Altered pyroclastic rocks in iron-formation in the Hamersley range, Western Australia [discussion]

With reference to conclusions published by G. LaBerge (for reference, see No. 1, 10 E67-00101), it is noted that some of LaBerge's generalizations are based on atypical examples. Stilpnomelane, dolomitic carbonate, and riebeckite do not show special concentration near pyroclastic units. Pyrite is not restricted to stilpnomelane units; pure stilpnomelane units are the only bands free of pyrite. There is little evidence for the type of cyclic sequence suggested by LaBerge. Volcanism alone will not explain the chert-siderite association. Because so many uncertainties exist, advocating a preferred hypothesis of origin is premature.