Volcanic-hosted Massive Sulfide Mineralization in Archean Yigarn Craton, Australia

A review of volcanic-hosted massive sulfide (VHMS) mineralization in the Archean Yilgarn Craton, Western Australia: Tectonic, stratigraphic and geochemical associations

Authors:

Hollis et al

Abstract:

The Archean Yilgarn Craton of Western Australia represents a world-class metallogenic province, hosting considerable resources of Au, Ni-sulfides and iron ore. Despite close geological similarities with the volcanic-hosted massive sulfide (VHMS)-rich Superior Province of Canada, there is a strong disparity in the number of discovered VHMS deposits between the two areas. This paper brings together recently published U-Pb zircon geochronology and stratigraphic constraints from across the Yilgarn Craton, with a large number of existing whole rock geochemical datasets (881 samples from ∼125 localities). Recognized VHMS occurrences are placed in a detailed tectonic and stratigraphic framework. Temporal and geochemical associations to mineralization are discussed. Areas of VHMS mineralization in the Yilgarn Craton are preferentially associated with areas of thinned, juvenile crust as revealed through regional (Nd, Pb) isotope variations. The characteristics identified here for prospective host sequences are: largely bimodal volcanic complexes, synvolcanic faults, a spatial and temporal association to HFSE-enriched synvolcanic intrusions, and the following geochemical signatures of felsic rocks. VHMS-bearing felsic rocks in the Youanmi Terrane and Eastern Goldfields are characterized by low Zr/Y, La/YbCN and Th/Yb ratios, high Sc/TiO2, Sc/V, HFSE and HREE contents, and flat HREE profiles similar to those of Abitibi greenstone belt, Canada, and the Pilbara Craton of Western Australia. Chondrite-normalized REE profiles for felsic rocks overlying 2.82-2.80 Ga plume-related basalts and large igneous complexes of the Youanmi Terrane are flat. Other VHMS-bearing felsic rocks are characterized by slight LREE enrichment (La/SmCN less than 3) and flattish HREE profiles. In the Youanmi Terrane four distinct periods of economic mineralization can be recognized: (i) greater than 2.9 Ga (e.g. Golden Grove, Ravensthorpe), associated with early bimodal-mafic greenstone belts subjected to extension; (ii) c. 2815 Ma (e.g. Austin, Just Desserts, Youanmi), following a major plume event and coeval with the emplacement of large igneous complexes across the northern Youanmi Terrane at shallow levels in the crust (Meeline and Boodanoo suites); (iii) 2760-2745 Ma (e.g. Hollandaire, Mt. Mulcahy) in areas of rift-related magmatism during the deposition of the Greensleeves Formation; (iv) c. 2725 Ma, in the Gum Creek greenstone belt associated with a second major plume event, broadly coeval with the emplacement of high-level sills of the Yalgowra Suite. In the Eastern Goldfields Superterrane, VHMS mineralization formed between c. 2700 and 2680 Ma (e.g. Teutonic Bore camp, Anaconda, Nimbus, Erayinia). All episodes of VHMS mineralization in the Yilgarn show strong temporal and spatial associations to suites of HFSE-enriched granitic intrusions (e.g. Eelya suite, Mt. Kenneth suite, Kookynie supersuite).