西准噶尔谢米斯台地区双峰式火山岩的发现及其地质意义

doi:10.19657/j.geoscience.1000-8527.2018.04.06

摘要/Abstract

摘要：

西准噶尔谢米斯台地区是研究准噶尔洋盆构造演化的关键地区,新发现的双峰式火山岩为开展研究提供了直接的载体,对其物质组成特征、岩石地球化学特征和锆石U-Pb年代学等进行研究,判别成因机制和大地构造环境,对恢复造山带大地构造格局有着重要的意义。本次研究获得如下认识:该套双峰式火山岩为碱性玄武岩-钙碱性流纹岩组合,流纹岩LA-ICP-MS锆石U-Pb年龄(431.8±2.3) Ma;玄武岩来源于俯冲流体交代的地幔部分熔融,流纹岩来源于地壳物质的部分熔融;双峰式火山岩形成于早志留世弧后盆地初始演化阶段;结合前人的研究成果,认为西准噶尔谢米斯台地区在早古生代存在完整的沟-弧-盆体系。

关键词: 双峰式火山岩, 地球化学, 锆石U-Pb测年, 沟-弧-盆体系, 西准噶尔

Abstract:

The Xiemisitai region in the Western Junggar is a key region to investigate the tectonic evolution of the Junggar ocean basin. The discovery of the Xiemisitai bimodal volcanics and their composition, petrogeochemistry, and zircon U-Pb age are important to discriminate formation mechanism and tectonic setting, reconstruct the tectonic framework of Western Junggar orogenic belt. The following acquaintances were obtained by this paper.The bimodal volcanics are composed of alkaline basalt and calc-alkaline rhyolite, and the LA-ICP-MS zircon U-Pb dating of the rhyolite is (431.8±2.3) Ma. The mafic magma was likely derived from partial melting of the mantle metasomatized by subduction-related fluid, and the felsic magma was derived from the partial melting of crust materials. The bimodal volcanics may have formed in an early Silurian incipient back-arc basin. Combined with previous studies, we suggest that there was a complete Early Paleozoic trench-arc-basin system in the Xiemisitai region, Western Junggar.

Key words: bimodal volcanics, geochemistry, zircon U-Pb dating, trench-arc-basin system, Western Junggar

中图分类号:

P588.1

翁凯, 马中平, 张雪. 西准噶尔谢米斯台地区双峰式火山岩的发现及其地质意义[J]. 现代地质, 2018, 32(04): 692-703.

WENG Kai, MA Zhongping, ZHANG Xue. Discovery of Bimodal Volcanics and Its Geological Significance in the Xiemisitai Region, Western Junggar, China[J]. Geoscience, 2018, 32(04): 692-703.

图/表 11

参考文献 47

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地层				主要岩石组合	化石
界	系	组	代号	主要岩石组合	化石
古生界	石炭系	洪古勒楞组	D₃C₁h	生物碎屑灰岩、钙质灰岩、泥质灰岩	腕足、珊瑚、海百合茎、苔藓虫
	石炭系	朱鲁木特组	D₃z	砾岩、含砾中粗砂岩、中粗砂岩	陆相植物化石
	泥盆系	朱鲁木特组	D₃z	砾岩、含砾中粗砂岩、中粗砂岩	陆相植物化石
		塔克台组	D₃tk	火山岩、火山碎屑岩、砂砾岩、煤层	陆相植物化石、腕足、珊瑚、海百合茎、苔藓虫
		呼吉尔斯特组	D₂h	砂砾岩夹粉砂岩
		沙尔布尔组	S₂s	生物碎屑灰岩、凝灰质砂砾岩、沉凝灰岩、安山玄武质火山角砾熔岩等
	志留系	沙尔布尔组	S₂s	生物碎屑灰岩、凝灰质砂砾岩、沉凝灰岩、安山玄武质火山角砾熔岩等
	志留系	谢米斯台组	S_1-4x	安山岩、流纹岩、玄武岩、火山角砾岩、含角砾凝灰岩、凝灰岩、凝灰质砂岩等

地层				主要岩石组合	化石
界	系	组	代号	主要岩石组合	化石
古生界	石炭系	洪古勒楞组	D₃C₁h	生物碎屑灰岩、钙质灰岩、泥质灰岩	腕足、珊瑚、海百合茎、苔藓虫
	石炭系	朱鲁木特组	D₃z	砾岩、含砾中粗砂岩、中粗砂岩	陆相植物化石
	泥盆系	朱鲁木特组	D₃z	砾岩、含砾中粗砂岩、中粗砂岩	陆相植物化石
		塔克台组	D₃tk	火山岩、火山碎屑岩、砂砾岩、煤层	陆相植物化石、腕足、珊瑚、海百合茎、苔藓虫
		呼吉尔斯特组	D₂h	砂砾岩夹粉砂岩
		沙尔布尔组	S₂s	生物碎屑灰岩、凝灰质砂砾岩、沉凝灰岩、安山玄武质火山角砾熔岩等
	志留系	沙尔布尔组	S₂s	生物碎屑灰岩、凝灰质砂砾岩、沉凝灰岩、安山玄武质火山角砾熔岩等
	志留系	谢米斯台组	S_1-4x	安山岩、流纹岩、玄武岩、火山角砾岩、含角砾凝灰岩、凝灰岩、凝灰质砂岩等

