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Analysis of Formation and Evolution of Salt Diapir in the Contractional Domain of Central Lower Congo Basin Based on Analogue and Discrete Element Modeling
CHENG Peng, LI Jianghai, LIU Zhiqiang
Acta Scientiarum Naturalium Universitatis Pekinensis    2021, 57 (3): 470-480.   DOI: 10.13209/j.0479-8023.2021.025
Abstract724)   HTML    PDF(pc) (9244KB)(175)       Save
Based on the seismic profile, analogue modeling and discrete element modeling method were carried out to study the deep genetic mechanism of the gravity instability structure and evolution process of the salt diapirs in the contractional zone of central Lower Congo Basin in the passive continental margin of Angola in West Africa. The effect of salt diapir activity on the migration of the sedimentary center of the mini-basin between the diapirs was further studied. The results show that the evolution process of salt diapirs in the contractional domain of central Lower Congo Basin is related to the stress conditions. In the early stage, it was mainly controlled by the effect of gravity spreading, and in the later stage, it was controlled by the effect of squeezing. According to the comparison between the results of analogue modeling and discrete element modeling and the seismic sections, the evolution process of salt diapir can be divided into the following three stages: 1) The early stage, the extended reactive diapir stage; 2) The mid stage, the passive diapir stage; 3) The late stage, squeezed active diapir stage. The sedimentary center of the mini-basin between the salt diapirs migrated to the diapirs with strong activities during the same period.
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Salt Structure Formation Modeling Controlled by Structure Inclination Angle: Take the Lower Congo Basin as an Example
WANG Dianju, LI Jianghai, CHENG Peng, LIU Zhiqiang, YU Fahao
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (2): 277-288.   DOI: 10.13209/j.0479-8023.2018.095
Abstract691)   HTML    PDF(pc) (28196KB)(132)       Save

Based on the data of three seismic work areas in the Lower Congo Basin, nine typical salt-related tectonic patterns are summarized in the basin and the distribution pattern of salt structures is confirmed. Established with the base tilt angle as a single variable based on the discrete element numerical simulation method, and evolution results of the structure and motion vectors are obtained. With the increase of the basement inclination angle, the flow velocity of salt rock and its overlying sediments gradually increases, and the subsequent terrigenous sediment transport distance is also longer. The basement inclination mainly has three kinds of control effects on the salt rock flow: differential compaction as the master control, differential compaction and gravity gliding combined, gravity gliding as master control. These three control effects are all affected by the basement inclination angle and appear in turn with the change of the angle. Based on the analysis results above, control pattern of basement inclination on salt rock flow in the passive margin basin of the South Atlantic is established.

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Petrological and Structural Characteristics of the Zunhua Neoarchaean Ophiolitic Mélange:
Proof of the Operation of Ancient Plate Tectonics
HUANG Xiongnan,LI Jianghai,CHEN Zheng,LIU Zhiqiang
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract862)            Save
In the north of Zunhua, plentiful structural lenses of basic and ultra-basic rocks including metamorphosed diabases (amphibolites), layer gabbros, ultramafic cumulates and mantle peridotites, are scattered in the strongly sheared Neoarchaean gneiss. The basic and ultra-basic rocks are comparable to a modern ophiolite suite and make up of an ophiolitic mélange in the strongly deformed gneiss. The podiform chromite associated with these structural lenses is only reported in ophiolites. Therefore, it is a convincing evidence for the existence of a Neoarchaean ophiolite in China. The Zunhua Neoarchaean ophiolitic mélange proves the operation of plate tectonics in North China 2500Ma ago.
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