0.00025 | 280 | 110 | 215 | 8 | 209 | 5 | 208 | 5 |
A79 | 0.05273 | 0.00141 | 0.24329 | 0.00604 | 0.03345 | 0.00081 | 0.01108 | 0.00055 | 317 | 26 | 221 | 5 | 212 | 5 | 223 | 11 |
A80 | 0.05213 | 0.00216 | 0.23471 | 0.00801 | 0.03265 | 0.00077 | 0.01025 | 0.00024 | 291 | 97 | 214 | 7 | 207 | 5 | 206 | 5 |
A81 | 0.05209 | 0.00131 | 0.25938 | 0.00608 | 0.0361 | 0.00086 | 0.01177 | 0.00034 | 289 | 25 | 234 | 5 | 229 | 5 | 237 | 7 |
A82 | 0.05014 | 0.00118 | 0.24192 | 0.00531 | 0.03498 | 0.00082 | 0.01113 | 0.00044 | 201 | 24 | 220 | 4 | 222 | 5 | 224 | 9 |
A83 | 0.05126 | 0.00122 | 0.24287 | 0.00541 | 0.03435 | 0.00081 | 0.01155 | 0.0006 | 253 | 24 | 221 | 4 | 218 | 5 | 232 | 12 |
A84 | 0.05027 | 0.00114 | 0.24534 | 0.00525 | 0.03539 | 0.00083 | 0.01176 | 0.00041 | 207 | 24 | 223 | 4 | 224 | 5 | 236 | 8 |
A89 | 0.0521 | 0.00237 | 0.22575 | 0.00875 | 0.03143 | 0.00075 | 0.00987 | 0.00023 | 290 | 107 | 207 | 7 | 199 | 5 | 199 | 5 |
A90 | 0.05305 | 0.00182 | 0.2649 | 0.0084 | 0.03621 | 0.00094 | 0.01376 | 0.00075 | 331 | 33 | 239 | 7 | 229 | 6 | 276 | 15 |
A91 | 0.05739 | 0.00113 | 0.23972 | 0.00441 | 0.03029 | 0.0007 | 0.00946 | 0.00032 | 507 | 23 | 218 | 4 | 192 | 4 | 190 | 6 |
A92 | 0.05076 | 0.00135 | 0.24604 | 0.00612 | 0.03515 | 0.00085 | 0.01173 | 0.00045 | 230 | 26 | 223 | 5 | 223 | 5 | 236 | 9 |
A93 | 0.05089 | 0.00279 | 0.24455 | 0.01197 | 0.03485 | 0.00086 | 0.01098 | 0.00025 | 236 | 127 | 222 | 10 | 221 | 5 | 221 | 5 |
A94 | 0.05114 | 0.00155 | 0.24377 | 0.00683 | 0.03457 | 0.00087 | 0.01167 | 0.00055 | 247 | 29 | 222 | 6 | 219 | 5 | 235 | 11 |
A95 | 0.05055 | 0.00109 | 0.24175 | 0.00488 | 0.03469 | 0.00081 | 0.01181 | 0.00045 | 220 | 24 | 220 | 4 | 220 | 5 | 237 | 9 |
A96 | 0.05018 | 0.00134 | 0.23857 | 0.00594 | 0.03448 | 0.00084 | 0.01149 | 0.00049 | 203 | 26 | 217 | 5 | 219 | 5 | 231 | 10 |
B02 | 0.05115 | 0.00119 | 0.24774 | 0.00541 | 0.03514 | 0.00084 | 0.01297 | 0.00054 | 248 | 25 | 225 | 4 | 223 | 5 | 260 | 11 |
B03 | 0.05067 | 0.00224 | 0.24165 | 0.00903 | 0.03459 | 0.00082 | 0.0109 | 0.00025 | 226 | 104 | 220 | 7 | 219 | 5 | 219 | 5 |
B04 | 0.05104 | 0.00235 | 0.24163 | 0.00953 | 0.03433 | 0.00082 | 0.01081 | 0.00025 | 243 | 109 | 220 | 8 | 218 | 5 | 217 | 5 |
B05 | 0.05079 | 0.00153 | 0.24968 | 0.00699 | 0.03567 | 0.0009 | 0.01274 | 0.00067 | 231 | 29 | 226 | 6 | 226 | 6 | 256 | 13 |
B06 | 0.05039 | 0.00095 | 0.24525 | 0.00437 | 0.03531 | 0.00082 | 0.01121 | 0.00038 | 213 | 25 | 223 | 4 | 224 | 5 | 225 | 8 |
B07 | 0.05429 | 0.00243 | 0.27463 | 0.01035 | 0.03669 | 0.00089 | 0.01147 | 0.00027 | 383 | 103 | 246 | 8 | 232 | 6 | 230 | 5 |
B08 | 0.05014 | 0.00223 | 0.24399 | 0.00913 | 0.0353 | 0.00085 | 0.01114 | 0.00026 | 201 | 104 | 222 | 7 | 224 | 5 | 224 | 5 |
B09 | 0.05141 | 0.00105 | 0.25807 | 0.00495 | 0.03643 | 0.00086 | 0.01414 | 0.00053 | 259 | 25 | 233 | 4 | 231 | 5 | 284 | 11 |
As shown in Figure
U-Pb isotopic dating for the single grain Zircon from granite of Mengku.
