The Lengshuikeng porphyry type Ag-Pb-Zn-Cd deposit: Insights from magmatism-mineralization timing sequence, chemical composition and in-situ Pb isotope of sulfide

Abstract

The Lengshuikeng deposit is a significant Ag-Pb-Zn-Cd deposits in the Gan-Hang Tectonic Belt (GHTB). Understanding its genesis is crucial for revealing the relationship between the tectonic evolution and the mineralization in this region. However, the metallogenesis of the Lengshuikeng deposit has remained unclear. To address this issue, a systematic analysis of chronological data, mineralogy, lithology, chemistry of sphalerite, and in-situ Pb isotope of the sulfides from the Lengshuikeng deposit are conducted to explore the relationship between magmatism and mineralization, metal sources, and ore-forming feature. The magmatism consists of two major stages: the Late Jurassic (Daguding Formation and a large scale of granite porphyry) and the Early Cretaceous (E’huling Formation and minor acid dyke). The mineralization age is restricted near 155 Ma, which is in keeping with the granite porphyry (158.0 ± 1.0–154.3 ± 3.0 Ma). The sulfides in the major stage (Gn-Sp(−Aca)-Py) (²⁰⁸Pb/²⁰⁴Pb: 38.07–38.44, ²⁰⁷Pb/²⁰⁴Pb: 15.48–15.62, ²⁰⁶Pb/²⁰⁴Pb: 17.68–17.90, ²³⁸U/²⁰⁴Pb (μ): 9.32–9.58, ²³²U/²⁰⁴Pb (ω): 38.06–40.16) exhibit consistent Pb isotopes with most of the granite porphyry and minor crystal tuff, which indicates that the metals primarily came from the granite porphyry. The crystal temperature of sphalerite is focused on 300–350°C. In consideration of C, H, and O isotopes in previous works, the hydrothermal fluid was primarily derived from the granite porphyry at a high temperature stage. Combined with the trace elements of sphalerite (relatively high Cu, Fe, In, Cd, low Ge and Mn) and the genesis diagrams (based on In, Ga, Ge, Fe, Cd, and Mn), this deposit is classified as a porphyry type deposit. Geochemical data, Nd isotopes in previous works and in-situ Pb isotopes (△β-△γ; V₁-V₂) from this research suggest that the granite porphyry and crystal tuff mainly emplaced by partial melting of the Neoproterozoic basement in compressive setting at the GHTB, resulting from the subduction of the Pacific Plate to the South China Craton. A comprehensive metallogenic model is defined, involving the tectonic setting, the genesis of granite porphyry, ore-controlling factors, and the mineralization process.