二维初至波层析成像揭示的兰坪盆地—扬子西缘浅层地壳结构
投稿时间:2024-01-02  修订日期:2024-03-22  点此下载全文
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作者单位邮编
王冠 中国地质科学院地质研究所 100094
熊小松* 中国地质科学院地质研究所中国地质科学院地球深部探测中心 
卢占武 中国地质科学院地质研究所 
李秋生 中国地质科学院地质研究所 
吴国炜 中国地质科学院地质研究所 
张新彦 中国地质科学院地质研究所 
基金项目:国家深地资源勘查开采重点专项(编号: 2016YFC0600302)、国家自然科学基金(编号: 42374119, 42274134, 42274134, C2330)和中国地质科学院基本科研业务费(编号: S2304; JKYQN202311)
中文摘要:兰坪盆地-扬子西缘位于青藏高原东南缘,在地质构造上属特提斯-喜马拉雅强烈挤压、碰撞造山带的东部,兼跨华南板块与古冈瓦纳板块两大构造单元。其浅层地壳是记录地壳形变、岩浆作用与成矿作用的重要载体。本文利用兰坪盆地-扬子西缘220 km长的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,获得了测线下方4 km以浅的上地壳浅层P波速度结构。成像结果显示,兰坪盆地沉积厚度从西到东逐渐减薄,扬子块体西缘东部表现出“两厚夹一薄”的特点;兰坪盆地内有多组逆冲断裂,金沙江断裂与程海断裂产状近垂直,前者两侧沉积厚度无明显变化,后者西侧沉积厚度小于东侧;金顶铅锌矿的形成可能与底部热隆有关,北衙金矿下方结晶基底向上突起,推测由岩浆上涌侵蚀围岩导致。
中文关键词:兰坪盆地  扬子块体西缘  层析成像  上地壳速度结构
 
Shallow Crustal Velocity Structure of the Lanping Basin–Western Margin of the Yangtze Plate Revealed by 2D First-arrival Seismic Tomography
Abstract:The Lanping Basin-the western margin of the Yangtze Plate is located in the southeastern margin of the Tibetan Plateau. It belongs to the eastern part of the Tethys-Himalayan strong extrusion and collision orogenic belt in geological structure, and spans the two major tectonic units of the South China Plate and the ancient Gondwana Plate. The detection of shallow crustal velocity structure is helpful to reveal the evolution history of shallow crustal structure and tectonic deformation in this area. In this paper, the first arrival wave(Pg phase) data of the deep reflection seismic profile covering 220 km in the Lanping Basin-the western margin of the Yangtze Plate are used to obtain the P-wave velocity structure of the upper crust below 4 km underground by tomography inversion method. The results show that the sedimentary thickness of Lanping Basin gradually decreases from west to east, and the eastern part of the western margin of the Yangtze plate shows the characteristics of ' two thick and one thin '. There are multiple sets of thrust faults in the Lanping Basin. The Jinshajiang fault and the Chenghai fault are nearly vertical. The sedimentary thickness on both sides of the former has no obvious change, and the sedimentary thickness on the west side of the latter is smaller than that on the east side. The formation of Jinding lead-zinc deposit may be related to the hot dome beneath. The crystalline basement under the Beiya gold deposit protrudes upward, which is speculated to be caused by the erosion of surrounding rock by magma upwelling.
keywords:Lanping Basin  Western Margin of the Yangtze Plate  tomographic imaging  upper crust velocity structure
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