Chlorite Exploration Indicators and Their Indicative Significance in the Cimabanshuo Porphyry Copper Deposit, Tibet

With the deepening of deep mineral exploration, traditional methods face bottlenecks in identifying concealed orebodies, making the establishment of a mineralogical exploration indicator system for collision-type porphyry deposits imperative. This study investigates chlorite from the Cimabanshuo Porphyry Copper Deposit in the Zhunuo Ore Concentration Area of the Western Gangdese via systematic petrographic and in situ geochemical analyses, to elucidate the spatial evolution of its trace element compositions and assess the validity and applicability of different trace elements for hydrothermal center indication. Based on micropetrographic observations, chlorite is classified into three types: biotite-altered (Chl-1), amphibole-altered (Chl-2) and vein-type (Chl-3), with Chl-1 and Chl-2 significantly affected by primary mineral compositions. Trace element results show that spatial variations in Ti, Li, Ni, Co, Mn, and Sr contents and Li/Mn and Ti/Sr ratios in chlorite can clearly indicate the mineralization center—Ti, Li, Ni and Co are systematically enriched in the proximal ore zone by temperature and fluid compositional effects, while Mn and Sr are enriched in the distal ore zone due to elemental redistribution during fluid migration. Fitting analysis of chlorite elemental ratios against the distance from sampling points to the mineralization center indicates the Li/Mn ratio decreases with increasing distance (R2 = 0.4665), consistent with elemental distribution and showing a certain correlation; in contrast, the Ti/Sr ratio has a fitting coefficient of determination of only 0.0581, which cannot serve as an effective analysis indicator for this study because the deposit’s plate collision metallogenic setting causes elemental migration to be disturbed by local geological factors. In addition, chlorite in the zones 0–500 m from the Cu I, Cu II, and Cu III orebodies and 1–1.5 km to the north is characterized by significant enrichment of Ti, Li, Ni, and Co, depletion of Mn and Sr and high Li/Mn ratios. Accordingly, a concealed hydrothermal center is inferred in the northern part of the Cimabanshuo Deposit beyond the proven orebodies. Comprehensive studies confirm that the spatial variation characteristics of trace elements in chlorite from the Cimabanshuo Porphyry Copper Deposit have high applicability for indicating hydrothermal mineralization centers.