据悉，黄铁矿是热液成矿系统中最常见的硫化物矿物。黄铁矿的普遍性和丰富性，再加上它在热液环境中记录和保存流体演化历史的能力，使其成为研究热液矿床成因的理想矿物，包括那些含有关键金属的矿床。然而，除了沸点外，很少有研究能够将黄铁矿化学变化与富矿型金矿化过程直接联系起来。
本文报道了不列颠哥伦比亚省Brucejack浅成低温热液金矿床中，黄铁矿的高分辨率二次离子质谱和电子探针分析结果。样品的δ34S和微量元素结果显示，Brucejack热液系统经历了流体化学的剧烈波动，这种波动先于并最终与超高品位成矿作用的发生相吻合。研究人员认为，这些波动，包括在含金的砷黄铁矿带出现异常负δ34S值(例如，-36.1‰)，随后，在非砷黄铁矿的同银金矿带，由强烈的断层阀诱发的阶段性沸腾(闪蒸)，和随后的热液系统被海水淹没引起的δ34S值急剧增加。
研究结果强调，海水的流入是形成富矿级银金矿化的必要步骤，通过添加阳离子絮凝剂和冷却，引发胶体金颗粒的聚集。此外，他们的研究证明了采用高分辨率的原位分析技术，来绘制热液系统中单个成矿事件的有效性。
附：英文原文
Title: Extreme shifts in pyrite sulfur isotope compositions reveal the path to bonanza gold
Author: McLeish, Duncan F., Williams-Jones, Anthony E., Clark, James R., Stern, Richard A.
Issue&Volume: 2024-5-13
Abstract: Pyrite is the most common sulfide mineral in hydrothermal ore-forming systems. The ubiquity and abundance of pyrite, combined with its ability to record and preserve a history of fluid evolution in crustal environments, make it an ideal mineral for studying the genesis of hydrothermal ore deposits, including those that host critical metals. However, with the exception of boiling, few studies have been able to directly link changes in pyrite chemistry to the processes responsible for bonanza-style gold mineralization. Here, we report the results of high-resolution secondary-ion mass spectrometry and electron microprobe analyses conducted on pyrite from the Brucejack epithermal gold deposit, British Columbia. Our δ34S and trace element results reveal that the Brucejack hydrothermal system experienced abrupt fluctuations in fluid chemistry, which preceded and ultimately coincided with the onset of ultra-high-grade mineralization. We argue that these fluctuations, which include the occurrence of extraordinarily negative δ34S values (e.g., 36.1‰) in zones of auriferous, arsenian pyrite, followed by sharp increases of δ34S values in syn-electrum zones of nonarsenian pyrite, were caused by vigorous, fault valve-induced episodic boiling (flashing) and subsequent inundation of the hydrothermal system by seawater. We conclude that the influx of seawater was the essential step to forming bonanza-grade electrum mineralization by triggering, through the addition of cationic flocculants and cooling, the aggregation of colloidal gold suspensions. Moreover, our study demonstrates the efficacy of employing high-resolution, in situ analytical techniques to map out individual ore-forming events in a hydrothermal system.
DOI: 10.1073/pnas.2402116121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2402116121