The Vijayan Complex (VC) of Sri Lanka is a Neoproterozoic arc terrain having no convincingly proven counterpart elsewhere in the Gondwana supercontinent. Therefore, little is known about the nature of its pre-Gondwanan ancestry. We present here new elemental and Sr-Nd isotope systematics of orthogneisses to envisage the origin and evolution of the VC. Samples with high and variable Sr-initials and negative ε_Nd > +4 are compatible with their derivation by melting of older rocks with a long crustal residence history. Most of the studied rocks show depleted-mantle-model ages (1.4–3.3 Ga) considerably older than the ∼1 Ga magmatic crystallization age of the VC. The rest of the samples show model ages of ∼0.9–1.1 Ga, coeval with the crystallization age of the VC, indicating separation from the mantle as juvenile inputs. Therefore, protolith sources of the majority of these rocks are mixtures of distinctive components formed much earlier than the time of predominant magmatism (∼1 Ga) in the VC. Major and trace elements and rare earth element ratios divide these samples into two categories. The “Depleted Group” represents protoliths similar to Proterozoic oceanic island basalt–like mantle materials that intensively interacted/mixed with different proportions of melts derived from juvenile and ancient lower crust. The “Enriched Group” represents mid-ocean ridge basalt–like mantle materials subsequently interacted/mixed with variable amounts of melts derived from Archean felsic and mafic crust. Geochemical-mixing modeling with ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd confirms the involvement of above multiple source components. Thus, our findings illustrate evidence for hybridization of mantle-derived melts from various juvenile and ancient crustal components. Therefore, this first finding of Paleoproterozoic to early Archean–aged components within the VC provides new insights to elucidate its pre-Gondwanan geodynamic setting, revising the previous understanding of it as an “exotic terrain” to Gondwana with only largely juvenile Neoproterozoic materials.

中文翻译：

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新的Sr-Nd同位素数据记录了斯里兰卡Vijayan复杂地带中的少年与古地幔-地幔融解相互作用

斯里兰卡的维杰扬河群（VC）是新元古代弧形地形，在冈瓦纳超大陆的其他地方都没有令人信服地证明过的对应物。因此，对冈瓦纳以前的血统的性质知之甚少。我们在这里介绍正片麻岩的新元素和Sr-Nd同位素系统，以设想VC的起源和演化。具有高和可变锶声母和负ε样本_的Nd> +4与具有较长地壳滞留历史的较旧岩石融化的结果兼容。大多数研究的岩石显示出幔幔模型年龄（1.4-3.3 Ga）要比VC的〜1 Ga岩浆结晶年龄大得多。其余样品的模型年龄约为0.9-1.1 Ga，与VC的结晶年龄相当，表明从地幔中分离是作为幼年的输入。因此，这些岩石中大多数的原生岩源是独特成分的混合物，这些成分的形成要比VC中主要的岩浆作用时间（〜1 Ga）早得多。主要元素和痕量元素与稀土元素的比例将这些样品分为两类。“贫化群”代表与元古代大洋玄武岩类似的原生石，像地幔物质，与不同比例的幼年和古代下地壳熔体进行强烈的相互作用/混合。“富集群”代表大洋中脊玄武岩样地幔物质，随后与来自太古代长石质和镁铁质地壳的各种熔体相互作用/混合。地球化学混合建模⁸⁷ Sr / ⁸⁶ Sr和¹⁴³ Nd / ¹⁴⁴ Nd证实了上述多个源组分的参与。因此，我们的发现说明了来自各种少年和古代地壳成分的地幔衍生熔体杂交的证据。因此，在风电场内对古元古代到早古宙时代成分的首次发现提供了新的见解，以阐明其在冈瓦纳之前的地球动力学环境，从而改变了以前对冈多瓦纳“异域”的认识，仅使用了幼年的新元古代材料。