Application of BEMD in Extracting Gravity Anomaly Components Showing Deep Ore-Forming Dynamic Background of Jiaodong Gold Cluster Region

The Jiaodong gold cluster region (JGCR) at the southeastern edge of the North China Craton (NCC), holding approximately 5000 t gold reserve, is the third largest gold cluster region in the world. The Bidimensional Empirical Mode Decomposition (BEMD) is applied in extracting gravity anomaly components showing deep geological architectures and geodynamics. The research results illustrate that (a) at a depth of about 27 km, there are three tectonic units, namely the mantle uplift (I) with gravity values ranging from 2 to 14 μm/s2, a mantle depression (II) with gravity values varying from 0 to −13 μm/s2, and a mantle flat (III) with gravity values ranging from −2 to 2 μm/s2. All giant gold deposits are distributed within the mantle depression. This implies that mantle uplift can trigger the concentration of hot, ore-forming fluids in mantle depressions, leading to the accumulation of large amounts of gold and the formation of giant deposits. (b) At about 17.1–12.5 km, there are three tectonic units: the Jiaolai–Jiaobei mantle uplift (I), showing a strong positive gravity anomaly with gravity values ranging from 1.5 to 10 μm/s2, the Sulu ultra-high pressure metamorphic block (II), displaying a negative gravity anomaly with gravity values ranging from −10 to −1.5 μm/s2, and the Jiaoxibei gold cluster region (III), exhibiting gravity background with gravity values varying from −1.5 to 1.5 μm/s2. (c) At about 8.9–5.3 km, there are a series of positive and negative gravity anomalies. Most granites with low density display negative gravity anomalies, among which there are some negative anomalies with positive anomalous edges which contain gold deposits. This illustrates an ore-forming pattern, a granite with negative gravity anomaly, around which there is alteration mineralization with positive gravity anomaly. Combined with other studies, it was concluded that the geological architectures at different depths as and the giant Jiaodong gold cluster region were formed by the asthenosphere upwelling triggered by NNW-ward subduction of the Izanagi Plate over a time period of approximately 200–100 Ma.