Constraints on the timing of lode‐gold mineralisation in the Wiluna greenstone belt, Yilgarn Craton, Western Australia

Abstract

40Ar‐39Ar ages of hydrothermal muscovites constrain the age of gold mineralisation in the Wiluna greenstone belt, Western Australia. A single muscovite sample from the Matilda M1 deposit, hosted in the greenschist‐amphibolite facies Matilda domain, has a 40Ar‐39Ar plateau‐like segment corresponding to an age of 2623 ± 12 Ma (2 σ). This is interpreted as the probable age of mineralisation and is similar to radiometric ages of mineralisation from other parts of the craton. Two muscovite samples from an altered microdiorite dyke from the East Lode deposit, located within the prehnite‐pumpellyite facies Wiluna domain have 40Ar‐39Ar plateau‐like segment ages of 2565 ± 12 Ma and 2563 ± 12 Ma. A third sample, consisting of muscovite from an altered high‐MgO basalt, has an enigmatic spectrum with no obvious plateau‐like segment and the highest temperature steps have apparent ages of ca 2600 Ma. Two alternative interpretations are considered for the data from the East Lode deposit: (i) mineralisation in the Wiluna...