Stratabound Cu–(Ag) deposits in the Coastal Cordillera of northern Chile were emplaced under an extensional setting during the Late Jurassic and Early Cretaceous. Las Luces and Altamira are two stratabound Cu–(Ag) deposits located approximately at the same latitude (~ 25°45′S), but the former is hosted by Jurassic volcanic and volcaniclastic rocks, and the latter by Cretaceous volcano-sedimentary sequences. Both deposits show similar hydrothermal alteration types with albitization and hematite–chlorite superimposed on low-grade regional metamorphism. Sulfide mineralization is represented mainly by pyrite, chalcopyrite, and a bornite– “chalcocite” assemblage. Chalcopyrite is relatively minor and can replace early pyrite. In addition, framboidal pyrite of possible diagenetic origin was observed in Altamira. Copper mineralization is dominated by a bornite– “chalcocite” assemblage; however, electron probe analyses show that “chalcocite” has a composition ranging from geerite to djurleite. The typical mymekitic-like exsolution texture observed in the bornite–Cu sulfides assemblage is interpreted as caused by sub-solidus re-equilibration on cooling of the bornite–digenite solid solution. Silver, the main by-product in these deposits, is probably incorporated in solid solution in Cu sulfides and bornite, although Ag–sulfide microparticles were occasionally observed within sulfides in Altamira. Copper sulfides of the geerite–djurleite series can contain high amounts of Ag, ranging between 202 and 789 ppm, whereas in bornite from Las Luces Ag can reach up to 270 ppm. The presence of low-temperature (~ 100 °C) hydrothermal Cu sulfides is consistent with formation temperatures of < 300 °C, based on previous fluid inclusion studies. Bulk stable isotope data shows that sulfur in these deposits have different sources. In Las Luces δ³⁴S values for bornite and pyrite (− 2.5 to + 2.9‰) indicate a magmatic source, whereas in Altamira the negative values for “chalcocite” (δ³⁴S: − 38.7 to − 10.7‰) are interpreted as sulfur derived by bacterial reduction of marine sulfate. The Las Luces and Altamira deposits were possibly formed by high water/rock ratios where basin-derived fluids leached metals from the volcanic/volcano-sedimentary host rocks. However, extensive leaching of the volcanic host rocks necessary to extract the Cu contained in silicate minerals is not consistent with the relatively small volume of hydrothermal alteration associated with these deposits, suggesting an additional magmatic contribution. In the revised genetic model, variable contributions of a magmatic and non-magmatic source are needed to form these stratabound Cu–(Ag) deposits.

在晚侏罗世和早白垩世，智利北部沿海科迪勒拉的层状铜（银）矿床在伸展环境下就位。Las Luces 和Altamira 是两个大致位于同一纬度（~25°45′S）的层状Cu-（Ag）矿床，但前者以侏罗纪火山岩和火山碎屑岩为主，后者以白垩纪火山-沉积序列为主。两种矿床都显示出相似的热液蚀变类型，钠长石化和赤铁矿-绿泥石叠加在低品位区域变质作用上。硫化物矿化主要以黄铁矿、黄铜矿和斑铜矿——“辉铜矿”组合为代表。黄铜矿相对较小，可以替代早期的黄铁矿。此外，在阿尔塔米拉（Altamira）观察到可能成岩成因的棱柱状黄铁矿。铜矿化以斑铜矿-“辉铜矿”组合为主；然而，电子探针分析表明，“辉铜矿”的成分范围从 geerite 到 djurleite。在斑铜矿-Cu 硫化物组合中观察到的典型的类粘粒状溶出织构被解释为由斑铜矿-闪锌矿固溶体冷却时的亚固相线再平衡引起。尽管在阿尔塔米拉的硫化物中偶尔会观察到银-硫化物微粒，但银是这些沉积物中的主要副产品，可能以固溶体形式结合在硫化铜和斑铜矿中。geerite-djurleite 系列的硫化铜可能含有大量的银，介于 202 和 789 ppm 之间，而来自 Las Luces 的斑铜矿中银含量可高达 270 ppm。根据先前的流体包裹体研究，低温（~ 100 °C）热液硫化铜的存在与 < 300 °C 的地层温度一致。大量稳定同位素数据表明，这些矿床中的硫有不同的来源。在拉斯卢塞斯 δ^{斑铜矿和黄铁矿的34} S 值（- 2.5 至 + 2.9‰）表示岩浆来源，而在阿尔塔米拉，“辉铜矿”的负值（δ ³⁴S: - 38.7 至 - 10.7‰) 被解释为通过海洋硫酸盐的细菌还原产生的硫。Las Luces 和 Altamira 矿床可能是由高水/岩比形成的，其中盆地衍生流体从火山/火山沉积母岩中浸出金属。然而，提取硅酸盐矿物中所含铜所需的火山主岩的广泛浸出与与这些沉积物相关的相对较小体积的热液蚀变不一致，这表明额外的岩浆贡献。在修改后的成因模型中，需要岩浆和非岩浆来源的不同贡献来形成这些层状Cu-(Ag)矿床。