Magmatic fertility of porphyry Ag-Pb-Zn deposits revealed by zircon and apatite chemistry: An example of the Lengshuikeng Ag-Pb-Zn deposit in South China

IF 3.4 2区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Journal of Geochemical Exploration Pub Date : 2025-03-20 DOI:10.1016/j.gexplo.2025.107757

Xinlu Hu , Yongpeng Ouyang , Runling Zeng , Jinwei Li , Libo Li , Yi Shang

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Abstract

Porphyry Ag-Pb-Zn deposits are globally rare, with limited understanding of their magma origins, compositions, and physical-chemical conditions. To address this, we conducted a comprehensive investigation of the chemical and SrNd isotopic composition of apatites, along with the UPb dating, trace element analysis, and LuHf isotopic analysis of zircons from the igneous rocks at the giant Lengshuikeng Ag-Pb-Zn deposit in South China. The igneous rocks at Lengshuikeng are primarily composed of granite porphyry, K-feldspar granite porphyry, and volcanic rocks of the Daguding and Ehuling Formations. LA-ICP-MS zircon UPb dating yielded ages 159.7 ± 2.0 Ma for the rhyolitic tuff of the Ehuling Formation, 159.0 ± 2.3 Ma for the granite porphyry, and 152.5 ± 1.9 Ma for the K-feldspar granite porphyry. Combined with previously published age data, we propose that the Ehuling Formation experienced at least two eruption stages: the first at ca. 160 Ma (S1), and the second at 147–138 Ma (S2). The K-feldspar granite porphyry intruded in two stages, dated at 152.5 Ma (S1) and 138–136.6 Ma (S2). The evolutionary sequence of igneous rocks is inferred as: Daguding Formation → Ehuling Formation (S1) → granite porphyry → K-feldspar granite porphyry (S1) → Ehuling Formation (S2) → K-feldspar granite porphyry (S2).

Zircons from these rocks show ε_Hf(t) values of −13 to −8.5. The (⁸⁷Sr/⁸⁶Sr)_i ratios and ε_Nd(t) values of apatite vary from 0.7075 to 0.7171 and from −12.7 to −4.5, respectively. Similar Sr-Nd-Hf isotopic compositions indicate a common source for these igneous rocks, all derived from partial melting of Paleo- to Mesoproterozoic continental crust. Comparable zircon Ce⁴⁺/Ce³⁺ and Ce/Ce^⁎ ratios and apatite Mn-Ce-Eu-Ga contents indicate similar oxidation states and water contents in the parental magmas. Compared to regional porphyry Cu deposits, the parental magma of the Lengshuikeng Ag-Pb-Zn deposit has lower oxygen fugacity and S concentration. Apatites from the ore-forming granite porphyry have significantly higher concentrations of Cu, Zn and Cl than those from other igneous rocks. Our study suggests that the metal and Cl⁻ contents within parental magma, rather than the oxidation state and water content, are key factors controlling porphyry Ag-Pb-Zn mineralization. Apatite Cu, Zn and Cl contents can serve as valuable indicators of magma fertility in porphyry Ag-Pb-Zn deposits.

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来源期刊

Journal of Geochemical Exploration 地学-地球化学与地球物理

CiteScore

7.40

自引率

7.70%

发文量

148

审稿时长

8.1 months

期刊介绍： Journal of Geochemical Exploration is mostly dedicated to publication of original studies in exploration and environmental geochemistry and related topics. Contributions considered of prevalent interest for the journal include researches based on the application of innovative methods to: define the genesis and the evolution of mineral deposits including transfer of elements in large-scale mineralized areas. analyze complex systems at the boundaries between bio-geochemistry, metal transport and mineral accumulation. evaluate effects of historical mining activities on the surface environment. trace pollutant sources and define their fate and transport models in the near-surface and surface environments involving solid, fluid and aerial matrices. assess and quantify natural and technogenic radioactivity in the environment. determine geochemical anomalies and set baseline reference values using compositional data analysis, multivariate statistics and geo-spatial analysis. assess the impacts of anthropogenic contamination on ecosystems and human health at local and regional scale to prioritize and classify risks through deterministic and stochastic approaches. Papers dedicated to the presentation of newly developed methods in analytical geochemistry to be applied in the field or in laboratory are also within the topics of interest for the journal.