秦岭商丹断裂带的构造变形与形成环境分析

An analysis of tectonic deformation and forming environment of Shang-Dan fault zone,Qinling

秦岭商丹断裂带是华北板块与扬子板块的构造缝合带,具有复杂的构成和长期的演化历史。文章选取了商丹断裂带的2条横剖面,综合运用宏观构造分析、显微构造分析、岩石有限应变测量、断层岩的变形温度估测及EBSD石英光轴组构测量分析等方法对商丹断裂带进行了精细的研究。研究结果表明:商丹断裂带两侧岩片相对倾斜,呈正花状;东段线理保留得比西段好,南北两盘线理差异明显,南盘以倾向线理为主,北盘以水平线理为主;商丹断裂带岩石均受到压扁作用,东段岩石比西段岩石所受的压扁作用更强;商丹带断层岩变形温度多集中于(500±30)℃范围内,东段温度比西段高,北盘温度比南盘高,由断裂带向两侧温度逐渐下降。EBSD组构分析结果表明,剪切带中石英主要以中低温菱面〈a〉组构和低温底面〈a〉组构为特征。

Shang-Dan fault zone, Qinling is the tectonic suture zone between the north China plate and the south China plate, and it has a complicated composition and a long-term evolution history. In this paper, two cross sections of Shang-Dan fault zone are selected, and the methods of macroscopic struc- ture analysis, microstructure analysis, rock finite strain measurement, temperature estimating of de- formed rocks and electron backscatter diffraction（EBSD） measurement of LPOs of quartzs are used to finely research Shang-Dan fault zone. The results are as follows： the foliatons on both sides of the Shang-Dan fault zone dip towards each other and show appositive flower structure; the lineations are retained better in the east part than that in the west, and the lineations in the south are obviously dif- ferent from that in the north, the lineations in the south fault zone are mainly dip lineations while in the north they are mainly horizontal lineations; rocks in Shang-Dan fault zone are deformed obviously by flattening deformation, and the deformation in the east is stronger than that in the west; the tem- perature of fault rocks in Shang-Dan fault zone is mainly about （500＋_30） ~C, the temperature in the east is higher than that in the west, the temperature in the north is higher than that in the south, and the temperature decreases beyond the center of the fault zone on both sides. The EBSD fabric analysis shows that the quart grains in rocks of the fault zone are characterized by the medium-low-temperature rhombohedral face （aS fabric ~nct lnw-t^rnnor^t,~ro h=~l f~.. ,＂~ f=h^io