柴北缘牦牛山组火山岩锆石U-Pb年龄及其地质意义

doi:10.19657/j.geoscience.1000-8527.2018.02.11

摘要/Abstract

摘要：

柴北缘牦牛山组磨拉石建造不整合覆盖在前泥盆系之上,记录了该地区早古生代洋盆关闭的时间。对柴北缘牦牛山一带牦牛山组上部火山岩段两个流纹质熔结凝灰岩样品进行锆石U-Pb同位素测定,两个样品的岩浆锆石²⁰⁶Pb/²³⁸U年龄加权平均值分别为(396.5±2.4) Ma(n=17,MSWD=3.3)和(395.8±1.2) Ma(n=20,MSWD=1.1),均被解释为火山岩喷发年龄。结合东昆仑造山带牦牛山组测年结果,认为柴达木盆地周缘牦牛山组火山岩形成时代为晚志留世—晚泥盆世,且东昆仑与柴北缘加里东造山作用结束的时间均为早泥盆世之前,而非传统认为的晚泥盆世。

关键词: 牦牛山组, 火山岩, 锆石U-Pb年龄, 泥盆纪, 柴北缘

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

中图分类号:

P588.14
P597

张耀玲, 倪晋宇, 沈燕绪, 王超群, 高万里, 胡道功. 柴北缘牦牛山组火山岩锆石U-Pb年龄及其地质意义[J]. 现代地质, 2018, 32(02): 329-334.

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.

图/表 5

参考文献 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