Abstract

The existing and recently acquired data on the isotope ages and compositions of volcanogenic Au–Ag deposits and occurrences of the Evensk group (Okhotsk–Chukotka volcanogenic belt, Northeast Russia) are summarized. The K–Ar isotope and Rb–Sr isochron ages of Au–Ag ores from the studied deposits and occurrences are 82.7 ± 3–77.5 ± 3 Ma and 84.1 ± 2–79.7 ± 5 Ma, respectively. Au–Ag mineralization was formed within ~5 Ma. Au–Ag mineralization typical of productive ore stages and practically unaffected by later thermal processes is characterized by low initial ⁸⁷Sr/⁸⁶Sr₍₀₎ = 0.7055–0.7059 ratios, which are close to the initial ⁸⁷Sr/⁸⁶Sr₍₀₎ ratios in wall-rock metasomatites (0.7033–0.7082) and unaltered host rocks (0.7045–0.7048), thus indicating a pronounced predominance of mantle Sr in the ores. The composition points of ore Pb on the ²⁰⁷Pb/²⁰⁴Pb–²⁰⁶Pb/²⁰⁴Pb evolution diagram are grouped in close proximity to the Pb isotope composition points in the depleted mantle with a trend towards the subduction-related volcanic rocks typical of the continental margin. A close genetic relationship between the ore and magmatic processes has been confirmed. It is assumed that this relationship is due to the functioning of a single mantle basaltic chamber, which served as a source of metal-bearing fluids and is probably the primary source of Au and Ag.

中文翻译：

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鄂温斯克群（俄罗斯东北部鄂霍次克-楚科奇火山带）金银矿床的年龄和同位素组成以及赋存情况

摘要

总结了有关火山金银矿床的同位素年龄和成分以及埃文斯克群（俄罗斯东北部鄂霍茨克-楚科奇火山带）矿点的现有和最近获得的数据。所研究的矿床和矿点的金银矿石的 K-Ar 同位素和 Rb-Sr 等时线年龄分别为 82.7 ± 3–77.5 ± 3 Ma 和 84.1 ± 2–79.7 ± 5 Ma。Au-Ag 矿化在约 5 Ma 内形成。Au-Ag 矿化是典型的生产矿石阶段，实际上不受后期热过程的影响，其特点是初始⁸⁷ Sr/ ⁸⁶ Sr ₍₀₎ = 0.7055–0.7059 比率较低，接近于初始⁸⁷ Sr/ ⁸⁶ Sr ₍₀₎比率围岩交代岩（0.7033-0.7082）和未蚀变的母岩（0.7045-0.7048）中，这表明矿石中地幔 Sr 占主导地位。²⁰⁷ Pb/ ²⁰⁴ Pb– ²⁰⁶ Pb/ ²⁰⁴ Pb 演化图上的矿石Pb 组成点与贫乏地幔中的 Pb 同位素组成点非常接近，并有向大陆典型的俯冲相关火山岩的趋势利润。矿石和岩浆过程之间密切的成因关系已被证实。据推测，这种关系是由于单个地幔玄武岩室的功能所致，该玄武岩室是含金属流体的来源，并且可能是金和银的主要来源。