Determination of the Bolejin Ductile Shear Zone in the Sonidzuoqi Area, Central Inner Mongolia and Its Geological Significance

Abstract

Abstract:

Based on the field geological investigation and microstructural observation, we recognized a NEE-striking sinistral thrust ductile shear zone in the Bolejin area of the north of Sonidzuoqi, central Inner Mongolia. The Bolejin ductile shear zone dips northward with angles of 70°-85°. There occur many typical macroscopic structures and microstructures such as mylonite rocks, mylonitic foliation, stretching lineation, S-C fabrics, asymmetrical folds, rotational porphyroclasts, domino structures and biotite-fishes in the ductile zone. In the light of field observation, the Bolejin ductile shear zone, about 10 km in length and 4 km in width, consists of several strong deformational zones and weak deformational domains. The deformational zones are approximately parallel to each other. The macroscopic structures, microstructures of the ductile shear zone, zircon U-Pb chronology, as well as regional geological data suggest that the Bolejin ductile shear zone is a structural feature of the Chaganobo-Arongqi fault. The shear zone was formed at 290-292 Ma in the early Early Permian. The Bolejin ductile shear zone resulted from the S-N collision between the North China and Siberian plates after the final closure of the Paleo-Asian Ocean. Thus, the determination of the Bolejin ductile shear zone has provided constraints on the Late Paleozoic tectonic evolution of the Xing’an Mongolian Orogenic Belt.

Key words: ductile shear zone, Early Permian, tectonic evolution, central Inner Mongolia, the Xing’an Mongolian Orogenic Belt

CLC Number:

P583
P597

ZHANG Xiangxin, PENG Yu, LEI Shihe, GAO Yongfeng, WANG Guang. Determination of the Bolejin Ductile Shear Zone in the Sonidzuoqi Area, Central Inner Mongolia and Its Geological Significance[J]. Geoscience, 2017, 31(03): 433-442.

Figures/Tables 7

References 38

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测点号	元素含量/10^-6			Th/U	同位素比值						年龄/Ma
测点号	Pb	U	Th	Th/U	²⁰⁷Pb/ ²⁰⁶Pb	1σ	²⁰⁶Pb/ ²³⁸U	1σ	²⁰⁷Pb/ ²³⁵U	1σ	²⁰⁷Pb/ ²⁰⁶Pb	1σ	²⁰⁷Pb/ ²³⁵U	1σ	²⁰⁶Pb/ ²³⁸U	1σ
1	220	671	207	0.31	0.053 2	0.002 43	0.043 94	0.000 63	0.325 18	0.014 71	336	76	286	11	277	4
2	217	551	220	0.40	0.054 0	0.002 67	0.046 87	0.000 55	0.349 20	0.016 75	372	114	304	13	295	3
3	242	670	375	0.56	0.055 5	0.002 29	0.043 12	0.000 58	0.332 28	0.013 62	432	67	291	10	272	4
4	595	1 144	173	0.15	0.052 4	0.003 27	0.046 98	0.000 56	0.339 12	0.020 81	301	145	297	16	296	3
5	304	699	477	0.68	0.055 1	0.002 15	0.045 16	0.000 58	0.346 82	0.013 24	414	62	302	10	285	4
6	137	200	148	0.74	0.054 0	0.004 47	0.045 47	0.001 11	0.340 07	0.026 46	372	131	297	20	287	7
7	274	374	229	0.61	0.067 8	0.003 64	0.050 86	0.000 79	0.475 80	0.024 12	862	79	395	17	320	5
8	1 061	1 139	978	0.86	0.061 1	0.006 14	0.044 60	0.000 79	0.375 86	0.037 15	644	224	324	27	281	5
9	182	390	109	0.28	0.055 0	0.002 53	0.052 10	0.000 59	0.398 86	0.018 13	414	81	341	13	327	4
10	419	378	253	0.67	0.054 8	0.006 12	0.049 23	0.000 82	0.372 16	0.041 05	405	254	321	30	310	5
11	157	594	59	0.10	0.053 0	0.002 28	0.046 91	0.000 56	0.342 91	0.014 15	330	100	299	11	296	3
12	141	281	217	0.77	0.052 3	0.005 60	0.043 01	0.000 79	0.310 36	0.032 69	300	245	274	25	271	5
13	296	862	138	0.16	0.054 2	0.002 16	0.049 42	0.000 50	0.369 57	0.014 23	381	92	319	11	311	3
14	118	184	142	0.77	0.063 1	0.004 24	0.047 53	0.001 02	0.412 78	0.027 50	710	105	351	20	299	6
15	214	419	314	0.75	0.051 5	0.002 52	0.047 85	0.000 81	0.342 50	0.017 01	263	83	299	13	301	5
16	286	831	200	0.24	0.061 2	0.002 40	0.044 89	0.000 50	0.382 35	0.014 61	647	63	329	11	283	3
17	154	233	203	0.88	0.059 9	0.003 44	0.046 52	0.000 81	0.380 37	0.020 34	598	86	327	15	293	5
18	204	445	66	0.15	0.055 0	0.002 23	0.055 80	0.000 67	0.427 24	0.017 66	412	71	361	13	350	4

