底辟热流体上涌的数值模拟及其对早古生代青藏高原柴北缘祁连弧形成的启示  

Numerical simulation of diapir flow—Enlightenment on formation of Qilian arc in northern Qaidam in the early Paleozoic

作　　者：原一哲 胡才博 魏东平[1,2] YUAN YiZhe;HU CaiBo;WEI DongPing(College of Earth and planetary Science,Universily of Chinese Academy of Sciences,Beijing 100049,China;Key Laboratory of Computational Geod ymamics,Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院大学地球与行星科学学院,北京100049 [2]中国科学院计算地球动力学重点实验室,北京100049

出　　处：《地球物理学报》2021年第5期1666-1682,共17页Chinese Journal of Geophysics

基　　金：国家自然基金项目(41874115);国家重点研发项目“华北克拉通成矿系统的深部过程与成矿机理”子课题(2016YFC0600101);国家重点研发项目“地球系统模式的改进、应用开发和高性能计算”子课题(2016YFB0200801)联合资助.

摘　　要：底辟流是研究地球内部物质循环与迁移的重要窗口,其动力学演化过程对于我们认识区域地质构造与演化具有重要意义.本文从热-结构力学的角度,建立三组不同的数值模型,研究底辟流上涌的动力学过程,分析底辟流半径、热-结构耦合、岩浆上涌通道对底辟流上涌过程的影响.该研究对认识早古生代祁连弧的形成过程具有重要启示.数值实验结果表明,底辟流半径越大底辟上涌速度越快;单个底辟很难直接上涌至上地壳底部,柴达木北缘超高压变质带和岩浆弧可能是由于多个底辟流持续上涌,最终发育稳定岩浆通道形成的,并且岩浆通道的形成对于超高压变质岩石的减压时间以及岩浆弧的形成时间均具有重要影响;具有稳定岩浆通道的单个底辟流从地幔深处90 km上涌至壳幔边界的过程中,在水平方向的侵蚀范围要比垂向侵蚀范围大一倍左右,研究结果表明安第斯型底辟流模型可以很好地描述早古生代柴达木北缘祁连弧的形成过程.The diapir flow is an important window for studying the material circulation and migration inside the Earth.Studying the dynamic evolution of the diapir flow is of great significance for us to understand the regional geological structure and evolution.In this paper,from the perspective of thermo-structural mechanics,three different numerical models are developed to study the dynamic process of diapir flow upwelling,and to analyze the influences of the diapir flow radius,thermal-structural coupling,and magma upwelling channel on diapir flow upwelling process.This study is of great significance to understand the formation process of the Qilian arc in northern Qaidam,northeastern Qinghai-Tibetan Plateau.The numerical experimental results show that the larger the diapir flow radius,the faster the diapir upwelling speed;it is difficult for a single diapir to directly ascend to the bottom of upper crust.The North Qaidam ultrahigh-pressure metamorphic zone and magmatic arc may be due to the continuous diapir flow upwelling,through stable magma channels,and the formation of magma channels has an important influence on the decompression time of ultra-high pressure metamorphic rocks and the formation time of magma arcs;During the upwelling of a single diapir with a stable magma channel from 90 km deep in the mantle to the crust-mantle boundary,the horizontal erosion range is about twice as large as the vertical erosion range;the diapir flow model in the Andean model can well describe the formation process of Qilian arc on the northern margin of Qaidam.

关 键 词：超高压变质岩 底辟流 祁连弧 

分 类 号：P314[天文地球—固体地球物理学] P313[天文地球—地球物理学]