The multifractal nature of the Ni geochemical field and implications for potential Ni mineral resources in the Huangshan–Jing'erquan area, Xinjiang, China

• Raw data are more suitable for calculating a multifractal spectrum in this area.
• α(q) is unrelated to q when | q | is sufficiently high.
• A value of | q | that is too low might result in an incomplete multifractal spectrum.
• Multifractal nature shows that further Ni deposits are expected to be discovered.

Multifractal theory is widely applied in assessing the distribution of the geochemical concentration field and potential metal mineral resources. We discuss the relationship between multifractal parameters and preprocessing of data on the Ni contents of 3064 regolith samples from the Sixth Party and Geophysical and Geochemical Party, Xinjiang Bureau of Geology and Mineral Exploration and Development and the role of the power exponent q in calculating a multifractal spectrum. We then analyze the multifractal properties of a Ni geochemical field and consider the implications of the multifractal properties for potential Ni-mineral resources in the Huangshan–Jing'erquan area of Xinjiang, China. The four main results are as follows. (1) Raw data covering the whole study area are more reliable than gridded data when calculating the multifractal spectrum of Ni, as gridded data have uncertainties caused by interpolation and the irregular variation of the multifractal parameters with increasing cell size. (2) If the value of | q | is too small, the multifractal spectrum calculated using the method of moments is incomplete. However, the use of an excessively large value of | q | is computationally wasteful. To depict correctly the multifractal spectrum, a reasonable range of q should be determined. This range can be obtained from the inflection point of the curve of α(q) ~ q or that of the curve of f[α(q)] ~ q, and it need not be symmetric around zero. We also discuss the probable cause of the appearance of a spike in the curve where element values approach the lower or upper limit. (3) Statistical histograms and Q–Q plots of Ni contents show that most element values follow a log-normal distribution, and a small number of high values are likely to follow a Pareto distribution; the function of τ(q) ~ q is nonlinear, and the multifractal parameter τ″(1) = − 0.0507 < 0. These results indicate that the spatial distribution of Ni in the study area is multifractal in nature. (4) The mean value (14 ppm) and maximum value (91.2 ppm) of Ni concentrations in the samples are greater than the average concentration (13 ppm) in the upper crust of the Chinese continent. The multifractal spectrum is left-deviated with Δα = 0.6942, R = 0.4935 > 0, and Δf = 2.1919 > 0, revealing a high potential for the existence of a Ni mineral resource in the study area. The geological conditions of the Huangshan–Jing'erquan area are favorable for magmatic Ni-sulfide deposits, and many Ni ore deposits have already been discovered in the region.