长江中下游构造带成因与燕山期的大洋俯冲  

Origin of the Mid-Lower-Yangtze tectonic belt and Yanshanian ocean subduction

作　　者：杨文采 YANG Wencai(Zhejiang University,Hangzhou,310058)

机构地区：[1]浙江大学,杭州310058

出　　处：《地质论评》2023年第5期1619-1627,共9页Geological Review

基　　金：浙江大学人才引进项目资助的成果。

摘　　要：位于扬子克拉通内部的长江中下游构造带是一个特别的岩石圈构造带,它的成因一直是个谜。前人认为这与晚侏罗世伊佐奈琦洋向亚欧大陆的俯冲有关,但是为什么伊佐奈琦洋俯冲只在长江中下游构造带局部形成深入内陆的铁铜和多金属成矿带?为了解这个问题,必须从华南地区的地球物理数据来分析研究区的岩石圈和软流圈的属性特征,并进行类似构造的全球对比。根据地球物理调查结果可知,长江中下游构造带的地壳主要体现地堑的特征;岩石圈呈现低S波速与高密度,此类浅地幔动力学构造系统与洋中脊向大陆的俯冲模式接近。根据太平洋区域侏罗纪—白垩纪大洋磁异常条带与古地磁研究可以推测,长江中下游构造带与铁铜多金属成矿带的形成原因,应该是伊佐奈琦洋的洋中脊与洋脊三叉连向下扬子克拉通地幔的俯冲。当然,证明这个推测还需要更多的调查数据。The Mid—Lower-Yangtze Tectonic Belt located in the interior of the Yangtze Craton is a peculiar lithospheric tectonic belt,and its origin has been a mystery.It was previously thought to be related to the subduction of the Late Jurassic Izanagi Ocean to Eurasia,but why did only the iron—copper and polymetallic ore belts form deeply inland in the Mid—Lower-Yangtze Tectonic Belt?To understand this problem,it is necessary to analyze the properties of the lithosphere and asthenosphere in the study area from geophysical data in South China,and make global comparisons of similar structures.Based on the results of geophysical surveys,the crust of the tectonic belt in the Mid—Lower-Yangtze Tectonic Belt mainly reflects the characteristics of grabens.The lithosphere exhibits low S-wave velocities and high densities.Such shallow mantle dynamic tectonic system was close to the pattern of subduction of mid-ocean ridges to continents.Based on the Jurassic—Cretaceous oceanic magnetic anomaly bands and paleomagnetic studies in the Pacific region,it can be speculated that the formation of the Mid—Lower Yangtze Tectonic Belt and the iron—copper polymetallic ore belt could be the results of subduction of the northern Izanagi ocean ridge and related triple ridge junction to the Yangtze Craton.Of course,more survey data is needed to prove this conjecture.

关 键 词：地球动力学 扬子克拉通 长江中下游构造带 地震波速与密度 洋中脊俯冲 

分 类 号：P548[天文地球—构造地质学]