LUO Jun-feng1, ZHOU Guang-hong2 *, SU Zhi-liang1, WEN Rui-cheng3, CAI Jian-long3, OU Yi3, LUO Tai-yi4

(1. Institute of Geology and Mineral Exploration, Guizhou Bureau of Non-ferrous Metals and Nuclear Industry, Guiyang 550005, China;
2. School of Geography and Resources, Guizhou Education University, Guiyang 550018, China;
3. Wengfu (Group) Co., Ltd., Fuquan 550509, China;
4. The State Key Laboratory of Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China)

Abstract: Phosphorite is an important phosphate ore resource, and is mainly developed in the platform facies of continental margin. The thickness of phosphorite is stable and slowly changing in a certain spatial range. Therefore, the polynomial trend surface analysis method is very suitable to describe this spatial evolution characteristics. In this study, data of 88 items associated with the B ore layer, which were not obviously disturbed by faults or uplift denudation, were collected from exploration projects of the Yingping oreblock Gaoping Mining area, Wengfu Phosphate Mine. Taking the thickness of the B ore layer as a dependent variable and the geographical coordinates of the exploration projects as independent variables, a demonstration study on the 1-5 orders polynomial trend surface analysis method applied in the exploration of sedimentary phosphate deposit in depth has been carried out. The main following results and understandings are obtained. 1) Coordinate selection: Based om the spatial scale of exploration area, the coordinate simplification through the coordinate translation can highlight the spatial evolution characteristics of dependent variables; 2) Data transversion: The data transversion of dependent variable and the proportional scaling of independent variable have no effect on the degree of correlation between variables, but the range normalization and range standardization have weak effect on the correlation between variables; 3) Optimal trend surface discrimination and anomaly characteristics: Based on the contour map of B ore layer thickness, combined with the collaborative changes of goodness-of-fit and F-test value of the trend surface, the 3 order polynomial trend surface is determined to be the optimal trend surface (with the goodness-of-fit of 77.39% and F-test value (F) of 39.11 which is larger than F0.001(7, 87) (about 3.94)), and the positive anomalies of the B ore layer thickness are mainly concentrated in the eastern central part of the Yingping oreblock. 4) Palaeogeomorphic characteristics: The contour map of negative value of the optimal trend surface indicates that the Yingping oreblock of the Late Doushantuo period is a lagoon gradually deepening eastward from the Wengfu Island in the western margin, the Tanjiayuan underwater highland and Wanzi Peninsula in the north and south sides, respectively, and may be restricted by the Shangtang-Qingping barrier island in the far-east side; 5) Exploration prediction: Based on the previous research results of lithofacies palaeogeography and exploration projects, combined with characteristics of the optimal polynomial trend surface, it is comprehensively predicted that the east side of the Yingping oreblock has great potential to find thick and large B phosphorite ore layer. The results show that the polynomial trend surface analysis is reliable in the exploration of the deep part of phosphorite deposit and is of important application value.

Keywords: polynomial trend surface analysis; exploration in depth; phosphorite; Yingping oreblock; Wengfu phosphorite deposit

ACTA MINERALOGICA SINICA Vol. 43, No. 4, 2023, Page 533