| 北山构造带南部上地壳二维初至波层析成像 |
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| 引用本文： | 吴国炜,熊小松,高锐,陈宣华,李英康,王冠,王小成,任海东.北山构造带南部上地壳二维初至波层析成像[J].地学前缘,2022,29(2):402-415. |
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| 作者姓名： | 吴国炜 熊小松 高锐 陈宣华 李英康 王冠 王小成 任海东 |
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| 作者单位： | 1.中国地质科学院 地球深部探测中心, 北京 1000372.自然资源部深地动力学实验室/中国地质科学院 地质研究所, 北京1000373.中山大学 地球科学与工程学院, 广东 广州 5102754.自然资源实物地质资料中心, 河北 廊坊 1011495.青海省有色地质矿产勘查局 地质矿产勘查院, 青海 西宁 8100076.青海大学 地质工程系, 青海 西宁 810016 |
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| 基金项目： | 国家自然科学基金;青海省科技厅基础研究计划项目;中国地质调查局地质调查项目;国家重点研发计划 |
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| 摘 要： | 花海盆地—北山构造带南部位于青藏高原东北缘以北地区,是特提斯洋和古亚洲洋两大构造域的交接部位,自新元古代晚期以来经历了多期次、多阶段的板块裂解-俯冲-碰撞-拼合的演化历史,尤其是中生代以来的逆冲推覆和走滑作用,以及受新生代以来印度板块和欧亚板块碰撞的远程效应影响,导致青藏高原东北缘的向北扩展,形成了现今复杂的地质地貌结构。其地壳结构记录了多期构造作用的叠加,上地壳结构更是促进我们理解青藏高原东北缘向外的扩展机制及其对周缘块体的改造作用的天然记录本。本文利用2018年中国地质科学院在北山构造带南部完成的180 km深反射地震剖面的初至波(Pg震相)数据,通过层析成像反演方法,获得了花海盆地—北山构造带4 km深度范围内的上地壳P波速度结构。其主要特征为:花海盆地、总口子盆地和扎格高脑盆地均表现为较低的速度和较小的垂向速度梯度;研究区内的晚古生代花岗岩体具有明显的高速异常和较大的垂向速度梯度特征;左行走滑的阿尔金断裂带在花海盆地内表现为向北倾的高角度走滑性质,深度至少切穿花海盆地基底;北山南缘断裂带的推测隐伏区呈现速度等值线下凹的低速异常特征。同时,反演揭示的多处低速异常区指示了北山构造带南部的多处断层发育情况。
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| 关 键 词： | 北山构造带南部 花海盆地 层析成像 上地壳速度结构 |
| 收稿时间： | 2022-01-30 |
2D Tomographic imaging of the P-wave velocity structure in the upper crust beneath the southern Beishan tectonic belt |
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| WU Guowei,XIONG Xiaosong,GAO Rui,CHEN Xuanhua,LI Yingkang,WANG Guan,WANG Xiaocheng,REN Haidong.2D Tomographic imaging of the P-wave velocity structure in the upper crust beneath the southern Beishan tectonic belt[J].Earth Science Frontiers,2022,29(2):402-415. |
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| Authors: | WU Guowei XIONG Xiaosong GAO Rui CHEN Xuanhua LI Yingkang WANG Guan WANG Xiaocheng REN Haidong |
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| Abstract: | The Huahai Basin-Beishan tectonic belt is located north of the northeastern margin of the Qinghai-Tibetan Plateau and is the junction zone connecting the Tethys and Paleo-Asian Ocean domains. Since the Late-Neoproterozoic it has undergone multi-era, multi-stage evolution involving multiple plate splitting, subduction, collision and merging events. The subsequent overthrusting and strike-slip faulting since the Mesozoic, in particular the northward expansion of the northeastern margin of the Tibetan Plateau caused by the far-field effect of the collision between the Indian and Eurasian plates in the Cenozoic, formed the present complex geological/geomorphological structure. The crustal structure records the overprinting of the tectonics, whereas the upper crust is a natural notebook valuable for understanding the outward growth of the NE Tibet and its role in the transformation of the adjacent tectonic units. In this paper, based on the first arrive seismic wave (Pg phase) data from the 180 km-long deep seismic reflection profile completed by the Chinese Academy of Geological Sciences in 2018, we applied the tomographic inversion method to determine the P-wave velocity structure in the upper crust beneath the Huahai Basin-southern Beishan tectonic belt, 0-4 km deep underground. It was found that the three basins, Huahai, Zongkouzi and Zhagehao Basins, have a relatively low P-wave velocity and small vertical velocity gradient; the Late-Paleozoic granite outcrop shows obvious high-velocity anomalies and large vertical velocity gradient; and the left strike-slip Altyn fault zone across the southern margin of the Huahai Basin is a north-dipping high-angle strike-slip fault as deep as cutting through the basin basement at the least. In addition, many low-velocity anomalies revealed the extend of fault development in the southern Beishan. |
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| Keywords: | southern Beishan Huahai Basin tomography upper crustal structure |
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