Stratiform to stratabound replacement of a mixed siliciclastic-carbonate host rock is a defining characteristic of many sediment-hosted base metal deposits. Mineralized rocks in clastic-dominated (CD-type) Zn-Pb ore deposits, which represent our highest value base metal resources, are generally thin (10¹ m), laterally extensive (10³ m), and stratiform to stratabound in fine-grained siltstone and mudstone facies. At the recently discovered Teena CD-type Zn-Pb deposit (Proterozoic Carpentaria province, Australia), the host rock was undergoing burial diagenesis when altered and mineralized by hydrothermal fluids that moved up to 2 km lateral to the fluid input conduit (growth fault) through intraformational intervals. In much of the deposit, carbonate dissolution was an important reaction permeability control, although significant amounts of mineralization also occur in carbonate-free siliciclastic beds. In this study, transmission electron microscopy (TEM) data has been generated on a drill core sample that preserves a sharp reaction front between mineralized and unmineralized domains of the fine-grained siliciclastic compositional end member (carbonate free). Petrographic and mineralogical data provide evidence that oxidized hydrothermal fluids moved through the protolith via reaction permeability that developed from feldspar dissolution. The nature of reactive fluid flow was determined by reactions that took place at the fluid-mineral interface. Pyrite formation during the earliest stage of the hydrothermal paragenesis increased the mineral reactive surface area in the protolith. Acidity was then generated in situ via self-sustaining reactions involving pyrite oxidation, transient Fe sulfate formation, and sphalerite precipitation, which provided positive feedbacks to enhance porosity creation and further fluid infiltration and mineralization. In the absence of carbonate, however, ore fluid pH was buffered by K-feldspar dissolution (~4.5), thereby ensuring sphalerite precipitation was not inhibited under more acidic conditions. All CD-type deposits in the Carpentaria province are hosted by a protolith comprising carbonate, K-feldspar, pyrite, and organic matter; these phases set the boundary conditions for the development of self-sustaining reactions during ore formation. Importantly, these self-sustaining reactions represent a Goldilocks zone for ore formation that is applicable to other sediment-hosted deposits that formed via replacement of mixed siliciclastic-carbonate host rocks (e.g., stratiform Cu).

中文翻译：

---

在碎屑为主（CD 型）锌矿床中通过自持反应进行层状围岩置换

混合硅质碎屑-碳酸盐岩主岩的层状至层界置换是许多沉积物基底金属矿床的决定性特征。碎屑为主（CD 型）Zn-Pb 矿床中的矿化岩石代表了我们最高价值的贱金属资源，通常较薄 (10 ¹ m)，横向广泛 (10 ³m)，在细粒粉砂岩和泥岩相中呈层状至层状。在最近发现的 Teena CD 型 Zn-Pb 矿床（澳大利亚元古代卡奔塔利亚省），主岩在被热液改变和矿化时正在经历埋藏成岩作用，热液移动到流体输入管道横向 2 公里（生长断层）通过信息间隔。在大部分矿床中，碳酸盐溶解是一种重要的反应渗透性控制，尽管在不含碳酸盐的硅质碎屑岩层中也发生了大量矿化。在这项研究中，透射电子显微镜 (TEM) 数据已在钻芯样本上生成，该样本保留了细粒硅质碎屑成分末端成员（不含碳酸盐）的矿化和未矿化区域之间的尖锐反应前沿。岩相学和矿物学数据提供的证据表明，氧化热液通过长石溶解形成的反应渗透性穿过原岩。反应流体流动的性质由发生在流体-矿物界面的反应决定。热液共生早期黄铁矿的形成增加了原岩中的矿物反应表面积。然后通过涉及黄铁矿氧化、瞬时硫酸铁形成和闪锌矿沉淀的自我维持反应就地产生酸度，这提供了正反馈以增强孔隙度的产生和进一步的流体渗透和矿化。然而，在没有碳酸盐的情况下，矿液 pH 值受到钾长石溶解的缓冲 (~4.5)，从而确保在更酸性的条件下不会抑制闪锌矿沉淀。Carpentaria 省的所有 CD 型矿床均由由碳酸盐、钾长石、黄铁矿和有机质组成的原岩承载；这些阶段为矿石形成过程中自持反应的发展设定了边界条件。重要的是，这些自持反应代表了矿石形成的宜居区，适用于通过替换混合硅质碎屑-碳酸盐岩（例如，层状铜）形成的其他沉积物型矿床。