摘要:商南岩体紧邻商丹断裂带北侧出露，其构造变形强烈，记录了秦岭造山带及商丹断裂带的构造变形及演化信息。本文在野外调查的基础上，综合显微构造分析、变形温度的估算、差应力及变形速率的计算、运动学涡度测量、年代学测试及地球化学分析等手段，对商南岩体进行了综合研究。结果显示商南岩体形成时代为422.1±5.9 Ma，具有与埃达克岩相似的地球化学特征，后期经历左行韧性剪切。糜棱岩记录的韧性变形温度为450 ℃～530 ℃，差应力的范围为35.99～22.27 MPa，应变速率为1.03232×10-14 s-1～3.81394×10-14 s-1，运动学涡度值为0.71～0.77。综合前人研究成果，本文认为商南岩体为加里东期加厚下地壳重融的产物，后期伴随着商丹断裂带左行走滑运动一起变形。
关键词: 秦岭造山带/
商丹断裂带/
商南岩体/
构造变形/
锆石U-Pb定年
Abstract:The Shangnan pluton is located close to the northern side of the Shangdan fault belt, which has strongly deformed and recorded information of tectonic evolution of the Qinling orogenic belt and the Shangdan fault belt. On the basis of field investigation, a comprehensive study by means of microstructure analysis, estimation of deformation temperature, calculation of differential stress and the strain rate, kinematic vorticity measurement, geochronological analysis and geochemical analysis are conducted on the Shangnan pluton in this paper. Results show that the Shangnan pluton was formed at 422.1±5.9 Ma with similar geochemical??characteristics??to the adakite, and has experienced left-lateral ductile shearing in later period. The formation temperature, differential stress and strain rate of the mylonite are 450 ℃～530 ℃, 22.27～35.99 MPa and 1.03232×10-14 s-1～3.81394×10-14 s-1 respectively. Based on the previous research results, it is believed that the Shangnan pluton was formed by partial melting of a thickened lower crust which was deformed accompanying the left-lateral strike-slip activity of the Shangdan fault belt in the later period.
Key words:The Qinling orogenic belt/
Shangdan fault belt/
Shangnan pluton/
Structural deformation/
Zircon U-Pb dating
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