Analysis | 207Pb/206Pb | 207Pb/235U | 206Pb/238U | 208Pb/232Th | 207Pb/206Pb | 207Pb/235U | 206Pb/238U | 208Pb/232Th | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
no. | Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
Ratio | Error (1 |
1 | 0.05174 | 0.00244 | 0.32303 | 0.0139 | 0.04528 | 0.00108 | 0.01152 | 0.00053 | 274 | 56 | 284 | 11 | 285 | 7 | 232 | 11 |
2 | 0.09115 | 0.00288 | 2.96352 | 0.08448 | 0.23585 | 0.0053 | 0.08061 | 0.00287 | 1450 | 25 | 1398 | 22 | 1365 | 28 | 1567 | 54 |
3 | 0.11509 | 0.00332 | 0.50952 | 0.01225 | 0.03212 | 0.00066 | 0.02102 | 0.00068 | 1881 | 19 | 418 | 8 | 204 | 4 | 420 | 13 |
4 | 0.04837 | 0.00265 | 0.22077 | 0.01108 | 0.03312 | 0.00085 | 0.01153 | 0.00063 | 117 | 69 | 203 | 9 | 210 | 5 | 232 | 13 |
5 | 0.04837 | 0.0022 | 0.27295 | 0.01145 | 0.04095 | 0.00092 | 0.01223 | 0.0006 | 117 | 57 | 245 | 9 | 259 | 6 | 246 | 12 |
6 | 0.05351 | 0.00279 | 0.29775 | 0.01415 | 0.04038 | 0.00104 | 0.01371 | 0.00078 | 350 | 62 | 265 | 11 | 255 | 6 | 275 | 16 |
7 | 0.0806 | 0.00218 | 2.27431 | 0.05585 | 0.2048 | 0.00394 | 0.05968 | 0.00155 | 1212 | 22 | 1204 | 17 | 1201 | 21 | 1172 | 30 |
8 | 0.0802 | 0.00341 | 2.36577 | 0.09085 | 0.2141 | 0.00577 | 0.05352 | 0.00277 | 1202 | 37 | 1232 | 27 | 1251 | 31 | 1054 | 53 |
9 | 0.05928 | 0.00248 | 0.29959 | 0.01132 | 0.03668 | 0.00082 | 0.00966 | 0.00046 | 577 | 45 | 266 | 9 | 232 | 5 | 194 | 9 |
10 | 0.04989 | 0.00375 | 0.23793 | 0.0163 | 0.03461 | 0.00119 | 0.00907 | 0.00072 | 190 | 96 | 217 | 13 | 219 | 7 | 182 | 14 |
11 | 0.07866 | 0.00333 | 0.34683 | 0.01279 | 0.032 | 0.00079 | 0.01233 | 0.00063 | 1164 | 37 | 302 | 10 | 203 | 5 | 248 | 13 |
12 | 0.0406 | 0.00217 | 0.22437 | 0.01119 | 0.04011 | 0.00095 | 0.01052 | 0.00055 | −255 | 72 | 206 | 9 | 254 | 6 | 212 | 11 |
13 | 0.0639 | 0.00299 | 0.31538 | 0.01317 | 0.03582 | 0.00089 | 0.01126 | 0.00067 | 738 | 48 | 278 | 10 | 227 | 6 | 226 | 13 |
14 | 0.07481 | 0.00441 | 0.3517 | 0.01817 | 0.03412 | 0.00108 | 0.01178 | 0.00078 | 1063 | 56 | 306 | 14 | 216 | 7 | 237 | 16 |
15 | 0.06821 | 0.00263 | 0.97745 | 0.03376 | 0.10399 | 0.00236 | 0.03233 | 0.00106 | 875 | 37 | 692 | 17 | 638 | 14 | 643 | 21 |
16 | 0.05116 | 0.00255 | 0.26673 | 0.01227 | 0.03784 | 0.00088 | 0.01057 | 0.00052 | 248 | 64 | 240 | 10 | 239 | 5 | 213 | 10 |
17 | 0.05025 | 0.00304 | 0.25181 | 0.01395 | 0.03636 | 0.00102 | 0.01037 | 0.00064 | 207 | 77 | 228 | 11 | 230 | 6 | 209 | 13 |
18 | 0.05379 | 0.003 | 0.27018 | 0.01369 | 0.03645 | 0.00098 | 0.00965 | 0.0006 | 362 | 67 | 243 | 11 | 231 | 6 | 194 | 12 |
19 | 0.05083 | 0.00373 | 0.26778 | 0.01802 | 0.03823 | 0.00125 | 0.00987 | 0.00055 | 233 | 96 | 241 | 14 | 242 | 8 | 199 | 11 |
20 | 0.06022 | 0.00487 | 0.2998 | 0.0217 | 0.03612 | 0.00142 | 0.01137 | 0.00113 | 611 | 90 | 266 | 17 | 229 | 9 | 229 | 23 |
