体波与面波频散联合反演华南陆内造山带岩石圈结构

As a classical intracontinental orogen, the mechanism of orogeny in South China is in hot dispute, including the lithospheric thickness and formation of wide-distributed magmatism. The fine lithospheric structures, including the velocity structure, Poisson's ratio, are helpful for the understanding of the dynamic process of orogeny. The joint inversion of P wave receiver function and surface wave dispersion is a good way to construct the lithospheric structure, while the traditional joint inversion depends on the assumption of constant value on Vp/Vs, which would lead the deviation on the final results. If introducing the S-wave receiver function and P-wave velocity from deep seismic sounding profiles to the joint inversion of receiver function and dispersion, we could get the Vs and Vp/Vs structure simultaneously. The methods have overcome the limitation of constant Vp/Vs, not only could they provide the lithospheric structure with higher resolutions, but also give the direct evidence of the lithospheric thickness. In this project, we will improve the joint inversion of receiver function and dispersion to get the lithospheric structure based on the permanent and mobile stations in South China. Combined with the geological and geochemical information, the results could provide more information on the lithospheric thickness and magmatism, improving the knowledge of intracontinental orogen.

华南地区为陆内造山作用典型构造域，其造山成因和机制历来存在广泛争议，主要议题包括岩石圈底界形态、大规模岩浆作用的深部机制。精细刻画岩石圈结构，如速度、泊松比等属性，有助于深入理解和认识陆内造山成因和机制。P波接收函数与面波频散联合反演是重建岩石圈速度结构的有效手段，然而传统方法假设波速比为常量，导致反演结果存在偏差。将S波接收函数和人工源深地震测深获得的P波速度结构引入到P波接收函数与面波频散联合反演中，同时反演获得不同深度Vs和Vp/Vs，可有效克服常量波速比的限制，不仅提高岩石圈速度结构成像精度，且为岩石圈厚度提供直接地震学证据。本项目拟改进P波接收函数与面波频散联合反演方法，进而综合利用华南区域固定台网和局部加密的流动台阵宽频带地震资料开展成像工作。综合地质、地球化学信息，研究结果可为该区岩石圈底界形态及大规模岩浆作用提供深部制约，深化认识该区陆内造山作用的动力学机制。

华南地区经历了从特提斯构造域向滨太平洋构造域的转换，研究者普遍认为古太平洋板块的俯冲作用不仅造成了该区数千公里宽的面型造山带，而且导致了花岗岩的大面积出露，以及多金属矿床的广泛分布。前人研究主要以地球化学和成矿学为主，缺乏相关的深部地球物理成像研究。本项目开展了野外密集地震台阵观测，发展了岩石圈几何结构的通用估算方法，利用该方法及先前发展的P波速度约束下的接收函数和面波频散联合反演，获得了华南大湖塘多金属成矿带、华夏大规模花岗岩省区域、扬子西缘等的岩石圈结构特征，揭示了华南岩石圈结构的强烈不均一性。结合成矿学和岩石地球化学，认为西太平洋板块俯冲形成了地幔过渡带的停滞板片和大地幔楔，大地幔楔内部的物质流动和来自地幔过渡带的挥发性物质导致华南东部的岩石圈减薄，并为大规模花岗岩成因、多金属成矿和中国东部南北重力梯度带的形成提供了深部控制条件。.研究结果为华南地区岩石圈状态及大规模岩浆作用、成矿作用研究提供了深部制约，深化认识了该区陆内造山作用的动力学机制。发表了标注SCI论文7篇，其中第一标注2篇，第二标注5篇。参与项目的研究生均顺利毕业，负责人也由副研究员晋升为研究员，并受邀为两个国际SCI期刊的Editor和Associate Editor。后期基于H-k叠加改进的ML-k方法，以及基于P波约束下的接收函数与面波联合反演的Joint_RFSW方法也会在接下来一两年发表并公开相关程序。