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Univ. West. Aust., Dep. Geol., Nedland, West. Aust., Australia
Archean volcanic-hosted massive sulfide mineralization in Western Australia ranges in age from ca. 3.46 to 2.70 Ga. Barite-rich, Zn-Pb-Cu mineralization is hosted by relatively large ion lithophile element-rich calc-alkaline volcanic rocks in the ca. 3.46 Ga Warrawoona Group and ca. 3.3 Ga Gorge Creek Group in the eastern Pilbara craton. The high lead contents and 100 Zn/Zn + Pb ratios of between 60 and 80 are typical ofPhanerozoic mineralization hosted by silicic volcanic rocks, rather than of most Archean massive Cu-Zn sulfide deposits. The abundance of sulfate in these deposits, combined with evidence for evaporitic sulfates elsewhere in the Warrawoona Group, also suggests at least local oxidation of reduced suliur in the upper layer of the ocean at this time. Lead-rich, Zn-Pb-Cu mineralization also occurs in the ca. 2.99 Ga Whim Creek Group in the western Pilbara craton. This volcanic and sedimentary sequence formed in a rapidly subsiding basin within older continental crust, and the volcanic rocks are characterized by relatively high large ion lithophile element contents. In the east Yilgarn craton, Cu-Zn mineralization occurs in a bimodal assemblage of tholeiitic basalts and rhyolites at Teutonic Bore, in the Norseman-Wiluna belt. This deposit was mined during the 1980s. In the western Yilgarn block, Cu-Zn mineralization occurs in an assemblage of ca. 3.0 Ga. deep-water, calc-alkaline volcanic and sedimentary rocks in the Golden Grove belt. Mineralization in this belt is typically associated with magnetite and includes the Scuddles and Gossan Hill deposits. Alteration at these deposits is similar to that of Mattabi-type deposits in the Canadian Archcan and includes iron-rich chlorite and carbonates in poorly developed, or laterally extensive, feeder zones. The lead content of the host volcanic sequence and mineralization in this belt is typically much lower than that of the Pb-rich Pilbara mineralization. The Scuddles deposit with a mine recoverable reserve of about 10 million tons of 11 percent Zn, 0.8 percent Pb, and 1.2 percent Cu is currently being mined.
This record provided courtesy of AGI/GeoRef.
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