The geological setting of extensive ~3.5 Ga greenstone sequences in the Pilbara Craton (Australia) has been controversial for many years. Models range from a purely oceanic origin to emplacement over a pre-existing, possibly Hadean, sialic basement. Here we present new isotopic (NdHf) and trace element and data for a geographically extensive suite of komatiitic-tholeiitic metavolcanic rocks which comprise much of the Pilbara Supergroup. Most of the samples have flat to mildly enriched normalised trace element patterns, often associated with a slight NbTa depletion. A small subset of samples, represented throughout the stratigraphy, show strong LREE enrichment and pronounced HFSE anomalies (low Nb/Th, high La/Nb and Zr/Y) either requiring a different magma source or the addition of an enriched component (possibly pre-existing continental crust). Despite this compositional diversity, the SmNd and LuHf data for all samples define ~3.5 Ga isochrons and yield homogeneous initial ratios (ε_Nd = 1.15 ± 0.19; ε_Hf = 2.29 ± 0.65) suggesting a magma source — or sources — slightly more depleted than the putative primitive (chondritic) mantle but consistent with recent observations of other primordial, deep mantle reservoirs. Published SmNd data for the Dresser Formation obtained during the Pilbara Drilling Project appear to be affected by alteration processes and are considered unreliable for the estimation of an accurate initial isotopic composition.

The data for the enriched samples are inconsistent with assimilation of known examples of locally exposed continental crust as a mechanism responsible for their trace element characteristics. If an alternate crustal contaminant is invoked it cannot be much older than the basaltic magmatism itself. As a consequence, we see no evidence for an extensive Hadean (>4.0 Ga) sialic basement in the region.

皮尔巴拉克拉顿（澳大利亚）的约3.5 Ga绿岩序列的地质环境已有多年争议。模型的范围从纯粹的海洋起源到在先前存在的，可能是Hadean的唾液腺基底上的定位。在这里，我们介绍了一个新的同位素（Nd Hf）以及痕量元素和数据，这些地理元素分布广泛，由大量的Pilbara超群组成的科莫替利特-特里维特变火山岩。大多数样品具有平坦至中等富集的归一化痕量元素模式，通常与微量Nb有关钽耗尽。在整个地层中代表的一小部分样品显示出强烈的LREE富集和明显的HFSE异常（低Nb / Th，高La / Nb和Zr / Y），或者需要不同的岩浆源或需要添加富集的成分（可能-现存的大陆壳）。尽管这样组成的多样性，钐Nd和路对于所有样品HF数据定义〜3.5镓等时线和屈服均相原比率（ε_的Nd  = 1.15±0.19;ε_的Hf  = 2.29±0.65），这表明一个岩浆源-或源-稍微更比假定的原始（软骨状）地幔更枯竭，但与其他原始，深地幔储层的最新观测结果一致。已发布Sm在皮尔巴拉（Pilbara）钻探项目期间获得的修整器地层的Nd数据似乎受到蚀变过程的影响，并且被认为对估计准确的初始同位素组成不可靠。

富集样品的数据与局部暴露的大陆壳已知实例的同化不一致，后者是造成其痕量元素特征的机制。如果调用了另一种地壳污染物，它的年龄不能比玄武岩浆岩本身的年龄大得多。结果，我们看不到该地区广泛存在的Hadean（> 4.0 Ga）唾液酸基底的证据。