华北地台东部北段中生代—新生代热隆与盖层地质构造的关系

The Relations of Thermo-uplift and Covering Geologic Structure in the Northern Segment of the Eastern Part in the North China Platform during the Mesozoic-Cenozoic Era

对华北地台东部北段中生代以来,较为复杂的地质构造平演化构造特征有各种不同的认识。作者以板块构造理论为基础,根据区内不同阶段的地质构造演化特征、深部地质资料、褶皱和断裂构造的发育和分布特征、以及岩浆侵入活动在时间上和空间上的分布规律等方面的研究,认为热隆对区内地质构造,特别是对盖层构造均演化和特征起着控制作用。洋中脊是大洋地壳中的高热能区,沿洋中脊形成热隆带,驱动洋壳向陆壳下面俯冲,与陆壳下部物质混合重熔成中酸性岩浆,构成高热能的活动核。这些岩浆又侵入到盖层中,同时,岩浆及围岩中的气体聚集在侵入体的顶部。因此,热隆是由侵入到盖层中的流动熔融体(岩浆)和气体构成。根据热隆构造不同部位的差异,作者提出了热隆构造的概念、模式,并将其划分为四个构造层次:1)隆核构造层;2)近隆构造层,3)中间构造层;4)外隆构造层。同时,总结了外隆构造层的各种断裂构造形式:1)滑落式断裂构造;①单式滑落断裂构造;②滑落式推覆构造;③复式滑落构造;2)逆冲式构造:①逆冲式断裂构造;②逆冲式推覆构造;③褶皱—逆冲推覆构造:3)滑落—逆冲式构造。作者还讨论了区内近东西向的伸展作用、北东向隆起带与断陷带内的构造差异和北东向较大规模推覆构造以及地堑构造与北东向热隆带的关系。作者认为,热隆对区内盖层构造、对某些内生矿田和外生矿田以及对古老片麻岩穹窿的成生分析都是十分重要的。

There have been different recognitions about the complex tectonic evolution and tectonic features in the area of the northern segment of the eastern part of the North China platform dating from the Mesozoic Era. Based on the plate tectonic theory, in this paper the authors put forward the viewpoint that thermo-uplift plays an important controlling role in the tectonics, especially in the evolution and the features of the covering structure in the same place, on the basis of the characteristics of the tectonic evolution in different stages, the depth information, the features of the development and distribution of the folds and fractures, as well as the magmatic activities in respect of space and time etc. within this area. Mid oceanic ridge is a high heat area in oceanic crust, along which themo-uplift zone is formed, thereby driving the oceanic crust subducting towards the continental crust, the mixing and remelting of the oceanic crust material and the lower continental crust material lead in the formation of medium-acid magma and a active core of high heat. Thereafter, the magma intrudes into covering layer accompanied by the concentration of the gases from the magma and wall rocks in the top of the intrusion body. Themo-uplift, therefore, is composed of melting body (magma) intruded into covering layer and related gases. According to the differences in the different structural positions, the authors put forward the concept and pattern of thermo-uplift in which four structural layers are classificated. 1) the thermo-uplift core structural layer, 2) the near-thermo-uplift structural layer, 3)midstructural layer,and 4) out-uplift structural layer. Meanwhile they also summarized the various fracture types of the out-uplift structural layer: 1) slide fracture structure including single slide fracture, slide nappe structure, and complex slide fracture structure, 2) thrust structure containing thrust fracture structure, thrust nappe structure and foldthrust nappe structure; and 3) slide-thrust structure. In addition the relationships of the north eastly directed thero-uplift to the east-westly trending extension to the Structural difference between the northeastly trending uplift zone and t e fault-subsided zone as well as to the larger northeastly directed nappe tectonics and graben structures are also discussed in this paper. The authors considered that the thermo-uplift structures should be vary important in the analyses of the covering structure, of some ndogenetic and some exogenic ore field structures and of the origin of some old gneiss domes.