摘要：
Objectives:This work shows the results of computing the 3D density disturbance images in Continent of China and interpretation of the these results based on geodynamics and petro-physics,especially for crust beneath craton terrains.Methods:We apply the scale-depth relationship of gravity anomalies and the multi-scale wavelet analysis for extracting crustal density information from surface Bouguer gravity data,and presents density disturbance images of the upper,middle and lower crust,which represent the three dimensional density structures in the studied area.Results:The craton terrains of Continent of China are generally characterized by high density in whole crust,especially having big and high-density crustal roots;on contrast,orogenic belts usually have low-density mountain roots.As current craton terrains usually have long evolution history and different evolution-event sequences,their crustal structures could be changed diversely.Their evolution might had some different stages and taken millions of years.In different evolutional stages,their crustal physical properties could change greatly.We must endow concepts of certain evolutional stage to the tectonic units in order to understand exactly their behaviors and attributes.From crustal density images one may obtain information about maturity of a craton terrane.The density structures beneath the current craton terrains can be divided into three types:(1) relatively high in whole crust,called as typical craton;Tarim,Alashan,East Huabai,Upper and Middle Yangtze belong to this type.(2) Relatively low in the upper crust,but high in the middle and lower crust,called as week-crystalline basement craton;Ordos and Jiamusi belong to this type.(3) Relatively high in the upper and middle crust,but low in the lower crust,called lack-root craton blocks;Qaidam and Junggar belong to the third type,they were probably flanks of an ancient craton.Conclusions:The craton terrains of Continent of China are generally characterized by high density in whole crust,especially having big and high-density crustal roots but including three different types.%本文根据重力场小波变换的尺度一源深度转换律,进行地面重力异常场多尺度分解,取得了反映中国地壳不同埋藏深度的小波细节,揭示了克拉通地体地壳的密度结构.中国大陆克拉通地体地壳密度结构的总体特点是:地壳密度总体偏高,尤其是在经历了岩浆底垫作用后,下地壳形成了粗大的和高密度的壳根,而造山带的下地壳通常有低密度的山根.现今的克拉通地体有几个演化的阶段,由陆地核演化为一定规模的克拉通地体可能经历漫长的时间.不同演化的阶段地体的物理性质有明显的变化,要赋予大地构造单元以演化阶段的内涵,才能准确理解它们的行为和属性.同时,根据地壳密度结构成像的结果,可以了解克拉通地体的成熟度.中国大陆克拉通地体或者内部地块的地壳密度结构大致可以分为三类.上中下地壳密度都偏高的属于第一类,称为典型的克拉通,塔里木、阿拉善、华北东部、上中扬子等属于第一类.第二类克拉通地体上地壳密度偏低,而下地壳密度偏高,称为弱结晶基底的克拉通,鄂尔多斯和佳木斯属于第二类.第三类上中地壳密度偏高,而下地壳密度偏低,称为无壳根的克拉通残片,柴达木和准噶尔盆地属于此类,它们可能是古克拉通地体的残片.
