Zircon U-Pb Ages and Geological Significance of Volcanic Rocks from Maoniushan Formation in the Northern Margin of Qaidam Basin

doi:10.19657/j.geoscience.1000-8527.2018.02.11

Abstract

Abstract:

The molasses of Maoniushan Formation rest unconformably on pre-Devonian strata and record the closure time of the Early Paleozoic ocean in the northern margin of Qaidam Basin. This research determinates zircon U-Pb isotopes from two rhyolite-tuff samples of volcanic rock member of upper Maomiushan Formation of Maoniushan mountain, northern margin of Qaidam Basin. The weighted mean ²⁰⁶Pb/²³⁸U ages of magmatic zircons from two samples are (396.5±2.4) Ma(n=17,MSWD=3.3)and (395.8±1.2) Ma(n=20,MSWD=1.1), interpreted as the formation time of the volcanic rocks. Combining past dating results about Maoniushan Formation of East Kunlun orogenic belt, we concluded that the formation time of the Maoniushan Formation around Qaidam Basin should be Late Silurian to Late Devonian, and the Caledonian movement of East Kunlun and northern margin of Qaidam Basin ended before Early Devonian instead of Late Devonian, as traditional thought.

Key words: Maoniushan Formation, volcanic rock, zircon U-Pb age, Devonian, Northern Qaidam Basin

CLC Number:

P588.14
P597

ZHANG Yaoling, NI Jinyu, SHEN Yanxu, WANG Chaoqun, GAO Wanli, HU Daogong. Zircon U-Pb Ages and Geological Significance of Volcanic Rocks from Maoniushan Formation in the Northern Margin of Qaidam Basin[J]. Geoscience, 2018, 32(02): 329-334.

