兴蒙、吉黑地区岩石圈电性结构特征

Features of the electric structure of the lithosphere beneath the Hinggan-Inner Mongolia and Jilin-Heilongjiang regions

采用具有国际先进水平的二维连续自动反演技术对收集的MT资料进行了二维反演和综合解释。得到了不同地区MT剖面的二维电性结构断面。通过二维反演断面发现了松辽盆地的东西边界较陡,而南部边界较缓的电性结构;发现在火山地区12～30km深度普遍存在低阻物体,为解释火山地区深部存在岩浆囊提供了依据。另外,于桦南—饶河重新实施的MT剖面,其二维反演断面也较清楚地揭示出:剖面西段为高阻特征且具有稳定的岩石圈厚度(80～90km),该区段对应佳木斯地块;剖面中部具有明显的电性梯度带,该梯度带为确定佳木斯地块的东界位置及其深部结构形态提供了依据;剖面东段则揭示了佳木斯地块以东地区浅部为逆冲推覆体,深部为多个高阻块体与低阻条带相间的电性结构。

Two-dimensional （2D） inversion and integrated interpretation of the gathered MT data were made by using 2D continuous automatic inversion technology and 2D electric structure cross-sections of the MT profiles were obtained in different areas. The 2D inversion cross-sections show that the eastern and western boundaries of the Songliao basin are steeper while the southern boundary is gender and that low-resistivity objects are commonly present at 15-30 km depth in volcanic areas, which offers a basis for interpreting the existence of a magma pocket at depth of volcanic areas. In addition, the cross-section of 2D inversion of the MT data resurveyed along Huanan-Laohe has also clearly revealed the following： the western segment of the cross-section has a high resistivity feature and a persistent lithospheric thickness （80-90 km）, corresponding to the Jiamusi massif. The central segment of the cross-section obviously contains an electricity gradient zone, which furnishes a basis for the determination of the eastern boundary of the Jiamusi massif and its deep structure configuration. The eastern segment of the cross-section reveals a thrust nappe at shallow depth in an area east of the Jiamusi massif and an electric structure composed of alternate high-resistivity strips and low-resistivity strips at depth.