Decoding the driving mechanisms of high-grade gold enrichment in the Jiaodong Peninsula: Insights from episodic releases of gold-rich fluids in the Jinqingding deposit

• Mineralization spanned ∼ 128 Ma to ∼ 109 Ma, suggesting multiple fluid pulses at Jinqingding. • As-fluids (Py-II) are crustal-derived, while Te-Ag-Bi melts (Py-III) carry mantle signatures. • Py-III hosts visible gold in pores and fractures, showing strong Au-Te-Ag-Bi correlations • Visible gold precipitated from exsolved Te-Ag-Bi-rich melts, causing high-grade enrichment. The Jinqingding gold deposit, situated within the Muping-Rushan belt of the eastern Jiaodong Peninsula, was considered the largest single quartz-vein gold deposit in China. It exhibits an average gold grade of 10 g/t, locally exceeding 1000 g/t, which is higher than most gold deposits in the region. The mechanism of such high-grade gold enrichment remains unclear. To address this, we conducted in-situ sericite Rb-Sr dating coupled with pyrite geochemical and sulfur isotopic analyses. Our new Rb-Sr age of ca. 109 Ma, integrated with published data, reveals that mineralization initiated as early as ca. 128 Ma and potentially persisted until ca. 109 Ma. Pyrite is categorized into three types. Pyrite-I (Py-I) is poor in gold and formed contemporaneously with potassic alteration. Pyrite-II (Py-II), linked to sericitic alteration, hosts invisible gold and has Au-As-poor cores (Py-IIa) and As-rich rims (Py-IIb). The As-rich fluids exerted a limited contribution to Au mineralization. Pyrite-III (Py-III) containing visible gold is accompanied by significant sericitic alteration. Its core (Py-IIIa) contains pores and fractures filled with native gold and shows strong Au-Te-Ag-Bi correlations, indicating localized high-grade precipitation from exsolved Te-Ag-Bi-rich melts. Pyrite δ 34 S values (+7.3 ‰ to + 11.1 ‰) align with other Jiaodong gold deposits. Whereas As-rich fluids in Py-II incorporated predominantly crustal-derived components, Te-Ag-Bi-rich melts in Py-III carried mantle-derived signatures. Sulfur isotopic trends imply multiple hydrothermal events or episodic fluid pulses. We conclude that Te-Ag-Bi-rich melts were the primary agents for visible gold transport and deposition, driving high-grade enrichment at Jinqingding.