点号	Th/ (μg·g^-1)	U/ (μg·g^-1)	Th/U	²⁰⁷Pb/²⁰⁶Pb		²⁰⁷Pb/²³⁵U		²⁰⁶Pb/²³⁸U		²⁰⁸Pb/²³²Th		谐和年龄		谐和度/%
点号	Th/ (μg·g^-1)	U/ (μg·g^-1)	Th/U	比值	1s	比值	1s	比值	1s	比值	1s	年龄/Ma	1s	谐和度/%
NO1	169.70	223.19	0.76	0.055 84	0.001 46	0.536 87	0.013 00	0.069 80	0.000 54	0.020 61	0.000 26	435	3	100.23
NO2	231.75	299.94	0.77	0.055 47	0.001 51	0.532 96	0.013 55	0.069 75	0.000 57	0.020 27	0.000 26	435	3	99.77
NO3	107.52	192.79	0.56	0.055 62	0.001 70	0.534 18	0.015 38	0.069 72	0.000 62	0.020 66	0.000 35	434	4	100.23
NO4	104.71	188.16	0.56	0.055 93	0.004 77	0.534 16	0.044 45	0.069 32	0.001 59	0.022 38	0.001 05	432	10	100.69
NO5	483.02	670.95	0.72	0.056 35	0.002 57	0.542 27	0.023 87	0.069 84	0.000 89	0.021 32	0.000 50	435	5	101.15
NO6	223.50	252.20	0.89	0.055 40	0.002 22	0.516 51	0.019 83	0.067 64	0.000 76	0.018 88	0.000 35	422	5	100.24
NO7	248.10	286.40	0.87	0.055 46	0.001 49	0.523 40	0.013 08	0.068 47	0.000 54	0.021 18	0.000 27	427	3	100.00
NO8	421.77	435.56	0.97	0.056 43	0.005 76	0.529 91	0.052 91	0.068 13	0.001 87	0.019 99	0.001 03	425	11	101.65
NO9	81.95	156.72	0.52	0.055 09	0.008 18	0.517 62	0.075 32	0.068 16	0.002 67	0.020 82	0.001 77	425	16	99.76
NO10	107.58	184.32	0.58	0.055 21	0.005 05	0.517 92	0.046 25	0.068 04	0.001 65	0.021 17	0.000 99	424	10	100.00
NO11	223.60	328.99	0.68	0.055 25	0.009 35	0.527 95	0.087 60	0.069 31	0.003 10	0.023 31	0.001 66	432	19	99.54
NO12	274.06	386.41	0.71	0.055 42	0.006 94	0.533 42	0.065 43	0.069 80	0.002 33	0.022 59	0.001 42	435	14	99.77
NO13	177.19	312.27	0.57	0.055 31	0.004 03	0.517 88	0.036 80	0.067 91	0.001 33	0.021 15	0.000 85	424	8	100.00
NO14	275.33	385.13	0.71	0.055 64	0.003 13	0.534 96	0.029 19	0.069 72	0.001 07	0.021 05	0.000 60	434	6	100.23
NO15	177.77	339.49	0.52	0.055 89	0.009 42	0.538 34	0.088 96	0.069 84	0.003 13	0.023 96	0.002 38	435	19	100.46
NO16	293.27	513.05	0.57	0.055 87	0.002 45	0.539 58	0.022 80	0.070 03	0.000 85	0.021 68	0.000 53	436	5	100.46
NO17	235.40	385.94	0.61	0.055 58	0.001 63	0.535 87	0.014 76	0.069 91	0.000 60	0.021 79	0.000 34	436	4	100.00
NO18	104.97	191.61	0.55	0.055 67	0.002 16	0.529 46	0.019 69	0.068 96	0.000 74	0.021 45	0.000 45	430	4	100.23
NO19	93.82	205.60	0.46	0.055 80	0.003 32	0.522 24	0.030 16	0.067 85	0.001 09	0.021 84	0.000 63	423	7	100.95
NO20	78.50	168.87	0.46	0.056 08	0.007 54	0.527 99	0.069 51	0.068 26	0.002 43	0.022 49	0.001 44	426	15	100.94

