Abstract The basin‐and‐range area in eastern North China is known for frequent occurrence of earthquakes, their great magnitudes and heavy losses thereby incurred. Seismic studies in the past usually emphasized the intersections, inflexions and branches of the faults. However, the intensities of many great earthquakes in this area do not show linear distribution, and the epicenters are horizontally dispersed at certain depths instead of along the strike of faults. Based on the sub‐mantle plume studies made by authors in the past decade, it is thought that there exists an uplifted sub‐mantle plume under the fault depression area in North China. The uplifting and intrusion of mantle materials caused the upper crust to be faulted, while low‐velocity and high‐velocity layers are alternatively distributed in the middle crust under the influence of the mantle and the lower crust. The middle and lower crust materials were detached from the top of the sub‐mantle plume to the surroundings while the sub‐mantle plume materials were detached outward. When the detached middle and lower crust come to the boundary of fault basins in the upper crust, they will be obstructed by the orogenic zone and the detachment will go slower. The shearing between them will cause the stress to accumulate and release alternatively, so that earthquakes occurred frequently in the areas of sub‐mantle plume and its surroundings.
The occurrence, mineralogy and geochemistry of eclogites in the Mt. Dabie area show that they were subjected to a high-pressure metamorphism to- gether with the country rocks, but their petrochemistry and REE geochemistry show some difference from those of the country rocks. The geochemical charac- teristics of the eclogites are similar to those of both continental tholeiitic basalt and oceanic tholeiitic basalt. The rocks probably subducted to the upper mantle with the Dabie metamorphic complex. When elevated to the surface, they were subjected to different stages of retrogressive metamorphism.
The solid mineral resources in mountain area and the petroleum in basin are two main areas of geological researches, with different emphasis and normally assigned to different department, so that interdisciplinary investigation is scarce to date. The Luxi uplift consists of Nikunshan-Muzishan, Mengshan, Culaishan-Xinfushan-Mengliangang and Taishan-Lushan-Yishan etc. spreading from south to north, furthermore, among these uplift there are distributed four neighboring fault depressions i.e. Siping, Wenmeng, Feicheng and Laiwu fault depressions. Between the fault depressions and the uplift developed the typical listric faults which control the Miocene dustpan-shaped sediments in the fault depressions. In the case of the Qikou depression, there are three subclasses of depressions as Qinan, Qibei and Banqiao with Nandagang and Beidagang buried-hill structure belt as the boundaries and taken on the dissymmetry form with the northern side deep and steep, the southern side shallow and nearly flat. The Qikou depression was faulted in the north and overlapped in the south. Comparative study of the sag and the structure of uplift and depression in the uplift area of Western Shandong becomes an urgent need. From the point of view of mantle branch, the authors propose that both the Luxi uplift and Qikou depression have the main structural features formed through coupling of mountain and basin.
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