Ductile slip zone between substrate and cap

The Qinling-Dabie Mountain Fold System, known as the "Kunlun-Qinling Fold System" in the region, is a crustal subtraction zone between the Tarim Plate, the North China Plate and the Yangtze Plate, as well as a combination zone between the North China and South China Plates. The internal composition and structure of the fold system are very complex, and according to the available data, it is a composite orogenic belt formed by the orogeny movements of Jinning, Caledonian, Hualixi, and Indochina. In this pipeline project section, it is called the "Qinling-Dabie Mountain Fold System", which lies across the Zhengyan Belt at the junction of Henan and Hubei Provinces, and is bounded by the Neixiang-Tongbai-** fault zone, and is divided into the North Qinling Fold Belt and the South Qinling Fold Belt, which belong to the North China Plate and the South China Plate.

The tectonic morphology of the second fold belt is very different, and the fold morphology in the North Qinling fold belt located in Henan Province is complex and faults are developed. The South Qinling Fold Belt, which is mainly located in Hubei, is a partition fold.

The North Qinling Mountains are a Caledonian orogenic belt, and the basement is composed of Upper Archean and Lower Proterozoic metamorphic rock series, which are covered by Middle and Upper Proterozoic deep-water volcanic-sedimentary rock systems. The Cambrian-Ordovician is still an active volcanic-sedimentary rock system, containing siliceous rocks of the Shochu Shooter, and several ophiolite belts are located in the above rock series. Along with the orogeny from the end of Caledonian to the early Hualixi, there are also a large number of granite invasions in this zone. The South Qinling Mountains belong to the fold belt of the Huali West and Indosinian periods.

The Neo-Archean-Mesoproterozoic form the basement of this belt, and recent studies have confirmed that there is a large ductile slip shear zone between the basement and the caprock, accompanied by a large number of Indosinian granite intrusions. Due to the continuous subduction and shrinkage of the ancient Qinling oceanic crust to the North China and South China plates, the two plates collided in the Neixiang-Tongbai-** area during the Devonian, and the ancient Qinling Ocean disappeared and merged into the Chinese plate. After the unification, the Qinling-Dabie Mountains were subducted, orogenic extrusion, and thrust overturning along the Neixiang-Tongbai-** line in the Jurassic-Cretaceous, and the geological bodies of different eras were closely superimposed together, forming a complex Qinling-Dabie Yashu tectonic belt.

At the same time, there was large-scale magmatic intrusion and volcanic activity, and mola-like and volcanic rock systems were developed in the intermountain or piedmont basins.

In the pipeline section, the North Qinling Fold Belt is a plain composed of Middle Pleistocene alluvial loose sediments in the geomorphology, and there is no bedrock outcropping. On the other hand, the landform of the South Qinling Fold Belt is mainly composed of bedrock, and continental basins were developed in the Cretaceous-Paleogene period. The crustal stability conditions in the pipeline section area are good, and the activity is weak. Geological disasters are not well developed, mainly including the collapse of bedrock and open-pit mining slopes, as well as the slight expansion and contraction of expansive rock and soil.