Abstract:

The Tanchang-Yawan area in Gansu Province constitutes an important antimony mineralization area of the western Qinling metallogenic belt. This study presents a comprehensive geochemical investigation of silver (Ag), arsenic (As), gold (Au), bismuth (Bi), copper (Cu), mercury (Hg), manganese (Mn), molybdenum (Mo), lead (Pb), antimony (Sb), tin (Sn), and zinc (Zn) in stream sediments, coupled with systematic antimony prospecting prediction. Results show distinctive geochemical characteristics of antimony compared to other metal elements. Fundamental geochemical parameters including element concentration Clark value, global concentration coefficient (Kk), stacking intensity (D), and coefficient of variation (Cv) of Sb demonstrate significantly higher than those of other metal elements, reflecting the high enrichment of Sb, strong post-genetic superimposition, and highly uneven distribution. It has the highest value of mineralization index （β） for Sb, revealing the best ore-forming prospect among metal elements. The Triassic strata is considered as the main ore source beds of Sb, evidenced by average Sb concentrations（3.45-10.29）×10-6 exceeding crustal background levels by 17-40 times , with the Triassic Zhalishan Formation (T1z) and Guojiashan Formation (T2gj) representing optimal ore source beds of Sb. The spatial distributions of various element anomalies are cotrlled by  regional faults, generally. The locations of Sb mineralization is highly consistent with the its enrichment center, revealing that anomaly of Sb can directely indicate the ore-forming of itself. There is a strong correlation between the mineralization of Sb and anomalies of As, Au, and Hg, so that Sb-As-Au-Hg act as a combined prospecting geochemical indicator for antimony prospecting. According to the distributions of anomaly of antimony and indicator established in this study, 10 antimony perspecting target areas were divided into Tanchang-Yawan area, and 6 antimony mineralization points were newly found.

Key words: Tanchang-Yawan area, stream sediment, antimony, geochemistry, perspecting indicator, ore prospecting prediction