An ongoing debate concerns what initiated the Great Oxidation Event (GOE) and associated glaciation between ~ 2.45 and 2.2 Ga. One possibility is the emergence of continental landmasses and the increase of subaerial igneous province weathering during the Late Archean. We test this hypothesis in the Hamersley Basin by reporting Nd-isotope data from a succession of iron formations (IFs), mudstone/siltstones and glacial diamictites from the Boolgeeda Iron Formation and overlying Turee Creek Group deposited during the GOE. In a ¹⁴⁷Sm/¹⁴⁴Nd - ɛNd_(t) diagram, the data define a negative trend indicating the contribution of a high ɛNd_(t) ~ +3 hydrothermal component and a strongly negative ɛNd_(t) ~ -9 crustal component, which is compatible with the Nd-isotope composition of the upper continental crust but also of the underlying felsic volcanics of the Woongarra Rhyolite and crustally-contaminated mafic volcanics of the Fortescue Group. A less pronounced negative trend originating from the same hydrothermal source but correlated with non-contaminated ultramafic Fortescue volcanics (ɛNd_(t) ~ -2) is observed for the older Joffre, Dales Gorge and Marra Mamba IFs. As Nd-isotopes are not sensitive to redox conditions, the major shift of Nd-isotopic compositions at ~ 2.45 Ga cannot be linked to a change in the weathering regime, rather to a change in the nature of the continental surface exposed to weathering. One explanation is that the Sm-Nd sources for sediments deposited before and during the GOE were locally derived from the underlying subaerial LIPs, reflecting a change in the geodynamic context of deposition and/or hydrographic network and catchment areas. Another explanation could be a significant change in the nature of fluid–rock interactions due to the increase role of weathering processes associated with the emergence of continental landmasses. Additional Nd isotope data from different cratons worldwide are needed, however, to infer as to whether or not the marked shift in Nd isotope compositions recorded in the Turee Creek Group reflect a change in the global hydrological cycle. Our data support the role of large subaerial magmatic provinces as triggers of the rise of atmospheric oxygen and the onset of glaciations at the beginning of the Proterozoic.

正在进行的辩论涉及是什么引发了大氧化事件 (GOE) 和大约 2.45 到 2.2 Ga 之间的相关冰川作用。一种可能性是太古代晚期大陆陆块的出现和地下火成岩省风化作用的增加。我们通过报告 GOE 期间沉积的 Boolgeeda 铁层和上覆 Turee Creek 群的一系列铁层 (IF)、泥岩/粉砂岩和冰川混叠岩的 Nd 同位素数据，在 Hamersley 盆地检验了这一假设。在¹⁴⁷ Sm/ ¹⁴⁴ Nd - ɛNd _(t)图中，数据定义了负趋势，表明高 ɛNd _(t) ~ +3 热液成分和强负 ɛNd _{(t) 的}贡献 ~ -9 地壳成分，与上大陆地壳的 Nd 同位素组成相容，也与 Woongarra 流纹岩的下伏长英质火山岩和 Fortescue 群地壳污染的基性火山岩相容。源自相同热液源但与未受污染的超基性 Fortescue 火山岩相关的不太明显的负趋势 (ɛNd _(t) ~ -2) 在较老的 Joffre、Dales Gorge 和 Marra Mamba IF 中观察到。由于 Nd 同位素对氧化还原条件不敏感，在 ~ 2.45 Ga 处 Nd 同位素组成的主要变化与风化制度的变化无关，而是与暴露于风化的大陆表面性质的变化有关。一种解释是，在 GOE 之前和期间沉积的沉积物的 Sm-Nd 源是局部地来自下面的地下 LIP，反映了沉积和/或水文网络和集水区的地球动力学背景的变化。另一种解释可能是由于与大陆陆块出现相关的风化过程的作用增加，流体-岩石相互作用的性质发生了重大变化。然而，需要来自世界各地不同克拉通的额外 Nd 同位素数据，推断图里溪群中记录的 Nd 同位素组成的显着变化是否反映了全球水文循环的变化。我们的数据支持大型地下岩浆区作为大气氧气上升和元古代初期冰川开始的触发因素的作用。