Amphibole control on copper systematics in arcs: Insights from the analysis of global datasets
Amphibole control on copper systematics in arcs: Insights from the analysis of global datasets
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DOI：
10.1016/j.gca.2021.05.034
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发表时间：
2021-06-16
影响因子：
5
通讯作者：
Williams, Helen
中科院分区：
文献类型：
--
作者：
Barber, Nicholas D.;Edmonds, Marie;Williams, Helen
铜是一种重要的资源，主要来源于岩浆。然而，形成弧岩浆中铜含量的过程仍有争议。现有的模型强调不同的岩石学代理人，解释大规模的铜系统学的趋势。以前的研究已经注意到“Cu悖论”，即具有高Sr/Y比值的岩浆，指示成矿潜力，具有最低的铜浓度。在这里，我们编制了一个多维数据库的火山全岩成分，并将其与简单的岩石学模型来阐明火山全岩成分与铜的控制。我们发现，钙碱性，高Sr/Y岩浆进行大量的角闪石和/或石榴石分馏，促进硫化物沉淀和铜贫化造成的主要元素的修改。我们证明了角闪石分馏的重要性，作为一个全球性的重要过程，促进钙碱性分化和硫化物分馏弧岩浆，以及它的作用，在信号中的一套正确的化学条件的岩浆，最终饲料铜斑岩矿床。这项工作还提出了角闪石作为潜在的斑岩形成条件的岩浆，我们应该很容易检测到的不同的地球化学指标的组合的地球化学和岩石学指标的可能性。尽管他们缺乏铜，高Sr/Y岩浆与斑岩矿床，这意味着岩浆形成这种矿床的倾向取决于其他因素比岩浆的散装铜含量。(C)2021年，任作者。由Elsevier Ltd.发布。这是CC BY许可证（http：//www.example.com licenses/by/4.0/）下的开放获取文章。creativecommons.org/
Copper, obtained from porphyry deposits formed in arc settings, is a critical resource, and is primarily sourced from magmas. However, the processes that shape the copper contents of arc magmas are up for debate. Existing models place emphasis on different petrological agents that explain large-scale trends in copper systematics. Previous studies have noted the "Cu paradox," where the magmas with high Sr/Y ratios, indicative of ore-forming potential, have the lowest copper concentrations. Here we compile a multidimensional database of volcanic whole rock compositions and couple it with simple petrological models to elucidate the controls on volcanic whole rock compositions with respect to Cu. We show that calc-alkaline, high Sr/Y magmas undergo major element modification caused by extensive amphibole and/or garnet fractionation, which promotes sulphide precipitation and copper depletion. We demonstrate the importance of amphibole fractionation as a globally important process that promotes both calc-alkaline differentiation and sulphide fractionation in arc magmas, as well as its role in signalling the right set of chemical conditions in magmas that ultimately feed copper porphyry deposits. This work also raises the possibility of amphibole as a geochemical and petrological indicator of potential porphyry-forming conditions in a magma, which we show should be readily detectable by a combination of different geochemical metrics. Despite their paucity in copper, high Sr/Y magmas are associated with porphyry deposits, implying that the propensity of magmas to form such deposits depends on factors other than a magma's bulk copper content. (C) 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/ licenses/by/4.0/).