Application of Portable X-Ray Fluorescence Analysis in Mineral Exploration: A Case Study from Cimabanshuo Porphyry Copper Deposit

The Cimabanshuo deposit, situated in the western Gangdese Belt, is a recently discovered porphyry Cu deposit formed in a post-collisional setting, approximately 10 km from the giant Zhunuo porphyry Cu deposit. Despite its proximity to Zhunuo, Cimabanshuo remains poorly studied, and the current exploration depth of 600 m leaves the potential for deeper resources uncertain. In this study, 840 samples from four drill holes along the NW-SE section (A-A′) were analyzed using portable X-ray fluorescence (pXRF). Based on the geochemical characteristics of primary halos, the deep mineralization potential of Cimabanshuo was evaluated. The results show that Co, Pb, and Ag are near-ore indicator elements; Zn, Cs, Hg, Sb, As, and Ba represent the frontal elements; and Te, Sn, and Bi occur as tail elements. Based on these distributions, a 14-element zoning sequence is defined along the A-A′ profile according to Gregorian’s zoning index, showing Mo-Co-Cu-Pb-Bi-Ag-Sn-Te-Sb-Hg-Cs-Zn-Ba-As from shallow to deep. This sequence shows a distinct reverse zonation pattern, in which tail elements occur in the middle and frontal elements appear at depth, suggesting the existence of a concealed ore body in the lower part of the deposit. Horizontally, the geochemical ratios Ag/Mo and Ag/Cu decrease from northwest to southeast along the profile, implying hydrothermal flow from southeast to northwest. Vertically, the ratios As/Bi, (As × Cs)/(Bi × Te), (As × Ba)/(Bi × Sn), and (As × Ba × Cs)/(Bi × Sn × Te) display a downward-decreasing then upward-increasing trend, further indicating hidden mineralization at depth. This inference is supported by the predominance of propylitic alteration and the deep polarization anomaly revealed by audio-magnetotelluric imaging. pXRF analysis provides a fast, efficient, and environmentally friendly approach, showing strong potential for rapid geochemical evaluation in porphyry Cu exploration.