【摘要】 位于东秦岭造山带商南—丹凤断裂带两侧的秦岭群与陡岭群之间的相关关系历来存在较大争议。它们是否属于同一块体,或者什么时候属于同一块体,又在什么时候裂解分开,不同学者从不同的角度给出了不同的认识。依据东秦岭地区1∶5万航空放射性资料和航空磁测资料分析认为:秦岭群以较平静的负磁场背景为主,对应航放总道及钍道为偏高场;而陡岭群则以磁异常幅值较大的正磁场为特征,对应航放总道及钍道为偏低场。综合东秦岭地区地震测深速度与视电阻率剖面分析结果研究认为,秦岭群的原岩组成以碳酸岩、泥质岩为主,形成于稳定大陆边缘的构造环境;而陡岭群的原岩组成以基性岩为主,形成于活动大陆边缘的构造环境。不少学者认为太古宙时期华北板块与扬子板块为一个统一陆块,秦岭群与陡岭群形成于2 000 Ma以前,但并没有给出太古宙统一板块的具体分裂时间。本研究推断至少在早元古代华北板块与扬子板块已经发生分离,并且它们之间可能已有大洋产生。更多还原

【Abstract】 Correlation between the Qinling and Douling Groups on the two sides of the Shangnan-Danfeng fault zone in the eastern Qinling Orogen has always been controversial. In this paper,we study the relationship between the Qinling and Douling Groups on both sides of the Shangdan fault,based on the 1∶ 50 k aeroradioactivity and aeromagnetic data in the eastern Qinling Orogen. The Qinling Group is dominated by a more subdue negative magnetic field background,while the Douling Group is characterized by a stronger positive magnetic background. The stratigraphic range of the Qinling Group corresponds to the higher field in the general channel and thorium channel,while that of the Douling Group corresponds to the lower field in the main channel and thorium channel. Based on the reinterpretation of the seismic velocity and apparent resistivity profile in the eastern Qinling region,it is found that there are significant differences between them. Based on the aerogeophysical data and previous studies in the region,it is concluded that the primary rock types of the Qinling Group are carbonate and argillaceous rocks deposited in a stable continental margin,while those of Douling Group are mafic rocksformed in an active continental margin. Many previous workers considered that the North China and Yangtze plates were amalgamated in the Archean,and that the Qinling and Douling Groups were formed before 2000 Ma,yet the timing of the breakup for this amalgamated block was unknown. In this paper,it is inferred that the North China and Yangtze plates were separated at least from the early Proterozoic,and that an ocean may have opened between them.更多还原