Figures/Tables 5

References 20

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测点	含量/10^-6		Th/U	同位素比值							年龄/Ma
测点	Pb	U	Th/U	²⁰⁶Pb/²³⁸U	1σ	²⁰⁷Pb/²³⁵U	1σ	²⁰⁷Pb/²⁰⁶Pb	1σ		²⁰⁶Pb/²³⁸U	1σ	²⁰⁷Pb/²⁰⁶Pb	1σ
B075-1-1	24	263	1.447 9	0.062 6	0.000 5	0.473 8	0.015 1	0.054 9	0.001 7	391		3	408	69
B075-1-2	8	103	0.932 9	0.062 7	0.000 6	0.480 5	0.025 3	0.055 5	0.002 9	392		3	431	116
B075-1-3	15	180	0.941 5	0.062 5	0.000 4	0.473 5	0.014 6	0.054 8	0.001 7	391		2	405	67
B075-1-4	15	174	1.000 8	0.063 1	0.000 5	0.484 8	0.017 1	0.055 6	0.001 9	394		3	438	76
B075-1-5	18	213	0.813 5	0.063 9	0.000 3	0.480 6	0.013 0	0.054 5	0.001 4	399		2	390	59
B075-1-7	27	295	0.677 0	0.063 1	0.000 4	0.489 0	0.010 9	0.056 2	0.001 2	394		2	460	49
B075-1-8	17	185	0.570 6	0.064 4	0.000 4	0.483 7	0.017 7	0.054 4	0.002 0	402		2	386	81
B075-1-10	14	149	0.745 2	0.064 4	0.000 4	0.485 5	0.017 9	0.054 5	0.002 0	402		2	394	82
B075-1-11	8	93	0.538 8	0.064 8	0.000 6	0.485 6	0.035 5	0.053 8	0.003 9	405		4	361	162
B075-1-12	11	139	0.813 4	0.058 0	0.000 5	0.437 6	0.026 8	0.054 8	0.003 3	363		3	403	133
B075-1-13	14	181	0.677 6	0.064 2	0.000 4	0.494 1	0.017 6	0.055 8	0.002 0	401		3	445	78
B075-1-14	17	209	0.874 6	0.063 7	0.000 3	0.480 3	0.012 6	0.054 7	0.001 4	398		2	398	58
B075-1-15	15	199	0.919 5	0.061 9	0.000 4	0.471 9	0.015 9	0.055 2	0.001 8	387		3	419	73
B075-1-16	17	234	0.816 7	0.062 6	0.000 4	0.481 8	0.014 1	0.055 8	0.001 6	391		2	446	64
B075-1-17	6	83	0.542 5	0.063 5	0.000 6	0.483 5	0.029 8	0.054 8	0.003 4	397		4	404	138
B075-1-18	10	139	0.688 8	0.063 7	0.000 4	0.491 5	0.019 8	0.055 8	0.002 2	398		3	445	89
B075-1-19	7	110	0.561 1	0.063 4	0.000 5	0.480 9	0.028 6	0.054 9	0.003 2	397		3	407	131
B075-1-20	11	155	0.649 1	0.063 9	0.000 4	0.493 4	0.018 0	0.055 9	0.002 0	399		3	447	79
B075-2-1	7	100	0.767 3	0.063 6	0.000 7	0.492 5	0.030 6	0.055 4	0.003 4	397		4	428	138
B075-2-2	16	208	0.895 0	0.063 4	0.000 4	0.479 9	0.017 2	0.054 9	0.001 9	396		3	408	77
B075-2-3	11	140	1.004 5	0.064 1	0.000 5	0.487 0	0.031 8	0.054 8	0.003 5	401		3	403	143
B075-2-4	19	225	1.453 0	0.064 0	0.000 4	0.482 8	0.013 4	0.054 7	0.001 5	400		2	400	61
B075-2-5	6	83	0.883 1	0.063 2	0.000 7	0.484 8	0.036 8	0.054 8	0.004 1	395		5	406	167
B075-2-6	17	210	1.223 4	0.063 7	0.000 5	0.470 4	0.017 3	0.053 4	0.001 9	398		3	344	81
B075-2-7	10	136	0.969 9	0.064 1	0.000 5	0.484 8	0.025 1	0.054 5	0.002 8	400		3	393	115
B075-2-8	15	192	1.150 7	0.063 1	0.000 5	0.520 4	0.024 1	0.059 3	0.002 6	394		3	577	97
B075-2-9	9	124	0.890 1	0.063 7	0.000 5	0.489 3	0.028 4	0.055 2	0.003 2	398		3	422	128
B075-2-10	5	69	1.141 9	0.063 1	0.000 8	0.488 0	0.046 8	0.055 3	0.005 3	394		5	424	214
B075-2-11	16	204	0.958 5	0.063 7	0.000 4	0.516 4	0.017 0	0.058 7	0.001 9	398		3	556	71
B075-2-12	12	161	0.808 5	0.063 6	0.000 4	0.490 9	0.020 7	0.055 9	0.002 3	398		3	447	92
B075-2-13	19	237	1.253 6	0.063 1	0.000 4	0.482 0	0.015 3	0.055 3	0.001 7	394		2	425	69
B075-2-14	14	190	0.921 5	0.062 5	0.000 4	0.473 9	0.019 3	0.054 9	0.002 2	391		3	410	90
B075-2-15	16	197	1.110 8	0.063 0	0.000 4	0.473 4	0.015 3	0.054 4	0.001 7	394		3	386	71
B075-2-16	15	200	0.819 3	0.063 3	0.000 4	0.469 5	0.017 3	0.053 7	0.001 9	396		2	358	82
B075-2-17	21	268	0.992 8	0.062 8	0.000 3	0.467 0	0.014 5	0.053 9	0.001 6	393		2	365	69
B075-2-18	11	154	0.731 3	0.062 6	0.000 4	0.482 0	0.020 6	0.055 7	0.002 4	391		3	442	94
B075-2-19	18	237	0.730 5	0.063 2	0.000 3	0.489 7	0.014 0	0.056 1	0.001 6	395		2	456	62
B075-2-20	15	206	0.767 5	0.063 3	0.000 4	0.487 0	0.016 3	0.055 7	0.001 8	396		2	439	73

