Komatiites of the Wildara-Leonora Belt, Yilgarn Craton, WA: The missing link in the Kalgoorlie Terrane?

摘要

The Wildara-Leonora Belt in the Kalgoorlie Terrane is located between the world-class nickel provinces of the Agnew-Wiluna Belt to the North and the Kambalda Domain to the South. It extends from the Wildara station to the gold mining center of Leonora and consists of a deformed package of mafic, komatiitic and sedimentary rocks. This package of rocks, which hosts a number of small nickel-sulfide occurrences, has been explored extensively for komatiite-hosted nickel deposits, most recently within the Sullivans Unit in the South-East of the Wildara-Leonora Belt. Lithostratigraphic similarities together with shared physical, geochemical and textural properties support a common affiliation between the Wildara-Leonora and the Agnew-Wiluna Belts. On this evidence, the Wildara-Leonora Belt represents the Southern extension of the largest komatiite-hosted nickel camp in the world. The apparently lesser prospectivity for nickel sulfide deposits is interpreted as a consequence of contrasting volcanic facies assemblages.Komatiites in the Wildara-Leonora Belt present geochemical and volcanological characteristics consistent with turbulent lava flow emplacement. However, compared with the Agnew-Wiluna Belt, the Wildara-Leonora Belt komatiites are not spatially associated with felsic volcanic units, but rather overlie a thick sequence of pillowed basalts and sulfidic sediments. The lower proportion of adcumulate, greater degrees of fractionation and lower degrees of contamination are consistent with komatiites in the Wildara-Leonora Belt having been emplaced in a more distal position to the rift environment, with lower magma flux and more tranquil emplacement than the Agnew-Wiluna Belt komatiites, and consequently having lower potential for giant nickel sulfide deposits such as those at Perseverance and Mt. Keith.