The thrust-decollement structure in western Guizhou and its control of Pb-Zn deposit

The western Guizhou area is located in the southwest margin of the upper Yangtze Block, which is influenced both by the Tethys tectonic process and the Pacific tectonic process. The most widely exposed sedimentary rocks in this area are mainly the Middle and Upper Devonian-Lower Triassic (D₂-T₁) carbonate. The Lower Devonian and Silurian shale and siltstones are overlaid to constitute the bottom detachment layer in this area. Shale, siltstones and carbonaceous shale in D₂-T₁ carbonate hard rock form the secondary detachment layer. In the Mesozoic, due to the remote recombination of the above two tectonic process, many tectonic activities and superimposed deformation occurred in western Guizhou. In the extrusion process, the decollements between the hard and the weak layer formed the complex tectonic pattern. The different scale thrust-decollement in different stage (interlayer decollement-multi detachment-small thrust-large thrust) has different effects for Pb and Zn enrichment. Pb and Zn enrichment was formed by interlayer decollement in accordance with bedding. Furtherly, multi detachment (small thrust) controls Pb-Zn enrichment slightly steeper than the strata. Small parallel displacement or tensile faults control the enrichment of steeply dipping lead-zinc deposits, whereas the large thrust faults control the enrichment of large and very large Pb-Zn deposits. Therefore, the thrust-decollement is the most important factor to control the enrichment of Pb-Zn deposit in western Guizhou.