测点	含量/10^-6		Th/U	同位素比值							年龄/Ma
测点	Pb	U	Th/U	²⁰⁶Pb/²³⁸U	1σ	²⁰⁷Pb/²³⁵U	1σ	²⁰⁷Pb/²⁰⁶Pb	1σ		²⁰⁶Pb/²³⁸U	1σ	²⁰⁷Pb/²⁰⁶Pb	1σ
B075-1-1	24	263	1.447 9	0.062 6	0.000 5	0.473 8	0.015 1	0.054 9	0.001 7	391		3	408	69
B075-1-2	8	103	0.932 9	0.062 7	0.000 6	0.480 5	0.025 3	0.055 5	0.002 9	392		3	431	116
B075-1-3	15	180	0.941 5	0.062 5	0.000 4	0.473 5	0.014 6	0.054 8	0.001 7	391		2	405	67
B075-1-4	15	174	1.000 8	0.063 1	0.000 5	0.484 8	0.017 1	0.055 6	0.001 9	394		3	438	76
B075-1-5	18	213	0.813 5	0.063 9	0.000 3	0.480 6	0.013 0	0.054 5	0.001 4	399		2	390	59
B075-1-7	27	295	0.677 0	0.063 1	0.000 4	0.489 0	0.010 9	0.056 2	0.001 2	394		2	460	49
B075-1-8	17	185	0.570 6	0.064 4	0.000 4	0.483 7	0.017 7	0.054 4	0.002 0	402		2	386	81
B075-1-10	14	149	0.745 2	0.064 4	0.000 4	0.485 5	0.017 9	0.054 5	0.002 0	402		2	394	82
B075-1-11	8	93	0.538 8	0.064 8	0.000 6	0.485 6	0.035 5	0.053 8	0.003 9	405		4	361	162
B075-1-12	11	139	0.813 4	0.058 0	0.000 5	0.437 6	0.026 8	0.054 8	0.003 3	363		3	403	133
B075-1-13	14	181	0.677 6	0.064 2	0.000 4	0.494 1	0.017 6	0.055 8	0.002 0	401		3	445	78
B075-1-14	17	209	0.874 6	0.063 7	0.000 3	0.480 3	0.012 6	0.054 7	0.001 4	398		2	398	58
B075-1-15	15	199	0.919 5	0.061 9	0.000 4	0.471 9	0.015 9	0.055 2	0.001 8	387		3	419	73
B075-1-16	17	234	0.816 7	0.062 6	0.000 4	0.481 8	0.014 1	0.055 8	0.001 6	391		2	446	64
B075-1-17	6	83	0.542 5	0.063 5	0.000 6	0.483 5	0.029 8	0.054 8	0.003 4	397		4	404	138
B075-1-18	10	139	0.688 8	0.063 7	0.000 4	0.491 5	0.019 8	0.055 8	0.002 2	398		3	445	89
B075-1-19	7	110	0.561 1	0.063 4	0.000 5	0.480 9	0.028 6	0.054 9	0.003 2	397		3	407	131
B075-1-20	11	155	0.649 1	0.063 9	0.000 4	0.493 4	0.018 0	0.055 9	0.002 0	399		3	447	79
B075-2-1	7	100	0.767 3	0.063 6	0.000 7	0.492 5	0.030 6	0.055 4	0.003 4	397		4	428	138
B075-2-2	16	208	0.895 0	0.063 4	0.000 4	0.479 9	0.017 2	0.054 9	0.001 9	396		3	408	77
B075-2-3	11	140	1.004 5	0.064 1	0.000 5	0.487 0	0.031 8	0.054 8	0.003 5	401		3	403	143
B075-2-4	19	225	1.453 0	0.064 0	0.000 4	0.482 8	0.013 4	0.054 7	0.001 5	400		2	400	61
B075-2-5	6	83	0.883 1	0.063 2	0.000 7	0.484 8	0.036 8	0.054 8	0.004 1	395		5	406	167
B075-2-6	17	210	1.223 4	0.063 7	0.000 5	0.470 4	0.017 3	0.053 4	0.001 9	398		3	344	81
B075-2-7	10	136	0.969 9	0.064 1	0.000 5	0.484 8	0.025 1	0.054 5	0.002 8	400		3	393	115
B075-2-8	15	192	1.150 7	0.063 1	0.000 5	0.520 4	0.024 1	0.059 3	0.002 6	394		3	577	97
B075-2-9	9	124	0.890 1	0.063 7	0.000 5	0.489 3	0.028 4	0.055 2	0.003 2	398		3	422	128
B075-2-10	5	69	1.141 9	0.063 1	0.000 8	0.488 0	0.046 8	0.055 3	0.005 3	394		5	424	214
B075-2-11	16	204	0.958 5	0.063 7	0.000 4	0.516 4	0.017 0	0.058 7	0.001 9	398		3	556	71
B075-2-12	12	161	0.808 5	0.063 6	0.000 4	0.490 9	0.020 7	0.055 9	0.002 3	398		3	447	92
B075-2-13	19	237	1.253 6	0.063 1	0.000 4	0.482 0	0.015 3	0.055 3	0.001 7	394		2	425	69
B075-2-14	14	190	0.921 5	0.062 5	0.000 4	0.473 9	0.019 3	0.054 9	0.002 2	391		3	410	90
B075-2-15	16	197	1.110 8	0.063 0	0.000 4	0.473 4	0.015 3	0.054 4	0.001 7	394		3	386	71
B075-2-16	15	200	0.819 3	0.063 3	0.000 4	0.469 5	0.017 3	0.053 7	0.001 9	396		2	358	82
B075-2-17	21	268	0.992 8	0.062 8	0.000 3	0.467 0	0.014 5	0.053 9	0.001 6	393		2	365	69
B075-2-18	11	154	0.731 3	0.062 6	0.000 4	0.482 0	0.020 6	0.055 7	0.002 4	391		3	442	94
B075-2-19	18	237	0.730 5	0.063 2	0.000 3	0.489 7	0.014 0	0.056 1	0.001 6	395		2	456	62
B075-2-20	15	206	0.767 5	0.063 3	0.000 4	0.487 0	0.016 3	0.055 7	0.001 8	396		2	439	73