藏北中仓地区晚白垩世岩浆岩成因及其对高原早期隆升的指示

doi:10.13745/j.esf.sf.2023.11.61

地学前缘 ›› 2024, Vol. 31 ›› Issue (6): 261-281.DOI: 10.13745/j.esf.sf.2023.11.61

藏北中仓地区晚白垩世岩浆岩成因及其对高原早期隆升的指示

吴浩¹^,²(), 杨晨¹, 吴彦旺³, 李才⁴, 刘飞¹, 林兆旭¹

1.桂林理工大学广西隐伏金属矿产勘查重点实验室, 广西桂林 541006
2.桂林理工大学广西战略性关键矿产资源成矿与勘查科技创新基地, 广西桂林 541006
3.天津城建大学地质与测绘学院, 天津 300384
4.吉林大学地球科学学院, 吉林长春 130061

收稿日期:2023-08-07 修回日期:2023-11-27 出版日期:2024-11-25 发布日期:2024-11-25
作者简介:吴浩(1989—),男,副教授,主要从事岩石大地构造研究工作。E-mail: wuhaojlu@126.com
基金资助:
国家自然科学基金项目(42303045);广西科技基地和人才专项(桂科AD21220033);山东省自然科学基金资助项目(ZR2020QD045)

Petrogenesis of Late Cretaceous magmatic rocks in the Zhongcang area of northern Tibet and their implications for early uplift of the plateau

WU Hao¹^,²(), YANG Chen¹, WU Yanwang³, LI Cai⁴, LIU Fei¹, LIN Zhaoxu¹

1. Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin 541006, China
2. Guangxi Science Innovation Base for Formation and Exploration of Strategic Critical Mineral Resources, Guilin University of Technology, Guilin 541006, China
3. School of Geology and Geomatics, Tianjin Chengjian University, Tianjin 300384, China
4. College of Earth Sciences, Jilin University, Changchun 130061, China

Received:2023-08-07 Revised:2023-11-27 Online:2024-11-25 Published:2024-11-25

摘要/Abstract

摘要：

青藏高原中部白垩纪晚期爆发了大规模的岩浆活动,并伴随着快速的地表隆升,然而其深部动力学机制一直存有较大的争议。本文对藏北中仓地区发育的闪长玢岩和英安岩开展了锆石U-Pb定年、全岩主微量元素和Sr-Nd-Hf同位素分析研究,以期为区域构造—岩浆演化提供新的约束。锆石U-Pb定年结果表明闪长玢岩和英安岩均形成于晚白垩世(90~85 Ma),其中闪长玢岩具有高Sr含量、低Y含量和高Sr/Y值的特点,显示与埃达克岩的亲缘性,结合其较高的Mg^#,研究认为是增厚榴辉岩相下地壳熔体混染地幔物质的产物。英安岩地球化学和同位素特征与闪长玢岩相似,反映了相同的岩浆源区,然而其强烈亏损Rb、Ba和Sr等易蚀变元素表明成岩后期经历了强烈蚀变作用。结合区域上同时期富Mg埃达克质岩浆爆发和大规模磨拉石沉积,本文认为青藏高原中部晚白垩世构造—岩浆活动形成于班公湖—怒江缝合带碰撞后增厚下地壳拆沉过程,而深部拆沉同时触发了地表快速抬升,并由此形成了白垩纪古高原,为现代高原的形成奠定了基础。

关键词: 班公湖—怒江缝合带, 晚白垩世, 岩石成因, 拆沉作用, 高原隆升

Abstract:

During the late Cretaceous, extensive magmatic activity erupted in the central Tibetan Plateau, accompanied by rapid surface uplift. However, the deep dynamical mechanisms behind this phenomenon have been a subject of considerable debate. This study conducts U-Pb zircon dating, as well as analyses of whole-rock major and trace elements and Sr-Nd-Hf isotopes on the diorite and rhyolite developed in the Zhongcang area of northern Tibet, aiming to provide new constraints on regional tectonic-magmatic evolution. The U-Pb zircon dating results indicate that both the diorite and rhyolite formed in the Late Cretaceous (90—85 Ma). The geochemical characteristics of the diorite show high Sr, low Y content, and high Sr/Y ratios, indicating an affinity to adakite. Combined with its high Mg^#, it is proposed to be a product of the mixing of underplated eclogite-facies lower crustal melts with mantle materials. The geochemical and isotopic characteristics of the rhyolite are similar to those of the diorite, reflecting a common magmatic source. However, its significant depletion in Rb, Ba, Sr, and other easily altered elements suggests it underwent intense alteration during the late diagenesis. Coupled with the contemporaneous eruption of high-Mg adakitic magma and large-scale molasse deposition in the region, this study posits that the tectonic-magmatic activity in the central Tibetan Plateau during the Late Cretaceous was a result of the thickening and detachment of the lower crust following the collision of the Bangong Lake—Nujiang suture zone. This deep detachment simultaneously triggered rapid surface uplift, forming a Cretaceous paleo-plateau and laying the foundation for the modern plateau’s formation.

Key words: Bangong Lake—Nujiang suture zone, Late Cretaceous, rock genesis, detachment, plateau uplift

中图分类号:

吴浩, 杨晨, 吴彦旺, 李才, 刘飞, 林兆旭. 藏北中仓地区晚白垩世岩浆岩成因及其对高原早期隆升的指示[J]. 地学前缘, 2024, 31(6): 261-281.

