Aqueous complexation has long been considered the only viable means of transporting gold to depositional sites in hydrothermal ore-forming systems. A major weakness of this hypothesis is that it cannot readily explain the formation of ultrahigh-grade gold veins. This is a consequence of the relatively low gold concentrations typical of ore fluids (tens of parts per billion [ppb]) and the fact that these “bonanza” veins can contain weight-percent levels of gold in some epithermal and orogenic deposits. Here, we present direct evidence for a hypothesis that could explain these veins, namely, the transport of the gold as colloidal particles and their flocculation in nanoscale calcite veinlets. These gold-bearing nanoveinlets bear a remarkable resemblance to centimeter-scale ore veins in many hydrothermal gold deposits and give unique insight into the scale invariability of colloidal flocculation in forming hyperenriched gold deposits. Using this evidence, we propose a model for the development of bonanza gold veins in high-grade deposits. We argue that gold transport in these systems is largely mechanical and is the result of exceptionally high degrees of supersaturation that preclude precipitation of gold crystals and instead lead to the formation of colloidal particles, which flocculate and form much larger masses. These flocculated masses aggregate locally, where they are seismically pumped into fractures to locally form veins composed largely of gold. This model explains how bonanza veins may form from fluids containing ppb concentrations of gold and does not require prior encapsulation of colloidal gold particles in silica gel, as proposed by previous studies.

长期以来，水络合一直被认为是将金输送到热液成矿系统中沉积地点的唯一可行方式。这个假设的一个主要弱点是它不能轻易解释超高品位金矿脉的形成。这是由于矿液中典型的金浓度相对较低（十亿分之十 [ppb]）以及这些“富矿”矿脉在一些超热液和造山带矿床中可能含有重量百分比的金。在这里，我们提供了可以解释这些静脉的假设的直接证据，即金作为胶体颗粒的运输及其在纳米级方解石细脉中的絮凝。这些含金纳米脉与许多热液金矿床中的厘米级矿脉有着显着的相似之处，并为形成超富集金矿床时胶体絮凝的尺度不变性提供了独特的见解。使用这些证据，我们提出了一个在高品位矿床中开发富矿金矿脉的模型。我们认为，这些系统中的金传输主要是机械的，并且是异常高过饱和度的结果，这种过饱和度阻止了金晶体的沉淀，而是导致胶体颗粒的形成，胶体颗粒絮凝并形成更大的质量。这些絮凝体在局部聚集，在那里它们被地震泵入裂缝中，在局部形成主要由金组成的矿脉。