The geological circle has been studying the South China Ocean for 40 years. Based on the existing studies, the geological features of the middle Neogene South China Ocean and related geological structures and mineralization issues have been further understood through the topics of Regional Geology of China: Jiangxi, Mineral Geology of China: Jiangxi, and Evolution and Mineralization in South China Ocean–Marginal Pacific. The Pingxiang–Shexian–Suzhou junction zone connects the Jinsha River–Red River junction zone to the north of Henei, which is the subduction zone of the South China Ocean in the middle Neogene. It formed the boundary between the Yangtse plate and the newly-defined China-Southeast Asia plate (referred to as the Jinsha River–Red River–Shexian–Suzhou junction zone), which is now a latitudinal tectonic belt bending southward. The South China Ocean is a Meso-Neoproterozoic ocean between the Yangzi Paleo-plate and the Cathaysia-Southeast Asia Paleo-plate, closed at about 820± Ma. The Jinning movement took place during the collision of the plates, resulting in a consolidation of the Yangtze Block and the Cathaysia-Southeast Asia Block, where they united into one. The region has been an essential part of the Eurasian plate since the Indo-Chinese period, and the South China Rift System had been formed from 815± Ma in the late Neogene to the early Paleozoic. The Tethys and Paleo-Pacific tectonic domains have formed the geological tectonic framework of southern China and plateaus, continents, seas, and island arcs of the neighboring areas since the late Paleozoic. The subduction zone of the South China Ocean has evolved into the “Jinsha River–Hong River–Qinzhou Bay–-Hangzhou Bay” mega metallogenic belt of tungsten-tin-copper-gold polymetallic precious and rare metals, featuring two major magmatic mineralization series of S and I types.

Formation strain can directly affect the generation of structural fractures. According to the magnitude of structural strain, the location and intensity of structural fracture development can be predicted, and the chief fracture development areas in the study area can be divided. This paper takes the fourth member of the Yingcheng formation (referred to as the YING-4 section) in the Xuzhong area of the Xujiaweizi rift in the Songliao basin as the research object. Based on establishing a detailed 3D structural model of the study area, we used the “structural restoration” method to restore the paleo-structure of the study area and calculated finite strain values to predict the planar distribution of structural fractures. The research shows that the YING-4 section in the study area mainly includes three fracture-making periods, namely the end of the Yingcheng formation, the Quantou–to–Qingshankou formation, and the Nenjiang formation. Among them, the tectonic deformation at the end of the Yingcheng formation and the Quantou–to–Qingshankou formation is relatively strong, which is the main formation period of the fracture. The study area is divided into three types of fracture development zones according to the relationship between strain size and test gas production. Type I fracture development zone has been verified by well-drilling, indicating that the prediction results of fractures using structural strain are reliable. Type Ⅱ fracture development zone can be used as an important direction for the next step of deep natural gas exploration. Type Ⅲ fracture development zone has low productivity, and the fractures have limited effect on reservoir reconstruction.

Investigation of spatial susceptibility of debris flow is a basis for carrying out geological hazard prevention and developing ecological restoration plans. It is difficult to efficiently and accurately identify potential debris flow gullies on a large spatial scale simply by relying on field surveys combined with remote sensing observations or debris flow simulations with small watersheds as units. Taking the Jinsha River Basin of China as an example, we propose a quantitative scheme to describe the intensity of extrinsic forces by calculating the stream power gradient (ω). We extracted gullies prone to debris flow, assuming that there is no spatial heterogeneity in the provenance supply conditions based on the fundamental understanding that debris flow is a high-energy gravity flow. In the situation where the threshold (ω=1×10⁻⁴ W/m²) is the mutational site of the gradient change trend of the relation curve between the number of debris flow gullies and ω value, a total of about 32 thousand debris flow gullies with lengths of more than 200 m were found. In the middle and lower reaches of the basin, these gullies are located within a 30-kilometer buffer zone along the Jinsha and Yalong Rivers, and there is a power function relationship between the number of debris flow gullies and the width of a buffer zone. However, extreme weather events are likely to increase in the future under global warming, and these areas should be the critical prevention areas of debris flow disasters, especially the cascade reservoir area. The results of this study provide a lattice data set of spatial locations of the gullies prone to debris flow and the stream power gradients in the Jinsha River basin, which can be used to retrieve the exact location of the high-energy gullies and can also be used as the basic data for the study of related geological hazards and surface processes in general.

The lower Cambrian Maidiping formation in the Mabian area of southern Sichuan is a crucial ore-bearing horizon for Kunyang-style phosphate ores. The sedimentary paleoenvironment controls the distribution of phosphate ore. Based on the field section measurements and borehole core observations of the phosphorus-bearing strata of the Maidiping formation in the Huangjiaping area of Mabian, the characteristics of the sedimentary phases, phosphate massifs, and the mode of phosphate ore genesis of the Maidiping formation were studied in detail. The study shows that the Maidiping formation has developed carbonate tidal flat sedimentary facies, and six micro-phases can be identified in three subphases: supratidal flat, strand flat, and subtidal flat. The supratidal flat includes supratidal beach and supratidal dolomite flat; the strand flat includes tidal channel, intertidal beach, and intertidal limestone flat; the subtidal flat is only developed with the low-energy subtidal flat, showing a sedimentary evolution sequence of sea recession and sea erosion in the vertical direction. Based on the finding, we established the bay–tidal flat depositional model in the Maidiping formation. The sedimentary facies strictly controls the enrichment of phosphorite, and the intertidal beach and tidal channel with high energy hydrodynamics in the strand flat is the most favorable environment for phosphorite formation. The sand–gravel phosphorite is the most widely developed phosphorite type in the Mabian area. The mineralization mode of phosphate deposits is that the rising ocean current brings phosphorus-rich seawater into the tidal flat environment of the bay, and the phosphorus condenses and accumulates in the form of colloid-chemical, by biological and chemical interactions, forming semi-solidified and weakly-solidified phosphate sediments, which are then subjected to water scouring, crushing, transporting, and precipitation again, and then formed into high-grade phosphate masses after compaction and consolidation.

This study uses the method of Audio-frequency magnetotelluric sounding (EH4) to detect and analyze the deep geological structure in the Donglifang mining area. The underground spatial electricity and structural characteristics were effectively determined. We built an EH4-based indicator system for localizing ore bodies and summarized the relationship between the apparent resistivity anomalies and the ore bodies in the EH4 profile. The shallow veined or columnar low-resistance bodies may correspond to the low–medium temperature hydrothermal gold, lead, and zinc polymetallic ore bodies; the columnar medium-resistance or medium–low resistance bodies correspond to the silica or porphyry copper–molybdenum polymetallic ore bodies; the medium-resistance bodies correspond to the medium acidic magmatic rocks (porphyrites and porphyries). We identified eleven concealed ore bodies in the deep of the mine area, five of which are consistent with the drill holes, and the remaining six have an excellent prospect of finding ore bodies. It is further inferred that larger-scale porphyry copper–molybdenum ore bodies are formed in the deep rock body. This study proves that the EH4 is an effective geophysical method for finding concealed rock (ore) bodies in the Dongxuofang copper-molybdenum polymetallic mine or this type of deposit.