21 | 0.0473 | 0.00214 | 0.20932 | 0.0087 | 0.0321 | 0.0007 | 0.00892 | 0.00038 | 64 | 55 | 193 | 7 | 204 | 4 | 179 | 8 |
22 | 0.05405 | 0.00334 | 0.28442 | 0.01602 | 0.03817 | 0.00111 | 0.00858 | 0.0006 | 373 | 75 | 254 | 13 | 241 | 7 | 173 | 12 |
23 | 0.05907 | 0.0024 | 0.66212 | 0.02439 | 0.08128 | 0.00181 | 0.03438 | 0.00121 | 570 | 43 | 516 | 15 | 504 | 11 | 683 | 24 |
24 | 0.05064 | 0.00245 | 0.21459 | 0.00944 | 0.03072 | 0.00072 | 0.00797 | 0.00046 | 224 | 59 | 197 | 8 | 195 | 5 | 160 | 9 |
25 | 0.05594 | 0.00261 | 0.26352 | 0.01113 | 0.03415 | 0.0008 | 0.00964 | 0.00045 | 450 | 53 | 237 | 9 | 216 | 5 | 194 | 9 |
26 | 0.06769 | 0.00524 | 0.32217 | 0.02212 | 0.0345 | 0.00134 | 0.01049 | 0.0009 | 859 | 80 | 284 | 17 | 219 | 8 | 211 | 18 |
27 | 0.06354 | 0.00206 | 0.75553 | 0.02205 | 0.08618 | 0.00166 | 0.02056 | 0.00084 | 726 | 32 | 571 | 13 | 533 | 10 | 411 | 17 |
28 | 0.05014 | 0.00296 | 0.33191 | 0.01801 | 0.04797 | 0.00129 | 0.02068 | 0.0011 | 201 | 77 | 291 | 14 | 302 | 8 | 414 | 22 |
29 | 0.23782 | 0.00377 | 6.55914 | 0.08439 | 0.19984 | 0.00325 | 0.01824 | 0.00075 | 3105 | 12 | 2054 | 11 | 1174 | 17 | 365 | 15 |
Previous petrological and geochemical studies [
Isotopic age histogram showing the major tectonic event in the area east to the Tibet Peateau (after [
Before the formation of the Lincang Batholith, the Paleo-Tethys Ocean and many intraoceanic islands distributed between the Baoshan and the Lanping-Simao-Indosinian blocks [
Formation and tectonic evolution model for the Lincang Batholith.
The Lincang Batholith was controlled by one deep-seated fault along the Lancang Jiang River and proposed in situ hybrid origin of the Batholith in the early to middle Triassic collision between the Baoshan-Shantai and Lanping-Simao-Indochina Blocks [
This paper research shows that the upper part of the Lincang Batholith experienced long-term denudation, resulting in the development of the weathering crust (Figure
The authors appreciate sincerely both the field research and inner discussion together with Professor Yong-Qing Chen from China University of Geosciences (Beijing), Research Fellow Ying-Xiang Lu from Yunnan Bureau of Geology and Mineral Resources, and Research Fellow Fang-Cheng Lin from Chengdu Institute of Geology and Mineral Resources. The authors thank Dr. Pengfei Li from University of Queensland for his perfect academic revision of the paper. The research was supported by the China Geology Survey (no. 200811008, no. 1212011121188), the Ministry of Science and Technology (no. 2006BAB01A03-3), the Chinese National Natural Foundation (no. 90814006) of the People’s Republic, and the China University of Geosciences in Beijing (no. 2-9-2001-280).