佳木斯地块及东缘岩石圈电性结构特征

Electrical structures of the lithosphere along the Jiamusi massif and its eastern edge

佳木斯地块及东缘是中国东北地区的重要地质构造单元.为探测该地区地壳深部结构与构造关系,沿桦南—饶河实施了240km的大地电磁测深的探测研究.采用光滑模型二维反演方法对桦南—饶河大地电磁剖面的探测数据进行了二维反演和综合地球物理解释.研究结果揭示了研究区断面域的电性结构:(1)剖面西段具有稳定的高阻特征且具有稳定的岩石圈厚度(约90km),在十几公里深度范围存在壳内高导层,该区段对应佳木斯地块.(2)剖面中部具有明显的电性梯度带,该梯度带反映了佳木斯地块的东界位置及其深部的结构形态.(3)剖面东段电性特征揭示了佳木斯地块以东区段浅部为逆冲推覆体,深部为多个高阻块体和低阻条带相间的电性结构,这些高阻块体可能为早期俯冲的岩石圈残片.

The Jiamusi massive and its eastern edge are important geologic structural unit in the northeast part of China, its structure meaning has drawn extensive attention. To detect the relationship of deep crust construction and structure between Jiamusi massive and its east region, a research of MT detection along the Huanan-Raohe line （about 240km） has been conducted. By adopting two-dimensional smooth model to inverse the MT data of Huanan-Raohe MT profile, the result has distinctly revealed electrical structure of the section： （1） In west segment of the section there is a geosphere which has a stable high resistivity feature and stable thickness about 90km, within the depth of more than ten kilometers exists a high conductivity layer, corresponding to Jiamusi massive, （2）The central part of the section obviously contains a geoelectro gradient zone, which indicates the east boundary of the Jiamusi massive and its deep configuration state, （3）The east segment of the section indicates that the east superficial segment of the Jiamusi massive is thrust nappe, and the several high resistivity bodies in the deep are probably earlier subducted lithosphere relic.