Abstract

Sm-Nd ages of pegmatite dikes that crosscut gold-bearing structures in the southern Yilgarn Craton, Western Australia, provide minimum age constraints of 2640 ± 11 Ma, 2628 ± 10 Ma, and 2620 ± 36 Ma for gold mineralization at the Westonia and Nevoria (Yellowdine Terrane) and Scotia (Norseman Terrane) gold deposits, respectively. Similarly, a post–gold mineralization dike at Westonia has a U-Pb zircon age of 2637 ± 8 Ma. These constraints are consistent with, and provide further support for, suggestions that the majority of gold deposits in the Yilgarn Craton formed during a regionally extensive gold mineralization event at ca. 2630 Ma (i.e., 2630 ± ≈ 10 Ma). In combination with recent geochronological results, these data also provide further evidence that, although mineralization appears to significantly postdate the majority of magmatic and metamorphic activity at higher crustal levels, widespread thermal reworking of the lower-middle crust, involving partial melting, amphibolite to granulite facies metamorphism, and lower crustal granitoid intrusion, occurred concurrently with gold mineralization at ca. 2630 Ma. It is probable that the large-scale hydrothermal fluid flow that produced widespread gold deposition was also part of this tectonothermal event. Models developed for other Archean terranes whereby gold mineralization postdates formation and cratonization of host granite-greenstone terranes, and is therefore unrelated to these processes, are not required to explain the timing of the majority of gold deposits in the Yilgarn Craton.

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