安徽省休宁—歙县整装勘查区晚侏罗世逆冲推覆构造特征及其与成矿作用关系

通过野外地质调查结合大地电磁测深综合构造解释，在休宁—歙县金多金属矿整装勘查区及邻区厘定出发育于晚侏罗世的较大规模逆冲推覆构造，其由逆冲断层、逆冲岩席、原地岩系、构造窗及伴生的牵引褶皱等组成。该逆冲推覆构造发育于"屯溪—休宁"红层盆地南缘，表现为晚元古代浅变质火山-碎屑岩系逆冲推覆于中侏罗统洪琴组碎屑岩之上。逆冲推覆构造由一系列分支逆断层组成，以前展式叠瓦状逆冲为特征，断层前缘陡立，向下变缓。逆冲推覆构造呈北东走向展布，勘查区内延伸可达40 km，推覆体面积大于600 km²。构造窗出露位置结合钻探、物探揭示，逆冲位移为2.0~8.0 km。根据逆冲断层时空配套以及岩浆活动与波及的沉积地层，判断晚侏罗世逆冲推覆构造活动时间为163.5~149.0 Ma。通过逆冲断层擦痕观察及古应力场分析，认为该期逆冲推覆构造形成于华南板块向北强烈挤压的区域动力学环境。逆冲推覆构造为成矿前构造，其与之后发生的伸展构造对岩浆的侵入及含矿热液的流通起着重要的作用，控制了整装勘查区内金、银、铅锌等中低温元素的分布与富集成矿。

Characteristics of Thrust-Nappe Structure and Its Relationship with Mineralization in Xiuning-Shexian Integrated Exploration Area,Anhui Province

Based on the field geological survey and the comprehensive tectonic interpretation of magnetotelluric sounding electromagnetic array profile, a large-scale thrust-nappe structure is developed in the Late Jurassic in the integrated gold polymetallic ore exploration area in Xiuning-Shexian and its adjacent area, which consists of thrust fault, thrust sheet, original rock series, structural window,and associated traction fold. The thrust-nappe structure is developed in the southern edge of "Tunxi-Xiuning" Mesozoic continental sedimentary basin, which shows that the Neoproterozoic shallow metamorphosed volcano clastic rock series is thrust napped on the clastic rock of Hongqin Formation in Middle Jurassic. The thrust-nappe structure is composed of a series of branch thrust faults, which are characterized by the pre-spreading imbricate thrust. The front edge of the fault is steep and becomes gentle downward. The thrust-nappe structure is distributed in the northeast direction extending up to 40 km in the area, and the nappe area is more than 600 km² in the integrated exploration area. According to the exposed position of the structural window and combined with drilling and geophysical exploration, the thrust displacement is 2.0-8.0 km. According to the time-space matching of thrust faults,the sedimentary strata,and magmatic activity, it is estimated that the formation time of the Late Jurassic thrust-nappe structure is 163.5-149.0 Ma. Based on the observation of the friction marks of the thrust faults and the analysis of the paleo-stress field, it is believed that the thrust-nappe structure was formed in the regional dynamic environment of the strong northward compression of the South China plate. The thrust-nappe structure is a pre metallogenic structure, its and the later extensional structures play an important role in the intrusion of magma and the circulation of ore-bearing hydrothermal fluid. The thrust-nappe structure controls the distribution and enrichment of gold, silver, lead-zinc, and other low-temperature elements in the integrated exploration area.