WU Hao, YANG Chen, WU Yanwang, LI Cai, LIU Fei, LIN Zhaoxu. Petrogenesis of Late Cretaceous magmatic rocks in the Zhongcang area of northern Tibet and their implications for early uplift of the plateau[J]. Earth Science Frontiers, 2024, 31(6): 261-281.

样号及测点	同位素比值及误差						年龄及误差/Ma
样号及测点	²⁰⁷Pb/²⁰⁶Pb	1σ	²⁰⁷Pb/²³⁵U	1σ	²⁰⁶Pb/²³⁸U	1σ	²⁰⁷Pb/²⁰⁶Pb	1σ	²⁰⁷Pb/²³⁵U	1σ	²⁰⁶Pb/²³⁸U	1σ
闪长玢岩(Q17T6)
Q17T6-01	0.048 46	0.001 72	0.139 64	0.004 99	0.020 80	0.000 23	122	63	133	4	133	1
Q17T6-02	0.049 44	0.002 17	0.162 37	0.006 74	0.023 88	0.000 28	169	75	153	6	152	2
Q17T6-03^*	0.053 62	0.003 48	0.100 96	0.005 59	0.014 11	0.000 26	355	92	98	5	90	2
Q17T6-04^*	0.053 81	0.003 29	0.096 38	0.005 51	0.013 29	0.000 25	363	95	93	5	85	2
Q17T6-05	0.085 46	0.002 49	2.453 25	0.070 67	0.209 01	0.002 86	1 326	35	1 258	21	1 224	15
Q17T6-06	0.056 34	0.001 30	0.598 10	0.014 27	0.076 85	0.000 92	466	32	476	9	477	6
Q17T6-07^*	0.046 05	0.011 50	0.082 04	0.020 35	0.012 92	0.000 36		408	80	19	83	2
Q17T6-08	0.101 40	0.001 69	3.852 33	0.099 79	0.269 27	0.004 80	1 650	24	1 604	21	1 537	24
Q17T6-09^*	0.053 03	0.004 00	0.100 90	0.006 79	0.014 03	0.000 30	330	115	98	6	90	2
Q17T6-10	0.060 96	0.007 88	0.734 99	0.088 17	0.087 44	0.004 22	638	291	559	52	540	25
Q17T6-11	0.052 81	0.004 31	0.114 37	0.008 10	0.016 40	0.000 36	320	122	110	7	105	2
Q17T6-12^*	0.053 99	0.003 63	0.104 13	0.006 19	0.014 25	0.000 27	371	99	101	6	91	2
Q17T6-13	0.063 07	0.001 47	0.872 24	0.022 43	0.099 43	0.001 13	711	35	637	12	611	7
Q17T6-14	0.070 35	0.001 44	1.442 59	0.028 12	0.148 29	0.001 15	939	27	907	12	891	6
Q17T6-15	0.064 24	0.007 69	0.124 54	0.014 57	0.014 06	0.000 35	750	265	119	13	90	2
Q17T6-16^*	0.046 05	0.006 24	0.083 36	0.011 14	0.013 13	0.000 30		251	81	10	84	2
Q17T6-17	0.051 70	0.002 93	0.127 01	0.006 76	0.018 09	0.000 32	272	90	121	6	116	2
Q17T6-18^*	0.050 31	0.002 63	0.095 86	0.004 57	0.014 17	0.000 22	209	81	93	4	91	1
Q17T6-19	0.151 67	0.008 02	5.861 31	0.260 87	0.280 27	0.008 01	2 365	93	1 956	39	1 593	40
Q17T6-20	0.067 31	0.015 02	0.128 28	0.028 41	0.013 82	0.000 38	848	482	123	26	88	2
Q17T6-21	0.117 21	0.002 49	5.668 28	0.177 07	0.350 11	0.009 61	1 914	25	1 927	27	1 935	46
Q17T6-22^*	0.055 77	0.003 61	0.105 90	0.006 24	0.013 94	0.000 26	443	98	102	6	89	2
Q17T6-23	0.075 06	0.001 02	1.362 61	0.024 22	0.130 81	0.001 69	1 070	17	873	10	792	10
Q17T6-24^*	0.061 39	0.008 62	0.111 29	0.015 43	0.013 15	0.000 29	653	316	107	14	84	2
Q17T6-25	0.070 26	0.022 80	0.128 20	0.041 37	0.013 23	0.000 46	936	670	122	37	85	3
Q17T6-26	0.054 08	0.004 48	0.171 14	0.013 83	0.022 95	0.000 42	374	190	160	12	146	3
Q17T6-27	0.052 31	0.001 87	0.199 82	0.007 55	0.027 60	0.000 33	299	65	185	6	175	2
Q17T6-28^*	0.053 54	0.003 46	0.099 09	0.005 63	0.013 95	0.000 24	352	98	96	5	89	2
Q17T6-29^*	0.046 05	0.004 48	0.087 30	0.008 31	0.013 75	0.000 28		204	85	8	88	2
Q17T6-30	0.060 84	0.018 02	0.306 06	0.090 34	0.036 48	0.000 93	634	585	271	70	231	6
Q17T6-31	0.103 91	0.002 13	3.805 46	0.078 32	0.265 68	0.002 93	1 695	22	1 594	17	1 519	15
Q17T6-32^*	0.051 87	0.003 58	0.097 24	0.006 09	0.013

藏北中仓地区晚白垩世岩浆岩成因及其对高原早期隆升的指示

Petrogenesis of Late Cretaceous magmatic rocks in the Zhongcang area of northern Tibet and their implications for early uplift of the plateau

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