Quantitative assessment of mineral resources by combining geostatistics and fractal methods in the Tongshan porphyry Cu deposit (China)

•Hurst exponent estimation vertical mineralization continuity•C–V fractal method is useful for identifying different orebodies.•3D geological and trend models are combined to recognize exploration targets.•3D alteration belt modeling for identifying ore-forming porphyry shape and center

Three-dimensional (3D) geological, geostatistical, and fractal/multifractal modeling are combined for the identification of new exploration targets in the Tongshan porphyry Cu deposit (China): (1) A 3D geological model of the deposit includes the strata, faults, altered rocks, intrusive bodies, and three orebodies using geological map, cross-sections, borehole dataset, and magnetic inversion; (2) geostatistical analysis involves omnidirectional and vertical semi-variogram calculations of the orebody, ordinary kriging interpolation of the orebody and 3D trend modeling using the assay data; (3) fractal models consisting of Hurst exponent estimation of the continuity of vertical mineralization and its concentration–volume (C–V) fractal model separation mineralized zones in a 3D block model; and (4) interpretation and validation: magnetic inversion was utilized to constrain intrusive rock shape between cross-sections and additional interpret orebody geometry model by ordinary kriging interpolation method using Tongshan borehole dataset. The results indicate that (a) the Hurst exponent is useful for identifying the vertical continuity of mineralization (with the range between 0 and 1200 m), (b) the C–V fractal model is useful for identifying thresholds of Cu values in oxidation-type, skarn-type, and magmatic-type orebodies in the Tongshan deposit, and (c) the 3D geological and trend model can be combined to recognize potential subsurface targets in the Tongshan deposit. The methods can be applied to estimate mineral resources through district-scale exploration.