Structural Style Of Superimposed Fold And The Indication Of Low-temperature Metallogenic Elements In Nanpanjiang Basin

Nanpanjiang Basin is an important metallogenic area of carlin-type gold deposit which is a key part of a large low-temperature metallogenic system in South China. Based on summarization of carlin-type metallogenic deposits, we found the metallogenic location are generally in intersection of secondary faults and acrossbrachy anticline, domes and brittle fracture zone, and in Paleo-denudation plane. Thus, the study of superimposed structure is significant to understand the metallogenic system in the study area.Based on detailed field structural analysis, this study focuses on the structural style and mechanism of the superimposed structure. According to deformation features of Nanpanjiang Basin, we infer three deformations. The first deformation is characterized by the EW-trending fold and thrust faults. These structures are interpreted as a part of Indosinian orogeny which is a result of Indochina-South China blocks overprinting on the Caledonian tectonic traces previous; The second deformation is defined by NW-trending fold and thrust faults. The structures are mainly located on edge of the platform and strongly overprinted previous deformation. This deformation indicates a NE-SW shortening on the region. We interpret this deformation as a part of the early episode of Yanshanian tectonic event; The third deformation is characterized by NE-trending high-angle dextral strike-slip fault, which is the result of obstructing of Nanpanjaing fault and northward-thrusting of the Youjiang thrust belt. We interpret this deformation as a part of the is late episode of Yanshanian tectonic event.Geochemical study of strata in Nanpanjiang basin exhibits anomalous concentration of elements. The metallogenic elements, such as As、Au、Ag、Sb, in the low-temperature system are positive anomaly in the Cambrian- Triassic strata. The abnormity is not obvious in basal and Devonian strata. The metallogenic elements generally concentrated in the margin of the platform, multi-deformed area or fault belt. The host rocks of these anomalous concentrations of metallogenic element are generally clay rocks, sandstone and carbonates.