Abstract

The timing and nature of metamorphism in the Kalgoorlie gold camp (Yilgarn Craton, Western Australia) are key aspects to genetic models for gold mineralisation. Despite this, existing constraints on metamorphism are equivocal as to whether the Fimiston and Oroya Au–Te lodes formed pre- or post-peak regional metamorphism. Evaluation of an actinolite (S₁)–chlorite (S₂) crenulation cleavage in the Hannan’s Lake Serpentinite on the western margin of the Golden Mile Super Pit supports a syn-D₁ timing for peak metamorphism and a post-peak metamorphic timing for the Fimiston and Oroya Au–Te lodes. These results support a key aspect of metamorphic models for gold mineralisation. If intrusion-related models are correct, they should not be premised on the argument that the Fimiston and Oroya Au–Te lodes are equivalent to other examples of metamorphosed, epithermal-type mineralisation in orogenic belts.

1. KEY POINTS

2. The definition of an S₁ cleavage in the Hannan’s Lake Serpentinite by actinolite supports a syn-D₁ timing (ca 2685–2680 Ma) for peak regional metamorphism (sub- to lower-greenschist facies) in the Kalgoorlie gold camp.

3. A syn-D₁ timing for peak regional metamorphism suggests that the D₂ (ca 2675–2665 Ma) Fimiston and Oroya Au–Te lodes and D₃ (ca 2650–2640 Ma) Mt Charlotte stockwork Au orebodies developed in post-peak metamorphic settings.

4. A post-peak metamorphic timing for the Fimiston and Oroya Au–Te lodes suggests that these mineralisation types do not represent metamorphosed equivalents of epithermal Au–Te mineralisation.

摘要

Kalgoorlie 金矿营地（Yilgarn Craton，西澳大利亚）变质作用的时间和性质是金矿化遗传模型的关键方面。尽管如此，关于 Fimiston 和 Oroya Au-Te 矿脉是形成峰前还是峰后区域变质作用，现有对变质作用的限制是模棱两可的。金域超级坑西缘汉南湖蛇纹岩中阳起石（S ₁）-绿泥石（S ₂）锯齿裂隙的评价支持了syn-D ₁Fimiston 和 Oroya Au-Te 矿脉的峰变质时间和峰后变质时间。这些结果支持金矿化变质模型的一个关键方面。如果与侵入相关的模型是正确的，它们不应该以 Fimiston 和 Oroya Au-Te 矿脉等同于造山带中变质、超热液型矿化的其他例子的论点为前提。

1. 关键点

2. 阳起石对汉南湖蛇纹石中S ₁解理的定义支持Kalgoorlie 金矿营地峰值区域变质作用（亚至低绿片岩相）的同步 D ₁时间（约2685-2680 Ma）。

3. 峰值区域变质作用的同步 D ₁时间表明 D ₂ ( ca 2675–2665 Ma) Fimiston 和 Oroya Au-Te矿脉和 D ₃ ( ca 2650–2640 Ma) Mt Charlotte stockwork Au 矿体在峰后变质作用中发育设置。

4. Fimiston 和 Oroya Au-Te 矿脉的峰后变质时间表明这些矿化类型并不代表超热液 Au-Te 矿化的变质等价物。