142Nd and 182W systematics of Neoarchean rocks from the Yilgarn Craton, W-Australia

The short-lived isotope systems ¹⁴⁶Sm-¹⁴²Nd and ¹⁸²Hf-¹⁸²W were active during the first ca. 500 Ma and 50 Ma after solar system formation. As a result of recent analytical advances, it is now possible to detect small ¹⁴²Nd-¹⁸²W variations (≤ 3ppm) within terrestrial samples providing unprecedented information on Earth’s accretion, early differentiation, as well as mantle mixing and homogenization rates.

Here, we present high precision ¹⁴²Nd/¹⁴⁴Nd and ¹⁸²W/¹⁸⁴W data for Neoarchean samples from the Yilgarn Craton, W-Australia, using previously published MC ICP-MS protocols [1,2]. We report µ¹⁴²Nd deficits as low as -4.2 ± 1.4 for 2.7 Ga mafic-ultramafic samples from the Kalgoorlie Terrane. A contemporaneous mafic-ultramafic suite from the Kambalda area displays small µ¹⁴²Nd values between +0.4 ± 1.2 to -1.5 ± 0.9 that seem to correlate positively with ε¹⁴³Nd. If interpreted to represent a differentiation model age, this event could not have happened earlier than 4.13 Ga. This suite reveals a correlation of long-lived ε¹⁴³Nd-ε¹⁷⁶Hf isotope systematics, suggestive of a pristine mantle source. We further suggest that µ¹⁸²W excesses from the Kalgoorlie and Kambalda suites (+5.3 ± 3.6 and +4.5 ± 1.6) demonstrate a missing late veneer component in the mantle source, in line with previously reported ε¹⁰⁰Ru excesses found in the same samples [3]. In conclusion, our results demonstrate that mantle-derived rocks from the Yilgarn Craton carry isotope signatures directly referring to Hadean processes.

[1] Hasenstab-Dübeler et al. (2022) Chem. Geol. 614, 121-141

[2] Tusch et al. (2019) GCA 257, 284-310

[3] Fischer-Gödde et al. (2021) Goldschmidt Abstract 4362