A Geological-Geophysical Prospecting Model for Deep-Seated Gold Deposits in the Jiaodong Peninsula, China

The North China Craton is one of China’s major gold-producing areas. Breakthroughs have been continually made in deep prospecting at depths of 500–2000 m in the Jiaodong Peninsula, and geophysical methods have played an important role. Given that the geophysical signals of deep-seated gold deposits are difficult to detect, due to their thick overburden layers, conventional geophysical methods are not suitable for deep prospecting. Therefore, this study upgrades the geological-geophysical prospecting model, which is based on the deep metallogenic model and geophysical method of large exploration depths. Based on the analysis of the metallogenic geological factors of the altered-rock-type gold deposits in the fracture zones of the Jiaodong Peninsula, this study proposes that the gold deposits are controlled by large-scale faults, generally occur near the contact interfaces between the Early Precambrian metamorphic rock series and Mesozoic granitoids, and exhibit a stepped metallogenic model. This model then becomes the prerequisite and basic condition for deep prospecting by geophysical methods. For this reason, the traditional geophysical model, which focuses on the exploration of shallow mineralization anomalies, is transformed into a comprehensive multi-parameter geological-geophysical qualitative prospecting model highlighting the exploration of ore-controlling structural planes. The model adopts various frequency domain methods (e.g., CSAMT, AMT, WFEM), reflection seismology, and other methods to detect the deep geological structure. The characteristics of parameters such as gravity and magnetism, resistivity, polarizability, and the seismic reflection spectrum are applied to identify the ore-controlling fault location and dip angle change, and to estimate the ore-bearing location according to the stepped metallogenic model. The prospecting demonstration of deep-seated gold deposits in the Shuiwangzhuang mining area indicates the effectiveness of the comprehensive model. The comprehensive deep prospecting model effectively solves the problem of deep prospecting of gold deposits controlled by faults, promotes the great breakthrough of deep prospecting in the Jiaodong Peninsula, and provides an important technology demonstration for deep prospecting throughout China.

Modeling the Effects of the Factors Affecting IGF in Coastal Areas and Variation of IGF in Jiaodong Peninsula of China Based on Finite Element Method

Based on finite element method, we develop a model of the induced geoelectric field (IGF) occurring in land-sea boundary regions during large geomagnetic field disturbances. The model is used first to study the effects of the changes in the lithospheric conductivity, ionospheric current, and ocean depth on the distribution of IGF in a typical land-sea boundary region. The results show that the changes in the lithospheric conductivity and ionospheric current (frequency, magnitude and direction) have major effects and ocean depth has minor effect on IGF in coastal areas. Then by incorporating a realistic 3-D conductivity variation of Jiaodong Peninsula (JDP) in China obtained from measured data, the model is used to simulate the IGF variation in JDP covering its land-sea boundaries for east-west and north-south ionospheric currents. The results show a new aspect that extremely large IGF development on the land side of the coastal bay areas perpendicular to the currnet compared to plane coastal areas. The results can stimulate detailed investigations of IGF (and GIC, geomagnetically induced current) in coastal areas.

The Construction of Ecological Security Patterns in Coastal Areas Based on Landscape Ecological Risk Assessment—A Case Study of Jiaodong Peninsula, China

Increasing land utilization, population aggregation and strong land–sea interaction make coastal areas an ecologically fragile environment. The construction of an ecological security pattern is important for maintaining the function of the coastal ecosystem. This paper takes Jiaodong Peninsula in China, a hilly coastal area, as an example for evaluating landscape ecological risk within a comprehensive framework of “nature–neighborhood–landscape”, based on spatial principal component analysis, and it constructs the ecological security pattern based on the minimum cumulative resistance model (MCR). The results showed that the overall level of ecological risk in the study area was medium. The connectivity between the areas of low landscape ecological risk was relatively low, and the high risk areas were concentrated in the north of the Peninsula. A total of 11 key ecological corridors of three types (water, green space and road corridors) and 105 potential corridors were constructed. According to the ecological network pattern, landscape ecological optimization suggestions were proposed: key corridors in the north and south of Jiaodong Peninsula should be connected; urban development should consider current ecological sources and corridors to prevent landscape fragmentation; and the ecological roles of potential corridors should be strengthened. This paper can provide a theoretical and practical basis for ecological planning and urban master planning in coastal areas in the future.