Three-dimensional modeling of alteration information with hyperspectral core imaging and application to uranium exploration in the Heyuanbei uranium deposit, Xiangshan, Jiangxi, China

Abstract

Hyperspectral technology is particularly good at identifying hydrothermally altered minerals and can offer support for three-dimensional (3-D) alteration modeling of hydrothermal deposit. We propose a 3-D alteration modeling method with hyperspectral core imaging to deepen hydrothermal alteration research for uranium exploration of the Heyuanbei uranium deposit in the western Xiangshan ore field, Jiangxi, South China. We use the following three steps: (1) identify and map the altered minerals of drill cores, (2) quantify all types of altered minerals using a pixel classification-based statistical algorithm, and (3) establish 3-D alteration model using a parallel section and a triangulated irregular network. Hyperspectral core imaging data from 14 drill cores from the Heyuanbei uranium deposit are used to establish a 3-D alteration model of the superimposed stratigraphy and structural information by this method. The modeling results indicate that large-scale illite and kaolinite–dickite alterations have developed in the Heyuanbei deposit. The illite alteration has the following obvious zoning characteristics: (1) the spatial correlation of short-wavelength illite and kaolinite–dickite, which developed in two volcanic formations, is high, and the alteration is stronger in the upper part of the drill cores than in the lower part of the drill cores; (2) the long-wavelength illite is mainly distributed in the lower volcanic formations. The zoning characteristics reveal that the hydrothermal fluid is acidic in the upper cores, whereas in the lower cores, alkaline fluid is present, and the fluid environment has the characteristics of a transition from early alkaline to late acidic conditions. Moreover, the short-wavelength illite is more closely related to fluorite-hydromica-type uranium mineralization than the long-wavelength illite, and the conversion action from long-wavelength illite to short-wavelength illite is favorable for uranium enrichment. Thus, short-wavelength illite, kaolinite, dickite, and fluorite can be used as prospective indicators for uranium exploration in the Heyuanbei mining area and nearby areas.