The Precordillera mafic–ultramafic belt (PMUB), located in central-western Argentina, comprises mafic and ultramafic bodies interlayered and/or in tectonic contact with marine siliciclastic units. Whole-rock, mineral geochemistry and Nd–Sr isotope analyses performed in magmatic rocks suggest a relatively different spatial and temporal evolution along the belt. The southern PMUB (south of 32° S) evolved as an intra-continental rifted margin with an enriched mid-ocean-ridge basalt (E-MORB) tholeiitic to alkaline magmatism, to a proto-ocean basin (the Cuyano proto-ocean) with tholeiitic normal-MORB geochemical signature. Based on neodymium model ages (TDM), the magmatic activity started during the late Neoproterozoic Era and continued into the early Palaeozoic Era. Instead, the northern PMUB (28–32° S) evolved as an intra-continental rifted margin with dominant tholeiitic E-MORB to continental flood basalt (CFB) magmatism during the early Palaeozoic Era. ϵNd values (+3.4 to +8.4), rare earth element trends and high-field-strength element systematics, together with an estimated potential mantle temperature of c. 50–100°C above ambient mantle, suggest the PMUB magmatism derived from an enriched mantle source related to the effect of a rising plume linked to the Iapetus Ocean opening. In particular, TDM estimations of 600–550 Ma agree with reported magmatism in central to southern Appalachians. The magmatism in the PMUB, and those registered in the Neoproterozoic Catoctin Formation and in the Southern Oklahoma Aulacogen in the conjugated Laurentian margin, seem to be contemporaneous, sharing a similar plume-enriched mantle source. In this context, the E-MORB signature identified along the PMUB can be described as a plume-distal ridge tectonic setting over an extended margin.

中文翻译：

---

智利和库亚尼亚地体之间的库亚诺原洋：新元古代—冈瓦纳西南缘早期古生代演化期间的裂谷和羽流相互作用

位于阿根廷中西部的 Precordillera 镁铁质-超镁铁质带 (PMUB) 由夹层和/或与海相硅质碎屑单元构造接触的镁铁质和超镁铁质体组成。在岩浆岩中进行的全岩、矿物地球化学和 Nd-Sr 同位素分析表明，沿带的空间和时间演化相对不同。南部 PMUB（南纬 32° 以南）演化为陆内裂谷边缘，具有富集的洋中脊玄武岩 (E-MORB) 拉斑玄武岩至碱性岩浆作用，形成原始海洋盆地（Cuyano 原始海洋）具有拉斑沸石正常-MORB地球化学特征。基于钕模型年龄（吨DM)，岩浆活动开始于新元古代晚期，一直持续到古生代早期。相反，在古生代早期，北部 PMUB（28-32° S）演变为陆内裂谷边缘，以拉斑斑玄武岩 E-MORB 为主，向大陆泛滥玄武岩（CFB）岩浆作用演化。ε钕值（+3.4 至 +8.4）、稀土元素趋势和高场强元素系统学，以及估计的潜在地幔温度C。高于环境地幔 50-100°C，表明 PMUB 岩浆作用来自与 Iapetus 海洋开口相关的上升羽流的影响有关的富集地幔源。特别是，吨DM600-550 Ma 的估计与报道的阿巴拉契亚中部到南部的岩浆作用一致。PMUB 中的岩浆作用，以及在新元古代 Catoctin 组和共轭劳伦斯边缘的俄克拉荷马州南部 Aulacogen 中记录的岩浆作用似乎是同时期的，共享一个类似的富含羽状流的地幔源。在这种情况下，沿 PMUB 确定的 E-MORB 特征可以描述为延伸边缘上的羽状远缘脊构造环境。