The East Eagle Ni-Cu-platinum group element deposit is a conduit-type deposit located in northern Michigan, in close spatial proximity to the currently producing Eagle deposit. Massive and semimassive (net-textured) sulfide mineralization at East Eagle occurs approximately 800 m lower in the stratigraphic sequence than that at Eagle and only ~200 m above the contact between Proterozoic and Archean rocks. Although sulfide mineralogy and textural types are similar at the two occurrences, there are important differences in their S isotope systematics. Massive sulfide mineralization at East Eagle is characterized by a relatively narrow range of δ³⁴S values from 1.5 to 3.2‰. Semimassive sulfides show a similar range from 2.1 to 3.8‰. In strong contrast to these values, those from disseminated sulfides that border the massive and semimassive mineralization define a much larger range from –4.3 to 22.8‰. The much more restricted range in δ³⁴S values recorded in the massive and semimassive sulfide mineralization compared to that of the disseminated mineralization is thought to reflect isotopic exchange reactions in the conduit involving accumulated sulfide and pulses of magma containing S of mantle origin. The ∆³³S values of all three major types of sulfide mineralization at East Eagle are near 0‰, with most values between –0.03 and 0.03‰. Unlike ∆³³S values from semimassive sulfide mineralization at Eagle, the ∆³³S values at East Eagle show no, or very limited, evidence for the involvement of S derived from Archean sedimentary rocks. The wide range in δ³⁴S values recorded in the disseminated mineralization provides strong evidence that S from Proterozoic sedimentary host rocks was involved in the mineralization; in some cases, as much as 85% of the S may have been of external origin. In addition to the wide range in δ³⁴S values, the disseminated mineralization is characterized by spatially heterogeneous δ³⁴S values. Meter-scale S isotope variations, as well as variations in Pt and Pd tenor, are consistent with multiple inputs of magma, each characterized by distinct S isotope ratios. Heterogeneity of several per mill at the centimeter scale indicates that the degree of supercooling exceeded the S diffusivity, preserving small-scale S isotope variability inherited from the sedimentary country-rock source. Elongate, branching plagioclase grains in many of the gabbroic rocks that host the disseminated sulfide mineralization are consistent with a rapid second stage of cooling.

中文翻译：

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密歇根州北部东伊格镍铜铂族元素矿床中的多种S同位素和S同位素异质性

东伊格尔镍铜铂族元素矿床是位于密歇根州北部的导管型矿床，在空间上紧邻目前生产的伊格尔矿床。东伊格尔的大规模和半大量（网状）硫化物矿化在地层序列中比伊格尔低约800 m，并且仅在元古代和太古代岩石之间的接触面上方约200 m处发生。尽管两次发生的硫化物矿物学和结构类型相似，但它们的S同位素系统却存在重要差异。在东鹰块状硫化物矿化的特征在于相对窄的范围δ的³⁴S值从1.5到3.2‰。半质量硫化物显示出相似的范围，从2.1到3.8‰。与这些值形成鲜明对比的是，与大规模和半大规模矿化接壤的弥散性硫化物得出的值范围介于–4.3至22.8‰之间。在δ的很大的限制范围³⁴相比，在浸染矿化的记录在大规模和semimassive硫化物矿化的价值观被认为是反映在涉及积累硫化物和含有地幔原点第岩浆的脉冲导管同位素交换反应。东鹰的所有三种主要硫化物矿化的∆ ³³ S值均接近0‰，大多数值在–0.03至0.03‰之间。不同于Δ ³³从在鹰semimassive硫化物矿化的价值观，所述Δ ³³在东鹰价值观显示没有或非常有限的，为S的参与的证据宙沉积岩的。宽范围中δ ^34个记录在浸染矿化的价值观提供强有力的证据表明期从元古代沉积主岩被卷入矿化; 在某些情况下，多达85％的S可能来自外部。除了广泛的δ ^34个的价值观，浸染矿化的特征在于通过在空间上异质δ ³⁴S值。米尺度的S同位素变化以及Pt和Pd历时变化与岩浆的多个输入一致，每个输入都有不同的S同位素比。每毫米几米的异质性表明过冷度超过了S的扩散率，保留了从沉积岩体来源继承的小规模S同位素变异性。在许多散布有硫化物矿化的辉长岩中，细长的分支斜长石晶粒与快速的第二阶段冷却相一致。