The Highland Valley Copper porphyry deposits, hosted in the Late Triassic Guichon Creek batholith in the Canadian Cordillera, are unusual in that some of them formed at depths of at least 4 to 5 km in cogenetic host rocks. Enrichments in ore and pathfinder elements are generally limited to a few hundred meters beyond the pit areas, and the peripheral alteration is restricted to narrow (1–3 cm) halos around a low density of prehnite and/or epidote veinlets. It is, therefore, challenging to recognize the alteration footprint peripheral to the porphyry Cu systems. Here, we document a workflow to maximize the use of lithogeochemical data in measuring changes in mineralogy and material transfer related to porphyry formation by linking whole-rock analyses to observed alteration mineralogy at the hand specimen and deposit scale. Alteration facies and domains were determined from mapping, feldspar staining, and shortwave infrared imaging and include (1) K-feldspar halos (potassic alteration), (2) epidote veins with K-feldspar–destructive albite halos (sodic-calcic alteration), (3) quartz and coarse-grained muscovite veins and halos and fine-grained white-mica–chlorite veins and halos (white-mica–chlorite alteration), and two subfacies of propylitic alteration comprising (4) prehnite veinlets with white-mica–chlorite-prehnite halos, and (5) veins of epidote ± prehnite with halos of chlorite and patchy K-feldspar. Well-developed, feldspar-destructive, white-mica alteration is indicated by (2[Ca-C] + N + K)/Al values <0.85, depletion in CaO and Na2O, enrichment in K2O, and localized SiO2 addition and is spatially limited to within ~200 m of porphyry Cu mineralization. Localized K2O, Fe2O3, and depletion in Cu, and some enrichment in Na2O and CaO, occurs in sodic-calcic domains that form a large (~34 km2) nonconcentric footprint outboard of well-mineralized and proximal zones enriched in K. Water and magmatic CO2-rich propylitic and sodic-calcic–altered rocks form the largest lithogeochemical footprint to the mineralization in the Highland Valley Copper district (~60 km2). Calcite in the footprint is interpreted to have formed via phase separation of CO2 from a late-stage magmatic volatile phase. Several observations from this study are transferable to other porphyry systems and have implications for porphyry Cu exploration. Feldspar staining and shortwave infrared imaging highlight weak and cryptic alteration that did not cause sufficient material transfer to be confidently distinguished from protolith lithogeochemical compositions. Prehnite can be a key mineral phase in propylitic alteration related to porphyry genesis, and its presence can be predicted based on host-rock composition. Sodic-calcic alteration depletes the protolith in Fe (and magnetite) and, therefore, will impact petrophysical and geophysical characteristics of the system. Wholerock loss on ignition and C and S analyses can be used to map enrichment in water and CO2 in altered rocks, and together these form a large porphyry footprint that extends beyond domains of enrichment in ore and pathfinder elements and of pronounced alkali metasomatism.

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将矿物学与高地谷铜区的岩石地球化学联系起来：对斑岩铜足迹的影响

高地谷铜斑岩矿床位于加拿大科迪勒拉山脉的晚三叠世 Guichon Creek 基岩中，其不寻常之处在于其中一些形成于至少 4 至 5 公里深处的共生主岩中。矿石和探路者元素的富集通常仅限于坑区以外数百米，外围蚀变仅限于围绕低密度葡萄石和/或绿帘石细脉的狭窄（1-3 厘米）晕圈。因此，识别斑岩铜系统外围的蚀变足迹具有挑战性。在这里，我们记录了一个工作流程，通过将全岩分析与在手标本和矿床规模上观察到的蚀变矿物学联系起来，最大限度地利用岩石地球化学数据来测量与斑岩形成相关的矿物学和材料转移的变化。蚀变相和域由测绘、长石染色和短波红外成像确定，包括（1）钾长石晕（钾盐蚀变），（2）具有钾长石破坏性钠长石晕（钠钙蚀变）的绿帘石脉， (3) 石英和粗粒白云母脉和晕和细粒白云母-绿泥石脉和晕（白云母-绿泥石蚀变），以及包括 (4) 白云母-绿泥石脉的两种青岩蚀变亚相绿泥石-葡萄石晕，和 (5) 绿帘石脉 ± 葡萄石与绿泥石晕和片状钾长石。发育良好的长石破坏性白云母蚀变表现为 (2[Ca-C] + N + K)/Al 值 <0.85，CaO 和 Na2O 消耗，K2O 富集和局部 SiO2 添加，并且在空间上是仅限于斑岩铜矿化约 200 m 内。局部的 K2O、Fe2O3 和 Cu 的消耗，以及 Na2O 和 CaO 的一些富集，发生在钠钙域中，在富含钾的矿化和近端区域的外侧形成一个大的（~34 平方公里）非同心足迹。 水和岩浆在高地谷铜矿区（约 60 平方公里），富含 CO2 的青橄榄岩和钠钙蚀变岩石形成了最大的岩石地球化学足迹。足迹中的方解石被解释为通过 CO2 与后期岩浆挥发相的相分离形成的。这项研究的一些观察结果可转移到其他斑岩系统，并对斑岩铜勘探产生影响。长石染色和短波红外成像突出了微弱和隐秘的变化，这些变化没有引起足够的材料转移，可以自信地将其与原岩岩石地球化学成分区分开来。Prehnite 可能是与斑岩成因相关的青岩蚀变中的关键矿物相，它的存在可以根据主岩组成进行预测。钠钙蚀变消耗了铁（和磁铁矿）中的原岩，因此将影响系统的岩石物理和地球物理特性。全岩烧失量和 C 和 S 分析可用于绘制蚀变岩石中水和 CO2 的富集情况，它们共同形成一个大的斑岩足迹，超出了矿石和探路元素的富集范围以及明显的碱交代作用。Prehnite 可能是与斑岩成因相关的青岩蚀变中的关键矿物相，它的存在可以根据主岩组成进行预测。钠钙蚀变消耗了铁（和磁铁矿）中的原岩，因此将影响系统的岩石物理和地球物理特性。全岩烧失量和 C 和 S 分析可用于绘制蚀变岩石中水和 CO2 的富集情况，它们共同形成一个大的斑岩足迹，超出了矿石和探路元素的富集范围以及明显的碱交代作用。Prehnite 可能是与斑岩成因相关的青岩蚀变中的关键矿物相，它的存在可以根据主岩组成进行预测。钠钙蚀变消耗了铁（和磁铁矿）中的原岩，因此将影响系统的岩石物理和地球物理特性。全岩烧失量和 C 和 S 分析可用于绘制蚀变岩石中水和 CO2 的富集情况，它们共同形成一个大的斑岩足迹，超出了矿石和探路元素的富集范围以及明显的碱交代作用。将影响系统的岩石物理和地球物理特性。全岩烧失量和 C 和 S 分析可用于绘制蚀变岩石中水和 CO2 的富集情况，它们共同形成一个大的斑岩足迹，超出了矿石和探路元素的富集范围以及明显的碱交代作用。将影响系统的岩石物理和地球物理特性。全岩烧失量和 C 和 S 分析可用于绘制蚀变岩石中水和 CO2 的富集情况，它们共同形成一个大的斑岩足迹，超出了矿石和探路元素的富集范围以及明显的碱交代作用。