The chemistry of the major reservoirs in the silicate Earth reflects a long history of differentiation into- and interaction between- incompatible element enriched crust and depleted mantle. Evidence from ¹⁴²Nd variability in ancient mantle-derived rocks imply such differentiation began very early in Earth's history, while the short-lived ¹⁴⁶Sm (half-life 103 Ma) was extant, but the size and composition of primitive reservoirs in the Hadean and early Archean is debated. Therefore, pivotal to the study of Earth evolution is the recognition of well-preserved ancient magmatic rocks that can provide robust constraints on source compositions to test geodynamic models. We present the first combined petrological, geochemical and isotope (^146-147Sm-^142-143Nd and ¹⁷⁶Lu–¹⁷⁶Hf) study of basaltic rocks from the East Pilbara Terrane, Pilbara Craton, Western Australia. The basaltic pillow lavas, from the ca. 3470 Ma Mount Ada Basalt of the Pilbara Supergroup, include quartz-phyric quartz-normative tholeiites, plagioclase-phyric olivine-normative tholeiites and clinopyroxene spinifex textured olivine-normative tholeiites and include samples that classify as siliceous high Mg basalts. Their major and trace-element compositions suggest that the basalts are high-degree partial melts (20–30%) produced at shallow mantle depths of 0.5–1 GPa, which is consistent with formation of both quartz-normative and olivine-normative parental magmas. Isotopic data from this sample suite defines Sm–Nd and Lu–Hf isochrons with dates of 3484 ± 113 Ma and 3463 ± 50 Ma, respectively. The samples yield coupled initial ε_Nd = +1.1 and ε_Hf = +2.1, and μ¹⁴²Nd values indistinguishable from the modern mantle. The uniform initial ε_Nd and ε_Hf in samples from this study and other Mount Ada Basalt basaltic samples across four greenstone belts indicates that this portion of the Paleoarchean mantle was well mixed at the scale of melt generation and evolved with slightly suprachondritic Sm/Nd and Lu/Hf. Absence of ¹⁴²Nd variations suggests the portion of the Paleoarchean Pilbara mantle sampled by these basalts retains no signature of Hadean Sm/Nd fractionation.

硅酸盐地球中主要储层的化学反应反映了将不相容元素富集的地壳和枯竭的地幔分化为相互作用和相互作用的悠久历史。古代地幔衍生岩石中¹⁴² Nd变异性的证据表明，这种分化早在地球历史上就开始了，而短暂的¹⁴⁶ Sm（半衰期为103 Ma）是现存的，但是哈德滩和哈德滩原始储层的大小和组成早期的太古宙被辩论了。因此，对地球演化研究的关键是对保存完好的古代岩浆岩的认识，该岩浆岩可以对源组成提供严格的约束，以测试地球动力学模型。我们提出了第一个组合的岩石学，地球化学和同位素（^146-147 Sm-^142-143 Nd和¹⁷⁶ Lu– ¹⁷⁶Hf）研究来自西澳大利亚州Pilbara Craton的East Pilbara Terrane的玄武岩。玄武岩枕头熔岩，来自加利福尼亚州。Pilbara超级集团的3470 Ma Mount Ada玄武岩，包括石英-天然石英-规范性钠钙石，斜长石-天然的橄榄石-规范性钠钙石和斜辉石刺刀质地的橄榄石-规范性钠钙石，并包括归类为硅质高Mg玄武岩的样品。它们的主要和微量元素组成表明，玄武岩是在0.5-1 GPa的浅地幔深度产生的高度部分熔体（20-30％），这与石英规范和橄榄石规范的父母岩浆形成一致。 。来自该样本套件的同位素数据定义了Sm–Nd和Lu–Hf等时线，其日期分别为3484±113 Ma和3463±50 Ma。样本产生耦合的初始ε_ND  = 1.1和ε_的Hf  = 2.1，μ ¹⁴²的Nd值从现代地幔难以区分。统一的初始ε_的Nd和ε_的Hf在本研究和其他摩阿达玄武岩玄武样品在四个绿岩带样本表示该古太古代地幔的这个部分在熔融生成的规模充分混合，并用稍suprachondritic SM / Nd和演进Lu / Hf。缺少^142种Nd变体表明，这些玄武岩采样的古旧Pilbara地幔部分没有保留Hadean Sm / Nd分馏的特征。