Although forming one unified class, orogenic gold deposits may be associated with a range of ore mineral assemblages controlled by a variety of gold deposition processes that have a direct impact on gold grade. Whereas, a better understanding of the deposition process may be critical for effective targeting of highly-endowed gold deposits, it is challenging to establish a direct comparison between mineral systems formed under different conditions. Accordingly our ability to predict whether contrasted mineral associations may be more or less prospective for high grade mineralization remains poor. In this paper, we compare fluid-rock interaction processes that led to the coeval formation of two contrasting gold mineral assemblages within the world-class Callie orogenic gold deposit. Stratabound and vein-hosted lodes formed within the same structural framework but with contrasting grades (∼3 g/t Au and ∼8 g/t Au, respectively). The stratabound mineralization consists of bedding-parallel sulfides in which gold is preserved in arsenopyrite micro-fractures. The vein-hosted mineralization consists of locally very high-grade (up to 10,000 ppm Au) visible gold concentrated in quartz veins. Both mineralization styles are hosted within different metasedimentary stratigraphic horizons with contrasting compositions. The stratabound mineralization occurs in iron-oxide rich siltstones whereas the vein-hosted mineralization occurs in carbonaceous siltstones. We investigate the fluid-rock interaction mechanisms of the two styles of mineralization at the Callie deposit by combining petrographic observation with whole-rock geochemistry, quantitative chlorite and gold analyses and thermodynamic modeling. Our results show that the stratabound mineralization occurred in response to sulfidation of the host-rock whereas decarbonation alteration, associated with the vein-hosted mineralization, records oxidation of the host-rock. Our investigation shows that gold deposition induced by oxidation of the host-rock produces the valuable, locally very-high grade visible gold mineralization whereas the sulfidation process lead to the formation of lower grade gold mineralization disseminated within the sulphide ore assemblage. We conclude that the nature of the host-rock applies a first-order control on the gold deposition efficiency in metasedimentary-hosted gold deposits.

尽管形成了一个统一的类别，但造山带金矿床可能与一系列受各种金沉积过程控制的矿石矿物组合有关，这些过程对金品位有直接影响。然而，更好地了解沉积过程可能对于有效瞄准高禀赋金矿床至关重要，但在不同条件下形成的矿物系统之间建立直接比较具有挑战性。因此，我们预测对比矿物组合是否或多或少具有高品位矿化前景的能力仍然很差。在本文中，我们比较了导致世界级 Callie 造山带金矿床内两种对比鲜明的金矿物组合同时形成的流体-岩石相互作用过程。层向和脉状矿脉形成于相同的结构框架内，但品位不同（分别为~3 g/t Au 和~8 g/t Au）。层控矿化由层理平行的硫化物组成，其中金保存在毒砂微裂缝中。脉状矿化由富集在石英脉中的当地高品位（高达 10,000 ppm Au）可见金组成。两种矿化类型都位于具有对比成分的不同变沉积地层层位内。层状矿化发生在富含氧化铁的粉砂岩中，而脉状矿化发生在碳质粉砂岩中。我们通过结合岩石学观察和全岩地球化学研究了 Callie 矿床两种成矿方式的流体-岩石相互作用机制，定量绿泥石和金分析和热力学建模。我们的结果表明，层状矿化发生在对主岩硫化作用的反应中，而与脉状矿化相关的脱碳蚀变记录了主岩的氧化。我们的调查表明，由母岩氧化引起的金沉积产生了有价值的、当地非常高品位的可见金矿化，而硫化过程导致形成在硫化矿组合内散布的低品位金矿化。我们得出的结论是，母岩的性质对变沉积赋存的金矿床的金沉积效率起到了一级控制作用。我们的结果表明，层状矿化发生在对主岩硫化作用的反应中，而与脉状矿化相关的脱碳蚀变记录了主岩的氧化。我们的调查表明，由母岩氧化引起的金沉积产生了有价值的、当地非常高品位的可见金矿化，而硫化过程导致形成在硫化矿组合内散布的低品位金矿化。我们得出的结论是，母岩的性质对变沉积赋存的金矿床的金沉积效率起到了一级控制作用。我们的结果表明，层状矿化发生在对主岩硫化作用的反应中，而与脉状矿化相关的脱碳蚀变记录了主岩的氧化。我们的调查表明，由母岩氧化引起的金沉积产生了有价值的、当地非常高品位的可见金矿化，而硫化过程导致形成在硫化矿组合内散布的低品位金矿化。我们得出的结论是，母岩的性质对变沉积赋存的金矿床的金沉积效率起到了一级控制作用。我们的调查表明，由母岩氧化引起的金沉积产生了有价值的、当地非常高品位的可见金矿化，而硫化过程导致形成在硫化矿组合内散布的低品位金矿化。我们得出的结论是，母岩的性质对变沉积赋存的金矿床的金沉积效率起到了一级控制作用。我们的调查表明，由母岩氧化引起的金沉积产生了有价值的、当地非常高品位的可见金矿化，而硫化过程导致形成在硫化矿组合内散布的低品位金矿化。我们得出的结论是，母岩的性质对变沉积赋存的金矿床的金沉积效率起到了一级控制作用。