STRATIGRAPHY, STRUCTURE, AND VOLCANIC-HOSTED MINERALIZATION OF THE MOUNT WINDSOR SUBPROVINCE, NORTH QUEENSLAND, AUSTRALIA

The Mount Windsor subprovince contains a major belt of mineralized Cambro-Ordovician subaqueous volcanogenic rocks at the northern end of the Tasman orogenic belt. The base of the stratigraphic sequence is a thick continent-derived siliciclastic package intruded by alkali andesites, typical of intraplate settings. This is overlain by massive subaqueous rhyolitic units and then by a mixed association of basaltic, andesitic, dacitic, and rhyolitic volcanics and volcaniclastics containing numerous small elongate pods of quartz-hematite or magnetite exhalite. The cessation in active volcanism is marked by a change to a sandstone-siltstone unit dominated by volcanic sources. The majority of volcanics form a coherent group of low to medium K calc-alkaline lavas similar to those in modern island-are settings. Extensional growth faults produced local variation in the stratigraphic thickness. The largest growth fault in the area is close to the Reward, Highway, and Handcuff deposits. The sequence has been multiply folded and faulted in the Paleozoic but the large-scale structure remains relatively simple. Volcanic-hosted massive sulfide (VHMS) deposits occur at the top of the massive rhyolite and in the mixed volcanic package above it. With the exception of the Reward pyrite pipe, the mineralization occurs as blanketlike deposits with low thickness/lateral extent ratios, The Thalanga, Reward, and Waterloo deposits are copper rich whereas Agincourt, Magpie, Liontown, Handcuff, and Warrawee are zinc rich and copper poor, with a significant barite component.