银额盆地航磁特征与地质构造

Aeromagnetic Characteristics and Geological Structure of the Yin’e Basin

摘要: 本文通过最新1:5万和1:10万航磁资料对银额盆地的地质构造进行了分析，确定了盆地的边界和范围。航磁资料显示盆地边界不规则，其范围较前人圈定范围有所扩大，前人认为的盆地面积为112,000 km²，航磁反映的盆地面积约为122,000 km²。同时对盆地的基底性质及其深度变化特点和构造格局开展了进一步研究，指出盆地的发生、发展主要受东西向断裂的控制，北东向断裂在后期的发展中对其进行了强烈的改造，形成了现在的构造格局。盆地构造面貌由“七坳二隆”构成，这与前人对盆地的“七坳五隆”的构造面貌的认识存在异同。通过对航磁异常的反演计算，确定了变质基底埋藏深度，并编制了盆地磁性基底深度图、构造单元划分图。利用航磁资料确定了坳陷、隆起和凹陷、凸起的分布范围，坳陷构成了盆地的主体。凹陷沉积厚度大，多为2000~7000 m，凸起不发育，披盖的沉积盖层薄，一般<2000 m。研究表明银额盆地是晚古生代至中、新生代多旋回叠合盆地，基底主要由弱磁性的前泥盆系变质岩系组成，在磁场上反映为以负为主的磁异常特征。沉积盖层主要为上古生代和中、新生代地层。盆地区的断裂构造发育，以北东向和北东东向为主，北西向断裂不发育。盆地沉积坳陷占据主导，其分布范围广，沉积厚度大，隆起不发育，范围相对不大。以上结论为今后在该盆地进行油气勘探提供参考依据。

Abstract: Based on latest 1:50,000 and 1:100,000 aeromagnetic data, geological structure of Yin’e Basin is analyzed, hence the boundary and scopes of the basin are determined. Aeromagnetic data has shown that the basin boundary is irregular, and its scope has been broader than delineated by predecessors. The area of the basin used to be considered as 112,000 km², while data reflected by aeromagnetic data is around 122,000 km². Besides, basement properties, depth variation characters and tectonic pattern of the basin were further studied, indicating that occurrence and development of the basin have been primarily controlled by fault structure of EW-trending, and was strongly reformed by NE-trending fault structure in later development, which formed current tectonic pattern. The tectonic structure of the basin is constituted of “7 depressions and 2 uplifts”, which is partly different from the previous understanding of “7 depressions and 5 uplifts” in this basin. Via inversion calculation of aeromagnetic anomalies, burial depth of metamorphic basement was determined, as well magnetic basement depth map and tectonic units’ division map were compiled. Distribution range of depressions, uplifts, sags as well as bulges was determined by means of aeromagnetic data, and the depressions constitute the main body of the basin. Sedimentary thickness of the depression is large, mostly ranging from 2000 to 7000 m, with undeveloped protrusions; sedimentary cover of the mantle is thin, generally less than 2000 m. Research has shown that Yin’e basin is a multi-cycle superimposed basin from Late Paleozoic to Meso-Cenozoic, and the basement is mainly composed of pre-Devonian metamorphic rock series, which is reflected in the magnetic field as negative magnetic anomaly. The sedimentary covers primarily consist of upper Paleozoic, middle and Cenozoic strata. The fault structures in the basin are developed mainly northeast and northeast oriented, with no development of northwest oriented faults. Sedimentary depression dominates the basin, with a wide distribution range, large sedimentary thickness, undeveloped uplift, and relatively small range. The above cognitions would provide references for further oil and gas exploration in this basin.