Porphyry Cu-Mo deposits (PCDs) are the world’s major source of Cu, Mo, and Re and are also a significant source of Au and Ag. Here we focus on the world-class Río Blanco PCD in the Andes of central Chile, where Ag is a by-product of Cu mining. Statistical examination of an extensive multielemental inductively coupled plasma-mass spectrometry data set indicates compositional trends at the deposit scale, including Ag-Cu (r = 0.71) and Ag-In (r = 0.53) positive correlations, which relate to Cu-Fe sulfides and Cu sulfosalts in the deposit. Silver is primarily concentrated in Cu ores in the central core of the deposit, and significant variations in the Ag concentration are related to the different hydrothermal alteration types. The concentration of Ag is highest in the potassic core (avg 2.01 ppm) and decreases slightly in the gray-green sericite (phyllic) zone (avg 1.72 ppm); Ag is lowest in the outer propylitic alteration zone (avg 0.59 ppm). Drill core samples from major hydrothermal alteration zones were selected for in situ analysis of Ag and associated elements in sulfide and sulfosalt minerals. To ensure representativeness, sample selection considered the spatial distribution of the alteration types and ore paragenesis. Chalcopyrite is the most abundant Cu sulfide in Río Blanco, with Ag concentration that ranges from sub-parts per million levels to hundreds of parts per million. The highest concentration of Ag in chalcopyrite is associated with the high-temperature potassic alteration stage. Bornite is less abundant than chalcopyrite but has the highest Ag concentration of all studied sulfides, ranging from hundreds of parts per million up to ~1,000 ppm. The Ag concentration in bornite is higher in lower-temperature alteration assemblages (moderate gray-green sericite), opposite to the behavior of Ag in chalcopyrite. Pyrite has the lowest Ag content, although concentrations of other critical elements such as Co, Ni, and Au may be significant. The highest Ag concentrations, i.e., thousands of parts per million up to weight percent levels, were detected in late-stage Cu sulfosalts (enargite, tennantite, and tetrahedrite). The Ag content in these sulfosalts increases with increasing Sb concentrations, from the Sb-poor enargite to the Sb-rich tetrahedrite. The earliest Ag mineralization event is related to the potassic alteration stage represented by early biotite and transitional early biotite-type veinlets and where the predominant sulfides are chalcopyrite and bornite. Silver mineralization during this stage was predominantly controlled by crystallization of Cu-Fe sulfides. The second Ag mineralization event at Río Blanco is associated with the transitional Cu mineralization stage, which is represented by the gray-green sericite alteration (C-type veinlets). In this alteration type, Ag was partitioned preferentially into chalcopyrite, bornite, and to a lesser extent pyrite. The last Ag mineralization event is related to the late quartz-sericite alteration stage, characterized by D- and E-type veinlets with pyrite-chalcopyrite and enargite-tennantite-tetrahedrite. Our data indicate that Ag was associated with several Cu mineralization episodes at Río Blanco, with Ag concentration apparently controlled by cooling, changes in pH, f_O2 and f_S2 of the hydrothermal fluids, and the intensity of alteration. Overall, our results provide information on critical metal partitioning between sulfides, plus the distribution of critical element resources at the deposit scale. Knowledge of the mineralogical occurrence of critical metals in PCDs is necessary to better assess their resources and evaluate the potential for their recovery.

中文翻译：

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智利中部世界一流的里奥·布兰科斑岩斑岩铜钼矿床中银的赋存与分布

斑岩型铜钼矿床（PCDs）是世界上铜，钼和，的主要来源，也是金和银的重要来源。在这里，我们专注于智利中部安第斯山脉的世界级RíoBlanco PCD，那里的Ag是Cu开采的副产品。对大量的多元素电感耦合等离子体质谱数据集进行的统计检查表明，在沉积规模上的成分趋势，包括与Cu-Fe硫化物有关的Ag-Cu（r = 0.71）和Ag-In（r = 0.53）正相关。矿床中还有铜亚硫酸盐。银主要集中在矿床中央核心的铜矿石中，Ag浓度的显着变化与不同的热液蚀变类型有关。钾素核心中的Ag浓度最高（平均2）。01 ppm），并在灰绿色绢云母（页岩）区略微降低（平均1.72 ppm）；Ag在外部的丙二酸改变区最低（平均0.59 ppm）。选择来自主要热液蚀变带的钻芯样品，对硫化物和亚硫酸盐矿物中的Ag及其相关元素进行原位分析。为确保代表性，样本选择应考虑蚀变类型和矿共生的空间分布。黄铜矿是里奥布兰科最丰富的硫化铜，银的浓度范围从百万分之几到百万分之几。黄铜矿中Ag的最高浓度与高温钾化蚀变阶段有关。硼铁矿的含量低于黄铜矿，但在所有研究的硫化物中的银含量最高，范围从百万分之几百到高达1,000 ppm。在低温蚀变组合中（中度灰绿色绢云母），堇青石中的银含量较高，这与黄铜矿中银的行为相反。黄铁矿的Ag含量最低，尽管其他关键元素（例如Co，Ni和Au）的浓度可能很高。在后期的铜亚硫酸盐（钙锰矿，钙钛矿和四面体）中检测到最高的Ag浓度，即百万分之几（按重量计）。这些硫盐中的Ag含量随Sb浓度的增加而增加，从贫Sb的辉石到富Sb的四面体。最早的Ag矿化事件与以早期黑云母和过渡的早期黑云母型脉为代表的钾质蚀变阶段有关，其中主要的硫化物是黄铜矿和斑铜矿。此阶段的银矿化主要受Cu-Fe硫化物的结晶控制。RíoBlanco的第二次Ag矿化事件与过渡Cu矿化阶段有关，该阶段以灰绿色绢云母蚀变（C型脉脉）为代表。在这种蚀变类型中，Ag优先分配为黄铜矿，斑铁矿和较小程度的黄铁矿。最后的银矿化事件与晚期石英-绢云母蚀变阶段有关，其特征为具有黄铁矿-黄铜矿和辉镁岩-辉石-四面体的D型和E型细矿。热液的_{O 2}和f _{S 2}以及变化的强度。总体而言，我们的结果提供了有关硫化物之间的关键金属分配的信息，以及在沉积规模上关键元素资源的分布。了解PCD中关键金属的矿物学知识对于更好地评估其资源和评估其回收潜力至关重要。