At the Antamina deposit, Peru, accurate classification of exoskarns and endoskarns can be problematic when textures are mottled. In this study, we use whole-rock geochemical compositions (62 elements) of 221 samples to differentiate texturally similar endoskarns and exoskarns by comparing their compositions to least altered precursors (wall rocks and intrusive rocks). We present a simple method for discriminating these skarn types using immobile element bivariate plots. The most effective discriminators partition endoskarn and exoskarn into distinct domains defined by the composition of each precursor; these include Al₂O₃ versus heavy rare earth elements and some high field strength elements. Using these geochemical parameters, undifferentiated skarn samples can be more reliably classified as endoskarn or exoskarn. The effectiveness of these element pairs is attributed to their significantly different initial concentrations in wall rocks versus igneous precursors and their immobility during skarn formation. While immobile elements can differentiate the skarns, mobile element gains and losses (quantified using isocon analysis) provide insight on the bulk mineralogical and mass changes that take place during skarn formation.

中文翻译：

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秘鲁Antamina矿床的矽卡岩分类和定量交代作用：全岩地球化学的见解

在秘鲁的安塔米纳（Antamina）矿床，纹理斑驳时，外骨骼和内矽卡岩的准确分类可能会出现问题。在这项研究中，我们使用221个样品的全岩石地球化学成分（62个元素），通过将结构相似的内生矽卡岩和外生矽卡岩与变化最小的前驱体（围岩和侵入岩）进行比较，来区分它们。我们提出了一种使用固定元素双变量图来区分这些矽卡岩类型的简单方法。最有效的鉴别器将内生矽胶和外生皮分成不同的区域，每个区域由每个前体的成分定义；这些包括Al ₂ O ₃与重稀土元素和一些高场强元素相比。使用这些地球化学参数，可以将未分化的矽卡岩样品更可靠地分类为内矽卡岩或外骨​​骼。这些元素对的有效性归因于它们在岩壁中的初始浓度与火成岩前体的显着不同，以及它们在矽卡岩形成过程中的固定性。尽管固定元素可以区分矽卡岩，但移动元素的得失（通过等值线分析进行量化）可以提供对矽卡岩形成过程中大量矿物学和质量变化的见解。