点号	Th/ (μg·g^-1)	U/ (μg·g^-1)	Th/U	²⁰⁷Pb/²⁰⁶Pb		²⁰⁷Pb/²³⁵U		²⁰⁶Pb/²³⁸U		²⁰⁸Pb/²³²Th		谐和年龄		谐和度/%
点号	Th/ (μg·g^-1)	U/ (μg·g^-1)	Th/U	比值	1s	比值	1s	比值	1s	比值	1s	年龄/Ma	1s	谐和度/%
NO1	169.70	223.19	0.76	0.055 84	0.001 46	0.536 87	0.013 00	0.069 80	0.000 54	0.020 61	0.000 26	435	3	100.23
NO2	231.75	299.94	0.77	0.055 47	0.001 51	0.532 96	0.013 55	0.069 75	0.000 57	0.020 27	0.000 26	435	3	99.77
NO3	107.52	192.79	0.56	0.055 62	0.001 70	0.534 18	0.015 38	0.069 72	0.000 62	0.020 66	0.000 35	434	4	100.23
NO4	104.71	188.16	0.56	0.055 93	0.004 77	0.534 16	0.044 45	0.069 32	0.001 59	0.022 38	0.001 05	432	10	100.69
NO5	483.02	670.95	0.72	0.056 35	0.002 57	0.542 27	0.023 87	0.069 84	0.000 89	0.021 32	0.000 50	435	5	101.15
NO6	223.50	252.20	0.89	0.055 40	0.002 22	0.516 51	0.019 83	0.067 64	0.000 76	0.018 88	0.000 35	422	5	100.24
NO7	248.10	286.40	0.87	0.055 46	0.001 49	0.523 40	0.013 08	0.068 47	0.000 54	0.021 18	0.000 27	427	3	100.00
NO8	421.77	435.56	0.97	0.056 43	0.005 76	0.529 91	0.052 91	0.068 13	0.001 87	0.019 99	0.001 03	425	11	101.65
NO9	81.95	156.72	0.52	0.055 09	0.008 18	0.517 62	0.075 32	0.068 16	0.002 67	0.020 82	0.001 77	425	16	99.76
NO10	107.58	184.32	0.58	0.055 21	0.005 05	0.517 92	0.046 25	0.068 04	0.001 65	0.021 17	0.000 99	424	10	100.00
NO11	223.60	328.99	0.68	0.055 25	0.009 35	0.527 95	0.087 60	0.069 31	0.003 10	0.023 31	0.001 66	432	19	99.54
NO12	274.06	386.41	0.71	0.055 42	0.006 94	0.533 42	0.065 43	0.069 80	0.002 33	0.022 59	0.001 42	435	14	99.77
NO13	177.19	312.27	0.57	0.055 31	0.004 03	0.517 88	0.036 80	0.067 91	0.001 33	0.021 15	0.000 85	424	8	100.00
NO14	275.33	385.13	0.71	0.055 64	0.003 13	0.534 96	0.029 19	0.069 72	0.001 07	0.021 05	0.000 60	434	6	100.23
NO15	177.77	339.49	0.52	0.055 89	0.009 42	0.538 34	0.088 96	0.069 84	0.003 13	0.023 96	0.002 38	435	19	100.46
NO16	293.27	513.05	0.57	0.055 87	0.002 45	0.539 58	0.022 80	0.070 03	0.000 85	0.021 68	0.000 53	436	5	100.46
NO17	235.40	385.94	0.61	0.055 58	0.001 63	0.535 87	0.014 76	0.069 91	0.000 60	0.021 79	0.000 34	436	4	100.00
NO18	104.97	191.61	0.55	0.055 67	0.002 16	0.529 46	0.019 69	0.068 96	0.000 74	0.021 45	0.000 45	430	4	100.23
NO19	93.82	205.60	0.46	0.055 80	0.003 32	0.522 24	0.030 16	0.067 85	0.001 09	0.021 84	0.000 63	423	7	100.95
NO20	78.50	168.87	0.46	0.056 08	0.007 54	0.527 99	0.069 51	0.068 26	0.002 43	0.022 49	0.001 44	426	15	100.94

样号	岩石类型	SiO₂	Al₂O₃	Fe₂O₃	FeO	CaO	MgO	K₂O	Na₂O	TiO₂	P₂O₅	MnO	烧失量	总量	Mg^#
xms-1	玄武岩	49.75	15.12	9.99	0.62	7.42	1.24	0.63	7.37	1.30	0.36	0.25	5.75	99.80	60.67
xms-2	玄武岩	48.80	14.86	10.00	0.56	8.17	1.13	0.70	7.30	1.31	0.38	0.27	6.35	99.83	60.89
xms-3	玄武岩	49.59	15.38	10.10	0.83	7.08	1.03	1.22	7.04	1.33	0.38	0.24	5.59	99.81	48.91
xms-4	玄武岩	50.94	15.28	10.42	0.42	6.63	0.81	0.73	7.71	1.32	0.37	0.22	4.99	99.84	59.80
xms-5	流纹岩	73.20	13.00	2.35	0.48	0.73	0.38	4.05	4.46	0.24	0.05	0.06	0.81	99.80	37.92
xms-6	流纹岩	77.79	10.52	1.54	0.39	1.35	0.29	2.25	4.32	0.23	0.06	0.04	1.09	99.87	36.45