江南造山带北缘鄣公山地区新元古代地层构造变形特征及其动力学机制
Structural deformation features and dynamic mechanism of Neoproterozoic strata in Zhanggongshan area, northern margin of the Jiangnan Orogen
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摘要: 提要：鄣公山地区位处皖赣交界地带，区内广泛分布一套浅变质的陆缘细碎屑岩为主含少量火山物质的复理石建造体，大量高精度同位素测年数据显示，该浅变质地层形成于820～840 Ma新元古代。经系统野外调查，在该地层中首次解析出5期褶皱变形，其中F1以原始层理（S0）为形变面形成的紧闭同斜、平卧等形态的露头尺度级片内无根褶皱；F2以早期构造面理(S1∥S0)为形变面的轴向近东西向开阔斜歪及同斜褶皱；F3属与大规模逆冲推覆构造相关的紧闭同斜或斜歪褶皱；F4为与燕山期花岗质岩浆热隆升有关的轴面北倾的透入性不对称紧闭下滑褶皱群；F5为分布于区域脆性平移走滑断裂带附近的倾竖褶皱，上述褶皱分别对应不同的构造变形旋回。本文重点阐述褶皱变形的几何学、叠加样式、变形序次、运动学特征，并对变形机制及大陆动力学等进行分析。Abstract: Abstract：Zhanggongshan area is located in the junction zone between Anhui Province and Jiangxi Province. The flysch formation, consisting mainly of continental margin epimetamorphic fine clastic rocks and subordinately of volcanic rocks, is widely distributed in the area. A mass of high precise isotopic dating shows that the epimetamorphic strata might have been formed in Neoproterozoic between 820 Ma and 840 Ma. On the basis of a systematic field investigation, 5 stages of fold deformation were recognized through the analysis of the strata. F1 is the outcrop scale rootless intrafolial fold shaped in tight congruous fold and recumbent fold with original bedding (S0) as he deformation face; F2 is nearly EW-trending open inclined fold and congruous fold with early structural foliation as the deformation face; F3 is the tight congruous fold or inclined fold related to large scale thrust nappe; F4 belongs to penetrative asymmetrical tight shear fold group related to heat uplift of Yanshanian granitic magmas; F5 is a plunging vertical fold distributed near the regional brittle shear strike-slip faults zone. These folds correspond to different tectonic cycles respectively. This paper emphatically describes the geometry, superposition pattern, deformation order and kinematic characteristics of fold deformation, and analyzes the deformation mechanism and geocontinental dynamics.
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