Application of the polynomial trend surface analysis in the exploration of orebodies in depth within the Wengfu phosphorus orefield: A case study of the Orelayer B in the Gaoping deposit

The polynomial trend analysis of collected data for measured thicknesses of the B ore-layers in cores of 297 boreholes in the Dazhai, Mofang and Xiaoba oreblocks of the Gaoping deposit shows that the spatial variations of the B ore-layer thicknesses in the Dazhai, Mofang and Xiaoba oreblocks can be characterized by using the two-order polynomial characterization, with the fitting degrees of 57%, 32% and 28%, respectively. The spatial variations of the B ore-layer thicknesses in cores of 385 drilling holes in the Gaoping deposit (including 88 holes in the Yingping oreblock) can be characterized by using the three-order polynomial characterization, with the fitting degree of 43%. The fitting degree is approximate inversely proportional to the complexity of the fault, the undulation degree of the footwall interface, and the thickness coefficient of the orebody, that is, when the exploration type is changed from simple (Type I) to complex (Type II and Type III), the fitting degree is correspondingly decreased. The negative value for the thickness of the B ore-layer represents the ancient seabed topographic characteristics of the Gaoping deposit. The C-shaped sea current channel, constrained by the NE-trending seafloor highland in the the Mofang oreblock and the seafloor highland in the northeast side of the Xiaoba oreblock, is an important mineralization area, with the Yingping depression in its southeast side and the Xinqiao depression in its northeast side. Combined with the existing exploration results, by using anomalies of the positive residual values at different spatial scales, it is predicted that the blank areas in the east side of the Yingping oreblock and the northeast side of the Mofang oreblock have potential to explore large and thick B ore-layers.