Trace and Rare Earth Element Chemistry of Quartz from the Tuztaşı Low-Sulfidation Epithermal Au-Ag Deposit, Western Türkiye: Implications for Gold Exploration from Quartz Mineral Chemistry

The Tuztaşı low-sulfidation epithermal Au–Ag deposit (Biga Peninsula, Türkiye) records a multi-stage hydrothermal history that can be decoded through the trace- and rare-earth-element (REE) chemistry of quartz. High-precision LA-ICP-MS analysis of five representative quartz samples (23 ablation spots; 10 analytically robust) reveal two fluid stages. Early fluids were cold, dilute meteoric waters (δ¹⁸O₍H₂O₎ ≈ –6.8 to +0.7 ‰), whereas later fluids circulated deeper, interacted with felsic basement rocks, and evolved chemically. Mineralized quartz displays marked enrichment in As (raw mean = 2 854 ± 6 821 ppm; filtered mean = 70 ± 93 ppm; one spot 16 775 ppm), K (498 ± 179 ppm), and Sb (57.8 ± 113 ppm), coupled with low Ti/Al (< 0.005) and elevated Ge/Si (0.14–0.65 µmol mol⁻¹). Chondrite-normalized REE patterns show pronounced but heterogeneous LREE enrichment ((La/Yb)ₙ ≤ 45.3; ΣLREE/ΣHREE up to 10.8) and strongly positive Eu anomalies (δEu ≤ 9.3) with slightly negative Ce anomalies (δCe ≈ 0.29); negligible Ce–Eu covariance (r² ≈ 0.05) indicates discrete redox pulses. These signatures pinpoint chemically evolved, reducing fluids conducive to Au–Ag deposition. By contrast, barren quartz is characterized by lower pathfinder-element contents, flatter REE profiles, higher Ti/Al, and subdued Eu anomalies. A composite exploration toolkit emerges: As > 700 ppm, As/Sb > 25, Ti/Al < 0.005, Ge/Si > 0.15 µmol mol⁻¹, and δEu ≫ 1 reliably demarcate ore-bearing zones when integrated with δ¹⁸O data, fluid-inclusion microthermometry, and structural mapping. The study provides one of the first systematic applications of integrated trace-element and REE analysis of quartz to a Turkish low-sulfidation epithermal system, offering a transferable template for vectoring mineralization in analogous settings worldwide