The 135 Ma Paraná-Etendeka Large Igneous Province (PELIP) is one of the largest areas of continental flood basalt (CFB) volcanism in the world and is widely agreed to be a product of intracontinental melts related to thermal anomalies from the Tristan mantle plume. The province rifted during the break-up of Gondwana, as the plume transitioned into an oceanic geodynamic environment. This study reports analyses of plume-derived basalts from the Brazilian side of the PELIP (the Serra Geral Group) to investigate major, trace and platinum-group element (PGE) abundances in an evolving plume-rift metallogenic setting, with the aim of contextualising metallogenic controls alongside existing magmatic interpretations of the region. The chalcophile geochemistry of these basalts defines three distinct metallogenic groupings that fit with three modern multi-element magma classifications for Serra Geral lavas. In this scheme, Type 4 lavas have a distinctive PGE-poor signature, Type 1 (Central-Northern) lavas are enriched in Pd, Au and Cu, and Type 1 (Southern) lavas are enriched in Ru and Rh. Our trace element melt modelling indicates that the compositional variations result from changes in the melting regime between the garnet and spinel stability fields, in response to the thinning and ‘unlidding’ of the rifting continent above. This process imposes progressively shallower melting depths and higher degrees of partial melting. Accordingly, Type 4 magmas formed from small degree melts, reducing the likelihood of sulphide exhaustion/chalcophile acquisition at source. Type 1 (Central-Northern) magmas incorporated components of the sub-continental lithospheric mantle (SCLM) in higher-degree partial melts; the SCLM was heterogeneously enriched via metasomatism prior to plume melting, and this produced enrichment in volatile metals (Pd, Cu, and Au) in these magmas. In contrast, the Ru-Rh enrichment in Type 1 (Southern) lavas is attributed to increased spinel-group mineral and sulphide incorporation from the mantle into higher degree partial melts close to the continental rift zone. Our models confirm the importance of contributions from SCLM melts in precious metal mineral systems within CFB provinces, and reinforce the role of heterogeneous metasomatic enrichment underneath cratons in boosting intracontinental prospectivity with respect to ore deposits.

135 Ma Paraná-Etendeka 大型火成岩省 (PELIP) 是世界上最大的大陆溢流玄武岩 (CFB) 火山区之一，被广泛认为是与来自特里斯坦地幔柱的热异常相关的大陆内融化的产物。该省在冈瓦纳大陆解体期间出现裂痕，因为羽流转变为海洋地球动力学环境。本研究报告分析了来自 PELIP（塞拉杰拉尔群）巴西一侧的羽状玄武岩，以研究不断演变的羽状裂谷成矿环境中的主要、痕量和铂族元素 (PGE) 丰度，目的是将成矿控制以及该地区现有的岩浆解释。这些玄武岩的亲硫地球化学定义了三个不同的成矿组，符合塞拉杰拉尔熔岩的三个现代多元素岩浆分类。在这个方案中，4 型熔岩具有独特的 PGE 贫乏特征，1 型（中北部）熔岩富含 Pd、Au 和 Cu，1 型（南部）熔岩富含 Ru 和 Rh。我们的微量元素熔体​​模型表明，成分变化是由石榴石和尖晶石稳定性场之间的熔化状态变化引起的，以响应上面裂谷大陆的变薄和“解开”。该过程逐渐形成更浅的熔化深度和更高程度的部分熔化。因此，4 类岩浆由小程度的熔体形成，从而降低了在源头处获得硫化物耗尽/亲硫体的可能性。类型 1（中北部）岩浆将次大陆岩石圈地幔 (SCLM) 的成分结合在更高程度的部分熔体中；SCLM 在羽流熔化之前通过交代作用被非均质富集，这导致这些岩浆中挥发性金属（Pd、Cu 和 Au）的富集。相比之下，1 型（南部）熔岩中的 Ru-Rh 富集归因于增加的尖晶石族矿物和硫化物从地幔进入靠近大陆裂谷带的更高程度的部分熔体。我们的模型证实了 SCLM 熔体在 CFB 省内贵金属矿物系统中的重要性，并加强了克拉通下异质交代富集在提高大陆内矿床前景方面的作用。