测点号	元素含量/10^-6			Th/U	同位素比值						年龄/Ma
测点号	Pb	U	Th	Th/U	²⁰⁷Pb/ ²⁰⁶Pb	1σ	²⁰⁶Pb/ ²³⁸U	1σ	²⁰⁷Pb/ ²³⁵U	1σ	²⁰⁷Pb/ ²⁰⁶Pb	1σ	²⁰⁷Pb/ ²³⁵U	1σ	²⁰⁶Pb/ ²³⁸U	1σ
1	220	671	207	0.31	0.053 2	0.002 43	0.043 94	0.000 63	0.325 18	0.014 71	336	76	286	11	277	4
2	217	551	220	0.40	0.054 0	0.002 67	0.046 87	0.000 55	0.349 20	0.016 75	372	114	304	13	295	3
3	242	670	375	0.56	0.055 5	0.002 29	0.043 12	0.000 58	0.332 28	0.013 62	432	67	291	10	272	4
4	595	1 144	173	0.15	0.052 4	0.003 27	0.046 98	0.000 56	0.339 12	0.020 81	301	145	297	16	296	3
5	304	699	477	0.68	0.055 1	0.002 15	0.045 16	0.000 58	0.346 82	0.013 24	414	62	302	10	285	4
6	137	200	148	0.74	0.054 0	0.004 47	0.045 47	0.001 11	0.340 07	0.026 46	372	131	297	20	287	7
7	274	374	229	0.61	0.067 8	0.003 64	0.050 86	0.000 79	0.475 80	0.024 12	862	79	395	17	320	5
8	1 061	1 139	978	0.86	0.061 1	0.006 14	0.044 60	0.000 79	0.375 86	0.037 15	644	224	324	27	281	5
9	182	390	109	0.28	0.055 0	0.002 53	0.052 10	0.000 59	0.398 86	0.018 13	414	81	341	13	327	4
10	419	378	253	0.67	0.054 8	0.006 12	0.049 23	0.000 82	0.372 16	0.041 05	405	254	321	30	310	5
11	157	594	59	0.10	0.053 0	0.002 28	0.046 91	0.000 56	0.342 91	0.014 15	330	100	299	11	296	3
12	141	281	217	0.77	0.052 3	0.005 60	0.043 01	0.000 79	0.310 36	0.032 69	300	245	274	25	271	5
13	296	862	138	0.16	0.054 2	0.002 16	0.049 42	0.000 50	0.369 57	0.014 23	381	92	319	11	311	3
14	118	184	142	0.77	0.063 1	0.004 24	0.047 53	0.001 02	0.412 78	0.027 50	710	105	351	20	299	6
15	214	419	314	0.75	0.051 5	0.002 52	0.047 85	0.000 81	0.342 50	0.017 01	263	83	299	13	301	5
16	286	831	200	0.24	0.061 2	0.002 40	0.044 89	0.000 50	0.382 35	0.014 61	647	63	329	11	283	3
17	154	233	203	0.88	0.059 9	0.003 44	0.046 52	0.000 81	0.380 37	0.020 34	598	86	327	15	293	5
18	204	445	66	0.15	0.055 0	0.002 23	0.055 80	0.000 67	0.427 24	0.017 66	412	71	361	13	350	4